Ultrasonic weld bumps off heat staking

Ultrasonic welding is to replace heat staking as a means of attaching the rear bumper to Ford Scorpio models built in Cologne. Roy Howell, manufacturing engineer responsible for process tooling and facilities at Ford in Dunton, says the decision was driven by quality rather than cost, but there were substantial cost savings. The problem with […]

Ultrasonic welding is to replace heat staking as a means of attaching the rear bumper to Ford Scorpio models built in Cologne.

Roy Howell, manufacturing engineer responsible for process tooling and facilities at Ford in Dunton, says the decision was driven by quality rather than cost, but there were substantial cost savings.

The problem with heat staking is the small but visible sink marks the process leaves on the outer surface of the bumper which is what the customer sees, after heat staking of the upstanding staking bosses. These attach the bumper’s reverse side to a cross-member fixed mechanically to the metal body panel.

Getting away from the heat stake process has coincided with improvements in the polycarbonate injection moulding process. It is now easier to mould and demould the bumper.

Sims Engineering of Harlow in Essex developed the ultrasonic welding machine delivered last week to Germany. Each bumper has two brackets at each end which are welded ultrasonically on to the bumper’s reverse side.

The original proposal for three ultrasonic welding machines to do the work was too expensive at up to £90,000 a machine for a `fixed head’ solution. It was decided that one machine could weld two brackets in one of three positions.

Sims, with welding head company Branson Ultrasonics of Hayes, Middlesex, built one machine costing £115,000. Instead of separate fixed welding heads, two pneumatically driven servo positioning systems from Festo, control movement of the welding head in each of the X, Y and Z axes.