A closer look: Coining

Coining is a precision stamping process that is utilized to create very closely toleranced features on a variety of metallic materials. It’s often used to create functional features that interact with other parts of a mechanism or to work-harden material to give it additional strength in localized areas.

Coining is not a process that removes material as in a traditional stamping operation that uses a punch and die to cut. Instead, the coining tool applies tremendous force to the work piece and creates the desired shape by displacing material.

A stamped/coined component made from stainless steel 305 material. The coined pocket geometry tolerances are 0.002 inch.

A stamped/coined component made from stainless steel 305 material. The coined pocket geometry tolerances are 0.002 inch.

Coining geometry is developed based on the shape of the desired feature, the material properties, and the volume of material displaced during the coining process.

The tool and the coining process itself must be designed so that the desired feature is created without pushing excess material into areas that would detract from the overall functionality of the part (i.e. distorting nearby holes or impeding press-fit functionality) and assembly.

To make this possible, tooling and metallurgical expertise are required for proper process design.

Once developed, tool maintenance procedures are crucial to assuring a coining process that is both precise and accurate. In addition, quality control procedures must be developed in tandem with part design, tooling design and manufacturing process development.

Some of these deep features can be quite intricate and difficult to reach with conventional measurement probes, so expertise in non-contact measurement with video or laser probing is beneficial.

A stamped/coined component made from stainless steel 304 material.  Tolerances of 0.002 inch are maintained and inspected using non-contact video equipment.

A stamped/coined component made from stainless steel 304 material. Tolerances of 0.002 inch are maintained and inspected using non-contact video equipment.

Other important factors to consider in engineering a successful coining process include:

  • Tool design and materials for cost-effective tooling, whether the program is for 500 thousand or ten million
  • Process stability in order to maintain a robust process
  • Secondary operations, such as post-coin surface treatments
  • Downstream manufacturing processes: integration of coined component with subsequent assembly operations and equipment
  • Lifecycle planning to make sure the systems and processes in place will last for the life of the part

Coining can be a very cost-effective procedure for producing a durable precision part with functionally critical features.