Billed as a "radical" new alternative to traditional hard gages that are dedicated to in-process measurement of specific parts, the Equator gaging system from Renishaw Inc. is based on a scalable and adaptable "parallel kinematic" structure that enables high-speed scanning, rapid moves between features and a high level of point-to-point repeatability, the company reports.

In a product-prelaunch application, Meyer Tool Inc., a manufacturer of hot-section jet engine components, was able to eliminate at least four hard gages in a work cell, according to Beau Easton, the company's quality manager. He noted that each hard gage can cost up to $20,000 to design, build and maintain, and Meyer Tool has more than 100 such gages.

Courtesy of Renishaw

A Renishaw Equator gaging system has eliminated at least four hard gages in a work cell at Meyer Tool. Below: An example of a hard gage at Meyer Tool.

The parts manufacturer primarily uses a work cell-based, comparator-type system with pneumatic digital probes for in-process dimensional measurement of parts on fixed nests. "The Equator allows us more flexibility in the cells because we don't need as many probes or as many different individual nests," Easton said, adding that each probe costs from $500 to $600.

Meyer's internal Orion SPC (statistical process control) data management system works in conjunction with Renishaw's Modus software, which drives the gaging system. Equator systems are available with two levels of software: a shop-floor version, which allows DMIS (dimensional measurement interface specification) programs to be executed but prevents operators from making modifications, and a programmable version that enables creating DMIS programs. Meyer has the latter version because the majority of its programming is done offline, with coordinate measuring machine programmers using Unigraphics 3-D part models, Easton explained. "We like to work most of the program out that way and then go in and do the physical simulation."

When switching between parts with the Equator, Meyer uses precision plates that have a couple of nesting points for the part to rest on and function similar to a quick-change tool, according to Easton. "You just pop in the plate, hit go and the Equator will find the part," he said. "It takes 20 to 30 seconds to swap plates instead of going and getting another fixture, putting probes in and remastering."

With the gaging system, there is no need to remaster after every part change, but Meyer does remaster, or reverify, every 3 hours to compensate for changes in the plant's temperature. Although the shop is environmentally controlled, the temperature can fluctuate slightly as machines warm up and cool down and workers enter and leave.

By enabling a manufacturer to quickly switch between parts, the system is suitable for flexible manufacturing processes or accepting parts from multiple machines, according to Renishaw. "The way we run right now, I have eight machines tethered to one Equator," Easton said. "Inspection is well under our actual grinding and machining times, so it's not a bottleneck." He added that Meyer also added an Equator, which costs about a third the price of a CMM, to its waterjet facility and is programming a third system.

The gaging system measurements at Meyer are correlated with those from a CMM, using a CMM-calibrated master part. "The master part sets the values the Equator expects to find inside its measuring envelope while the software automatically applies the compensation values from nominal taken by the CMM," said Bridget Nolan, SPC manager. "It must check within 10 percent of allowable tolerance from nominal."

Easton explained that Meyer settled on 10 percent because that provides an appropriate 10:1 gage-to-tolerance ratio. "We're making sure our gage is 10 times more accurate than our machining process," he said.

For more information about Meyer Tool Inc., Cincinnati, call (513) 853-4400 or visit www.meyertool.com. For Renishaw Inc., Hoffman Estates, Ill., call (847) 286-9953 or visit www.renishaw.com.