Mark Those Parts...

For more than two decades, manufacturers, wholesalers, and retailers have relied on printed bar code labels to control inventory for an endless stream of products. Now, OEMs are rapidly moving to imprint 2D codes directly on parts not just to manage inventory but to enhance data collection for safety, liability and warranty purposes.

Companies in industries ranging from automotive and aerospace to defense, electronics and medical devices typically employ lasers, dot-peening equipment and chemical etching to fix a direct part mark identification (DPMI) on a component. Not only must the mark survive downstream factory processes, but it must also stand up to the wear and tear of rugged environments during the product life cycle.

"You can't put a paper bar code on a piston head," notes Nick Infelise, product manager for Omron, a major supplier of direct part mark (DPM) readers. He adds that the 2D Data Matrix codes used in most DPM applications also allow manufacturers to store far more information than with 1D bar codes—typically 512 characters versus only 15 characters.

Design engineers are getting involved with this growing DPM trend on several levels. First, they must design parts with an eye toward enhancing their readability by machine vision equipment during manufacturing and later at the customer's receiving docks or at repair stations. Frequently, too, design engineers must choose the marking equipment, as well as the hand-held or fixed-mount equipment used to read the marks.

Meanwhile, government and industry groups are pressing for even wider use of DPM, as well as for new specifications to insure that marks meet prescribed quality standards.

To meet the objectives of the Defense Department's Unique Identification (UID) initiatives, contractors who supply mission-critical components, serialized and repaired equipment, and items costing more than $5,000 are now required by contract to mark and verify DPM codes on these parts.

To help manufacturers cope, RVSI Acuity launched a program early this year to educate engineers in the defense industry on how to comply with the UID requirements. The effort involves a site visit, briefings to engineers, IT, quality control, and contracts personnel, and a review of potential parts requiring a mark. RVSI then comes back to the company with recommendations on equipment and processing steps needed to meet DoD's requirements.

RVSI Acuity also publishes a UID newsletter with FAQs and recommendations on marking and reading methods and is holding free online training seminars on UID and Data Matrix verification issues on a dedicated website (http://www.UIDsupport.com).

Early this year, the company introduced a UID compliance kit that helps engineers meet MIL-STD-130L for direct part making. The kit shows how to determine whether the data elements in the Data Matrix mark are properly formatted, and it provides verification tools to insure that the UID mark is legible for the life of the product. Among the equipment included in the kit: high-performance Data Matrix reader/verifier with integrated lighting, optics, CCD imager, processor, digital I/O, communications and networking ports.

John O'Brien, VP for UID systems, notes that it is important for engineers to distinguish between regular reader stations—either fixed or hand held—that read parts during the manufacturing process and verification stations, which are located adjacent to where the part is originally marked. The verification station typically is positioned perpendicular the part, is equipped with more processing power, and takes more measurements. At this station, companies can verify that marks meet industry standards, as well as spot instances of degrading mark quality. For example, inconsistencies in the shape or size of dots may indicate wear on the tip of a dot-peening stylus.

While RVSI predicts that the military applications may soon account for 50 percent of the DPM applications it serves, another major reader supplier—Cognex—also sees rising demand in automotive, aerospace and electronics components. "The need for cradle-to- grave traceability of critical parts is the big driver," says Justin Testa, senior VP of the Cognex ID Products business unit. Testa notes, for example, that a good DPM system can be a big cost saver for auto companies during recalls, when they can sharply reduce the number of cars needing to be checked at dealers because of the ability to trace specific parts back to Vehicle Identification Numbers.

In addition to the major OEMs themselves, major industry organizations such as the Automotive Industry Action Group and the Air Transport Association have published guidelines for Data Matrix. Where there is no specific standard, Data Matrix ECC200 is recommended. This ANSI code is the most widely supported for DPMI applications involving metal, glass, ceramic, or plastic materials.

Testa says that engineers can expect to pay from $2,000 to $3,500 for the machine vision system that makes up a fixed-reader station in an automation line. However, a single part may need to pass through several readers during a manufacturing operation. The more powerful verifier stations, which are often bundled with marking equipment, can cost as much as $10,000. "You are not going to get read rates on direct part mark codes approaching 100 percent with a $200 hand-held reader," says Testa.

Readers also are becoming easier to operate and program. Omron's V530-R2000 controller, for example, offers automatic setup and controls two tiny CCD cameras—often with a choice of integrated lighting options to handle different surfaces. A hand-held keypad provides access to the controller's systems menus for needed adjustments, and a display unit outputs the results as parts pass through the system. Omron Product Manager, Nick Infelise, notes that the R2000 is especially popular in semiconductor and LCD production, where managers are looking for automated, high-volume solutions that require few adjustments.

With DPMI rapidly growing for parts ranging from wafers and printed circuit boards to engine parts and medical devices, attention is increasing to ensure that that marks are of sufficient quality to be easily read throughout a part's lifecycle. Manufacturers of marking equipment and readers are stressing the importance of installing verification stations that spot degrading mark quality as early as possible so that companies can meet their own internal quality goals.

AIM Global, a worldwide trade association dedicated to automatic identification, is also working with industry to draft a new 2D DPM verification standard, which could be in place by the end of 2006. The existing print quality standard, ISO 15415, was developed for paper labels and has limited application to direct part marking, according to AIM President Dan Mullen.

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