Laser marking helps to reduce losses

An electronics manufacturer previously experienced several hundred thousand dollars a year in losses when incorrect parts were added to, and/or the wrong operations were performed, on assemblies. The difficulty in tracking assemblies made it necessary to keep more than the desired amount of work-in-process (WIP) inventory. And, a limited amount of space on some of the assemblies made marking the parts a challenge.

Claire Lasers (www.clairelasers.com ; Kitchener, Ontario) developed an application that uses a laser to apply a 2D Data Matrix code to each part. 2D Data Matrix codes provide the capability to incorporate much more information in a code that can be printed in a significantly smaller space than traditional 1D codes.

2D code technology also does not require the contrast used by 1D codes on labels, which enables 2D codes to be directly marked onto parts. In the traceability solution for the electronics manufacturer, each 2D code is checked for readability immediately after marking with a Cognex DataMan 100 ID reader. From this point, the assembly is inspected prior to each critical operation to ensure that the correct components are installed and the right operations are performed. The laser marking and vision systems have eliminated the problem of incorrectly labeled or identified parts in the manufacturing process, enabling the manufacturer to substantially reduce WIP inventory.


Challenge of intermixed product assembly
The electronics manufacturer produces thousands of different part numbers of high-value electronic products intermixed on the same assembly line. The large number of different products built on the line, coupled with the fact that many of the parts that distinguish these products are so similar, made it difficult for assemblers to verify that they were assembling the products correctly.

The difficulty in identifying parts combined with the fast pace of the assembly line, resulted in a large amount of assemblies that required rework or had to be scrapped. An additional issue was the inability to easily track the WIP inventory, which resulted in large amounts of money tied up in raw materials in process. The finished assemblies have much higher value than the parts that are assembled to create them, so the company was concerned that their inventory records did not accurately reflect the value of products in their facility.

Advantage of laser marking
The two most popular methods of marking electronic components are inkjet printing and laser marking. Inkjet printing utilizes a transfer printer that applies ink to the surface of the assembly. The main drawbacks of the ink printing process are the lack of durability of the printing and the difficulty in providing serialized part tracking.

Laser marking, on the other hand, offers an easy way for electronics manufacturers to create permanent, abrasion-proof marks on their products that are resistant to chemicals like solvents and oils, and can withstand even the harshest of environments. In addition, laser marking ensures that fragile parts are protected and do not suffer from any thermal stress during the laser marking process. These features—coupled with its fast throughput—have made laser marking the method of choice for marking in the electronics industry.

Product identification and traceability solution
The manufacturer asked several laser identification system suppliers to provide their ideas on how its problems could be addressed. The application was particularly challenging because the space to apply identification was limited on many assemblies and the high value of the assemblies demanded 100% accuracy. Another concern was that the assemblies were not positioned and fixtured on the assembly line with the level of accuracy normally required for laser inspection and machine vision. Denis J. Gendron, president of Claire Lasers, worked with the manufacturer to define the requirements of the application. He developed an application of his company’s ClearMark laser marking system that is capable of generating a 2D Data Matrix code in the required space.

Successful adoption of 2D Data Matrix codes in the manufacturing process requires reading rates that meet or exceed the read rates achieved with traditional 1D barcode technology. Laser marking sometimes produces codes with low contrast, poor cell position, or inconsistent cell size. In addition, the surface being marked can be matted, cast, or highly reflective. Reading such marks can present a difficult challenge. To overcome the direct part mark printing challenges, the Dataman 100 fixed mount readers were selected from Cognex (www.cognex.com; Natick, MA), which incorporate reading software that can locate and read the 2D Data Matrix codes despite the range of surfaces, print quality, angles, and contrast changes.

Verifying code quality
The recently approved AIM (Association for Automatic Identification and Mobility) Direct Part Mark (DPM) Quality Guideline DPM-1-2006 provides the necessary metrics and lighting definitions necessary to handle the variety of marking techniques and part materials used in DPM applications. Data Matrix codes are imprinted using a variety of methods, so their color and shape can deviate considerably and the variety of surfaces and materials on which they are imprinted rarely provides a uniform white background. The AIM DPM Quality Guideline was built off of the ISO15415 standard, which permitted only one lighting configuration, while the new standard specifies four including the addition of directional lighting. The new standard also outlines a defined method for setting the optimal image brightness, which provides range of exposure and gain settings to compensate for the differences in surface reflectance in DPM applications.

“I picked the DataMan 100 ID reader to address the 2D Data Matrix code reading challenge because, in my experience, its software consistently delivers reliable readings even when the appearance of the code has been degraded,” Gendron said. “The DataMan user interface is exceptionally easy to use. The small size of the DataMan readers makes them ideal for cramped assembly system applications.”

Gendron and his team designed a motorized platform that moves the reader into position based on the location of the assembly or part prior to reading. The motor moves the reader around the station until the reader locates the part. The station locates the assembly and reads the code in a couple of seconds, which is fast enough for the application. The speed could easily be increased by using a faster linear motion system.

Claire Lasers also provided the ClearView solution, to integrate the marking system in the factory control system. This communication is triggered by an operator scanning a work order code. The data is retrieved from the manufacturing database and is shown in a human machine interface for potential operator inspection. Parts are then laser marked with the ClearMark laser marking system based on the retrieved data.

Identification of assembly tooling
A serialized 2D Data Matrix code is applied to the subassembly after it has been completely processed and inspected. The carriers that hold the subassembly also receive a 2D Data Matrix code. This is because the manufacturer has made a substantial investment in tooling for this application and wants to carefully manage this investment as well. The marks on the container can be erased, making it possible to re-mark the container when needed. The containers are divided into groups according to which type of assembly they are carrying. One container in each group also has a standard 1D group control barcode. The group control barcode is used to determine which channel or stations the groups of containers will be directed to on the line.

“The laser marking and vision system has helped the electronics manufacturer substantially improve the performance of its operations,” Gendron concluded. “The identification of the part at each critical station of the assembly system provides the ability to accurately track the assembly process, avoid operator error and has dramatically reduced scrap and rework rates on the line.

Marking the incoming inventory with the unique identifier also enables real-time inventory control. Manufacturers are quite pleased with the results of this application and many are looking for other opportunities to apply laser marking and machine vision to generate more quality and productivity improvements.”



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