Manufacturing in Mexico

Manufacturing in Mexico grew rapidly in the late 1960s with the end of the US farm labor agreement known as the bracero program. This sent many unskilled farm laborers back into the Northern border region with no source of income. As a result, the US and Mexican governments agreed to The Border Industrialization Program, which permitted US companies to assemble product in Mexico using raw materials and components from the US with reduced duties. The Border Industrialization Program became known popularly as The Maquiladora Program or shortened to The Maquila Program.
Over the years, simple assembly operations in Mexico have evolved into complex manufacturing operations including televisions, automobiles, industrial and personal products. While inexpensive commodity manufacturing has flown to China, Mexico attracts U.S. manufacturers that need low-cost solutions near-by for higher value end products and just-in-time components.
Larger foreign firms with global experience can set up operations in Mexico readily. Smaller companies are usually advised to seek professional help from a qualified consulting firm or by working with a partner in Mexico.
Advantages.
Mexico's low landed costs are attractive when considered in comparison to other developing country options. It is suited to serve as a manufacturing venue for short to medium-run products that have a high degree of engineered content. Its proximity to the United States enables technical and production personnel to coordinate activities to bridge temporary and physical distances. The closeness to markets, as well as to the consumer base, fulfills the just-in-time requirements of both. Additionally, Mexico's efforts to enforce patent and intellectual property laws are advanced compared with those in place in other low-cost nations. Political risk associated with the country is minimal.
Although the average wage rate in Mexico is higher than in China and other emerging Asian economies, the workforce in Mexico has a large pool of highly educated and skilled engineers. Also, freight charges from China has significantly increased over the years, which make up for the difference in labor cost.
Methods of operation.
There are five common methods by which foreign companies setup manufacturing operations in Mexico.
Contracting.
Companies are well advised to consider the contract manufacturing or subcontract manufacture option when the work to be performed requires approximately 25 individuals or less, or is sporadic. Once this number is surpassed, other options would provide savings as a result of economies of scale derived from increased labor content.
Companies with high quality requirements must be certain to identify and work with firms capable of meeting and maintaining their exacting standards. If quality standards can be maintained, contract manufacturing / subcontract manufacturing can be the best option for firms seeking to manufacture product without making the large capital and organizational investment required on their own. Manufacturers with high intellectual property content must be assured that such property is protected.
While contract manufacturing or subcontracting has the potential to be an excellent situation for the foreign company due to the fact that the responsibility for production, quality, and delivery is held by the contract manufacturer or subcontractor, it is often very difficult to find a company in Mexico that has the ability to operate as a true contract manufacturer or subcontractor.
Joint venture.
A second means by which manufacturers can set up operations in Mexico is through the establishment of a joint-venture agreement with an indigenous party. Joint venturing can be an effective means to achieving organizational goals given the local partner's detailed knowledge of the market and its prevailing conditions. Relationships with firms that have established distribution channels may be of particular value to parties seeking to supply product to domestic markets.
Establishing and maintaining a joint-venture relationship can be challenging in that both parties must share a compatibility of organizational culture, as well as pursue similar goals and objectives. Encountering a partner with sufficient similarity of process and purpose can often prove to be a significant challenge.
Wholly owned subsidiary.
A firm can establish itself in Mexico through the formation of a wholly owned subsidiary. As is the case with initiating operations in any foreign environment, this can be the most complex, costly and risk-laden alternative. In addition to committing the organization to the investment of “bricks and mortar,” the manufacturer must take the time, make the effort and assume the cost of assembling the skill sets required to navigate new waters. Expertise must be sought, acquired and retained in such diverse areas as labor law, human resources, payroll and benefits administration, environmental law, customs law, logistics, import/export operations, accounting, taxation, real estate law, etc. Although there is much involved with the establishment of a wholly owned subsidiary, it does enable the organization to have 100% control over all of its activities.
Shelter Operation.
A fourth option that allows firms to fully control their own production and quality, to benefit from the experience of an organization that knows the local market, and which eliminates the need to make sizeable investments in physical and human assets is the manufacturing Shelter. Established in 1966, Cal Pacifico S.A. de C.V. was the second company to operate under the then new Maquiladora Program in Mexico and pioneered the shelter service provider model, providing those services to clients in that same year. The model proved so successful that later Cal Pacifico brought to Mexico to manufacture under the shelter operation method a long list of multinational manufacturers such as Asahi Overseas Corp., Bayer Corp., Eli Lilly & Co., 2 divisions of Emerson Electric Co., Esselte Pendaflex Corp., 2 divisions of General Dynamics Corp., Haemonetics Corp., 2 divisions of Hughes Corp., ITT General Controls, Medtronic, Inc., Northrop Grumman Corp., Pall Corp., Polk Audio, Inc., Scott USA, Smith Goggle Co., Sony Corporation of America, 7 divisions of Teledyne, Inc., The Carlyle Group, and Tyco, Inc. among others. Working through a shelter service provider, foreign-based manufacturers are able to initiate operations quickly without actually establishing a legal presence in the country. They are in Mexico as a department or subsidiary of their chosen shelter service provider. In essence, firms opting to use this vehicle are “sheltered” from many of the risks and liabilities that normally affect firms that choose to incorporate directly. Under the typical shelter arrangement, manufacturers send machinery & equipment, raw materials and supervisory personnel to train and manage workers, while the shelter service provider performs the tasks and functions that are not “core” to the manufacturing process. The manufacturer controls those areas that affect profitability and sustained growth. Shelter service providers typically offer their clients services in some or all of the following areas: human resources, payroll and benefits administration, logistics, import/export operations, accounting, taxation, legal, risk management, plant and park management, procurement, environmental, customs compliance, and real estate leasing. Those shelter services provide for the perfect match of offshore operational knowledge and manufacturing expertise... the technical support capabilities of the shelter service provider and the product manufacturing talents of its client(s).
This is a value-added outsourcing arrangement in that it gives manufacturers a means by which to greater leverage core competencies and intellectual assets. An organization that does this becomes more nimble, and experiences faster and higher levels of innovation. Additionally this arrangement is attractive to firms seeking to pursue strategies of leveraged growth. As a manufacturer expands under a shelter arrangement, they absorb only a portion of the additional overhead that an expansion of activities requires.
Outsourcing.
A quickly growing fifth option for foreign companies to set up manufacturing operations in Mexico is to "Outsource" their manufacturing operation to an independent Corporation "Maquiladora". The manufacturing outsource option is a hybrid of both the "shelter" system and traditional "contract manufacturing or subcontracting". The way that the manufacturing outsource option works is that a foreign company essentially hires the maquiladora to manufacture the foreign company's products for them in Mexico (much like in a "contract manufacturing / subcontract" situation) but with an inexpensive Mexican workforce that utilizes the equipment, tooling, and processes of the foreign company (much like in a "shelter" situation).
The key difference between a manufacturing outsource situation and a contract manufacturing / subcontracting situation, is that in a contract manufacturing / subcontracting situation the contract manufacturer / subcontractor already has the equipment, tooling, procedure, supply chain, and expertise in place and is currently manufacturing products that are very similar to the products that the foreign company needs. In contrast, a manufacturing outsource company utilizes the foreign company's equipment, tooling, supply chain, and procedure combined with in-house expertise to manufacture the foreign company's product in exactly the same way the foreign company makes it themselves.
The key difference between a manufacturing outsource situation and a "shelter" situation, is that in a shelter situation the foreign company must have a constant physical presence in Mexico to manage and oversee their operation, as the shelter provider bills the foreign company for the services provided (see “shelter” above) without taking responsibility for production, quality, and delivery of the product. In contrast, a manufacturing outsource company bills the foreign company on a “price per piece” basis which shifts the responsibility for production, quality, and delivery to the manufacturing outsource company; therefore allowing the foreign company to concentrate on their core competencies without having to manage a foreign manufacturing operation.
The manufacturing outsource option is rapidly becoming a reality for many foreign companies interested in utilizing Mexico's cost-effective workforce.


