Tooling Design: What Shapes a Powder Metal Part?

Tooling design begins with the part you want to make. Before that part can move into production, the tooling has to be designed around its shape and the way it will be compacted.

That can make seemingly small design decisions worth a closer look. A tight tolerance may add complexity. The shape of a hole could make the tooling simpler or harder to build. In some cases, a small adjustment to the part can make a noticeable difference in the manufacturing process.

This is why tooling is worth thinking about early. Before getting into the design decisions that can affect a project, it helps to understand the role powder metal tooling plays during compaction.

How Does Powder Metal Tooling Work?

Powder metal tooling gives a part its shape during compaction. Metal powder is fed into a die cavity and compacted under high pressure by the punches, creating a “green” part that is later sintered.

The tooling setup is designed specifically for the component being produced:

• The die: Contains the cavity that forms the outside profile of the part. Its shape is based on the component geometry and how the part will be compacted.
• The punches: Apply pressure to the metal powder inside the die. A part may require multiple punches depending on its shape and the number of levels that need to be formed.
• Part removal: The compacted part needs to be removed from the die after pressing. This affects the types of features that can be formed directly into the part.

A feature that looks simple on a drawing may require a different approach once it is translated into tooling.

What Design Decisions Affect Tooling?

Once a part moves into tooling review, some features require more engineering attention than others. Catching those considerations early can reduce revisions before tooling is built.

Complex Part Geometry

Certain geometries can make tooling design more involved. Specialized gear profiles, for example, may require additional engineering evaluation before the tooling approach can be finalized.

A component designed with kidney-shaped lightening holes may be evaluated for alternative feature shapes. Changing those holes to round profiles can reduce tooling complexity and lower tooling costs without affecting part performance.

Tight Tolerances

Tighter tolerances leave less room for variation during manufacturing. When those requirements go beyond what the part needs to function, they can add unnecessary complexity to the tooling and development process.

Material Selection

Different powder metal materials behave differently during processing. Some materials, particularly stainless steel grades, can experience greater dimensional change and may require additional design analysis before production begins.

How Does Production Volume Affect Tooling Design?

Production volume is part of the tooling conversation, but higher quantities don’t necessarily mean the basic tooling design has to change.

Atlas notes that the fundamental tooling design remains fairly consistent across a wide range of production volumes. Once annual demand reaches higher levels, typically above 100,000 parts, additional tooling sets may be needed to support production efficiency.

For higher-volume programs, backup tooling gives the manufacturer another set to work with as production continues. That additional tooling becomes part of the overall investment when production demands call for it.

What Happens During a Powder Metal Tooling Review?

Before a tooling cost or lead time can be estimated, the manufacturer needs enough information to evaluate the part and how it will move into production.

That review starts with four pieces of information:

• Part print or CAD model: Shows the component geometry, tolerances, and other part requirements that can affect the tooling approach.
• Material specification: Gives the engineering team information about how the selected material will behave during compaction and sintering.
• Annual production volume: Helps determine the tooling strategy and whether backup tooling sets may be needed.
• Application details: Provide context for the part’s requirements and what the component needs to accomplish.

Once that information is available, the manufacturer can look at how the part translates to powder metallurgy and identify any design changes needed before tooling is built.

What Affects Tooling Cost and Lead Time?

Some parts take longer to work through than others. A complex geometry may need a closer look before the tooling approach is settled. Tight tolerances can also require more time during the design process.

The information provided at the start matters too. You’ll need:

• A complete drawing
• Clear part requirements
• Accurate production expectations

This information gives the manufacturer a better basis for estimating tooling cost and lead time.

Why Leave Room for Design Changes Before Tooling Is Built?

A finished drawing provides the starting point for tooling review, but it does not mean every feature must remain exactly as designed. Evaluating a component before tooling is built gives engineers an opportunity to identify design modifications that may improve manufacturability, simplify tooling, or reduce overall production costs.

Small Changes Can Have a Big Impact

Consider a design that consists of two separate components requiring individual manufacturing operations and then assembly. In some cases, those components can be consolidated into a single powder metal part. Eliminating the assembly step can streamline production, reduce processing costs, and simplify the overall manufacturing workflow.

The same approach can be applied to individual part features. Looking at how a design translates into tooling gives engineers another chance to simplify individual part features while maintaining the intended function of the part.

Tooling Design Starts With the Part

Good tooling design starts well before production begins. The decisions made during part design can influence tooling complexity and how efficiently a project moves toward production.

Taking the time to review the design early gives engineers a chance to make changes while there is still flexibility. A small adjustment to a feature or tolerance could simplify the tooling approach and help set clearer expectations for cost and lead time.

Press Ahead With Your Design

There’s plenty more to consider before a powder metal part reaches production. Get practical tips you can bring to your next project with the PM Design Guide.