Orbital vs. Radial

What’s the difference?

Posted on 02/20/2019 | by The Orbitform Blog Team

 

We hear it all the time – what is the difference between orbital and radial riveting. It’s an important subject to discuss when designing a new assembly and looking for the right fastening or forming process. To help you better understand each process and find the right solution, we have put together a few comparisons to consider.

 

Forming a tenon

The most obvious difference in orbital and radial riveting is the tool path of the peen. With orbital riveting, the peen is held at a fixed angle, typically 6°, and rotates over the fastener in a circular motion. As it rotates along the tenon, it gently forms the material. The 6° angle uses up to 80% less force than a press and creates approximately a 10% sideload. Radial riveting is quite different. The radial peen tool begins in the center and forms outward in a fleurette design. This process creates less side load but requires more force as it travels directly over the tenon.

Common uses and considerations

Due to the forming force required, radial riveting is most often used with small and delicate parts, such as endoscopic medical tools or inside watch components. As the size of the rivet increases, so too does the forming force, making it harder for radial riveting to be completed on larger diameter rivets due to the tooling path. As the tooling path travels directly over the top of the rivet and approaches 0 °, shank swell is increased due to the increased forming force, which can limit the joint’s ability to articulate. With orbital riveting less forming force is required due to the angle of the peen and tool path. The indirect force applied to the tenon creates less shank swell and can allow for articulating joints. The range of assemblies benefiting from this type of riveting include pinion gears, industrial sprinklers, striker wires, etc. etc.

Maintenance

The largest consideration manufacturers should consider is the long-term cost of maintenance and tooling to be used for each type of forming. The tooling path of radial riveting is quite larger than that of orbital riveting. It takes 13 rotations of fleurettes to complete one full 360 ° pass with radial riveting, whereas an orbital path only takes one. For this reason, the internal components between the two types of powerheads differ greatly. Orbital heads include three industrial standard bearings held in place by a snap ring. Maintenance includes removing the snap ring, cleaning, greasing and replacing the bearings. This process, on average, takes around a half hour and should be completed every 40 hours of part contact. The bearings are a standard bearing that can be found at any tool supply shop, meaning you are able to replace bearings quickly in an emergency. The total cost to replace all internal components for an orbital head is minimal. Conversely, radial riveting requires more internal components to create the tool path. The range of movement creates friction and heat, causing internal components to break down quicker. It is critical to grease the internal bearing, pre-load spring and thrust cup every 40 machine hours (not contact hours as in orbital riveting) to limit heat. Also, the rubbing of the pre-load spring and thrust cup to create the florets and rotation creates galling and increased wear. As these components break down, required maintenance and machine downtime due to maintenance increases. Due to the complexity of the components, the cost of replacing internal components of a radial head is three to four times that of orbital riveting.

Making the choice

When choosing between orbital and radial riveting, total cost of ownership, joint function, size, forming force required, and future machine maintenance costs must be taken into consideration. The financial obligations and time required for maintenance are not to be taken lightly, as it can greatly affect your throughput. As you approach the initial design phase of a new project, call the experts at Orbitform to discuss your assembly requirements to determine the appropriate riveting process. Our Applications Engineers and Lab Technicians stand ready to work with you to find the best solution for your assembly.