Forming Solid Rivets: Standard vs. Captured Peen Tools
When it comes to designing orbital riveting equipment, the size of the powerhead and the material being formed are critical to manufacturing a successful part. In addition, the shape of the peen tool used to form the rivet or tenon is important. Ultimately, the shape of the peen tool affects the final form geometry, the forming process, and resulting joint. For solid rivets, manufacturers typically use either standard or captured peens, depending on a few different factors.
There are two types of standard peen tools that can be used to form a solid rivet or tenon - flat and conical. These peen shapes allow the material to flow outward without restriction. This can be beneficial when stack up height or rivet length tolerance is variable, as the material can continue to move until the desired finished form height is met. There is also some forgiveness when it comes to alignment of the part under the powerhead. When using standard flat or conical peen tools, it often takes less force to form compared to using a captured peen tool. Drawbacks to using a flat or conical peen include a higher likelihood of cracking around the edges and a lower push/pull force when compared to joints formed with a captured peen.
Captured peen tools are developed specifically for each application and have a cavity on the end of the peen that restricts the flow of material. While this does require more force to form, it can result in a slightly stronger and more aesthetically appealing joint. Captured head forms also exhibit less cracking as the material is pressed together within the cavity during the forming process. With captured peens, the part stack up and rivet length must be more precise to ensure finished form specifications will be met. The part must also be centered to the powerhead to ensure all of the rivet material is captured within the peen.
When it comes to forming solid rivets, the required peen tool is often dependent on finished form specifications. Whether aesthetic appeal is critical, or part stack up is variable, it’s important to know how the peen tool will affect the forming process and resulting joint.
To ensure your parts meet your functional or aesthetic specifications, Orbitform offers the opportunity to form sample parts in our Solutions Lab to determine the required peen tool. Contact us today to determine the right assembly equipment and tooling for your part.