Vacuum assisted resin transfer molding

Vacuum Assisted Resin Transfer Molding (VARTM) or Vacuum Injected Molding (VIM) is a closed mold, out of autoclave (OOA) composite manufacturing process. VARTM is a variation of Resin Transfer Molding (RTM) with its distinguishing characteristic being the replacement of the top portion of a mold tool with a vacuum bag and the use of a vacuum to assist in resin flow. The process involves the use of a vacuum to facilitate resin flow into a fiber layup contained within a mold tool covered by a vacuum bag. After the impregnation occurs the composite part is allowed to cure at room temperature with an optional post cure sometimes carried out.
Process.
Typically, this process uses a low viscosity (100 to 1000 cP) polyester or vinyl ester resin along with fiberglass fibers to create a composite. Normally the process is capable of producing composites with a fiber volume fraction between 40 and 50%. The resin to fiber ratio is important for determining the overall strength and performance of the final part, with mechanical strength being most influenced by the type of fiber reinforcement. The type of resin used will primarily determine the corrosion resistance, heat distortion temperature, and surface finish. Resins used in this process must have low viscosities due to the limited pressure differential provided by the vacuum pump. High performance fibers, such as carbon fiber, can also be used. However, their usage is less common and is mainly for the fabrication of high end parts.
Air Leakages.
For VARTM to create high quality composite parts it is crucial that air leakages are avoided. Air leakages can cause resin to improperly flow through the mold and also lead to the formation of air bubbles. Defects in the form of voids occur when the composite cures with air bubbles inside of it. Air leakage can be caused by a defect in the vacuum bag, an improper application of the sealant tape, or an improper seal at the points where the hose meets the vacuum bag.
Air leakages can be detected using various methods. In some situations air bubbles, and consequentially air leakages can be detected simply through a visual inspection of the composite. The most simple ‘Leak isolation’ method involves monitoring the vacuum pressure level to determine if there are air leaks. If the vacuum pressure level does not decrease after vacuuming all of the air out of the mold, then it can be determined that there is no air leakages. However, if there was a drop in the vacuum pressure level it would be an indication that there was an air leakage. Unfortunately, this method for identifying the presence of an air leak does not determine the air leak's location.
Sound magnification is also utilized to locate leaks. Since air leaks make noise, this method utilizes a microphone to amplify sound to a set of speakers or headphones to help in the identification of leaks. This allows a user to detect an air leak and use the microphone to help them find the location of the leak. Unfortunately, this method is ineffective in noisy environments.
Heated air can also be utilized to detect leaks. In this method heated air is forced through the mold prior to the use of a vacuum pump. If there are any air leaks in the process's set up the hot air will be expelled through the leak. An infrared detector, can then be used to determine if there are any heat releases on the surface of vacuum bag, which would be an indication of the presence of an air leak.
VARTM vs RTM.
Both VARTM and RTM are closed mold processes where pressure is used to inject resin into the mold. There are few differences in the materials used in VARTM vs RTM, with the resin and fiber basically being the same for both processes. Therefore, if factors such as fiber to resin ratio and cross-sectional fiber distribution were held constant for each process, the molded part performances would be similar.
RTM has a fiber preform placed between mold halves, while VARTM uses the bottom part of the mold tool and a vacuum bag with resin flow caused by the use of a vacuum. RTM results in small-medium-sized parts that can also be complex in shape, while VARTM can also create very large parts. VARTM also advantageously has lower equipment costs than RTM. The single sided nature of the VARTM mold has the drawback of only allowing for one side of the composite to have an A-class finish. However, parts can be manufactured with an A-class finish on both sides with RTM due it having both a top and bottom mold.
Advantages and Applications.
This process offers the benefit of not requiring an expensive autoclave while also being capable of producing large, complex aerospace-grade parts. Products produced using this method vary widely in their application with parts being used in transportation, wind energy, marine, infrastructure, and aerospace applications. The process's ability to create large and complex parts has allowed it to effectively reduce manufacturing costs when utilized to produce parts that are traditionally constructed of numerous small components. For instance, LOCKHEED Martin Space Systems (LMSS) experienced a manufacturing cost saving of up to 75% when it began to produce the quarter section of the equipment bay for the Trident II D5 missile using VARTM.


Void (composites)

A void is a pore that remains unfilled with polymer and fibers in a composite material. Voids are typically the result of poor manufacturing of the material and are generally deemed undesirable. Voids can affect the mechanical properties and lifespan of the composite. They degrade mainly the matrix-dominated properties such as interlaminar shear strength, longitudinal compressive strength, and transverse tensile strength. Voids can act as crack initiation sites as well as allow moisture to penetrate the composite and contribute to the anisotropy of the composite. For aerospace applications, a void content of approximately 1% is still acceptable, while for less sensitive applications, the allowance limit is 3-5%. Although a small increase in void content may not seem to cause significant issues, a 1-3% increase in void content of carbon fiber reinforced composite can reduce the mechanical properties by up to 20% Void content in composites is represented as a ratio, also called void ratio, where the volume of voids, solid material, and bulk volume are taken into account. Void ratio can be calculated by the formula below where e is the void ratio of the composite, Vv is the volume of the voids, and Vt is the volume of the bulk material.
Formation of Voids.
Voids are considered defects in composite structures and there are several types of voids that can form in composites depending on the fabrication route and matrix type. Among other factors that can influence the quantity and location of voids are pre-preg impregnation, surface morphology, curing parameters, compaction pressure, fiber bridging, excessive resin bleed, and the thickness of layup .
A resin with a high viscosity will likely produce voids in a composite. It is difficult for a resin or matrix with a high viscosity to penetrate the original void spaces between adjacent fibers. This will cause voids to form close the fiber surface. Preventing these voids becomes a more daunting task when the fibers are packed tightly together in a composite
A high void proportion can be obtained in a composite due to errors in processing as well. If the temperature used for curing is too low for the particular matrix used, complete degassing might not occur. However, if the temperature used for curing is too high for a particular matrix, gelation might occur too rapidly and voids may still be present . For example, if a laminate composite is cured at a temperature that is too low for the particular matrix used, the resin viscosity could remain high and hinder removing the void spaces between individual plies Some resins can cure at room temperature while other resins require temperatures up to 200 °C, but curing above or below the required temperature for a particular matrix can increase the amount of voids present in a composite. If the injection pressure in a resin injection pultrusion process is not high enough, the resin or matrix might not be able to penetrate the fiber bed to completely wet out the fibers without voids. Entrapped air or bubbles can be formed in the resin during resin mixing or as a result of mechanical gas entrapment by dual scale fingering in fibrous reinforcements. If these bubbles are not removed before the wetting of the fibers or curing of the composite, the bubbles could become voids that can be found throughout the final composite structure.
Reduction of Voids.
Because voids are viewed as defects in composite materials, many methods are applied for reducing voids in composites. Traditionally, using vacuum bagging system and autoclave under pressure and heat will minimize or prevent voids from forming.
The vacuum bagging system combined with autoclave is a common method used in industrial processes to achieve a low void content for thermoset composites. Vacuum evacuation is the way reducing exciting amount of voids by physically transporting the voids out of the resin and fiber network through vacuum lines, and it is influenced by the viscosity of resin. Autoclave pressure is used to assist vacuum in removing trapped air and excess resin while at the same time preventing volatiles from coming out of the resin at high temperatures.
Optimization of injection flow rate is often calculated to minimize voids in Resin Transfer Molded (RTM) or Vacuum Assisted Resin Infusion (VARI) composites. During the injection phase, a liquid resin impregnates the fibers before curing and solidification, often creating voids in the part during the injection. Through an algorithm between fluid flow velocity (v) and the percentages of macro-voids (V1) and micro-voids (V2)
an optimized rate can be obtained and the voids in RTM and VARI composites can be reduced, thus improving properties of the composite.


5356 aluminium alloy

5356 aluminium alloy is an alloy in the wrought aluminium-magnesium family (5000 or 5xxx series). Unlike most aluminium-magnesium alloys, it is primarily used as welding filler. It is one of the most popular aluminium filler alloys, alongside 4043. It possesses relatively high strength, but at the expense of being more vulnerable to cracking. It is the preferred filler when making lap or butt welds on the popular 6061 aluminium alloy, or when the welded parts are to be anodized.


