The types of weld pressure rolls, or squeeze boxes as they sometimes are called, that apply the pressure required for the weld are as varied as the welding units used to supply the heat. Squeeze boxes for rotary contact wheel welding typically have two or three roll units, with the contact wheel serving as one of the rolls.
The number of rolls in the weld squeeze box is proportionate to the size and shape of the product being welded. There are no hard and fast rules; however, common guidelines for round tube or pipe size ranges are as follows:
3/8 to 2 in. uses two-roll units.
1/2 to 3 1/2 in. uses three-roll units.
2 to 10 in. uses four-roll units.
Larger than 10 in. uses five or more rolls.
Today, much more so than in the past, many shapes--square, rectangular, hexagonal--are welded in the finished shape rather than being reshaped after being welded round. The weld boxes used for the shapes are custom-designed for each application and usually have no more than five rolls.
