Issue: Jan 2003


Flexible Flyers



GM's C-Flex process allows on-the-fly model changes and changeovers without new tooling and without skipping a beat.

by John Peter

Key to the success of General Motors Global platform strategy is a new flexible manufacturing system.

C-Flex is a programmable body shop tooling system that replaces body specific tooling for welding sub-assemblies. Multiple variations of assemblies such as floor pans, deck lids, hoods and engine compartments can be manufactured using the same set of tools and robots simply by reprogramming the tool.








 
The programmable C-Flex units allow for GM to build up to 24 different sub-assembly variations utilizing the same tooling.


C-Flex was initially installed in the Moraine, Ohio and Oklahoma City, Okla., plants that build the GMT 360 and 370 sport utility vehicles. The system has just been installed at the Lansing Assembly Plant in Lansing, Mich., where the Cadillac CTS sports sedan is built. The plant is just beginning test builds on the Cadillac SRX cross-over vehicle, which goes on sale this summer. Lordstown, Ohio (Epsilon) and Orion. Michigan (Delta) are to come on line in 2004.

"C-Flex allows us to build the (Sigma-based) CTS and SRX on the same set of tools," says Gary Cowger, group vice president of GM manufacturing and labor relations. With the C-Flex system in place, any other derivative of the Sigma platform can be brought on line with a very small investment in tooling. Cowger says that introducing a new model like the SRX would normally cost $150 million. GM brought SRX on line for about $30 million. And subsequent programs could cost less because the initial investment has already been made.

"The limitation to the C-Flex-enabled tooling is volume," Cowger says, "not models." Another benefit of this math-based tool is quick response.

"If you want to make a change on the run for styling, for quality, for QRD," Cowger offers, "you can make it quickly and you can make it right in the middle of a run."


"C-Flex allows us to build the CTS and SRX on the same set of tools."
 -- Gary Cowger, group vp, manufacturing and labor relations

The system can also reduce body shop size by as much as 150,000 sq.ft.

Each C-Flex cell is identical right down to the base plates. The units are designed by GM and built by outside sources. Faunic Robotics built the unit in the Lansing body shop, but C-Flex engineer Mart Winn says that they have used five different manufacturers for the units in other plants. Each of the four programmable five-servo driven, modular, plug and play C-Flex units are easily changed-out since the software program resides off the unit. Winn says that as the designers and manufacturing engineers become more accustomed to the new global platform strategy, they should be able to use a standard set of tooling and make all of the necessary changes in the software.

As the assembly is conveyed into the system, a Balough Greeter reads a tag that defines the build data for that specific vehicle. The system can run up to 24 different styles.

Materials are fed to the cell down one of several different lines allowing for variations from one job to the next.

GM says that the C-Flex units are within 3 mil right out of the box and are reliable up to .15 mm. The system is monitored by a laptop computer, which checks and displays all of the operations in real time. Shimming is done electronically, with the operator entering data that moves the tool up or down, eliminating the need to shim by hand. The computer also catalogs all of the changes.

Lansing is currently building two models with eight variations including right and left-hand drive and front wheel and allwheel drive.




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