- Category: Maintenance
- Created: 2017-08-02
The (often) overlooked areas of preventive maintenance for laser cutters
by Robert Farrell, president, Farrell MarCom Services LLC
As a manufacturing strategy consultant, Patrick Medlin puts his 25 years of experience to work to define and execute plans built upon the principles of lean manufacturing, specifically by increasing throughput while reducing inventory and operating expenses. Medlin serves as president of Advanced Technology Sales & Service Inc. in Greensboro, N.C. Under his direction, the company has become one of the most recognized machine tool distributorships throughout the southeastern United States. I sat down with Medlin recently to learn about preventive maintenance for laser cutters and some of the often overlooked aspects of it.
Let’s begin by learning a little about your background.
My experience spans a variety of business and manufacturing-related disciplines, including CNC programming, workflow, plant layouts, scheduling, information systems, accounting, marketing, sales and operations.
Over the years, I’ve gained a wealth of practical hands-on experience with cutting-edge manufacturing processes, such as those produced with laser and waterjet cutting equipment. Process improvement continues to be a passion of mine, and I’ve led and coordinated the successful implementation of lean manufacturing, Kaizen and a new multi-site manufacturing software package.
I enjoy the challenges of building and maintaining profitable operations or helping failing operations become profitable. In 2001, after spending several years in the metals fabrication industry, I formed ATS to fill a real need for local, better and more responsive service and support.
Lasers require daily, weekly, monthly and annual preventative maintenance operations to maintain peak operating levels.
Generally speaking, what are some of the regular preventive maintenance steps that a laser operator should take?
On a daily basis, it’s important to ensure that the nozzle is properly aligned and the cutting head and height sensor are clean and free of dust buildup. Also, check the water level in the chiller and confirm that operating air supply lines are free of moisture and contaminants. And confirm assist gas and purge gas supply levels. These steps only take a few minutes to perform, but you would be surprised at how often they are overlooked.
What about longer term preventive maintenance steps?
A number of steps should be performed monthly. Slats should be cleaned or replaced if broken or worn down too far. And, while you’re at it, be sure to remove excess laser dust and slag from inside the machine, as well. Air filters and chiller condenser coils should also be inspected and cleaned. Confirm set-point temperatures on the chiller and replace water and add treatment chemicals as needed.
Also, be sure to check auto-lubrication reservoir levels and follow factory lubrication intervals. Take the time to walk around and inspect hoses for holes and signs of wear, check the dust collector and empty the dust container, and be sure to inspect the laser safety enclosure for any cracked or broken windows. Finally, reload factory tech tables (cutting conditions library) and sub-routine programs.
In addition to checking the water levels in the laser’s chiller, operators also need to confirm that operating air supply lines are free of moisture and contaminants.
What happens if the chiller check-point temps and auto-lube reservoir levels aren’t set correctly?
The operator’s manual will contain the correct settings for the chiller temperature set-points and will also specify the correct oil to use when filling the auto-lube reservoir. Typically, the set-point temperatures on the chiller don’t require adjusting, but it’s good practice to verify them and to compare them against the actual temperatures.
If the actual temperatures vary more than 3 to 5 degrees, it’s usually an early indication that the chiller may need attention. Whether it is low water, clogged filters or condenser coils, or low refrigerant pressure, the earlier these types of issues are corrected, the more time and money will be saved.
What are some of the key preventive maintenance differences between CO2 and fiber lasers?
The primary preventative maintenance differences between CO2 and fiber lasers are the optics inside the resonator and in the beam delivery system. All CO2 lasers have resonator optics that help generate and intensify the laser beam; most fiber lasers do not. All CO2 lasers have beam path optics (bend mirrors) that deliver the laser beam from the resonator to the cutting head. Fiber lasers employ a fiber optic cable to deliver the beam from the resonator to the head, eliminating the need for bend mirrors.
The CO2 laser’s bend mirrors are also enclosed in beam path bellows that are susceptible to holes from constant movement and back reflections, meaning they must be replaced periodically. Beam path optics can also become misaligned from serious head crashes due to part tip-ups.
All optics must be cleaned, realigned and periodically replaced to maintain optimum cutting efficiency. However, CO2 lasers are more forgiving in general and their cutting head optics are less sensitive to dusty environments than their fiber laser counterparts. While there are far less preventive maintenance requirements with fiber lasers, cleanliness and strict adherence to factory optics cleaning and maintenance procedures and performing those tasks in a controlled, dust-free environment are critical to fiber’s successful operation.
What areas are often overlooked when it comes to preventive maintenance for fiber lasers?
Unfortunately, there are several, but all are easily avoidable. I mentioned slag buildup and cutting head crashes earlier. When cut parts tip up as a result of excess slag, you run the risk of the head crashing into the protruding part. This can cause serious damage to the head, resulting in thousands of dollars for replacement.
