Radially forming a Dome Shaped Rivet
Recently, a manufacturer approached Orbitform with a new challenge. Both ends of their rivet would be visible on the outside of their assembly and they required the formed side to match the manufactured end. While we typically receive several of these requests, this application was challenging due to the shape of the manufactured end of the rivet.
Forming a dome
A dome shaped finished form was required and the dimensions were critical to match the manufactured end and remain aesthetically pleasing. However, due to the size of the dome, material flow during forming was challenging to overcome.
Initially, the customer requested the orbital forming process for this rivet. To accomplish the dome shaped finished form, the rivet required a pre-form stick up that was 150% of the diameter of the rivet. A typical rule of thumb pre-form stick up is 50-100% of the diameter of the rivet. Anything larger becomes a challenge when orbitally forming due to the tooling path of the process. Under pressure, the large amount of material began to buckle and twist and was thus unable to accomplish the dome shape.
Orbitform partnered with the customer through a series of lab developments to test different parameters in an attempt to accomplish the finished form. Adjusting the RPM, advance rate and force did not change the results. Orbitally forming a smaller pre-form stick up was successful but did not match the dimensions of the manufactured head. Finally, our lab technicians turned to radial forming.
The tool path for radial forming follows a floret pattern where the tool travels directly across the top of the rivet to displace the material from the center outward. While this process does require more force than orbital forming, it results in less side load into the part, reducing the risk of buckling and twisting.
Upon forming the rivet with the radial process, the results of the lab development work improved. After testing various speeds and advance rates, the required dome shape was accomplished. The finished form of the rivet met the customer’s critical dimension requirements and was nearly identical to the manufactured head. The customer now had the correct process solution and parameters to meet their requirements.
Orbitform up for the Challenge
When faced with a challenge for a specific finished form for your assembly, Orbitform offers the ability to leverage our unbiased approach to forming and fastening to find the right process for you. With the ability to run your part across multiple assembly processes, we can find the solution that delivers the outcome you require. Contact us today to see how we can partner with you to solve your toughest assembly challenges.