Guides sort out welding woes

It is not every day that INA Bearing Company is asked for a 12m linear guidance system, but that is exactly what the Production Engineering Department at Lansing Linde needed when it was faced with machine downtimes on a computer-controlled welding machine used in the fabrication of truck chassis. The machine in question is used to weld counterbalance and reach truck chassis. The overhead twin-wire welding head was fed by two separate wire feeds, which were transferred from the bulk packs on the floor to the head via two 12m conduits. It was these conduits that were continually jamming, causing machine breakdowns, which took significant time to repair and set up. Lansing Linde's production engineers wanted to raise the wire containers off the ground onto a moving cradle close to the top of the machine in order to reduce the length of the wire. The cradle needed to be connected to the machine head so that it could follow as the welding operation takes place. The overall machine travel was about 12m. INA's engineers evaluated a number of possible solutions to the support of this cradle including shaft and ball bushings and profiled monorail systems. The final choice was to use KUE 45 for the top horizontal rail and a Hydrel UFB flat rail for the lower horizontal rail on which a couple of track rollers NATR 30 PP will run. This configuration was chosen to limit the difficulty of aligning the two rails to each other. The rails were to be supported on two box section steel girders mounted on the four main machine supports. Lansing Linde fabricated the support structure, the moving cradle, the INA linear system and a large platform at the rear of the machine to facilitate loading of the containers. It was found however that the steel box section and machine supports were not accurate enough to align the rails and this caused excessive friction. Further discussions took place with INA's engineering department and it was decided to incorporate an INA spherical plain bearing GE 30 SW mounted between each of the two KWE carriages and the cradle to introduce some compliance into the system. The track rollers were refitted to the base of the cradle on an adjustable bracket, which allowed the position of each of the track rollers against the rail to be optimised. This addition to the design allows the KWE carriages enough independent movement to substantially reduce the friction in the system. Initial trials show the system to be operating well.