Joining

Joining is the permanent connection of two or more workpieces. The German standard DIN 8593 arranges the processes in groups – from assembling by placing and inserting, through pressing on and in, to welding, soldering and adhesive bonding.

For handling technology the first groups matter most: placing, sliding in, hooking in, plugging on, bolting, pressing in. In all of them a part not only has to be brought to a place but moved into another part in a specific direction and orientation.

When a part is set down, only its weight acts, vertically downward. In joining, forces across that direction are added: the part is pushed against a locating feature, pressed into a fit, rotated about a pin. If the centre of gravity is not below the suspension point, a moment arises as well.

A rope or chain transmits tension only. Every lateral force deflects the load, and it swings back as soon as the operator lets go. Anyone joining this way holds the part in position by muscle power – exactly the strain the device was supposed to remove.

If the part is only lifted and set down, a rope balancer is enough. If it is joined, a rigid kinematic system is needed: an articulated arm or a lifting axis that transfers lateral forces and moments into the structure and holds the part steady in any position.

The gripper has to match. It holds the part in the joining orientation – not the orientation in which it lies in the container – and keeps the joint accessible. It often needs a rotating or tilting unit to change between pick-up and joining orientation.

Two parts never meet exactly. A perfectly rigid system would jam. Hand-guided devices solve this through the operator, who feels the resistance and corrects. This requires a device that moves easily and without breakaway resistance.

Lead-in chamfers, locating pins and guide tapers on the parts ease joining more than any improvement to the device. Where they are missing, it is worth asking the design department.