Aluminum prototype mold

FIGURE 4.3 Example of an aluminum prototype mold for mounting strips of a lamp housing... 

In many cases, a single parameter determines the costs of a product so significantly that it can be used for the total evaluation or, as already described above, at least for parts of a product. It can be referred back to a weight-cost ratio in many sub-areas of the mold calculation. In some cases, weight-cost ratios can be used for the evaluation of the entire mold. A similar procedure is shown in Figure 5.6. The effective bounding volume of the component was chosen as the reference value for determining costs for aluminum prototype molds. 

FIGURE 5.6 Example for mold costing of aluminum prototype molds based on the effective component bounding volume (all 1-cavity molds)... 

The economic compromise for a prototype mold material is often aluminum or epoxy filled with aluminum powder. The latter material has a thermal conductivity approaching that of solid aluminum, which is nearly five times that of mold grade steel (and therefore introduces a variant into the prototype process). Either material can be machined into the correct cavity shape filled epoxy has the additional capability to be cast around a part form. 

Recently, prototype molds are being fabricated from particle-filled polyurethane and epoxy syntactic foams using computer-aided multiaxis routers. Plugs, used to mechanically prestretch polymer sheet, are also usually machined from syntactic foams. For certain pol5miers, heated aluminum plugs or solid nylon plugs are desired. 

Aluminum or Kirksite can be used to construct prototype molds. However, molds from these materials will never produce close tolerance parts with finished edges since telescoping edges cannot be produced in these soft metals. Flash-free... 

An inexpensive, satisfactory prototype mold can be made by casting aluminum to an undersized shape and finishing the casting with aluminum powder filled epoxy or polyester. This type mold will produce accurate prototype parts and can easily accommodate design changes. The parts, however, will not be flash-free. 

Prototype Mold. A simplified mold construction often made from a light metal casting alloy, such as aluminum, used to obtain information for the final mold and/or part design. 

The prototype mold (for technical parts made from aluminum) has established itself in the area of continuously improved CAD/CAM technology (for mold making). 

Prototype molds have to be manufactured quickly and as close-to-production as possible, to provide the customers with fast prototype components and to secure processing to be close-to-production. The (single) cavity is generally manufactured from soft material (aluminum or unhardened mold steel). The mold structure is usually not very complex so that changes can be made quickly. Using prototype molds, small batches of up to 1,000 pieces of each product can be manufactured. 

Prototype molds, because of their low volume requirements, can often be produced from less expensive materials. Brass, aluminum, or mild steel may be acceptable for low volumes and will machine much more rapidly than hardened steel. It may be acceptable to prepare cavity inserts that can be incorporated into standard mold base assemblies. 

Consequently, their use is best confined to short run or prototype use. In normal production, the improved heat transfer capability of a metal mold will more than repay the greater cost. Aluminum is most commonly used for thermoforming molds other options include cast or sprayed low melting point alloys, porous sintered metals, and copper alloys (Chapter 17). 

The differences between prototype and production molds are mainly durability and the addition of cooling to a production mold to decrease cycle times. Often a production mold is a multiple cavity tool that produces many replicates of the same part at once. Production molds usually are made from aluminum, steel, or other durable materials with good heat transfer characteristics. Tool steel is usually used for long run items. 

Prototype tools, where small quantities (perhaps of 50-100 moldings) are needed for test and evaluation, can be made of materials such as mild steel, aluminum, or epoxy resin tooling compounds. The tool life is limited and there is no long-term alternative to having a correct production tool manufactured. 

Aluminum is used for single molds, molds for prototypes, and large numbers of identical molds, as found on wheel-type blowing equipment or equipment with multiple die arrangements. (Regarding prototyping, it is best to utilize a material that the production mold will use to duplicate heat transfer conditions.) Aluminum may tend to distort after prolonged use. Thin areas, as at pinch-off areas, can wear in aluminum. 

As with unreinforced thermoplastics, aluminum Kirksite or epoxy molds are satisfactory for GRTP prototype work. 

Although hand molds may be made of soft metals such as aluminum or brass, and the cavities may produce acceptable parts, such metals quickly develop rough surfaces and rapidly lose their practicality after a few dozen cycles. It is best to use conventional metals as used for production molds for the respective process. Molds then may be used not only for prototyping but also for modest production while waiting for fuU-size produchon tooling. 

Whereas aluminum and zinc alloys or low-hardness steels can be used for small-series molds (prototypes and pre-series), the processing of SMC to serial parts is done in heated steel molds. 

Molds from aluminum (aluminum casting and CNC-milled) or sheet steel are used today for rotational molds. Electroplated molding has established itself for special rotational molds for PVC plastisols. There are also a couple of other materials that can be used in prototype production. 

Aluminum is the key for mold making for even faster production times (see also Chapter 3,2), The search for cost and time savings requires permanent alternative and innovative approaches. Thus, even in prototype making, an area in which mainly steel was used in the past, the materials are tested for their suitability. 

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