Forging is a preferred manufacturing method for many industries because it produces high-strength components, significantly reduces waste, and generates cost savings, especially compared to alternatives such as machining and casting.
The initial investment in forging is the tooling used to create parts. Once the tooling is developed, the process is highly repeatable, especially in impression die forging processes. Just one set of tooling can produce thousands of near-net parts, especially if it is well-maintained. The payoff of choosing forging is in per-unit cost at volume and material savings. For example, forging a part (with a favorable geometry) might use 80% of the input material (after trimming flash). In comparison, machining from a billet (to the same geometry) may use only 25% of the initial material.
Beyond tooling design, other factors that influence the cost of impression die forging include:
Raw Material
Material is often the largest single component of a forged part’s cost, so it’s important to assess whether the design choices made account for forging’s ability to increase strength.
To give an example, a nickel-chromium-molybdenum 4340 steel might be chosen for a demanding application. However, with forging’s beneficial impacts on mechanical properties, a less costly alloy, such as 4140, may be sufficient. In this case, switching could yield substantial cost savings.
Part Size & Weight
More metal is used to forge a part than ends up in the finished item, mainly due to the need for flash, which is essential in impression die forging to ensure the tool cavity is filled. Depending on the part geometry, flash can account for as much as 50% of the finished part weight.
The amount of material needed can be reduced by exploring forging’s ability to create near-net-shape parts. For example, it’s often possible to form strengthening ribs and reduce the presence of material that doesn’t contribute to part function.
Part Symmetry
Complex shapes with ribs, bosses, and eccentric or offset features require complex tooling and higher forces. Symmetrical shapes are easier to forge because forces are lower and grain flow requires less management.
Production Volume
Higher volumes mean lower tooling cost per part, although the frequency of die resinking and overall die life must be considered. However, as higher volumes can support the use of more complex tooling, overall unit costs can be lower when production quantities are large.
Number of Dies Needed
For some orders, it may be necessary to have multiple sets of tooling available. In the case of an order requiring a high production rate, this will allow switching dies so output can continue while a set is resinked. Dies can only be used a limited number of times before they need replacing, which can result in an order spread over an extended period and multiple die sets.
Multi-Stage Needs
Impression die forging usually involves three steps: busting, blocking, and finishing. The first of these distributes metal from a hot billet to where it’s needed; the second forms a near-final part shape with larger radii and generous draft angles; and the third brings the part to final dimensions.
Symmetrical parts may be produced with only two steps, while complex part may require more stages, increasing processing costs because it involves more part handling.
Post-Forging Treatments
Forged parts may require additional finishing operations, including machining, shot blasting, and heat treatment, to create precise forms (such as tight-tolerance holes and screw threads) or to improve appearance or in-service performance. These post-forging treatments will increase costs, but when volumes are large enough to support more complex tooling, this may reduce the extent of secondary treatments needed.
Share Your Project Details
Founded in 1967, Trenton Forging is a Michigan-based manufacturer specializing in asymmetrical and symmetrical impression die forging. Since our founding, we’ve built high-strength, near-net components for critical applications in industries ranging from automotive to defense. We’re known for our industry-leading turnaround times and value-added, in-house capabilities, including machining, die resinking, and reverse engineering.
If you have a part that needs forging, share your project details with us today for a more accurate cost estimate.
