Case Studies: CMM Provides 213% Improvement
December 22, 2009
When Cotta Transmission Co. LLC (Beloit, WI) determined their old coordinate measuring machine (CMM) was beyond its useful life, Xspect Solutions (Wixom, MI) provided a proposal that combined a new Wenzel bridge-type CMM equipped with OpenDMIS software and a level of basic gear measuring capability that optimized Cotta’s current needs.
Cotta Transmission Co. LLC, an industrial and specialty transmission manufacturer, purchased a new Wenzel LH 12.30.10 CMM, equipped with OpenDMIS software with a special gear checking module.
Todd Wells, Cotta quality manager, explains, “When I joined Cotta as the quality manager, the organization was already extremely discontent with their current CMM equipment. Actually, the CMM operators were using the DCC [direct computer control] CMM as a manual machine because of fears it would crash, and they would often re-inspect product multiple times because they had little confidence in the results. A team was assembled to rectify the situation. The 1970s CMM that we were using had been rebuilt once already, and when we conducted an accuracy study it was obvious it was not repeatable any more.”
For example, Cotta performed one study where the same part was inspected several times on a program that was written to run in automatic mode. The measurement results varied more than 220% from the required design tolerance.
With this new knowledge of the CMM’s inability to repeat, the team mandated subcontracted CMM inspection for specific parts with tolerances too critical for the old CMM until a new CMM could be purchased. They estimated that their work level would require an expenditure of at least $100,000 during the next 12 months to accommodate subcontracting to an outside CMM service.
Cotta needed a new CMM to meet customer needs and to continue to deliver a quality product on time. They wanted to purchase a new Wenzel CMM, and liked OpenDMIS software, but they were not confident their budget or timing requirements would permit it. They contacted Xspect Solutions, Wenzel’s operation in North America and discussed the situation with Nick Moceri, Xspect’s regional sales manager, and Keith Mills, president.
Potential Solution“After listening carefully, Xspect Solutions developed a program for us that took advantage of a combination of circumstances that ultimately gave us the machine we wanted within our budgeted cost, delivered on time,” Wells says, “which actually ended up being ahead of time.”
Wenzel CMMs have precision manufactured impala black granite bases and bridges, precision and hemispherical-cylindrical air bearings, and standard Renishaw probing systems with volumetric accuracy of 2.5 microns. “As a result, Wenzel machines are typically not the cheapest CMM on the spreadsheet,” Mills says. “However, for Cotta, we were able to put together a proposal that involved a special CMM that we had loaned to another customer while waiting for a larger Wenzel machine to be built for them. Because we already had the loaner CMM being returned, we were able to make the necessary arrangements to tie in the logistics and machine exchange, as well as customize the CMM to meet the Cotta accessories and software needs. The new machine and software would be able to handle the entire range of products Cotta is producing.”
Wells adds, “We had been looking at machines equivalent in size to the Wenzel 12.30.10 that were 1995 vintage. We ended up with a 2008 Wenzel structure with new controller, probing, PC and software. In addition, we received software that included the gear measuring module, allowing us to develop basic gear data right on our CMM. This also allowed us to move our small gear measuring machine out of the CMM room and into a location closer to our gear manufacturing department.”
Successful InstallationWithin a week of installation, Cotta technicians had already successfully created part programs from computer-aided design (CAD) files and inspected a number of part designs. They duplicated the study conducted on the old CMM on the new Wenzel and the results showed a 213% improvement in the measurement variation. In addition, their CMM operators liked the ability to preview machine movement with the OpenDMIS software. They also purchased an offline OpenDMIS software seat that allows them to develop new inspection programs while the machine is being used. The decision to purchase this additional seat was the result of some feedback obtained from another Xspect Solutions’ customer who wished they had an offline software seat. Also, as part of their purchase package, Cotta received four days of training for three of their people.
“We did another interesting thing,” Wells says. “Because our old CMM was not worth rebuilding again, we decided to dismantle it and use the granite base and bridge and turn them into inspection surface plates. We had them lapped and calibrated and have them in use again in our shop. Xspect Solutions also offered to take our old Renishaw PH9 probe in trade for the new PH10M that was supplied with the CMM, and also gave us a useful styli change rack that mounts directly on the base plate.”
The Wenzel LH 12.30.10 is a bridge-type CMM with a measuring envelope of 1,200 by 3,000 by 1,000 millimeters, which provides adequate table capacity for some of the larger transfer cases that Cotta produces. With this machine design the Y-axis guideway is machined directly into the granite base plate, providing long-term accuracy and stability. The machine has a maximum 3-D measuring speed of 700 millimeters per second with maximum acceleration of 2,000 millmeters/second2. It is equipped with a Renishaw PH10M probing system and a HT400 teach pedant that eliminates the keyboard interaction necessary with conventional CMM teach pendants.
Wells concludes, “The installation and calibration of the Wenzel CMM was well within our needed time frame, which was notable because the machine was configured when the installation was taking place. Communication with Xspect Solutions’ administrative and technical personnel has been seamless, including the coordination of any of the loose ends that normally occur with a project like this. We were even allowed to tour one of Wenzel’s other customers to get familiar with the same CMM prior to the arrival of our new machine. This has been a very successful supplier/ customer project.”
Xspect Solutions Inc.
- Within a week of installation, Cotta technicians had successfully created part programs from computer-aided design (CAD) files and inspected a number of part designs.
- They duplicated the study conducted on the old CMM on the new Wenzel and the results showed a 213% improvement in the measurement variation.
- CMM operators like the ability to preview machine movement with the OpenDMIS software.