Metal casting

In metalworking and jewelry making, casting is a process in which a liquid metal is delivered into a mold (usually by a crucible) that contains a negative impression (i.e., a three-dimensional negative image) of the intended shape. The metal is poured into the mold through a hollow channel called a sprue. The metal and mold are then cooled, and the metal part (the "casting") is extracted. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods.
Casting processes have been known for thousands of years, and have been widely used for sculpture (especially in bronze), jewelry in precious metals, and weapons and tools. Highly engineered castings are found in 90 percent of durable goods, including cars, trucks, aerospace, trains, mining and construction equipment, oil wells, appliances, pipes, hydrants, wind turbines, nuclear plants, medical devices, defense products, toys, and more.
Traditional techniques include lost-wax casting (which may be further divided into centrifugal casting, and vacuum assist direct pour casting), plaster mold casting and sand casting.
The modern casting process is subdivided into two main categories: expendable and non-expendable casting. It is further broken down by the mold material, such as sand or metal, and pouring method, such as gravity, vacuum, or low pressure.
Expendable mold casting.
Expendable mold casting is a generic classification that includes sand, plastic, shell, plaster, and investment (lost-wax technique) moldings. This method of mold casting involves the use of temporary, non-reusable molds.
Sand casting.
Sand casting is one of the most popular and simplest types of casting, and has been used for centuries. Sand casting allows for smaller batches than permanent mold casting and at a very reasonable cost. Not only does this method allow manufacturers to create products at a low cost, but there are other benefits to sand casting, such as very small-size operations. The process allows for castings small enough fit in the palm of one's hand to those large enough for a train car bed (one casting can create the entire bed for one rail car). Sand casting also allows most metals to be cast depending on the type of sand used for the molds.
Sand casting requires a lead time of days, or even weeks sometimes, for production at high output rates (1–20 pieces/hr-mold) and is unsurpassed for large-part production. Green (moist) sand, which is black in color, has almost no part weight limit, whereas dry sand has a practical part mass limit of . Minimum part weight ranges from . The sand is bonded using clays, chemical binders, or polymerized oils (such as motor oil). Sand can be recycled many times in most operations and requires little maintenance.
Loam molding.
Loam molding has been used to produce large symmetrical objects such as cannon and church bells. Loam is a mixture of clay and sand with straw or dung. A model of the produced is formed in a friable material (the chemise). The mold is formed around this chemise by covering it with loam. This is then baked (fired) and the chemise removed. The mold is then stood upright in a pit in front of the furnace for the molten metal to be poured. Afterwards the mold is broken off. Molds can thus only be used once, so that other methods are preferred for most purposes.
Plaster mold casting.
Plaster casting is similar to sand casting except that plaster of paris is used instead of sand as a mold material. Generally, the form takes less than a week to prepare, after which a production rate of 1–10 units/hr-mold is achieved, with items as massive as and as small as with very good surface finish and close tolerances. Plaster casting is an inexpensive alternative to other molding processes for complex parts due to the low cost of the plaster and its ability to produce near net shape castings. The biggest disadvantage is that it can only be used with low melting point non-ferrous materials, such as aluminium, copper, magnesium, and zinc.
Shell molding.
Shell molding is similar to sand casting, but the molding cavity is formed by a hardened "shell" of sand instead of a flask filled with sand. The sand used is finer than sand casting sand and is mixed with a resin so that it can be heated by the pattern and hardened into a shell around the pattern. Because of the resin and finer sand, it gives a much finer surface finish. The process is easily automated and more precise than sand casting. Common metals that are cast include cast iron, aluminium, magnesium, and copper alloys. This process is ideal for complex items that are small to medium-sized.
Investment casting.
Investment casting (known as lost-wax casting in art) is a process that has been practiced for thousands of years, with the lost-wax process being one of the oldest known metal forming techniques. From 5000 years ago, when beeswax formed the pattern, to today's high technology waxes, refractory materials, and specialist alloys, the castings ensure high-quality components are produced with the key benefits of accuracy, repeatability, versatility, and integrity.
Investment casting derives its name from the fact that the pattern is invested, or surrounded, with a refractory material. The wax patterns require extreme care for they are not strong enough to withstand forces encountered during the mold making. One advantage of investment casting is that the wax can be reused.
The process is suitable for repeatable production of net shape components from a variety of different metals and high performance alloys. Although generally used for small castings, this process has been used to produce complete aircraft door frames, with steel castings of up to 300 kg and aluminium castings of up to 30 kg. Compared to other casting processes such as die casting or sand casting, it can be an expensive process. However, the components that can be produced using investment casting can incorporate intricate contours, and in most cases the components are cast near net shape, so require little or no rework once cast.
Waste molding of plaster.
A durable plaster intermediate is often used as a stage toward the production of a bronze sculpture or as a pointing guide for the creation of a carved stone. With the completion of a plaster, the work is more durable (if stored indoors) than a clay original which must be kept moist to avoid cracking. With the low cost plaster at hand, the expensive work of bronze casting or stone carving may be deferred until a patron is found, and as such work is considered to be a technical, rather than artistic process, it may even be deferred beyond the lifetime of the artist.
In waste molding a simple and thin plaster mold, reinforced by sisal or burlap, is cast over the original clay mixture. When cured, it is then removed from the damp clay, incidentally destroying the fine details in undercuts present in the clay, but which are now captured in the mold. The mold may then at any later time (but only once) be used to cast a plaster positive image, identical to the original clay. The surface of this plaster may be further refined and may be painted and waxed to resemble a finished bronze casting.
Evaporative-pattern casting.
This is a class of casting processes that use pattern materials that evaporate during the pour, which means there is no need to remove the pattern material from the mold before casting. The two main processes are lost-foam casting and full-mold casting.
Lost-foam casting.
Lost-foam casting is a type of evaporative-pattern casting process that is similar to investment casting except foam is used for the pattern instead of wax. This process takes advantage of the low boiling point of foam to simplify the investment casting process by removing the need to melt the wax out of the mold.
Full-mold casting.
Full-mold casting is an evaporative-pattern casting process which is a combination of sand casting and lost-foam casting. It uses an expanded polystyrene foam pattern which is then surrounded by sand, much like sand casting. The metal is then poured directly into the mold, which vaporizes the foam upon contact.
Non-expendable mold casting.
Non-expendable mold casting differs from expendable processes in that the mold need not be reformed after each production cycle. This technique includes at least four different methods: permanent, die, centrifugal, and continuous casting. This form of casting also results in improved repeatability in parts produced and delivers near net shape results.
Permanent mold casting.
Permanent mold casting is a metal casting process that employs reusable molds ("permanent molds"), usually made from metal. The most common process uses gravity to fill the mold. However, gas pressure or a vacuum are also used. A variation on the typical gravity casting process, called slush casting, produces hollow castings. Common casting metals are aluminum, magnesium, and copper alloys. Other materials include tin, zinc, and lead alloys and iron and steel are also cast in graphite molds. Permanent molds, while lasting more than one casting still have a limited life before wearing out.
Die casting.
The die casting process forces molten metal under high pressure into mold cavities (which are machined into dies). Most die castings are made from nonferrous metals, specifically zinc, copper, and aluminium-based alloys, but ferrous metal die castings are possible. The die casting method is especially suited for applications where many small to medium-sized parts are needed with good detail, a fine surface quality and dimensional consistency.
Semi-solid metal casting.
Semi-solid metal (SSM) casting is a modified die casting process that reduces or eliminates the residual porosity present in most die castings. Rather than using liquid metal as the feed material, SSM casting uses a higher viscosity feed material that is partially solid and partially liquid. A modified die casting machine is used to inject the semi-solid slurry into reusable hardened steel dies. The high viscosity of the semi-solid metal, along with the use of controlled die filling conditions, ensures that the semi-solid metal fills the die in a non-turbulent manner so that harmful porosity can be essentially eliminated.
Used commercially mainly for aluminium and magnesium alloys, SSM castings can be heat treated to the T4, T5 or T6 tempers. The combination of heat treatment, fast cooling rates (from using uncoated steel dies) and minimal porosity provides excellent combinations of strength and ductility. Other advantages of SSM casting include the ability to produce complex shaped parts net shape, pressure tightness, tight dimensional tolerances and the ability to cast thin walls.
Centrifugal casting.
In this process molten metal is poured in the mold and allowed to solidify while the mold is rotating. Metal is poured into the center of the mold at its axis of rotation. Due to inertial force, the liquid metal is thrown out toward the periphery.
Centrifugal casting is both gravity and pressure independent since it creates its own force feed using a temporary sand mold held in a spinning chamber. Lead time varies with the application. Semi- and true-centrifugal processing permit 30–50 pieces/hr-mold to be produced, with a practical limit for batch processing of approximately 9000 kg total mass with a typical per-item limit of 2.3–4.5 kg.
Industrially, the centrifugal casting of railway wheels was an early application of the method developed by the German industrial company Krupp and this capability enabled the rapid growth of the enterprise.
Small art pieces such as jewelry are often cast by this method using the lost wax process, as the forces enable the rather viscous liquid metals to flow through very small passages and into fine details such as leaves and petals. This effect is similar to the benefits from vacuum casting, also applied to jewelry casting.
Continuous casting.
Continuous casting is a refinement of the casting process for the continuous, high-volume production of metal sections with a constant cross-section. It's primarily used to produce a semi-finished products for further processing. Molten metal is poured into an open-ended, water-cooled mold, which allows a 'skin' of solid metal to form over the still-liquid center, gradually solidifying the metal from the outside in. After solidification, the strand, as it is sometimes called, is continuously withdrawn from the mold. Predetermined lengths of the strand can be cut off by either mechanical shears or traveling oxyacetylene torches and transferred to further forming processes, or to a stockpile. Cast sizes can range from strip (a few millimeters thick by about five meters wide) to billets (90 to 160 mm square) to slabs (1.25 m wide by 230 mm thick). Sometimes, the strand may undergo an initial hot rolling process before being cut.
Continuous casting is used due to the lower costs associated with continuous production of a standard product, and also increased quality of the final product. Metals such as steel, copper, aluminum and lead are continuously cast, with steel being the metal with the greatest tonnages cast using this method.
Upcasting.
The upcasting (up-casting, upstream, or upward casting) is a method of either vertical or horizontal continuous casting of rods and pipes of various profiles (cylindrical, square, hexagonal, slabs etc.) of 8-30mm in diameter. Copper (Cu), bronze (Cu·Sn alloy), nickel alloys are usually used because of greater casting speed (in case of vertical upcasting) and because of better physical features obtained. The advantage of this method is that metals are almost oxygen-free and that the rate of product crystallization (solidification) may be adjusted by in a crystallizer - a high-temperature resistant device that cools a growing metal rod or pipe by using water.
The method is comparable to Czochralski method of growing silicon (Si) crystals, which is a metalloid.
Terminology.
Metal casting processes uses the following terminology:
Some specialized processes, such as die casting, use additional terminology.
Theory.
Casting is a solidification process, which means the solidification phenomenon controls most of the properties of the casting. Moreover, most of the casting defects occur during solidification, such as "gas porosity" and "solidification shrinkage".
Solidification occurs in two steps: "nucleation" and "crystal growth". In the nucleation stage, solid particles form within the liquid. When these particles form, their internal energy is lower than the surrounded liquid, which creates an energy interface between the two. The formation of the surface at this interface requires energy, so as nucleation occurs, the material actually undercools (i.e. cools below its solidification temperature) because of the extra energy required to form the interface surfaces. It then recalescences, or heats back up to its solidification temperature, for the crystal growth stage. Nucleation occurs on a pre-existing solid surface because not as much energy is required for a partial interface surface as for a complete spherical interface surface. This can be advantageous because fine-grained castings possess better properties than coarse-grained castings. A fine grain structure can be induced by "grain refinement" or "inoculation", which is the process of adding impurities to induce nucleation.
All of the nucleations represent a crystal, which grows as the heat of fusion is extracted from the liquid until there is no liquid left. The direction, rate, and type of growth can be controlled to maximize the properties of the casting. Directional solidification is when the material solidifies at one end and proceeds to solidify to the other end; this is the most ideal type of grain growth because it allows liquid material to compensate for shrinkage.
Cooling curves.
Cooling curves are important in controlling the quality of a casting. The most important part of the cooling curve is the "cooling rate" which affects the microstructure and properties. Generally speaking, an area of the casting which is cooled quickly will have a fine grain structure and an area which cools slowly will have a coarse grain structure. Below is an example cooling curve of a pure metal or eutectic alloy, with defining terminology.
