For years, extrusion and sealant-dispensing companies have integrated their equipment into new automotive programs with their own unique metering systems, pumps, glue heads, nozzles, etc. None of the systems in the past had the capability of controlling the standoff distance from the glue nozzle to the work piece, and this is a critical distance to maintain with certain extrusion processes. The technology for controlling this distance has been developed by Precitec, Inc., and is currently being used on a number of robotic and pedestal adhesive stations at some very well-known automotive end-user plants.

DaimlerChrysler has specified the Precitec sensor system for use at its two Dodge truck plants located in Warren, Mich., and St. Louis. The adhesive stations at the two plants are using the Precitec linear drives mounted directly on pedestal stands with the robot moving the work piece under the linear drive. (See Figure 1.)

The automotive body parts involved with the applications are most often areas of the vehicle where the need for eliminating what is referred to as "body-sealer squeeze-out" is crucial. An example would be the joining of an inner door panel with the outer door panel. Another example would be the joining of a vehicle roof to the frame or pillars. If any glue or sealant squeezes out from the joining area, there is a possibility of it ending up on the exposed surface of the vehicle where the finishing paint is applied. This would be unacceptable quality.

The Precitec adhesive sensor system incorporates an inductive analog sensor at the tip of the glue nozzle and provides the 0- to 10-volt feedback to the motor controller, which continuously monitors the glue nozzle to work-piece gap. (See Figure 2 for components overview.)

The system will automatically adjust for correction to the programmed gap the user enters via remote control. The typical gap for the critical adhesive applications is 2 mm to 4 mm.

The greatest benefit is ensuring a uniform bead line. If the glue nozzle is too far away from the work piece, you can end up with a swirling line, or if the nozzle is too close, you can end up with a flat line. Neither of these is desirable.

Other benefits include a reduction of wasted glue or sealer being dispensed and the reduction of robot programming, i.e., program a straight-line robot-path distance from point A to point B and let the Precitec system correct for height differences between the points. The Precitec system can currently correct for height differences of +/-15 mm.

Additional information on the adhesive sensor system is available from Precitec, Inc., 55820 Grand River Ave., Suite 250, New Hudson, MI 48165; phone 248-446-8100; fax 248-446-9409; or e-mail bradt@precitec.com. Or Circle No. 76.