Choosing a Riveting Machine
Riveting machines are custom machines designed and built for a particular riveting process. The riveting process involves fastening two laminated materials together with a metal fastener called a rivet. Because it is a repetitive and high input force operation, it is an ideal process for automation. However, not all riveters are created equal and there are a number of factors that must be considered when choosing which machine to use.
Rivets are typically used to join metal parts, but they can also be pressed in place with plastic or other non-metal materials. This allows for lighter assembly and reduces the overall weight of the product. The riveting process is commonly used in the automotive industry and on many different types of aircraft. Using a proper riveting machine can help ensure that the rivets are properly bonded and that they are not going to fail over time.
To achieve a quality bond, the rivet must be deformed during the setting process. This deformation is accomplished with either a rivet impactor or an orbital or roller forming machine. Riveting machines can be powered by pneumatic or hydraulic cylinders, with some being manually operated and others automatically feed the rivets while they are being set.
Generally speaking, impact riveters create a large amount of downward pressure on the rivet to deform it and bind the materials together. This type of riveter is most often used for high-speed operations with a cycle time of 0.5 seconds or less. This type of riveter is very loud during the operation and produces significant vibrations. It is also not suitable for links that need to be mobile.
Orbital riveters (also known as radial or spiralform riveters) utilize a rotary motion to deform the rivets, resulting in a more evenly distributed connection than impact riveting. These machines are quieter than impact machines and produce lower vibrations during operation.
Some manufacturers use a combination of both impact and orbital riveting for optimal results. The best method to choose depends on the assembly objectives and constraints that the fastening process must meet. For example, the assembly cycle time, space requirements, plant utilities available and finished part aesthetics are all critical factors when selecting a riveting machine.
For a quick and easy project, some folks will use a hand set to set their rivets. These tools are small and usually clamp to a workbench. The rivet is set on an anvil and the rivet head is inserted into a tool that then holds it in place while a few well-placed whacks with a hammer roll the edges. This is a fast and inexpensive method, but it doesn’t create as strong a connection as a rivet rolled with a machine.
For higher-level professional applications, riveters and ratchet rivet guns are used to insert nuts in a variety of sizes. These machines are usually electrically, pneumatically (pop riveters and air riveters) or hydraulically actuated. Some even come with a built-in vacuum to remove excess air from the rivet. Some systems also feature a process monitoring system, such as Orbitform’s Watchdawg shown in Figure 8.1. These systems utilize dedicated sensors to monitor the setting force and punch movement throughout the process. This data is plotted on a graph to form what is known as a force-displacement curve. If the process curve fits within a pre-determined tolerance of a trained reference curve, then the joint is considered passed and the assembly can move forward.