Note that before the thermal arrest the material is a liquid and after it the material is a solid; during the thermal arrest the material is converting from a liquid to a solid. Also, note that the greater the superheat the more time there is for the liquid material to flow into intricate details.
The above cooling curve depicts a basic situation with a pure metal, however, most castings are of alloys, which have a cooling curve shaped as shown below.
Note that there is no longer a thermal arrest, instead there is a freezing range. The freezing range corresponds directly to the liquidus and solidus found on the phase diagram for the specific alloy.
Chvorinov's rule.
The local solidification time can be calculated using Chvorinov's rule, which is:
Where "t" is the solidification time, "V" is the volume of the casting, "A" is the surface area of the casting that contacts the mold, "n" is a constant, and "B" is the mold constant. It is most useful in determining if a riser will solidify before the casting, because if the riser does solidify first then it is worthless.
The gating system.
The gating system serves many purposes, the most important being conveying the liquid material to the mold, but also controlling shrinkage, the speed of the liquid, turbulence, and trapping dross. The gates are usually attached to the thickest part of the casting to assist in controlling shrinkage. In especially large castings multiple gates or runners may be required to introduce metal to more than one point in the mold cavity. The speed of the material is important because if the material is traveling too slowly it can cool before completely filling, leading to misruns and cold shuts. If the material is moving too fast then the liquid material can erode the mold and contaminate the final casting. The shape and length of the gating system can also control how quickly the material cools; short round or square channels minimize heat loss.
The gating system may be designed to minimize turbulence, depending on the material being cast. For example, steel, cast iron, and most copper alloys are turbulent insensitive, but aluminium and magnesium alloys are turbulent sensitive. The turbulent insensitive materials usually have a short and open gating system to fill the mold as quickly as possible. However, for turbulent sensitive materials short sprues are used to minimize the distance the material must fall when entering the mold. Rectangular pouring cups and tapered sprues are used to prevent the formation of a vortex as the material flows into the mold; these vortices tend to suck gas and oxides into the mold. A large sprue well is used to dissipate the kinetic energy of the liquid material as it falls down the sprue, decreasing turbulence. The "choke", which is the smallest cross-sectional area in the gating system used to control flow, can be placed near the sprue well to slow down and smooth out the flow. Note that on some molds the choke is still placed on the gates to make separation of the part easier, but induces extreme turbulence. The gates are usually attached to the bottom of the casting to minimize turbulence and splashing.
The gating system may also be designed to trap dross. One method is to take advantage of the fact that some dross has a lower density than the base material so it floats to the top of the gating system. Therefore, long flat runners with gates that exit from the bottom of the runners can trap dross in the runners; note that long flat runners will cool the material more rapidly than round or square runners. For materials where the dross is a similar density to the base material, such as aluminium, "runner extensions" and "runner wells" can be advantageous. These take advantage of the fact that the dross is usually located at the beginning of the pour, therefore the runner is extended past the last gate(s) and the contaminates are contained in the wells. Screens or filters may also be used to trap contaminates.
It is important to keep the size of the gating system small, because it all must be cut from the casting and remelted to be reused. The efficiency, or "", of a casting system can be calculated by dividing the weight of the casting by the weight of the metal poured. Therefore, the higher the number the more efficient the gating system/risers.
Shrinkage.
There are three types of shrinkage: "shrinkage of the liquid", "solidification shrinkage" and "patternmaker's shrinkage". The shrinkage of the liquid is rarely a problem because more material is flowing into the mold behind it. Solidification shrinkage occurs because metals are less dense as a liquid than a solid, so during solidification the metal density dramatically increases. Patternmaker's shrinkage refers to the shrinkage that occurs when the material is cooled from the solidification temperature to room temperature, which occurs due to thermal contraction.
Solidification shrinkage.
Most materials shrink as they solidify, but, as the adjacent table shows, a few materials do not, such as gray cast iron. For the materials that do shrink upon solidification the type of shrinkage depends on how wide the freezing range is for the material. For materials with a narrow freezing range, less than , a cavity, known as a "pipe", forms in the center of the casting, because the outer shell freezes first and progressively solidifies to the center. Pure and eutectic metals usually have narrow solidification ranges. These materials tend to form a "skin" in open air molds, therefore they are known as "skin forming alloys". For materials with a wide freezing range, greater than , much more of the casting occupies the "mushy" or "slushy" zone (the temperature range between the solidus and the liquidus), which leads to small pockets of liquid trapped throughout and ultimately porosity. These castings tend to have poor ductility, toughness, and fatigue resistance. Moreover, for these types of materials to be fluid-tight, a secondary operation is required to impregnate the casting with a lower melting point metal or resin.
For the materials that have narrow solidification ranges, pipes can be overcome by designing the casting to promote directional solidification, which means the casting freezes first at the point farthest from the gate, then progressively solidifies toward the gate. This allows a continuous feed of liquid material to be present at the point of solidification to compensate for the shrinkage. Note that there is still a shrinkage void where the final material solidifies, but if designed properly, this will be in the gating system or riser.
Risers and riser aids.
Risers, also known as "feeders", are the most common way of providing directional solidification. It supplies liquid metal to the solidifying casting to compensate for solidification shrinkage. For a riser to work properly the riser must solidify after the casting, otherwise it cannot supply liquid metal to shrinkage within the casting. Risers add cost to the casting because it lowers the "yield" of each casting; i.e. more metal is lost as scrap for each casting. Another way to promote directional solidification is by adding chills to the mold. A chill is any material which will conduct heat away from the casting more rapidly than the material used for molding.
Risers are classified by three criteria. The first is if the riser is open to the atmosphere, if it is then it is called an "open" riser, otherwise it is known as a "blind" type. The second criterion is where the riser is located; if it is located on the casting then it is known as a "top riser" and if it is located next to the casting it is known as a "side riser". Finally, if the riser is located on the gating system so that it fills after the molding cavity, it is known as a "live riser" or "hot riser", but if the riser fills with materials that have already flowed through the molding cavity it is known as a "dead riser" or "cold riser".
Riser aids are items used to assist risers in creating directional solidification or reducing the number of risers required. One of these items are "chills" which accelerate cooling in a certain part of the mold. There are two types: external and internal chills. External chills are masses of high-heat-capacity and high-thermal-conductivity material that are placed on an edge of the molding cavity. Internal chills are pieces of the same metal that is being poured, which are placed inside the mold cavity and become part of the casting. Insulating sleeves and toppings may also be installed around the riser cavity to slow the solidification of the riser. Heater coils may also be installed around or above the riser cavity to slow solidification.
Patternmaker's shrink.
Shrinkage after solidification can be dealt with by using an oversized pattern designed specifically for the alloy used. "s", or "s", are used to make the patterns oversized to compensate for this type of shrinkage. These rulers are up to 2.5% oversize, depending on the material being cast. These rulers are mainly referred to by their percentage change. A pattern made to match an existing part would be made as follows: First, the existing part would be measured using a standard ruler, then when constructing the pattern, the pattern maker would use a contraction rule, ensuring that the casting would contract to the correct size.
Note that patternmaker's shrinkage does not take phase change transformations into account. For example, eutectic reactions, martensitic reactions, and graphitization can cause expansions or contractions.
Mold cavity.
The mold cavity of a casting does not reflect the exact dimensions of the finished part due to a number of reasons. These modifications to the mold cavity are known as "allowances" and account for patternmaker's shrinkage, draft, machining, and distortion. In non-expendable processes, these allowances are imparted directly into the permanent mold, but in expendable mold processes they are imparted into the patterns, which later form the mold cavity. Note that for non-expendable molds an allowance is required for the dimensional change of the mold due to heating to operating temperatures.
For surfaces of the casting that are perpendicular to the parting line of the mold a draft must be included. This is so that the casting can be released in non-expendable processes or the pattern can be released from the mold without destroying the mold in expendable processes. The required draft angle depends on the size and shape of the feature, the depth of the mold cavity, how the part or pattern is being removed from the mold, the pattern or part material, the mold material, and the process type. Usually the draft is not less than 1%.
The machining allowance varies drastically from one process to another. Sand castings generally have a rough surface finish, therefore need a greater machining allowance, whereas die casting has a very fine surface finish, which may not need any machining tolerance. Also, the draft may provide enough of a machining allowance to begin with.
The distortion allowance is only necessary for certain geometries. For instance, U-shaped castings will tend to distort with the legs splaying outward, because the base of the shape can contract while the legs are constrained by the mold. This can be overcome by designing the mold cavity to slope the leg inward to begin with. Also, long horizontal sections tend to sag in the middle if ribs are not incorporated, so a distortion allowance may be required.
Cores may be used in expendable mold processes to produce internal features. The core can be of metal but it is usually done in sand.
Filling.
There are a few common methods for filling the mold cavity: "gravity", "low-pressure", "high-pressure", and "vacuum".
Vacuum filling, also known as "counter-gravity" filling, is more metal efficient than gravity pouring because less material solidifies in the gating system. Gravity pouring only has a 15 to 50% metal yield as compared to 60 to 95% for vacuum pouring. There is also less turbulence, so the gating system can be simplified since it does not have to control turbulence. Plus, because the metal is drawn from below the top of the pool the metal is free from dross and slag, as these are lower density (lighter) and float to the top of the pool. The pressure differential helps the metal flow into every intricacy of the mold. Finally, lower temperatures can be used, which improves the grain structure. The first patented vacuum casting machine and process dates to 1879.
Low-pressure filling uses 5 to 15 psig (35 to 100 kPag) of air pressure to force liquid metal up a feed tube into the mold cavity. This eliminates turbulence found in gravity casting and increases density, repeatability, tolerances, and grain uniformity. After the casting has solidified the pressure is released and any remaining liquid returns to the crucible, which increases yield.
Tilt filling.
"Tilt filling", also known as "tilt casting", is an uncommon filling technique where the crucible is attached to the gating system and both are slowly rotated so that the metal enters the mold cavity with little turbulence. The goal is to reduce porosity and inclusions by limiting turbulence. For most uses tilt filling is not feasible because the following inherent problem: if the system is rotated slow enough to not induce turbulence, the front of the metal stream begins to solidify, which results in mis-runs. If the system is rotated faster it induces turbulence, which defeats the purpose. Durville of France was the first to try tilt casting, in the 1800s. He tried to use it to reduce surface defects when casting coinage from aluminium bronze.
Macrostructure.
The grain macrostructure in ingots and most castings have three distinct regions or zones: the chill zone, columnar zone, and equiaxed zone. The image below depicts these zones.
The chill zone is named so because it occurs at the walls of the mold where the wall "chills" the material. Here is where the nucleation phase of the solidification process takes place. As more heat is removed the grains grow towards the center of the casting. These are thin, long "columns" that are perpendicular to the casting surface, which are undesirable because they have anisotropic properties. Finally, in the center the equiaxed zone contains spherical, randomly oriented crystals. These are desirable because they have isotropic properties. The creation of this zone can be promoted by using a low pouring temperature, alloy inclusions, or inoculants.
Inspection.
Common inspection methods for steel castings are "magnetic particle testing" and "liquid penetrant testing". Common inspection methods for aluminum castings are "radiography", "ultrasonic testing", and "liquid penetrant testing".
Defects.
There are a number of problems that can be encountered during the casting process. The main types are: "gas porosity", "shrinkage defects", "mold material defects", "pouring metal defects", and "metallurgical defects".
Casting process simulation.
Casting process simulation uses numerical methods to calculate cast component quality considering mold filling, solidification and cooling, and provides a quantitative prediction of casting mechanical properties, thermal stresses and distortion. Simulation accurately describes a cast component's quality up-front before production starts. The casting rigging can be designed with respect to the required component properties. This has benefits beyond a reduction in pre-production sampling, as the precise layout of the complete casting system also leads to energy, material, and tooling savings.
The software supports the user in component design, the determination of melting practice and casting methoding through to pattern and mold making, heat treatment, and finishing. This saves costs along the entire casting manufacturing route.
Casting process simulation was initially developed at universities starting from the early '70s, mainly in Europe and in the U.S., and is regarded as the most important innovation in casting technology over the last 50 years. Since the late '80s, commercial programs are available which make it possible for foundries to gain new insight into what is happening inside the mold or die during the casting process.


