Advanced Laser Marking Processes Solve Manufacturing Challenges

Before we get started, let’s make something clear: “laser marking” may not be as narrow a topic as you think. The definition of laser marking process is “a method that uses a focused laser beam to alter the surface of a target material.” This could mean engraving, etching, color change, or ablation among other effects. This blog post highlights how laser marking was implemented in three very different advanced manufacturing applications: marking on an automotive seat frame, marking on a medical cannula, and the selective removal of plastic coating from a copper wire for an electronic component.

Why select laser marking?

Marking is used in many industries for product identification, serialization, and aesthetics. There are a number of ways to accomplish this depending on desired mark type, size, material, and required throughput. Available technologies include laser, dot peen, industrial inkjet printing, and electro-chemical etching. We expound on these technologies in some detail in a previous blog post entitled Marking Methods: When Lasers Make Sense, but here’s a quick technology comparison:

Laser marking is achieved by focusing laser energy onto a work piece and scanning it in a defined pattern over a desired area. The intense interaction causes the work piece material to change properties leaving a visible mark. Laser marking has a number of significant advantages over other marking technologies:

• Direct, non-contact marking method
• Offers high contrast and fast processing times
• Chemical, water, and oil-free process
• Flexible programming to produce text, barcodes, and pictures
• No retooling necessary for different marks
• High legibility
• Long term durability

The following graphic shows a wide range of possible laser marks on several different materials.

The type of mark can be determined by the material, laser choice, and intended use of the parts. Sometimes this can be broken down by industry – for example, the automotive industry typically has high-wear parts and desires to have engraved or deep engraved to survive usage.

 Three Case Studies

Following are three real-life examples of how advanced laser marking techniques are utilized in manufacturing today. Each one outlines the application challenge, manufacturing goal, selection criteria, and type of laser used to produce the successful outcome.

1.) Automotive Component Manufacturing

Challenge: An automobile seat manufacturer found that the adhesive labels used to identify their frames were falling off with normal use during the product lifetime. This caused a loss of cradle-to-grave traceability of the parts. They needed a direct marking method that was resistant to the typical wear and tear on seats in an automobile.

Goal: The manufacturer needed to create a dark, human-visible mark directly on the frame that would not only be machine readable and human legible from any angle, but also survive the wear and tear of a car’s average 12-year lifespan. The company also desired to connect the solution to their ERP/MRP for product traceability.

Selection Criteria: The criteria for selecting a marking solution was cost-effectiveness of investment based on a relatively low value part and low volume production. Dot peen, although a lower cost solution, was slower and had consumable cost to consider. Ink jet and pad printing resulted in a dark mark on relatively dark stainless steel material and was both difficult to read and susceptible to wear.

Solution: The manufacturer switched to an infrared (IR) nanosecond fiber laser, which helped them achieve a dark and resilient mark, to which they added a white background (using the same laser!) for added clarity and contrast. The data matrix mark was machine-readable and, with a networked solution, easily connected to ERP/MRP systems.

2.) Medical Device Manufacturing

Challenge: A medical device manufacturer needed to mark human readable text and bands on 304 stainless steel cannula used in surgery. For these devices, it is critical that there are no occlusions where bacteria could grow, no oxidation or corrosion from exposed iron atoms, and the mark needs to survive multiple rounds of passivation / cleaning.

Goal: Produce a clean, smooth mark – legible from any angle – that would survive repeated cleaning and passivation cycles.

Selection Criteria: In this case, ink jet printing was not an acceptable solution as the ink could dissolve in a body during surgery and would be easily washed away during the passivation process. Chem-etch and dot peen were also not suitable due to consumable cost and formation of occlusions. The best solution was laser marking as it is a non-contact process which could keep the part sterile. Although the picosecond laser is a higher cost solution, the high cost per part and added safety guarantee supported the higher initial investment.

Solution: The manufacturer first tested a nanosecond fiber laser, but found that the marks were inconsistent and would often fade with multiple cleaning cycles. Additionally, a close look at the parts showed that the oxide layer built on the surface during the marking process was prone to micro-cracks due to overheating of the part. They started testing a picosecond laser, which provided the desired dark marks and a close look showed that the mark effect was from a different reason- namely a light-trapping microstructure formed on the surface. This structure was also impervious to corrosion and withstood passivation process. As an added bonus, they found the process window to be wide, so it was easy to achieve and easily applicable to other parts.

Producing darker marks than a nanosecond fiber laser, the picosecond solution gave the company bands and numbers with human readable text. This helped make the marks highly visible during surgical procedures.

 3.) Cable Harness Manufacturing

Challenge: The manufacturer needed to remove a plastic coating from selective sections of a copper wire to produce electrical conductivity. Manual wire stripping was slow, labor intensive, and often led to nicks on the copper material. Furthermore, some of the smaller copper wires were too small to handle manually.

Goal: The manufacturer wanted to completely remove the plastic without damaging the copper wire underneath, leaving a smooth finish.

Selection Criteria: The equipment selection criteria was a fast process time for a lower cost/large volume part. In this case, none of the other marking techniques was suitable to remove the material.

Solution: The manufacturer first tried using old-fashioned hand wire strippers to remove the plastic, but ended up damaging the copper wire. They tried melting the plastic off, but that process left plastic residue on the conductive wire. Next, they opted for a carbon dioxide (CO₂) laser to remove the plastic, but still found residual plastic and some heat damage to the wire. They eventually arrived at a UV diode pumped solid state laser which enabled them to completely ablate the plastic in only two passes without damaging the copper wire – and the finish on the copper wire was smooth and consistent as required.

Although not a “marking” application, it is using a laser to ablate and remove material for an added purpose for manufacturing. Sometimes, a little outside of the box thinking can achieve the desired result with a laser that might be labeled as a “marking laser!”

Summing it all up

In this blog, we looked at three specific use cases of laser markers coming from different industries. This showed differences in mark types: engraving, black marking and ablation, and differences in laser choices: fiber, picosecond, and UV.

Here is a quick overview of the features of the three industrial laser marker types we presented in the use cases.

These case studies show areas where advanced uses of laser marking are being used in today’s manufacturing. However, these are but a few of innumerable examples of innovative uses of laser marking. Continue to check this space for the next ideas!