STRUCTURAL OPTIMIZATION OF A MOTION AND FORCE CONTROL CYLINDER

Resistance spot welding technology of various coated steel and aluminum alloys is widely used. These welded materials contain base metal, coated layers of metal or cladding metal with different thermal conductivity, electrical conductivity and expansion-contraction properties. They require a proper variable electrode force control during a short welding time to avoid welding spattering, reduce welding defects and increase welding strength. However, a constant electrode force method is usually used in spot welding machines because of too low response speeds of air cylinders.In this research, a dummy force control cylinder was made to simulate the analyses and experiments of structural parameters about a newly developed motion and force compound control cylinder. The dummy force control cylinder is the same sizes as the force control part of the new cylinder in pipe diameter, pipe lengthes and piston diameters. Its transient and frequency responses are mainly dependent on pipe diameter and piston stroke. Experiments indicate that the optimal parameters are about 0.5 (mm) piston stroke and 4-6 (mm) pipe diameter for a servovalve of 8 (mm) spool diameter and 1 (mm) stroke.