A portable measuring arm with a resolution to 0.001 in. lets engineers at Kautex in Indiana quickly measure blow-molded gas tanks right out of the mold. They use the information to adjust cooling rates that keep the 3 5 2-ft tanks within specs. "We now finish tooling setups that once took six days in three," says Engineering Manager Frank Olbertz.
Engineers put the stylus from the lightweight FaroArm, from Faro Technologies, Lake Mary, Fla., on significant points of the tank and press a stylus button. A computer records the dimensional data. For spot checks, Arm software uses the tank CAD file as a measuring template. Software then notes when measured points fall outside the allowable range and alerts the operator about the defect.
The FaroArm helps solve a problem with large gas tanks: They cool unevenly and need constant monitoring to hold dimensional tolerances, ±5 mm on flat areas and ±3 mm elsewhere. Thick sections cool more slowly and shrink more than thin sections. So knowledge of cooling rates aids in the placement of cooling surfaces that help harden the plastic.
Before acquiring the FaroArms, Kautex checked prototypes and occasional production parts on a large, conventional coordinate-measuring machine. The machine was slow so only a few spot checks were practical. Most checks of production parts were via mechanical, nonmeasuring "attribute gages" that touched control points on a tank to show if it met minimum or maximum dimensions. Tooling setup involved a lot of measuring with rulers, shims, and verniers.
"We take more spot checks now because the FaroArm is fast," said Olbertz. Kautex also uses the Arm as a go/no-go attribute gage, where surfaces need only fit some minimum or maximum dimension.