Riveting machines insert fasteners through aligned holes in parts to be joined and press or hammer them from the insertion side to provide the second, retained head. The process may be manually operated with hand riveters and handheld riveting guns, electrically or pneumatically (pop or air riveters), or automatically by a multihead automated rivet machine that is either mechanically or hydraulically actuated. The choice of the right type of machine for a particular assembly process depends on such factors as: the quality and strength of the resulting joint, the number of rivets to be installed, the work area footprint, required production capacity, plant utilities available, finished part aesthetics, and assembly cycle time requirements.
Defining these factors up front helps manufacturers determine the capabilities and constraints of their chosen rivet machine. Then they can begin the search for the fastest, most efficient riveting machine that is capable of meeting or exceeding their requirements. Riveting machine types are divided into two broad groups — impact and orbital forming or radial.
Impact riveting machines have much shorter cycle times than standard orbital or radial riveting machines, and can be used for high volume production and to handle very brittle materials such as clutch assemblies or circuit boards. Riveting machines can also be equipped with load-deflecting components that allow them to withstand higher loads and still maintain their shorter cycle times.
Orbital forming or radial riveting machines have a spinning forming tool that, when gradually lowered into the material stack-up, deforms or ‘upsets’ the inserted rivet to form the head of the fastener and to fasten it into place. These machines offer a little more control over the assembly force being applied and are ideal for projects that include fragile or sensitive components. They can be used with offset drivers for closer spacing between rivet heads.
Depending on the type of riveting machine selected, an operator can control the setting force or the amount of ‘upsetting’ that is applied to the rivet by adjusting a dial on the machine. Some models also feature a built-in force-displacement sensor, such as the ‘Watchdawg’ process monitoring system from Orbitform (shown in Fig 8.1), which can be used to monitor the operation of the riveting machine and verify that the correct amount of downward force is being applied to the material stack-up. This ensures that the rivets are being set with the correct force and the correspondingly proper forming or upset action is being achieved. This can prevent the premature failure of the rivet and improve overall machine performance and reliability. It is also possible to combine the features of an impact riveting machine with an orbital forming or radial riveting machine for maximum versatility in any assembly application. For more information on the types of riveting machines available, contact an expert at a fastener supplier.