Dymalloy

Dymalloy is a metal matrix composite consisting of 20% copper and 80% silver alloy matrix with type I diamond. It has very high thermal conductivity of 420 W/(m·K), and its thermal expansion can be adjusted to match other materials, e.g. silicon and gallium arsenide chips. It is chiefly used in microelectronics as substrate for high power and high density multi-chip modules, where it aids with removal of waste heat.
Dymalloy was developed as part of CRADA between Sun Microsystems and Lawrence Livermore National Laboratory. It was first researched for use in space-based electronics for the Brilliant Pebbles project.
Dymalloy is prepared from diamond powder of about 25 micrometers size. The grains are coated by physical vapor deposition with 10 nanometers thick layer of alloy of tungsten with 26% rhenium, forming a tungsten carbide layer that assists bonding, then coated with 100 nanometers of copper to avoid carbide oxidation, then compacted in a mold and infiltrated with molten copper-silver alloy. Adding 55 vol.% of diamond yields material with thermal expansion matching that of gallium arsenide; slightly higher amount of diamond allows matching to silicon. Copper can be used instead of copper-silver alloy, but the higher melting point may cause partial transformation of diamond to graphite. The material shows some plasticity. High mechanical strain causes brittle failure in the diamond grains, and ductile failure in the matrix. The diamond grains give the alloy a degree of surface texture; when a smooth surface is desired, the alloy can be plated and polished.
In 1996, the price for a 10×10×0.1 cm substrate was quoted as USD 200.
Similar alloys are possible with the metal phase consisting of one or more of silver, copper, gold, aluminium, magnesium, and zinc. The carbide-forming metal can be selected from titanium, zirconium, hafnium, vanadium, niobium, tantalum, and chromium, where Ti, Zr, and Hf are preferable. The amount of carbide-forming metal must be sufficient to coat at least 25% of the diamond grains, as otherwise, the bonding is insufficient, the heat transfer between matrix and diamond grains is weak which leads to loss of effectivity towards the level of the matrix metal alone, and the material may deform at higher temperatures, and must be low in order to prevent formation of too thick carbide layer that would hinder heat transfer. The volume of diamond should be higher than 30 vol.%, as lower ratio does not provide significant increase of thermal conductivity, and lower than 70 vol.% as higher ratio of diamond makes thermal expansion matching to semiconductors difficult. The grains should also be completely surrounded with metal, to avoid deformation due to different thermal expansion coefficients between diamond and metal; the carbide coating assists with this.
A similar material is AlSiC, with aluminium instead of copper-silver alloy and silicon carbide instead of diamond.


Pipe Cutting

Pipe cutting, or pipe profiling, is a mechanized industrial process that removes material from pipe or tube to create a desired profile. Typical profiles include straight cuts, mitres, saddles and midsection holes. These complex cuts are usually required to allow a tight fit between two parts that are to be joined via arc welding.
Hot cutting.
Hot cutting is performed by means of a thermal torch (plasma or oxyfuel) and is mounted to the last axis of a multi-axis machine. The axes of the multi-axis machine are powered by electric motors and are synchronized to create a path for the torch and pipe that yield a desired profile. The synchronization of axes is accomplished either mechanically, via cams, levers and gears, or electronically, via microprocessors and controllers.
Cold cutting.
Where the high temperatures and sources of ignition required by hot cutting are not desirable, air- or hydraulically-powered pipe cutting machines are used. These comprise a clamshell or chain-mounted cutting head holding a tool steel and feed mechanism which advances the tool a set amount per revolution round the pipe. Tools may be styled to cut and/or prepare the bevel for welding in a single or multiple passes.
Popular in offshore, pipe processing, ship building, pressure vessel, structural and mechanical contracting manufacturing because of the complex cuts and profiles typical required in their respective industries. Some common pipe cutting applications are: pipe work, offshore jackets, industrial steel structures, stadiums, cranes, nozzles, and pipe laying stingers.


