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Why Use Heat in Your Riveting Assembly?

At Orbitform, we developed a unique riveting process called Hot Upset. This rivet/forming solution uses heat and force to form rivets or part tenons. 

Hot Upset Sequence

• providing greater strength

• increased hole-fill

• improved resistance to push-pull forces

• an overall tighter joint due to material contraction during cooling



Like electro-forging, the heated material becomes malleable and collapses under pressure applied by the Powerhead. This process makes it possible to form a round fastener into a square hole, creating a high-torque joint. 

Round Tennon Square Hole Fill


Our customer, an automotive part manufacturer, needed to assemble a product with hardened rivets, each with an extended tenon stick-out. Two rivets had to be formed during one machine cycle to meet the production requirements. 


We examined both Orbital and Radial Forming options in our applications lab, but due to the extreme hardness of the rivets, final form characteristics did not meet our customer’s specifications. Also, some samples showed signs of cracking, which was unacceptable in this application. We then tested our Hot Upset forming solution, which resolved the forming challenges.



Orbitform designed and built a custom Hot Upset system. 


The design included two standard Orbitform modular Powerheads, the same Powerheads used in our Orbital, Radial, and Roller Forming products. Using powerheads instead of standard weld cylinders eliminates the need for an external air/oil tank and intensification valve. 


Installing a part clamping pressure pad adds stabilization during the forming process. 


The customer’s safety specifications included light curtains, guarding, and palm button activation. 


Adding process monitoring, including an LVDT, load cells, and Powerhead advance and retract sensors, ensures specifications are met.



Hot Upset typically has a 3-4 second cycle time, generally slower than other riveting processes. In addition, hot parts require special handling considerations. We offer both AC and DC Hot Upset systems. In the case of our customer, we built a DC system for its power consumption savings versus the lower initial cost of an AC system. DC-powered systems are more efficient and precise than their AC counterparts but come at a higher price. The cost of ownership includes power consumption and tooling electrodes. Hot Upset systems also require a chiller to maintain optimal tooling temperature.


Contact us to discuss how the hot upset process can improve your product assembly. Orbitform… solutions delivered. 


Hot UpsetAutomotive