3 questions to ask for better laser cutting

Brent Donner is known for pushing the envelope. Back in the s he went to college to study metallurgy. That experience gave him a foundation for how different metals react to different manufacturing methods. He also has a natural knack for asking the right questions and experimentation.

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All this has helped him build a reputation as a laser cutting operator who can tweak settings and achieve cut edges in thick plate that few others can&#;cutting material 1.5 inch (and even thicker) cleanly, without a trace of burr. &#;For some reason, it has always come naturally for me,&#; he said. &#;I don&#;t know why.&#;

Since Donner has consulted with various fabricators, helping them get more out of their laser cutting systems. In he launched a job shop in New Ulm, Minn., DLC Manufacturing and Fabrication. It remains a small shop with a handful of highly skilled technicians (people who will be featured in the pages of this magazine later this summer).

When Donner visits operations as a consultant, quite often he sees how people miss some of the fundamentals of laser cutting. So before delving into operational complexities, he first asks a few basic questions.

1. Are you cleaning your cutting lens or cover glass properly?

Cleaning procedures differ depending on the laser type. For a fiber or disk laser, operators need to clean the cover glass, or shoots glass, protecting the optics in the cutting head.

When he purchased his first fiber machine, Donner said he referred to the manufacturer&#;s recommendations. From this, Donner said he has tweaked and perfected his cleaning method, extending the life of the cover glass even longer. His method is proprietary, but generally speaking, he scrutinizes the cover glass for any remaining film after cleaning and uncovers ways to remove it. After this, the glass is clear, film-free, and ready for cutting. &#;In our fiber laser, we usually go six to eight months before we need to use a new [cover] glass,&#; Donner said. &#;But the cutting conditions have to be just right.&#;

For a CO2 laser, operators need to clean the cutting lens. Donner and his team cleans his lasers using TRUMPF&#;s Topol polish. &#;A lot of operators really don&#;t know how to apply it,&#; Donner said. &#;Often when I walk into a facility, I see that the lens is severely scratched. Instead of polishing it regularly, they just put in a new lens. But over the long term, that can get really expensive.&#;

So how do you teach an operator how to properly apply lens polish? &#;Every operator is different,&#; he said. When observing them, Donner pays attention to their dexterity, cleaning motion, and the force they apply to the lens, then determines how they should perfect their polishing technique. They never should apply excessive pressure, which can scratch the lens severely. At the same time, they need to apply enough pressure to remove contaminants effectively. It can be quite the balancing act.

Donner applies a judicious amount of polish in a circular pattern across the lens, but this technique just happens to work for him. &#;You need to figure out how the operator works.&#;

To really polish a lens correctly, an operator needs to see the imperfections. For CO2 systems, Donner suggests purchasing a polarizer, which costs a few hundred dollars. But when it&#;s used properly, the investment pays for itself in no time. The operator simply places the lens on top of the device, which shines a bright light through the lens from below, a little like the base of an overhead projector used in schools. &#;As you turn the polarizer&#;s top lens, it will polarize the cutting lens you place on top, and, if the lens is bad, you will be able to see internal cracks and other imperfections.&#;

Donner has followed a regular, careful cleaning regimen for his 6-kW CO2 laser for almost a decade, and even in this high-powered system, he said that the shop needs to replace the cutting lens only every six to eight months.

2. Is your nozzle really centered?

To perform a tape shot, operators shoot the beam at low power through tape for about one second, then look at the resulting hole and make sure it&#;s centered.

&#;Operators take this tape, shine a light up to it, and they try to see if the hole is in the center,&#; Donner said. &#;But that hole might be only 1 mm across. How are you really going to see if that hole is centered to the nozzle? So I bring a 10X magnifying light, a Bausch + Lomb Sight Saver, with a 3&#;8-in.-diameter hole to look through. It&#;s the best $30 you&#;ll ever spend.

&#;I usually bring it to the shop, set it up, and tell the operator to look over my shoulder. I ask him, &#;Is this nozzle centered?&#; And the operator usually sees it [in the magnifying light] and says, &#;Wow, I can actually see it.&#; You may have been cutting at 80 inches per minute. But now, if you have the nozzle precisely centered, you will gain anywhere from 20 to 40 percent in your cutting speed, as long as your cutting conditions are correct.&#;

3. When was your last focus test?

Quite often Donner asks this question, and operators give him a blank look. &#;They sometimes don&#;t know what a focus-test program is.&#;

He clarified that on many modern machines, the focus test occurs automatically. On older machines, though, the actual test varies depending on the machine manufacturer. Some machine-makers have what they call &#;light tests&#; and other methods.