Corrugated box design

Corrugated box design is the process of matching design factors for corrugated fiberboard (sometimes called corrugated cardboard) boxes with the functional physical, processing and end-use requirements. Packaging engineers work to meet the performance requirements of a box while controlling total costs throughout the system. Corrugated boxes are shipping containers used for transport packaging and have important functional and economic considerations.
In addition to the structural design discussed in this article, printed bar codes, labels, and graphic design are also vital.
Functions.
Corrugated boxes are used frequently as shipping containers. Boxes need to contain the product from manufacturing through distribution to sale and sometimes end-use. Boxes provide some measure of product protection by themselves but often require inner components such as cushioning, bracing and blocking to help protect fragile contents. The shipping hazards depend largely upon the particular logistics system being employed. For example, boxes unitized into a unit load on a pallet do not encounter individual handling while boxes sorted and shipped through part of their distribution cycle as mixed loads or express carriers can receive severe shocks, kicks, and so forth.
Ordinary shipping containers require printing and labels to identify the contents, provide legal and regulatory information, and bar codes for routing. Boxes that are used for marketing, merchandising and point-of-sale often have high graphics to help communicate the contents. Some boxes are designed for the display of contents on the shelf known as "Retail Ready Packaging". Others are designed to help dispense the contents. Popular for their strength, durability, lightness, recyclability, and cost-effectiveness, corrugated boxes are used for the shipping of a variety of items. Due to the quality and safety of packaging items in corrugated boxes, they are used widely in the food industry. The boxes handle the pressure that comes with stacking, making them ideal for easy transporting.
More than 95% of all products in the United States are shipped in corrugated boxes. Corrugated paperboard accounts for more than half of all the paper recycled in the US.
Stacking strength.
One of the important functions of a corrugated box is to provide crush resistance (product protection) and adequate strength for stacking in warehouses. If long-term storage of corrugated boxes in high humidity is expected, extra strength and moisture resistance is called for. The method of loading boxes on pallets strongly affects stacking. Vertical columns provide the best box performance while interlocking patterns of boxes significantly reduce performance. The interaction of the boxes and pallets is also important.
A box can be designed by optimizing the grade of corrugated board, box design, flute direction, and inner supports. Support from the product also provides "load sharing" and can be an important factor. Box closures sometimes can have effects on box stacking strength.
A box can be designed by optimizing the grade of corrugated board, box design, flute direction, and inner supports. Support from the product also provides "load sharing" and can be an important factor. Box closures sometimes can have effects on box stacking strength.
Box compression testing is a means of evaluating boxes, stacks of boxes, and unit loads under controlled conditions. Field conditions of stacking and dynamic compression do not have the same degree of control. Compression strength can be estimated based on container construction, size, and use parameters: actual package testing is often conducted to verify these estimates.
A box can be designed by optimizing the grade of corrugated board, box design, flute direction, and inner supports. Support from the product also provides "load sharing" and can be an important factor. Box closures sometimes can have effects on box stacking strength.
Handling strength.
Many items are shipped individually (in part or entirely) by express carrier, mail, or other mixed logistics systems. The demands of multiple manual handlings, automated sortation, and uncontrolled stacking in trucks or air containers put severe stress on boxes, box closures, and the contents. Boxes designed for unit load handling and storage may not be suited to mixed logistics systems. Less than truckload shipping puts more stress on corrugated shipping containers than shipment by uniform pallet loads in trucks or intermodal containers. Boxes sometimes need to be heavier construction to match the needs of the distribution system. Package testing is often matched to the expected shipping hazards. ASTM International and the International Safe Transit Association test protocols reflect this.
Other factors.
Several texts offer guidance on the box design process. The Wiley Handbook of Packaging Technology offers guidance on considerations and options. ASTM D5639 Standard Practice for Selection of Corrugated Fiberboard Materials and Box Construction Based on Performance Requirements discusses material choices and box structures which may be good options for specified package performance.
Depending on the contents, some corrugated boxes need extra stiffness or a heavier grade of board. Boxes with hand holes or handles sometimes need higher strength board, reinforcement attached with adhesives, or embedded fibers.
Process.
Packaging engineers design corrugated boxes to meet the particular needs of the product being shipped, the hazards of the shipping environment, (shock, vibration, compression, moisture, etc.), and the needs of retailers and consumers. Engineers and designers start with the needs of the particular project: cost constraints, machinery capabilities, product characteristics, logistics needs, applicable regulations, consumer needs, etc. Often designs are made with Computer Aided Design programs connected to automated sample making tables. Several design and construction options might be considered.Samples are often submitted to package testing based on ASTM or other standard test protocols such as the International Safe Transit Association. Structural design is matched with graphic design. For consumer based designs, marketing personnel sometimes use Focus groups or more quantitative means of assessing acceptance. Test markets are employed for major programs.
The process starts by making corrugated board on a corrugating line, a long series of linked machines which may be the size of an (American) football field. A finished piece of single-wall corrugated board is a single corrugated layer sandwiched between two liners.
Skilled workers prepare job tickets for each stack of box blanks and route the blanks to fabrication machines. Printing dies and patterns are prepared on large, flexible, rubber or tin sheets. They are loaded onto rollers and the box blanks are fed through it, where each is trimmed, printed, cut, scored, folded, and glued to form a box. Finished boxes are then stacked and sent to a banding machine to be wrapped and shipped.
Design.
The most common box style is the Regular Slotted Container (RSC). All flaps are the same length from score to edge. Typically the major flaps meet in the middle and the minor flaps do not, unless the width is equal to the length. The size of a box can be measured for either internal (for product fit) or external (for handling machinery or palletizing) dimensions. The manufacturer's joint is most often joined with adhesive but may also be taped or stitched. The box is shipped flat (knocked down) to the packager who sets up the box, fills it, and closes it for shipment. Box closure may be by tape, adhesive, staples, strapping, etc.
Boxes are usually specified and ordered by the internal dimensions.Box styles in Europe are typically specified by a 4-digit code provided by the European Federation of Corrugated Board Manufacturers (FEFCO); an RSC is coded 0201.
Many other styles of corrugated boxes and structures are available. One common source is the Fibre Box Association:
Retail display.
Retailers often ask for merchandise to be delivered to them in shipping containers which allow the easy stocking of full caseloads. The goal is to put the case directly onto shelves and stocking locations without individually handling the unit packs or primary packages. Retailers often require products to come in shelf-ready packaging to reduce stocking costs and save labor expenses.
Several specialized box designs are available.
Government, military, and export.
Many items being supplied to governments are handled very well: boxes are unitized, shipped on covered trucks or intermodal containers, and storage is in warehouses. Normal "domestic boxes" and commercial packaging are acceptable.
Military materiel, field supplies, and humanitarian aid often encounter severe handling and uncontrolled storage. Special box specifications for government shipments are often applicable. Weather-resistant fiberboards, box construction, box closure, and unitizing are needed.
Dangerous and hazardous goods.
Shipment of dangerous goods or hazardous materials are highly regulated. Based on the UN Recommendations on the Transport of Dangerous Goods model regulations, each country has coordinated design and performance requirements for shipment. For example, in the US, the Department of Transportation has jurisdiction and published requirements in Title 49 of the Code of Federal Regulations. Corrugated boxes are described in 4G requirements. Performance (severe drop test, etc.) needs to be certified for the box and contents.
Some carriers have additional requirements.
Box closure.
The means of closing a box is an important aspect of design. It is affected by the types of equipment available to production lines, the measured laboratory performance, the field performance, and the ability of end-users to easily and safely open the box.
Box closures include:


Central Institute of Tool Design

Central Institute of Tool Design or CITD is an institute in India providing programs in Tool Engineering and Technology . The CITD main campus is in Hyderabad, Telangana, with a branch campus in Vijayawada and an extension centre in Chennai.
History.
The institute was established in 1968 by the government of India with the assistance of United Nations Development Programme (UNDP) and the International Labour Organization (ILO) as an executing agency.
Objective.
The objective of CITD is to meet the requirements of industry in the fields of tool design and manufacture and to train technical personnel in these fields. The institute has strong links with industries to impart practical knowledge by way of undertaking tooling assignments.
Functions.
1) to provide consultancy and advisory services including assistance in the design and development of tools.
2) to recommend measures to standardise tools, and tooling elements, components of jigs, fixtures, dies etc.
3) to provide skill development in cutting edge technologies like CAD/CAM, AI, Electronics, Pneumatic, civil.
Facilities.
The Central Institute of Tool Design has a tool room with sophisticated CNC machines like CNC EDM (Charmilles Roboform 54), CNC Wirecut EDM (AGIE Cut Classic-III & Electronics), 4- and 5-Axis High-Speed Machining Centres, Kellenberger CNC Cylindrical Grinding Machine and 3D Coordinate measuring machine with scanning and digitization facilities. The institute is equipped with EMCO table top CNC turning and milling machines with closed loop systems to impart training in CNC Programming.
The calibration laboratory has Universal Horizontal metroscope ULM OPAL 600 Carl Zeiss Technology (Germany) and Slip Gauge Measuring Unit 826 with Millitron 1240 (Mahr, Germany) to calibrate limit gauges, micrometers, dial indicators, etc. The Automation Centre is equipped with simulator training kits like Advanced Pneumatics Trainer, Advanced Electro Pneumatics Trainer with PID controls, Advanced Hydraulics Trainer, Advanced Electro Hydraulics Trainer, Closed-loop Hydraulics Trainer with PID Controls, PLC Trainer, Sensors Technology Trainer, Modular Production System with testing, processing, handling and sorting stations, cut section models of elements, transparent working models of hydraulics element etc.
The CAD/CAM Centre is equipped with hardware like Compaq workstations, IBM, DELL systems, Pentium IV systems and software like AutoCAD, MDT Ideas NX11, Pro-E Wildfire, Catia V5, UG, Ansys, Nastran, Hypermesh, MasterCam, DelCam, SolidWork, Solid edge, etc.
CITD has a library with a collection of technical books in tool engineering. IT subscribes to international journals like "CIRP Annals", "American Machinist", "Journal of Engineering Materials & Technology" (ASME), "Precision Engineering" (Japan), "Precision Tool Maker", etc. For the dissemination of information, the centre publishes a computerised current awareness abstracting bulletin and provides a technical enquiry service. The institute extends its services to developing countries by imparting knowledge and skills to their personnel in the field of Tool Design, CAD/CAM and Low-Cost Automation Techniques.
Activities.
CITD conducts regular and part-time training programmes in the field of Tool Design & Manufacture, Low Cost Automation, Mechatronics and Computer Aided Design & Computer Aided Manufacture. It conducts short-term courses, special-purpose clinics in Tool Engineering, seminars, tailor-made programmes, in disciplines for the benefit of working personnel.
CITD provides a consultancy and servicing facility to industry, including assistance in design and development of tools, and it also recommends measures to standardise tools and tooling elements, components of jigs and fixtures, dies and moulds and other tools. CITD is a member on technical committees of the Bureau of Indian Standards.


