Rivet plugs

The core piece of the processing is the setting unit

The setting tool for processing sealing plugs has a strong hollow piston cylinder as its base, which is guided at both ends of the piston rod with a large distance between them. Due to the piston diameter of 40 mm it has large power reserves for industrial use. The extension of the piston rod is fitted with a clamping mechanism that is adapted to the rivet plug used. A vacuum generator is integrated in the setting unit to remove the torn mandrel after the setting process. Different pressure intensifiers with oil reservoirs are used for the drive, which are equipped with the transmission ratios 9,7, 38 and 61, depending on the requirements of the setting forces. The setting unit is well suited for mounting on a linear unit, for extension with an automatic feed of the rivet plug and ideal for robot applications. A main focus during the design of the setting unit was the realisation of the process monitoring.

Manual workstation as semi-automatic solution

In semi-automatic solutions, the setting tool is suspended movably in its correct position for processing and the weight is compensated by a balancer. This is a tool stand with articulated arm. The pressure intensifier and the mandrel container are arranged so that the tube lengths are as short as possible without restricting the movement possibilities. If the control is purely pneumatic, a foot valve is often used for the control. The vacuum is then switched by a pneumatic timer to transport the mandrel into the mandrel container. This pneumatic solution is also possible with process monitoring (pressure and displacement). However, the measurement amplifier, the pressure sensor and the analogue displacement sensor must then be provided with a power supply. In this case, the indication of the process monitoring is shown on the display of the measurement amplifier.

Fully automatic and monitored processing

With the fully automatic setting unit, the workpiece is automatically positioned and also transported further after the setting process. The setting unit is mounted on a linear unit with which the rivet plug can be positioned in the workpiece bore. The unit is mounted on a multi-axis handling system or on a robot. In another version, the robot takes over the positioning of the workpiece.

The rivet plug is blown into the transfer with compressed air and inserted into the mouthpiece with a pick-and-place. In the case of a vertical arrangement, the rivet plug must be held in place by the vacuum or by a pre-pressure before positioning in the workpiece can take place. The linear unit is used to position the rivet plug in the bore of the workpiece and the setting process is initiated. After the mandrel is broken off, the setting unit moves back and the pressure intensifier is relieved, releasing the mandrel and allowing it to be sucked off.

The feeding system consists of a spiral conveyor, which can also be equipped with sound insulation and cover if required. The rivet plugs are fed in suspended position from the spiral conveyor into a non-driven accumulation section which is equipped with an accumulation monitoring system. After the accumulating section there is the separating unit from which the rivet plug is shot into the transfer.

The feeding system is mounted with the control unit on a base plate. If larger quantities of rivet plugs are to be stored, a bunker in front of the bowl feeder and a level monitoring system in the bowl feeder can be provided.

The pressure intensifier and the mandrel container are arranged in the system according to the movements of the setting unit and the hose lengths selected to be as short as possible. The pressure sensor for process monitoring is located on the pressure intensifier. On a third console is the measurement amplifier for process monitoring, which is connected to the plant control system (PLC) via Profibus or Profinet.

For process monitoring, the pressure and the path of the setting process are recorded and the curve is monitored by means of defined windows. The entry and exit of the curve must take place at a specified position in the windows so that the setting process can be evaluated with IO.

Simplified you can see with the first window whether the bore diameter was within the tolerance range. With the second window you can see if the breaking load, which is necessary for a completely finished setting process, has been reached. A hose sensor can be used to monitor the successful transport of the mandrel into the mandrel container.

Handheld devices for flexibility and backup

If different rivet plugs are to be processed in smaller quantities, the hand-held hydro-pneumatic setting tools RPT03, RPT23 or RPT43 with automatic pin suction are used.