3.8 Prototyping

Prototypes of forgings fill the gap in the evaluation process between computer simulations and the manufactured end product. There are two general types, which serve a variety of purposes: soft and hard metal. Soft prototypes are made from materials such as wood, foam and plastic, and are not suitable for functional testing. Hard metal prototypes, as the name implies, are made from metal. Their usefulness in functional testing depends on the extent to which their critical properties approximate those of the forged end product.

Ultimately, the only way to produce a prototype that has the same properties as the forging is by forging in production tools. This is not always feasible because the cost and lead time associated with the procurement of forging tools may be prohibitive. Therefore, alternate processes are often employed. The selection of the prototyping process is driven by:

  • The selected forging process
  • The purpose of the prototype
  • The properties of the end product that are to be evaluated

Open die forgings are generally made in low quantities with minimal or no cost for special tools. Prototypes are usually forged and machined by the same processes as the production parts.

Rolled rings can usually be made from standard tools. Where standard tools are not available, the rings may be rolled to the approximate configuration and machined to the final shape. Grain flow is usually circumferential, so that performance is not affected by machining operations.

Impression die forgings Some of the most common prototyping processes for impression die forgings are listed in Table 3-8:

Table 3-8 Prototyping Processes for Impression Die Forgings
Purpose Process Remarks
1. Visual appearance evaluation; clearance, installation and removal studies (mockups). Nearly any method that produces the required shape, such as hogouts, stereolithography, wood or foam. Mechanical and physical properties are not important to the evaluation.
2. Approximate the performance of the end product. A. Hogout made from a similar material and heat treated as required. Static properties can be closely approximated; dynamic properties may be difficult to approximate.
B. Open die forged and finish machined. Very low tooling cost, good approximation of static properties, better approximation of dynamic properties than hogouts.
C. Blocker die forging finish machined as necessary. Somewhat higher tooling cost, better approximation of static and dynamic properties than open die forging.
3. Certify product performance. Forge in production tools and finish. Flash may be removed by hand to negate trim dies.

Return to Table of Contents