Commercial airplanes do not require as many fasteners as they used to, but riveting, specifically traditional riveting, is still an integral part of airframe assembly. That is why rivet guns, along with drills, are among the most popular tools in the aerospace industry, even today. But how does a pneumatic rivet gun work? And more importantly, are aerospace companies getting the most out of theirs?
To put it simply, riveting is the joining of one surface to another using a rivet. The rivets are driven through previously drilled holes of the adjoining surfaces, and then one end is bucked or deformed to lock the surfaces into place. In the assembly of an aircraft, several sheets of material have to be joined together to form the airframe or fuselage. This makes riveting essential to ensuring that the airframe will be able to withstand extreme tension, compression, and torsion stresses once it takes flight.
The quality of riveting is largely dependent on three things: the characteristics of the rivet itself, the quality of the hole through which the rivet goes, and the squeeze force from the rivet gun. This is where the significance of the pneumatic rivet gun comes in.
The principle behind how the rivet gun drives the fastener into a lap joint is pretty straightforward. The rivet body is inserted into the firing end of the gun with its mandrel facing out. Then the mandrel is inserted into the pre-drilled hole while the rivet is still in the gun, after which the operator pulls the trigger, releasing pressurized air that powers the piston and rivet set (which drives the rivet into the hole). The gun is connected to an air compressor through a hose, and this supplies the gun with enough energy to push the rivet, then buck the tail end, locking the adjoining surfaces together with its squeeze force.
The moving parts inside a rivet gun are critical to the riveting process. These include the regulator that controls the amount of compressed air entering the gun, the throttle valve and its trigger which allow the compressed air in, and the piston inside the sliding valve, which is pushed by the compressed air.
The process is set in motion when the operator pulls the trigger, opening the throttle valve. This allows an opening through which the pressurized air from the compressor tank escapes into the sliding valve and pushes the piston against the rivet body. The pressure of the supplied air against the piston is just enough for it to drive the rivet into the hole and deform the tail end of the rivet, securing the lap joint. The air then escapes to the atmosphere through the exhaust while a spring pushes the piston back to its initial position, ready for another cycle of riveting.
In cases where two operators can work in the same area at the same time, one of them can handle the gun while the other presses a solid block of metal or a bucking bar at the other side of the workpiece. The force from the pneumatic gun and the force exerted by the operator on the bucking bar from the other side compress the rivet and deform the tail end against the bar.
Other pneumatic rivet guns work in a slightly different manner. Instead of placing the rivet inside the gun and then firing it in the drilled hole, the rivet is first inserted into the hole with the pin sticking out on the other side. Then the firing end of the gun is positioned over the pin. As the trigger is squeezed, the teeth inside the gun take hold of the pin and pull it, compressing the rivet body. Other than this, the mechanisms inside the rivet gun behave in a similar way as previously discussed.
Before the rivet gun can be used, it has to be lubricated. This is critical to minimizing the friction among the moving parts inside the gun and ensuring that the same pressure setting consistently delivers the same result. To lubricate the rivet gun, apply oil to the built-in fitting on the gun before connecting to the air compressor. Once the supply hose is secured into the fitting, point the firing end downwards or away from people, then pull the trigger so the air can distribute the oil inside the gun evenly
The assembly of an aircraft requires thousands of rivets, putting both the tool and the operator at risk if an improper technique is used. These are additional steps that can be taken to ensure proper riveting techniques for better riveting quality and operator safety.
Before every use, check for loose fasteners or housing, misalignments, cracks, or any defect that might interfere with the tool's performance or safety.
Wear personal protective gear like safety glasses and anti-vibration gloves.
Lean into it when riveting. Use your body weight to help your arms in pushing the rivet gun against the workpiece to prevent wrist injuries.
Throughout the riveting process, ensure perpendicularity between the gun and the workpiece.
Identify the optimum air pressure setting that can drive the rivet properly at the least time possible. In doing this, you ensure that both you and the rivet gun are not subjected to more load than is needed.
Establish a pattern and rhythm for riveting based on the position of the holes and be mindful of the pneumatic hose as you work to avoid accidents.
Ensure consistent air supply by draining the compressor's air filter regularly and doing regular maintenance.
The tool is only as good as its user, but it also works the other way around. The effectiveness of a tool is what stands between a good operator and a productive day in assembly. Aside from proper maintenance of the tools currently in your racks, the following riveting tools can help bring the most out in your operators and do wonders for their productivity:
The pneumatic rivet gun is among the most widely used tools in the aerospace industry because of the thousands of rivets needed to connect airframe parts. If used and maintained properly, it will do its job well and for a long time, while keeping the operator safe and free from wrist injuries. Atlas Copco offers the highest quality pneumatic rivet gun on the market and the service solution to match, so you can get the most out of your pneumatic rivet gun.
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