Ram Position Sensing for Manual Punch-Riveting Tool


A German manufacturer of cold-forming tools for joining sheet metal uses position sensing to control the operation of a manual punch-riveting, or clinching, tool. A high-pressure inductive sensor mounted directly into the wall of a small pneumohydraulic cylinder detects the position of the hydraulic ram, preventing the operating cycle from starting unless the ram is fully retracted.

Customer Values

  • Reliable, continuous tool operation in time-sensitive production environments
  • Significant enhancement of tool function with minimal effect on size or weight
  • Low risk of internal damage due to best-in-class sensing distances
  • Industry-standard interface requires little modification to control systems

Specific Product Advantages

  • Sensor performance unaffected by 500 bar (7255 psi) operating pressure
  • Patented Condist® technology of Extra Distance family delivers best-in-class sensing distances
  • Small, lightweight embeddable sensors with high-pressure capability
  • Rugged inductive sensor with metal housing and ceramic sensing face

Customer Application


Automotive technicians assembling prototype vehicle bodies during pre-production use manual punch-riveting tools to join individual sheet-metal parts. Several thousand joints are required per vehicle, and tools must be compact since space is often limited.


Bad joints, which are very costly to repair, can occur if the technician does not set the tool correctly before triggering it. During use, the tool-head is often partly hidden from view, so a sensing system must confirm that the operating ram is fully retracted and prevent the tool from operating if the ram is not in the correct position.


A pneumohydraulic cylinder drives the ram, and the compact nature of the tool limits the allowable sensor size. The sensing face is exposed to the high-pressure side of the hydraulic circuit, so the sensor must withstand continuous pressures up to 500 bar (7255 psi) and pressure spikes of 1000 bar (14,510 psi).

Customer Solution


Robust inductive sensors from the Contrinex Extra Distance family, High Pressure range, withstand the high operating pressure of this application. The extended operating distance of patented Condist® technology allows the use of thick, hermetically sealed ceramic discs on the sensing faces without compromising the sensors’ performance.


These lightweight M5- and M8-diameter embeddable sensors are 27 mm and 30 mm in length, respectively. The sensors are mounted directly into the wall of the cylinder and do not interfere with the normal operation of the tool. Sensing distances of 1mm (M5 sensor) and 1.5 mm (M8 sensor) eliminate any risk of internal mechanical damage through contact with the ram.


The sensors have an industry-standard PNP normally-open configuration and connect with the customer’s control system via a flexible PUR-sheathed cable. Vacuum-encapsulated electronics ensure excellent resistance to shock and vibration, and no additional electrical or mechanical protection is required.


Previously, users of the punch-riveting tools were unable to check the position of the operating ram with the tool in situ and either incurred downtime or risked costly bad joints. Contrinex high-pressure inductive sensors satisfy the manufacturer’s requirement for small, lightweight, ultra-reliable sensors with an attractive total cost of ownership.