On an older Mazak machine, for instance, the beam turns on at low power, and the operator turns a knob and finds absolute focus by observing the beam color, which turns blue once it&#;s dialed in. &#;You then write the number down,&#; Donner said, &#;bring the head back up, do that three times in row, take an average of those numbers, and that&#;s the number you plug into the controller.&#;

In his shop, Donner runs TRUMPF lasers, which have a focus test that marks a series of lines of different widths on a coupon, the number of which depends on the lens diameter (3.75, 5, 7.5, and 10 in.). The test then engraves the controller settings next to those lines, giving each a positive number, negative number, or zero.

&#;You need to find the thinnest line in the coupon and make sure that the focus setting in the controller is at zero for that thinnest line,&#; Donner explained. If the thinnest line is at a -3, then the operator dials in the focus by 3 mm and retests until he sees that thinnest line is at zero.

Donner reiterated that the exact method for testing the laser focus depends on the machine manufacturer. Regardless, a fab shop&#;s technicians should know how to calibrate the focus so that the focus reading on the CNC matches the beam&#;s actual focus position in the workpiece.

A Foundation for Solid Cutting Conditions

These three fundamentals are just the beginning, of course. Shops may need to look into factors like shielding gas flow or adding extra protection to the beam delivery optics in the CO2 system. But these at least provide a starting point to develop finely tuned cutting conditions, which can vary, depending on a host of environmental factors, such as the material being cut and the shop&#;s location.

&#;If I have a 6-kW laser in Minnesota, it will not cut under the same conditions as a laser in Florida,&#; Donner said. &#;You have different temperatures, different humidity levels, and numerous other factors, so you need to adjust your laser to match those conditions.&#;

He added that developing good cutting conditions depends entirely on the job at hand, but conditions should be set only after the machine is as clean and calibrated as it should be.

In effect, these fundamentals really should be the starting line for optimizing the laser. Then it&#;s off to the races. Once you reach the finish line, the laser will cut so cleanly, with such fine edge quality, that deburring may no longer be needed for certain parts.

Donner summed it up: &#;Once you have these fundamentals, you can really dial in your parameters. Often you can get the machine to perform better than it did new.&#;

DLC Manufacturing and Fabrication Inc., 507-359-, www.donnerlaser.com

As laser cutting, engraving and marking systems become more common in business and education, reliable manufacturers are bound to take precautions to ensure the safety of laser machines. However, since laser safety standards vary around the world, it is wise to look carefully to ensure that the laser cutter is indeed safe for your intended use and environment. If you purchase a system without assessing its security, it could result in property damage or serious user injury.

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As the laser system owner, you are responsible for meeting all workplace safety requirements for your operation. Not complying with local and federal regulations or ignoring safety obligations not only puts employees at risk, but also increases liability in the event of an accident. Even if you unknowingly bring an unsafe laser system into your facility, you may be found guilty of negligence. We always recommend that you do your own research, but first, here are seven questions to help you assess the safety of a laser machine before you buy one.

Is the laser system properly labeled?

A quick indication that the system is not in compliance with basic safety regulations is if the system does not display the required safety labels. U.S. and international regulations require all laser manufacturers to place warning labels at specific locations on the system to indicate specific hazards. If the system is not properly labeled, it does not meet minimum safety requirements and should not be used. Good machinery and equipment will take corresponding safety measures and set warning signs in the parts that are easy to cause damage. The emergency stop button should be set on the control cabinet or the position that is easy to operate. This and similar buttons not only remind users of their safety, but also make them easy to use. Monport models are equipped with panic buttons and warning labels placed on the outside of the body.

Does the design include a metal casing?

The design of an excellent laser system should include a strong metal housing to protect the user from exposure and injury. The surface of the engraving machine should be smooth and clean, and the color of the paint layer should be uniform and consistent, without defects such as bubbles, accumulation and scratches. The protective layer should be complete and uniform without drawbacks such as fading, blotching, peeling and rusting, and according to industry standards, the laser safety enclosure is made of metal thick enough to prevent the laser beam from penetrating. Systems made of plastic should be avoided as they are not effective in preventing the beam from burning through the shell and causing significant injury. In addition to the housing material, ensure that all housing doors or access panels have a tight enclosed design, which is necessary to prevent any laser energy from escaping. Long exposure to the laser is a risk, and when carving some other chemical materials that can produce toxic gases, a good sealing environment is the protection of the sculptor. No good system without these can truly be considered laser safe. Therefore, be sure to check all enclosure openings when you receive the machine.