When cleaning the lens and lens window, be sure to take the time to do it thoroughly and correctly using proper cleaning supplies. Also, even though substituting after-market lenses, lens windows, nozzles, insulators or non-spec consumables might save a few dollars, in the long run it’s always best to stick with high-quality OEM parts designed for the specific machine.
What’s the best method for removing or preventing slag buildup?
Several companies offer a motorized tool for removing slag buildup from slats. I’ve also seen companies have moderate success in preventing slag buildup by spraying the slats with a solution similar to anti-spatter for welding. From my experience, the best, long-term solution is to use copper slats. While the upfront investment is significant, after four to five years, when it is time to replace them, you receive a good portion of your money back for the copper scrap.
Another cost-saving tip is to make sure that you develop slats that are double-sided so that when the top side becomes too worn, the slat can simply be flipped over. The overall height of the slats is so important because it affects how high the material sits inside of the laser. When the slats become too short, the laser will experience height sensor alarms when processing thin-gauge material because the Z-axis travel is close to exceeding the soft limits of the machine’s parameters.
What’s often overlooked with CO2 lasers?
Again, there is often the temptation to substitute after-market lenses, mirrors, nozzles and consumables for OEM parts. But, opting for cheaper parts usually comes back to haunt you. I also see problems stemming from a failure to have the chiller serviced, which should be done annually, as well as a failure to replace beam path bellows that may have holes or tears. Laser gas is another area that’s often overlooked – running low or out of gas can contaminate the resonator.
Patrick Medlin, president of Advanced Technology Sales & Service, has more than 25 years of experience working in manufacturing environments.
What can happen if the chiller isn’t serviced or bellows aren’t replaced?
The chiller is a critical component for any laser, be it CO2 or fiber. When neglected, it can cause premature failure of components inside the resonator, power supplies and optics. If bellows aren’t replaced once they develop holes, the beam path becomes contaminated, which shortens the life expectancy of the optics, causes the beam to grow in diameter and ultimately affects focal length at the lens.
All of these effects introduce more variables and inconsistencies into the cutting process. The end result is lost parts due to blow-outs as well as poor edge quality and slower cutting speeds.
What are some early warning signs that maintenance may soon be required?
A noticeable reduction in cutting speed, feed rate or edge cut quality is a clear indicator that something isn’t right. Other warning signs include a more frequent need to realign the nozzle or if the nozzle is hot to the touch. Likewise, departures from factory tech tables with regard to power, frequency, duty and gas pressure are also red flags.
Does preventive maintenance vary much from brand to brand?
Preventive maintenance of fiber lasers varies very little from one brand to another. This is attributed to the diminishment of items that require maintenance, specifically the elimination of nearly all optics. The frequencies, procedures and costs of preventive maintenance on CO2 lasers can vary greatly among brands, and most of the differences can be attributed to the resonator. The differences between cross-flow and fast-flow (RF and DC) resonators are numerous and a topic for another day.
Is preventive maintenance sometimes put off because it cuts into production schedules?
The better question for laser owners to ask is, “Do I want my machine’s downtime to be planned or unplanned?” One of our customers is a world-renowned heavy truck manufacturer that strictly follows preventive maintenance schedules. Over the past 12 years, I can count on one hand the number of times their lasers have been down for unexpected, unscheduled repairs.
It’s also important to remember that most preventive maintenance can be performed during off hours. Our service department also offers preventive maintenance agreements that can be tailored to weekends or non-peak shifts.
What’s the best advice you can offer a laser owner to maximize its productivity?
Lasers are only making money when they’re operating at peak performance. It’s, therefore, important to closely follow preventative maintenance protocol. Follow optics cleaning procedures closely and regularly, track your productivity and machine downtime, and ask to see the machine alarm history to help identify and address recurring problems.
Furthermore, understand and plan for secondary operation bottlenecks that may put a strain on schedules and machinery. Remember to keep machine programming software current, minimize part tip-ups and follow OEM recommended maintenance schedules.
In the end, it’s true what they say about an ounce of prevention: Take the time to create and follow a daily and monthly maintenance checklist and find laser operators who understand the importance of it and are interested in taking ownership of the machines they run.
Before we wrap up, can you tell us a little about your company?
Advanced Technology Sales & Service is a service-based organization that understands the importance of maximizing uptime for our customers. Our prior background in metal fabrication guides us in our service and support. Our seven days a week, on-site service underscores that commitment to fabricators throughout North Carolina, South Carolina, Virginia, Tennessee and West Virginia.
While we sell, service and refurbish a wide variety of metalcutting, punching, bending and finishing equipment, Mitsubishi fiber and CO2 automated laser systems are our specialty. We also provide a number of services, including machine relocation, installation, repairs and preventive maintenance programs as well as basic operator, advanced applications and maintenance training.