Bridgeport (machine tool brand)

Bridgeport is a brand of milling machine and machining center produced by Bridgeport Machines, Inc. from 1938 until 2004, when it was then acquired by the machine tool conglomerate Hardinge, Inc.
History.
The original corporation was founded in Bridgeport, Connecticut, and started selling its machines in 1938. It became known in the following decades for small and medium-sized vertical milling machines, with a form of quill equipped multiple-speed vertical milling head with a ram-on-turret mounting over a knee-and-column base. The American Precision Museum's biography of Rudolph Bannow reports that he conceived the design in 1936 as the logical machine on which to mount the milling head already being built by the Bridgeport Pattern and Model Works (which he owned with a partner Magnus Wahlstrom). The first Bridgeport milling machine (serial number 1) is on display at the Museum.
Due to the overall success of the company's milling machines, the term "Bridgeport" is often used to refer to "any" vertical milling machine of the same configuration, regardless of make. Many other companies have cloned the form. Today, the Bridgeport brand still produces this configuration in both manual and computer numerical control (CNC) versions, and such machining centers are now equally as prominent as their manual counterparts.
Bridgeport manual milling machines have come in many types and sizes over the years, including (but not limited to) the C head (original), R head (heavy duty C head), M head, J head (and high speed, 5440 RPM version), 2J1 1/2 head (1.5 HP Vari-Speed), 2J2 (2HP Vari-speed), and Series II head (4HP Vari-speed). All of the heads offer variable speeds, the earlier ones via a step pulley (cone pulley) and the later ones via either continuously variable transmission (CVT) systems or variable-speed drive. Typical table sizes are 9″ × 49″ (Y and X, respectively) and 10″ × 54″. Machine tapers for tool holding include Morse tapers (on early models) and the R8 taper (a widely used standard that Bridgeport created) on most models. Both Morse and R8 allow for both collets and solid holders, and a drill chuck can be held by either of the latter. Machine slides are of the dovetail type, and rotary bearings are mostly of the roller and ball types.


Industrial management

Industrial management is a branch of engineering which facilitates creation of management system and integrates the diverse engineering processes. Industrial Management deals with industrial design, construction, management, and application of science and engineering principles to improve the entire industrial infrastructure and industrial processes.
Industrial Management focuses on the management of industrial processes. Industrial Managers can be said to be responsible for proper and the most efficient interaction of 4Ms: Man, Material, Machine and Method (which every organization needs).
Industrial management also involves studying the performance of machines as well as people. Specialists are employed to keep machines in good working condition and to ensure the quality of their production. The flow of materials through the plant is supervised to ensure that neither workers nor machines are idle. Constant inspection is made to keep output up to standard.
As a part of engineering and particularly related to the manufacturing engineering industry, studies the structure and organization of industrial companies. It comprises those fields of industrial issues that are necessary for the success of companies within the manufacturing sector.
Who is an Industrial Manager?
An Industrial Manager incorporates the principles of manufacturing system, logistics, supply chain management, materials management, entrepreneurship, among other things. Industrial Managers plan how to efficiently and economically use resources in a business including labor, materials, machines, time, capital, energy, and information. An Industrial Manager also has to deal with creating new systems to solve problems related to waste and inefficiency associated with a business/ industrial process. This field is ever in need of competent personnel capable of applying logic and reasoning to identify strengths and weaknesses of alternative solutions, conclusions, or approaches to such problems. A Masters in Industrial Management specially provides the students a broad-based knowledge and skills required for industrial needs.
Term industrial company.
The term industrial company is generally applied to a manufacturing firm that – contrary to a crafts business – produces consumer durables in factories from raw materials in mass and serial production (a division of labor) using modern manufacturing machines.
History of industrial management.
https://www.infoplease.com/encyclopedia/social-science/economy/concepts/industrial-management/the-development-of-industrial-management
Courses of study.
Study programs in industrial management are very popular in economies with a high value of manufacturing output, such as the United States and Germany. Especially German research universities incorporate a large number of advanced courses in engineering in their graduate program in industrial management and are, thus, more like M.Eng.- programs. Degree programs are also offered under the title "industrial administration".
Specialization in Industrial Management.
Specialization in Industrial Management is designed to address and solve real life problems relating to industrial set-ups. Collaboration with relevant industries and financial institutes is its modus operandi. This specialization is one of the very few aimed at mid-career professionals who wish to make the move to senior management within industrial and manufacturing organizations. It is designed to provide the business expertise essential for all senior managers by integrating specific engineering subjects with the management of technology and manufacturing systems. The specialization also examines the latest business thinking and provides expert knowledge on engineering and technology issues and theories. Topics such as finance, marketing, management strategy are integrated with modern industrial issues such as project and quality management, manufacturing effectiveness, advanced manufacturing technology and supply chain management.


