Aiming for zero defects, Cummins Engine implements parts traceability program

Read how a Cummins Engine facility is using Bumpy Bar Code from Mecco Marking Systems to raise the level of quality.

Contents:
Using Bumpy Bar Code
Into the Production Process
System Benefits

In Jamestown, New York, the Cummins Engine plant produces the company's M-11 heavy-duty diesel engine used in trucks, motor homes, and specialty applications. The plant receives cast iron engine blocks from the foundry in a normalized condition, and the employees perform all machining on the blocks with very tight tolerances.

Achieving the required level of precision is the responsibility of Quality Engineer Tom Patton. "I had two ultimate goals for this plant," he says. "I wanted to achieve QS-9000 certification, and I wanted to achieve a Six Sigma defect rate." The plant has achieved the QS certification and is now working toward Six Sigma standards.

Using Bumpy Bar Code
The plant recently implemented a new parts traceability method called Bumpy Bar Code (BBC). Supplied by Mecco Marking Systems, (Ingomar, Pennsylvania), the system simultaneously marks parts with a 3D "bumpy" bar code and an 8-digit serial number. The process takes less than 15 seconds and doesn't delay the production cycle.

Here's how the system works. It pneumatically activates a chisel-shaped pin for the bar codes and a tapered pin for the numbers, producing 3D marks that can be imparted onto most surfaces and withstand practically all manufacturing processes. The marks will not degrade over time, and, unlike printed paper tags, cannot contaminate a manufacturing process.

The system uses indented, "bumpy" marks shown as "highs" and "lows" in surface height rather than black and white variations as in a more common 2D bar code. The BBC reader combines laser technology with a charge-coupled device (CCD) image array that reads and processes the marks. When the reader is activated, a beam projects across the bumpy bar code and laser light is reflected back to the reader and collected by the CCD array. Compared to the original laser beam, the reflected light is captured at slight angles, which represent differences in height between the BBC bars and spaces. The angles are digitized and processed by an on-board digital signal processor.

BBC readers can be integrated with PCs, PLCs, robots, and other factory data equipment. They also plug into portable data terminals, which store data for subsequent downloading, or RF transmission.

The system can be used on flat, convex, and concave curved surfaces, and can mark thin sections and softer metals such as aluminum without deformation.
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Into the Production Process
At the Jamestown facility, each engine block is identified by an 8-digit process number stamped on the side of the block. The marks are made by a Mecco SP-202 dual-pin, microprocessor-controlled BBC marker, which consists of a computer controller, dot matrix marking head, and two DC linear actuators for X-Y motion. Capabilities include automatic sequencing, random number generation, and data storage. The marker also accepts RS-232 or terminal input.

When blocks are taken offline for quality checks, tool change checks, temporary banks, or other reasons, machine operators record the event, the time, and the block's exact placement at the time of removal. The bumpy codes make it easier to record and archive this information and allow quick identification of any questionable blocks. A manual, portable reader is used for this function. Workers can quickly use the reader to determine a process number while on the line or after blocks are removed.

Among the data that can be recorded are sequential process number, date, and time of the block at the station, as well as a feature code that identifies why a block was removed from the line. Other information includes the part number and machine from which the part was taken.
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System Benefits
Patton says the system lets him find engine blocks that are out of process before they leave the plant. It also lets him answer customer questions about how the block was made.

"No matter how old the block is, the BBC mark can be read," he adds. "Paint doesn't hide it, heat doesn't bother it, and contaminants won't degrade it."

Patton says that in the future, every component and block will require traceability. "Because BBC is the only marking technology not affected by heat treating, chemical baths and finishing processes, it is the only marking method usable on components used inside the engine."

"We have very tight tolerances. In order to achieve even higher quality, the block line team processes parts to manufacturing control limits that are half of the blue print specifications. That level of quality—and the fact we can prove it—is part of why 40% of the 18-wheelers you see are powered by a Cummins engine."

For more information, contact Mecco Marking Systems, Rochester Rd., Ingomar, PA 15127 USA. Tel: 888-369-9199.

Edited by Nancy Katz