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Transmission plant scores 6 sigma.

Building transmission for farm and off-highway equipment at modernized Case Poclain facility, 120 miles east of Paris, shows the meaning of "world-class machining."

A large machining shop, part of the Case Poclain transmission factory in St Dizier, France, is achieving 6 Sigma quality in parts cut on three flexible machining systems (FMSs). That means the FMSs are certified to produce fewer than 3.4 faulty parts per million.

According to Michel Motura, manager of manufacturing engineering in the 791,676-sq-ft factory, this achievement comes as a result of team effort between the plant and Case European staff manufacturing people. French workers build about 120 transmissions a day, which go into Case IH farm tractors and construction equipment assembled in France, Britain, Germany, and the US. Case is a subsidiary of Tenneco, Inc, Houston, TX.

"Not only have we achieved 6 Sigma in our machining, but we've done so with almost no postprocess gaging or SPC," points out Robin Wilson, manager of manufacturing engineering for Case agricultural plants in Europe. "Such results are possible because we build quality into the process, and then we audit with CMMs only to make sure quality stays in."

Wilson says quality begins in the plant's on-site foundry, where casting location points are milled on a CNC milling machine that uses a probe to equalize the machining stock.

On machine-tool fixtures, the location points have air checks. These ensure that parts are loaded properly and seated fully.

Installed at a cost of 320 million French francs (about US $40 million in 1986), the three FMSs use several thousand single- and multi-spindle tools. These are all preset in the tool-room to predetermined settings.

As needed, tools are delivered to individual machines in "tool life" kits. Records are kept on machining cycles for individual tools and kits, and projected tool-life is programmed into each machine's CNC.

Built-in checks

Each of the total 34 metalcutting machine tools in the three FMSs has a broken-tool detection system. Further, each machine tool has broken-drill detection, and all taps are equipped with infrared tap-depth controls.

Thousands of in-process dimensional checks are performed in the FMSs. Most are done by touch-probes carried in tool magazines. Closed-loop controls provide tool-position compensation for minor deviations.

In each FMS, there is a master pallet for checking machine-tool zero points and a master fixture for checking alignments. FMS operators perform their own basic maintenance, such as changing filters.

Every weekend, a dedicated maintenance crew comes into the plant and performs advanced maintenance, setting checks, and alignment checks. They focus on two machines each weekend.

To audit quality, inspectors pull random sample parts daily and measure their critical dimensions on two DEA DCC CMMs in a climate-controlled QC lab. One CMM is a DEA Epsilon Model 3304, measuring to 6-8 microns. The other is a DEA Model 1102, measuring to 4-6 microns. Any nonconformities can be quickly traced to the machine tool and pallet that produced them.

Renault and Mandelli

Two of the three FMSs were designed and built by Renault Automation in Castres and Beauchamp, France. The third comes from Mandelli SpA, Piacenza, Italy. For the sake of uniformity and simplicity in parts, training, and operation, two of the three FMSs make use of Mandelli machining centers.

FMS No 1, which cuts housings for transaxles and transmissions, contains nine Mandelli machining centers, four Renault multi-head drilling and tapping machines, three special boring machines, and a washing machine. This FMS came from Renault.

FMS No 2 cuts flat parts such as front covers, sandwich plates, and housings for flywheels and power takeoffs (PTOs). A Mandelli system, this FMS includes 11 machining centers, two multi-head machines, and four washing machines.

FMS No 3, from Renault, cuts axle housings. Major equipment in this system includes three Renault multi-head machines, two Nodier EMAG CNC lathes, one assembly machine with an Acma robot, and one washing machine.

Within FMSs Nos 1 and 2, transfer of fixtured parts is performed under computer control on rail-mounted shuttle cars. In FMS No 3, a computer controlled gantry from EMAG provides part transport.

"Overall supervision and control of No 1 and No 3 FMSs is performed by a hierarchical system directed by a Stratus mainframe," explains Etienne Denni, manager of plant maintenance. "This is a dual or tandem system. While one unit does computation and control, the other trails along in real time. Should a failure occur in the first unit, the second takes over without missing a beat."

Control for FMS No 2 comes from a DEC MicroVAX computer. The mainframe for FMSs Nos 1 and 3 is built by Stratus Computer Corp, Marlborough, MA, while the MicroVAX comes from Digital Equipment Corp, Maynard, MA.

In addition to the three FMSs, this plant includes nine automated cells for special machining and other operations. Cell No 1, for example, contains 13 machines that cut and harden rear axles for transmissions. Another cell containing seven machines cuts ring gears. A third cell uses laser welding to assemble clutch cups.

TACS is boss

Designed especially for this factory, the supervisory software is called TACS--Transmission Assembly Control System. This software not only exercises control over parts availability, kitting, assembly, and test, but also launches each transmission build-order.

"TACS also issues and tracks barcoded tags for each subassembly," says Christophe Averous, plant product reliability manager. "In addition, the software tracks kits and pallets and maintains records for assembly settings."

Following final assembly of a transmission, inspectors perform leak tests on it. The technique involves use of fluorescent material and ultraviolet light for detection.

Finally, the completed transmission is hooked up mechanically, electrically, and hydraulically and is put through gear-shifting, acceleration, and stress tests under realistic operating conditions. After signoff by final inspection, the transmission is painted, labeled, and shipped to a Case IH assembly plant.

50 percent each year

Christophe Averous concludes by describing the plant's ambitious plans to improve product quality even further. "It's difficult to do when you've signed off for 6 Sigma, but we aim to reduce part defects, cycle times, and cost of nonconformity each by 50 percent each year.

"We achieved it in 1991, and we'll likely do it again in 1992."
COPYRIGHT 1992 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:flexible manufacturing systems improves Case Poclain products' quality
Author:Quinlan, Joseph C.
Publication:Tooling & Production
Date:Dec 1, 1992
Previous Article:Overcoming CIM hurdles.
Next Article:Taking a chance on teams.

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