Orbital Vs Radial
What’s the difference?
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.
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.
Creating Stability in a Bushing Flare
Forming a flare
Orbitally forming a flare is a unique process. As a forming force is applied, material flows to the path of least resistance, lead by the geometry of the peen tool. Finished form is dependent on the design of the surrounding assembly area, as well as the tooling needed for the process.
Recently, we were approached by a customer to flare their bushing assembly. Design engineers were working toward orbitally forming a flare for retention, dimensional requirements, and increasing the surface area of the formed tenon. Upon testing in our Solutions Lab, forming was very successful. The material flowed smoothly outward, creating the dimension requirements the customer required.
This is where our story begins.
Troublesome Finished Form
Orbitform was able to produce prototype parts in our lab for the customer to take into testing. These parts met all the specifications the engineers believed they required. However, upon testing, it was discovered that the finished form was troublesome.
The peen used in testing created a very smooth, shiny and visually appealing finished form, but the surface lacked the necessary friction to provide the necessary stability for the customer’s assembly. Unbeknownst to Orbitform’s engineers, assembling the bushing into its full component required a surface that provided friction or grip that simply was not there. This detail concerned the engineers. Could the current forming process provide the necessary finished form?
The engineers once again turned to Orbitform’s Lab Technicians to find an answer. Upon review of the new functional requirement, our technicians worked to redesign the peen tooling to form rings into the tenon as it was being formed. In order to design the tooling, our engineers took the desired finished form and reverse engineered the design into the tooling.
Finished Form Requirement
Testing occurred once again within the lab to ensure the newly designed tooling was able to create the rings within the flare. This forming process determined that the height of the rings was extremely important: too low and stability was lost was lost in the assembly, too high and the rings cracked. Through several rounds of design and lab testing, Orbitform was able to determine the precise height of the rings for the finished form requirement. Through collaboration and testing, the desired functionality was achieved.
Once the design was successfully achieved, this orbital flaring process needed to be recreated for manufacturing. Orbitform worked directly with the bushing manufacturer to design and build a machine that fit their company specifications, volume, and required functionality.
Your Flaring Application
Forming a flare orbitally is a unique process that can achieve many functional requirements. Leveraging the cold forming process of moving the material to the path of least resistance allows Orbitform to control the finished form, no matter how unique it may be. We stand ready to work with you for development on your unique finished form for your flaring application.