Automotive assembly technicians rely on fixture gauges to verify part accuracy and analyze fit and quality problems. The industry standard gauge material is aluminum, which produces fixtures with outstanding accuracy but take weeks to machine. To decrease the time required to introduce new vehicle designs, fixture makers have started investigating methods and materials for rapid production of master gauges. As part of this effort, MSX International (Madison Heights, MI) has reduced production time by developing fixtures using a combination of fiberglass and a seamless epoxy paste to produce both outer and inner dimensions on a single fixture.

The company is using Ren XD 4569-1 R/H seamless epoxy modeling paste from Vantico (East Lansing, MI). This cut fixture production time by 25 percent, and retained the precision and strength needed for a long service life. Dan Crowton, fixtures and plastics foreman, says, "Fabricating fixtures from fiberglass and epoxy was a labor-intensive process that required extensive spotting during assembly of the inner and outer sections of the tool. With the seamless epoxy, we can produce both fixture sides on the same support structure to save time and hold tolerances to ±0.01 inch."

To build the paste fixtures, the company starts by machining a tooling aid for the outside of the fixture and then lays up a fiberglass and epoxy laminate for the outer dimension. A support structure is installed, and then the surface for the inner dimension is built by applying 0.8- to 1.5-inch-thick layers of the seamless epoxy paste using an automated mixing and dispensing machine. The equipment features a special nozzle designed to extrude the sag-resistant paste directly onto vertical or overhanging contours on the fixture base.

The epoxy paste is allowed to cure for 24 hours at room temperature, and the fixture is then machined to the required dimensions. The resulting seamless epoxy surface requires virtually no secondary finishing. A benefit is strength to hold threaded inserts used in the fixtures. The epoxy paste surfaces are also easy to remachine to reflect design changes.

For more information on epoxy paste, call Vantico at 517-351-5900, visit or Reply 2.