Photoelectric module stops robot gripper collisions

When an automated assembly cell, where space is at a premium, required a solution for avoiding collisions between the robot gripper and its surroundings – populated with other assembly and material handling equipment – the designers of the robotic system turned to Contrinex.

A small robot with a multi-finger gripper is used as a tender to transfer parts from an assembly area to an end-of-line test machine. A risk was identified that in the event of a malfunction in other equipment or an unplanned human intervention, the robot gripper could collide with other pieces of assembly equipment.

The system designers wanted an overriding anti-collision system to prevent a collision causing damage to the robot or more likely some of the other more delicate elements of the test or assembly equipment.

In the manufacturing cell, robotic handling systems manipulate electromechanical sub-assemblies, presenting them for automated testing. The part is transported by a small robot with a compact multi-finger gripper, whose patch is programmed according to the geometry of both the parts and the production equipment.

As the products being manufactured change with design revisions or new variants are added, or if other equipment is accidentally moved or fails, there is a risk of collisions between the robot and its surroundings.

To remove the risk of damage to a robot gripper or the assembly infrastructure, a collision avoidance system was sought by the designers of the robotic system. The engineers wanted to implement hardware anti-collision measures rather than change the robot’s software or programming and so looked for a sensor-based system.

Contrinex’s MiniDist Brut photoelectric modules offered a small, reliable and cost-effective means of fitting a measuring system into the grippers themselves. These miniature diffuse distance measuring sensor modules are embedded in the outward-facing surfaces of the gripper jaws to monitor the proximity of obstructions in real time when transporting parts between operations.

MiniDist Brut sensors are designed with the needs of OEMs and system integrators in mind to provide an unobtrusive fit-and-forget solution. The miniature devices weigh as little as 3.1 grams for the bare PCB unit, which has a compact 4.5mm x 4mm x 11mm envelope. The sister version in a plastic housing is still very small at only 6mm x 5mm x 18mm.

With sensing distances of up to 35mm, MiniDist Brut devices offer designers highly versatile options when specifying equipment, especially for integration in tight spaces with insufficient room for traditional sensors. An industry-standard PNP and analogue voltage output ensure optimum flexibility, with an output range of 0.3V to 3V and in-situ adjustment between 1 to 25mm making the unit easy to integrate. The modules are supplied with a 2m 4-wire PVC-sheathed cable, which was cut to length and wired to a connection in the wrist of the robot.

The miniature sensors provide reliable and unobtrusive operation whilst preventing accidents and maintaining the production throughput without compromising the safety of people or equipment around it.

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