Die casting

Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter, and tin-based alloys. Depending on the type of metal being cast, a hot- or cold-chamber machine is used.
The casting equipment and the metal dies represent large capital costs and this tends to limit the process to high-volume production. Manufacture of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It is especially suited for a large quantity of small- to medium-sized castings, which is why die casting produces more castings than any other casting process. Die castings are characterized by a very good surface finish (by casting standards) and dimensional consistency.
History.
Die casting equipment was invented in 1838 for the purpose of producing movable type for the printing industry. The first die casting-related patent was granted in 1849 for a small hand-operated machine for the purpose of mechanized printing type production. In 1885 Ottmar Mergenthaler invented the Linotype machine, which cast an entire line of type as a single unit, using a die casting process. It nearly completely replaced setting type by hand in the publishing industry. The Soss die-casting machine, manufactured in Brooklyn, NY, was the first machine to be sold in the open market in North America. Other applications grew rapidly, with die casting facilitating the growth of consumer goods, and appliances, by greatly reducing the production cost of intricate parts in high volumes. In 1966, General Motors released the "Acurad" process.
Cast metal.
The main die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is also possible. Specific die casting alloys include: zinc aluminium; aluminium to, e.g. The Aluminum Association (AA) standards: AA 380, AA 384, AA 386, AA 390; and AZ91D magnesium. The following is a summary of the advantages of each alloy:
, maximum weight limits for aluminium, brass, magnesium, and zinc castings are estimated at approximately , and , respectively. By late-2019, press machines capable of die casting single pieces over- were being used to produce aluminium chassis components for cars.
The material used defines the minimum section thickness and minimum draft required for a casting as outlined in the table below. The thickest section should be less than , but can be greater.
Design geometry.
There are a number of geometric features to be considered when creating a parametric model of a die casting:
Equipment.
There are two basic types of die casting machines: "hot-chamber machines" and "cold-chamber machines". These are rated by how much clamping force they can apply. Typical ratings are between .
Hot-chamber die casting.
Hot-chamber die casting, also known as "gooseneck machines", rely upon a pool of molten metal to feed the die. At the beginning of the cycle the piston of the machine is retracted, which allows the molten metal to fill the "gooseneck". The pneumatic- or hydraulic-powered piston then forces this metal out of the gooseneck into the die. The advantages of this system include fast cycle times (approximately 15 cycles a minute) and the convenience of melting the metal in the casting machine. The disadvantages of this system are that it is limited to use with low-melting point metals and that aluminium cannot be used because it picks up some of the iron while in the molten pool. Therefore, hot-chamber machines are primarily used with zinc-, tin-, and lead-based alloys.
Cold-chamber die casting.
These are used when the casting alloy cannot be used in hot-chamber machines; these include aluminium, zinc alloys with a large composition of aluminium, magnesium and copper. The process for these machines start with melting the metal in a separate furnace. Then a precise amount of molten metal is transported to the cold-chamber machine where it is fed into an unheated shot chamber (or injection cylinder). This shot is then driven into the die by a hydraulic or mechanical piston. The biggest disadvantage of this system is the slower cycle time due to the need to transfer the molten metal from the furnace to the cold-chamber machine.
Mold or tooling.
Two dies are used in die casting; one is called the "cover die half" and the other the "ejector die half". Where they meet is called the parting line. The cover die contains the sprue (for hot-chamber machines) or shot hole (for cold-chamber machines), which allows the molten metal to flow into the dies; this feature matches up with the injector nozzle on the hot-chamber machines or the shot chamber in the cold-chamber machines. The ejector die contains the ejector pins and usually the runner, which is the path from the sprue or shot hole to the mould cavity. The cover die is secured to the stationary, or front, platen of the casting machine, while the ejector die is attached to the movable platen. The mould cavity is cut into two "cavity inserts", which are separate pieces that can be replaced relatively easily and bolt into the die halves.
The dies are designed so that the finished casting will slide off the cover half of the die and stay in the ejector half as the dies are opened. This assures that the casting will be ejected every cycle because the ejector half contains the "ejector pins" to push the casting out of that die half. The ejector pins are driven by an "ejector pin plate", which accurately drives all of the pins at the same time and with the same force, so that the casting is not damaged. The ejector pin plate also retracts the pins after ejecting the casting to prepare for the next shot. There must be enough ejector pins to keep the overall force on each pin low, because the casting is still hot and can be damaged by excessive force. The pins still leave a mark, so they must be located in places where these marks will not hamper the casting's purpose.
Other die components include "cores" and "slides". Cores are components that usually produce holes or opening, but they can be used to create other details as well. There are three types of cores: fixed, movable, and loose. Fixed cores are ones that are oriented parallel to the pull direction of the dies (i.e. the direction the dies open), therefore they are fixed, or permanently attached to the die. Movable cores are ones that are oriented in any other way than parallel to the pull direction. These cores must be removed from the die cavity after the shot solidifies, but before the dies open, using a separate mechanism. Slides are similar to movable cores, except they are used to form undercut surfaces. The use of movable cores and slides greatly increases the cost of the dies. Loose cores, also called "pick-outs", are used to cast intricate features, such as threaded holes. These loose cores are inserted into the die by hand before each cycle and then ejected with the part at the end of the cycle. The core then must be removed by hand. Loose cores are the most expensive type of core, because of the extra labor and increased cycle time. Other features in the dies include water-cooling passages and vents along the parting lines. These vents are usually wide and thin (approximately ) so that when the molten metal starts filling them the metal quickly solidifies and minimizes scrap. No risers are used because the high pressure ensures a continuous feed of metal from the gate.
The most important material properties for the dies are thermal shock resistance and softening at elevated temperature; other important properties include hardenability, machinability, heat checking resistance, weldability, availability (especially for larger dies), and cost. The longevity of a die is directly dependent on the temperature of the molten metal and the cycle time. The dies used in die casting are usually made out of hardened tool steels, because cast iron cannot withstand the high pressures involved, therefore the dies are very expensive, resulting in high start-up costs. Metals that are cast at higher temperatures require dies made from higher alloy steels.
The main failure mode for die casting dies is wear or erosion. Other failure modes are "heat checking" and "thermal fatigue". Heat checking is when surface cracks occur on the die due to a large temperature change on every cycle. Thermal fatigue is when surface cracks occur on the die due to a large number of cycles.
Process.
The following are the four steps in "traditional die casting", also known as "", these are also the basis for any of the die casting variations: die preparation, filling, ejection, and shakeout. The dies are prepared by spraying the mould cavity with lubricant. The lubricant both helps control the temperature of the die and it also assists in the removal of the casting. The dies are then closed and molten metal is injected into the dies under high pressure; between . Once the mould cavity is filled, the pressure is maintained until the casting solidifies. The dies are then opened and the shot (shots are different from castings because there can be multiple cavities in a die, yielding multiple castings per shot) is ejected by the ejector pins. Finally, the shakeout involves separating the scrap, which includes the gate, runners, sprues and flash, from the shot. This is often done using a special trim die in a power press or hydraulic press. Other methods of shaking out include sawing and grinding. A less labor-intensive method is to tumble shots if gates are thin and easily broken; separation of gates from finished parts must follow. This scrap is recycled by remelting it. The yield is approximately 67%.
The high-pressure injection leads to a quick fill of the die, which is required so the entire cavity fills before any part of the casting solidifies. In this way, discontinuities are avoided, even if the shape requires difficult-to-fill thin sections. This creates the problem of air entrapment, because when the mould is filled quickly there is little time for the air to escape. This problem is minimized by including vents along the parting lines, however, even in a highly refined process there will still be some porosity in the center of the casting.
Most die casters perform other secondary operations to produce features not readily castable, such as tapping a hole, polishing, plating, buffing, or painting.
Inspection.
After the shakeout of the casting it is inspected for defects. The most common defects are misruns and cold shuts. These defects can be caused by cold dies, low metal temperature, dirty metal, lack of venting, or too much lubricant. Other possible defects are gas porosity, shrinkage porosity, hot tears, and flow marks. "Flow marks" are marks left on the surface of the casting due to poor gating, sharp corners, or excessive lubricant.
Lubricants.
Water-based lubricants are the most used type of lubricant, because of health, environmental, and safety reasons. Unlike solvent-based lubricants, if water is properly treated to remove all minerals from it, it will not leave any by-product in the dies. If the water is not properly treated, then the minerals can cause surface defects and discontinuities.
Today "water-in-oil" and "oil-in-water" emulsions are used, because, when the lubricant is applied, the water cools the die surface by evaporating depositing the oil that helps release the shot. A common mixture for this type of emulsion is thirty parts water to one part oil, however in extreme cases a ratio of one-hundred to one is used. Oils that are used include heavy residual oil (HRO), animal fat, vegetable fat, synthetic oil, and all sorts of mixtures of these. HROs are gelatinous at room temperature, but at the high temperatures found in die casting, they form a thin film. Other substances are added to control the viscosity and thermal properties of these emulsions, e.g. graphite, aluminium, mica. Other chemical additives are used to inhibit rusting and oxidation. In addition emulsifiers are added to improve the emulsion manufacturing process, e.g. soap, alcohol esters, ethylene oxides.
Historically, solvent-based lubricants, such as diesel fuel and kerosene, were commonly used. These were good at releasing the part from the die, but a small explosion occurred during each shot, which led to a build-up of carbon on the mould cavity walls. However, they were easier to apply evenly than water-based lubricants.
Advantages.
Advantages of die casting:
Disadvantages.
The main disadvantage to die casting is the very high capital cost. Both the casting equipment required and the dies and related components are very costly, as compared to most other casting processes. Therefore, to make die casting an economic process, a large production volume is needed. Other disadvantages are:
Variants.
Acurad.
Acurad was a die casting process developed by General Motors in the late 1950s and 1960s. The name is an acronym for accurate, reliable, and dense. It was developed to combine a stable fill and directional solidification with the fast cycle times of the traditional die casting process. The process pioneered four breakthrough technologies for die casting: thermal analysis, flow and fill modeling, heat treatable and high integrity die castings, and indirect squeeze casting (explained below).
The thermal analysis was the first done for any casting process. This was done by creating an electrical analog of the thermal system. A cross-section of the dies were drawn on Teledeltos paper and then thermal loads and cooling patterns were drawn onto the paper. Water lines were represented by magnets of various sizes. The thermal conductivity was represented by the reciprocal of the resistivity of the paper.
The Acurad system employed a bottom fill system that required a stable flow-front. Logical thought processes and trial and error were used because computerized analysis did not exist yet; however this modeling was the precursor to computerized flow and fill modeling.
The Acurad system was the first die casting process that could successfully cast low-iron aluminium alloys, such as A356 and A357. In a traditional die casting process these alloys would solder to the die. Similarly, Acurad castings could be heat treated and meet the U.S. military specification .
Finally, the Acurad system employed a patented double shot piston design. The idea was to use a second piston (located within the primary piston) to apply pressure after the shot had partially solidified around the perimeter of the casting cavity and shot sleeve. While the system was not very effective, it did lead the manufacturer of the Acurad machines, Ube Industries, to discover that it was just as effective to apply sufficient pressure at the right time later in the cycle with the primary piston; this is indirect squeeze casting.
Pore-free.
When no porosity is allowed in a cast part then the pore-free casting process is used. It is identical to the standard process except oxygen is injected into the die before each shot to purge any air from the mould cavity. This causes small dispersed oxides to form when the molten metal fills the die, which virtually eliminates gas porosity. An added advantage to this is greater strength. Unlike standard die castings, these castings can be heat treated and welded. This process can be performed on aluminium, zinc, and lead alloys.
Vacuum-assisted high-pressure die casting.
In vacuum assisted high pressure die casting, a.k.a. vacuum high pressure die casting (VHPDC), a vacuum pump removes air and gases from die cavity and metal delivery system before and during injection. Vacuum die casting reduces porosity, allows heat treating and welding, improves surface finish, and can increase strength.
Heated-manifold direct-injection.
Heated-manifold direct-injection die casting, also known as direct-injection die casting or runnerless die casting, is a zinc die casting process where molten zinc is forced through a heated manifold and then through heated mini-nozzles, which lead into the moulding cavity. This process has the advantages of lower cost per part, through the reduction of scrap (by the elimination of sprues, gates, and runners) and energy conservation, and better surface quality through slower cooling cycles.
Semi-solid.
"Semi-solid die casting" uses metal that is heated between its liquidus and either solidus or eutectic temperature, so that it is in its "mushy region". This allows for more complex parts and thinner walls.
Low Pressure Die Casting (LPDC) uses compressed air instead of a piston to inject molten metal into the die. The process begins with the preparation of the die. The die is preheated to a temperature that will ensure good metal flow and avoid premature solidification of the molten metal. A holding furnace (crucible) filled with molten metal is located beneath the sealed die. The furnace is pressurized to inject the molten metal into the die cavity through a tube. The pressure is usually around 7 to 15 psi. The molten metal is left to solidify in the die. This takes anywhere from a few seconds to a few minutes, depending on the size and complexity of the part being cast. Once the casting has solidified, the die is opened, and the casting is ejected or removed manually.


Kite square

A kite square is a device used to measure the "out-of-squareness" of a machining center or coordinate measuring machine.
“Square-ness” or “Out-of-Square” is one of the critical measurement in machine tool metrology. For rectangular measurements, it refers to angular deviation of working axes between one carriages to another. The value of Monarch VMC was previously found as 4 arc sec.
The Kite Square Technique, together with a displacement sensing instrument, can measure the alignment of any points on a line of interest. Its main components are two perpendicular bars and three calibrated artifacts (Balls). The general principle of measuring with a kite square is once one of the diagonal is aligned to working axis, the displacement deviation on artifacts in other diagonal will appear (if any) as the kite square arms are perpendicular to each other.


Traditional engineering

Traditional engineering, also known as sequential engineering, is the process of marketing, engineering design, manufacturing, testing and production where each stage of the development process is carried out separately, and the next stage cannot start until the previous stage is finished. Therefore, the information flow is only in one direction, and it is not until the end of the chain that errors, changes and corrections can be relayed to the start of the sequence, causing estimated costs to be under predicted.
This can cause many problems; such as time consumption due to many modifications being made as each stage does not take into account the next. This method is hardly used today, as the concept of concurrent engineering is more efficient.
Traditional engineering is also known as over the wall engineering as each stage blindly throws the development to the next stage over the wall.
Lean manufacturing.
Traditional manufacturing has been driven by sales forecasts that companies need to produce and stockpile inventory to support. Lean manufacturing is based on the concept that production should be driven by the actual customer demands and requirements. Instead of pushing product to the marketplace, it is pulled through by the customers' actual needs.