TIPS FOR SUCCESSFUL LASER MARKING IN JOB SHOPS
As more job shops invest in this technology to meet customer demands, many discover that the learning curve leaves them wondering where to begin. These simple insights will save them time, money and increase their productivity on the laser.
The demands of modern day job shops haven’t changed much over the years. They are still looking for ease of use, highly versatile, low cost solutions to fulfill their customer’s demands. Many have come to see laser marking as a business venture that meets all those criteria. As with all forms of technology, this has a learning curve and the most common question I hear when providing support on-site or over the phone is, “Where do I begin?”
DEVIL IN THE DETAILS
Before taking on a new job, ensure you have the proper piece of equipment to meet your customer needs. A simple understanding of the properties of laser radiation will help gauge the practicality of the job. Lasers are monochromatic, meaning they consist of one wavelength of light in the spectrum. The three basic wavelengths of industrial solid-state lasers are ultraviolet (355 nm), green (532 nm) and infrared (1060 nm to 10,604 nm), with IR being the most common.
Although CO2 and continuous-wave lasers are commonly used for marking, our focus here is on solid-state pulsed lasers. Each wavelength has its own ‘niche’ in the laser marking industry: the wavelength determines its feasibility for marking specific materials. In other words, your marking is limited by the level of absorption your material has with the wavelength of light you are using. The IR laser has the most versatility and is capable of marking both ferrous and non-ferrous metals, ceramics and a limited array of plastics, whereas the green and UV lasers excel with precious metals, electrical components, glass and low pigment plastics. Being cognizant of what your laser can and cannot mark will help avoid pitfalls.
Properly optimizing CAD files for importation into your laser software or creating the files on your own is a good start, but realize that this step, if done haphazardly, can not only cost you time but sacrifice throughput as well. When possible, use the laser fonts provided with your machine. They have already been optimized for laser marking by way of continuous polylines whereas text in an imported CAD file is most often broken line segments.
Take, for instance, the capital letter “A” in an Arial font. With continuous polylines, you have two start points and two stop points. Now compare that to the same letter but comprised of broken line segments. This gives you twelve start points and eleven endpoints, with a slight pause occurring at each one. The mark time difference is in the range of less than a second, but that only applies to one character of the text you are marking! Compound that by 25 more characters in a line of text and seconds of time are wasted in the mark.
If your laser marking software allows it and your material is thermally sensitive, sort your order of marking so that the scan mirrors make the smallest jumps possible between objects. This will result in more laser-on time and less overall cycle time.
CRAWL BEFORE YOU WALK
It can be overwhelming to find the proper balance between an acceptable mark and a fast one. Without the hands-on experience to learn how laser marking parameters interact with each other and what effects are achievable, the process will soon become self-defeating.
Start with the basics by using a test matrix: a simple array of objects, usually hatched squares or text, which varies process critical parameters such as power, velocity, frequency, or overlap. Matrices are easy to make with most modern laser marking software and some suppliers even have matrix generators. When you mark these test grids on scrap material, you can easily see the transition from bad marks to acceptable ones. From this point, altering the power density or energy density will bring you closer to the mark you are looking for.
Power density is dependent on the laser power and your beam diameter in the optimum focal plane. For every laser processing mode (engraving, annealing, ablation, etc.) a certain power density is needed to produce the desired results. Once your power density is established, you can begin making changes to your energy density.
It is advisable to make small changes at first, in five to ten percent increments, both in the positive and negative directions. The energy density is derived from the velocity, the frequency, the power density itself, and most importantly the pulse overlap. Two helpful hints to keep in mind are that with lower frequencies both your peak power and power density is high. Also, higher velocities will result in lower energy density. These should be enough clues to aid you in refining your parameters. Always remember: when in doubt, consult the experts.
INVEST IN YOUR MACHINE
Contemplate having an operator properly trained by your laser supplier. The more efficient they are at programming the laser, the quicker the job will be completed. After working with enough laser parameters to see the same processes repeatedly, laser parameter application starts to become instinctive. In essence, by sending an operator to training classes you will further solidify this knowledge and, in turn, should see a decrease in the amount of scrapped parts.
When you first receive your machine, take the time to set up a proper preventative maintenance schedule. Simple tasks such as cleaning the lens once a week and changing the filters in regular intervals will ensure your machine remains as perfect as the day it was delivered. The added benefit is that there is less downtime caused by neglect and your machine will help ensure receive the maximum return on your investment.
It may seem like common sense but, in the long run, these simple tips will save you time, money and increase your productivity on the laser, guaranteeing you deliver quality work to your customers in a timely manner.
About the Author: Brian Litherland is the TruMark lead application engineer at TRUMPF Inc., 111 Hyde Road, Farmington Industrial Park, Farmington, CT 06032, 860-255-6046, Fax: 860-255-6421, email@example.com, www.us.trumpf.com.