Is there a redundant interlock on the operating door and access panel?

According to all major international standards, a qualified laser system requires additional interlocking devices on the doors and access panels used in all operations. These interlocking devices prevent the laser from firing when the door is open. This basic design feature helps ensure safe operation and avoid exposure to laser radiation.

Is the viewing window made of safety glass?

Although plastic observation Windows meet the minimum requirements for laser safety, they are not as safe as laminated glass. If the stray laser beam comes into direct contact with the plastic window, it will quickly burn through and escape the shell. For CO2 lasers, laminated safety glass with an optical density of 6+ is recommended. The glass should have at least two layers with a thin film in between to keep the glass intact even if hit directly by a laser beam or heavy object. Toughened glass is unsafe because it can shatter into small pieces and allow the laser energy to escape. Systems with fiber laser sources should have an additional protective layer, usually blue or green, to contain fiber laser radiation, which is especially harmful to the eye if viewed directly. If you're not sure what to look for, you can ask the manufacturer for window safety certification for all laser sources included in the system. Monport's Fireproof machines are equipped with PC glass, which not only effectively protects against laser damage but is also stronger and more fire-resistant than ordinary acrylic glass.

Is there a high temperature alarm?

Because the materials can be flammable, another important safety feature in laser systems is a high temperature sensor and alarm. If unusually high temperatures are detected in the laser processing area, the system is designed to turn off the laser source and trigger an audible alarm. Be sure to double-check with the manufacturer, as this feature is not mandatory. For added safety, some laser systems can be configured with optional fire suppression. While these safety features are helpful, it is important not to leave the laser system unattended during use and to monitor its safe operation.

Is the laser source air-cooled by low-voltage power supply?

Despite safety concerns, there are many low-cost systems that use glass laser tubes, which are powered by HVDC and cooled with water. Basically, cold water is circulated around a glass laser to prevent it from overheating. There is a serious risk of electric shock in the event of water leakage, damage to the glass laser tube, or direct contact with any high pressure element. Electric shocks can be fatal when the voltage exceeds V and the current ranges from 30 to 150mA. In any environment, but especially in schools, careful consideration should be given before purchasing a laser system built using high-pressure glass lasers. A safe choice is an air-cooled laser system with a low-voltage power supply. The Monport power supply controls the start and stop of the laser, and it is equipped with a guard switch for testing various issues such as external ventilation. In addition, Monport laser power is rigorously tested to deliver the highest quality and efficiency on the market. Of course, in the process of use, the sculptor should pay more attention to the laser and high pressure part of the machine, non-professional personnel are strictly prohibited to disassemble the machine without authorization.

How to choose a reliable and secure laser engraving machine? The safety of laser systems needs to be ensured before purchasing them, as not all manufacturers follow the same safety standards. If you work in an environment and strength to choose the right machine for you, but there is an important problem, a very safe machine also needs the correct operation process, so it is very important to learn the correct use of engraving machine for your personal safety.

Safety specifications for using laser engraver:

1. In the process of working the machine, the operator is forbidden to leave without authorization to avoid unnecessary losses.

2. When the machine is working, the top cover plate of the machine must be covered to prevent the laser from deviating and wounding people.

3. Non-professional personnel are strictly prohibited to disassemble the machine due to laser and high pressure parts in the machine.

4. As this kind of laser is invisible light, inflammable and explosive items are strictly prohibited to be placed near the equipment to prevent fire from laser deflection.

5. It is strictly prohibited to place any irrelevant fully reflective or diffuse reflective objects in the device to prevent the laser from directly reflecting on the human body or flammable objects.

6. In the process of working the machine, the operator must observe the working condition of the machine at any time (such as: hook edge deformation, whether the paper is blown up by the air pump to block the laser, abnormal sound of the machine, the temperature of the circulating water, etc.).

7. Do not push or pull the trolley or beam by hand.

8. The machine is located in the environment without pollution, no strong electricity, strong magnetic interference and influence.

9. When the voltage is unstable, it is forbidden to start the machine, otherwise the voltage regulator must be used. It is forbidden to be used by untrained personnel.

10. The continuous working time of the machine shall not exceed 5 hours (more than half an hour rest is required during the work).

11. It is strictly prohibited to turn on the ammeter in the state of large value, so as not to breakdown the laser power supply and shorten the life of the laser tube.

12. the basic limit of the use of laser power (that is, the ammeter can not exceed 20mA)

13. In case of machine failure or fire, please cut off the power immediately.

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