This document covers some basic safety information on the processes of laser engraving.
DISCLAIMER: Laser Engravers emit deadly high voltage and laser radiation capable of causing instant blindness and tissue damage. Lasers are a fire hazard. Keep extinguishers close and NEVER leave the machine unattended. The lasing process caused dangerous, and sometimes deadly, smoke and gasses that will kill you and literally ruin your machine! This documentation is for educational reference only. Use at your own risk. The manufacturer's procedures and guidelines always supersede this information. Always follow all safety recommendations and MSDS data. By accessing this document you acknowledge that you have read and understood, in their entirety, AND AGREE TO our TERMS & CONDITIONS.
----- THIS DOCUMENT COVERS MEDIUM INFRARED ~10.6μm CLASS 4 CO2 LASERS ONLY -----
Here are the topics covered in this KB Article:
- CO2 LASER BASICS
- PERSONAL PROTECTIVE EQUIPMENT (PPE)
- EQUIPMENT OPERATION
- HAZARDOUS MATERIALS
- HIGH VOLTAGES PRESENT
- CARE & MAINTENANCE
- MORE RESOURCES
The carbon dioxide laser (CO2 laser) was one of the earliest gas lasers to be developed. It was invented by Kumar Patel of Bell Labs in 1964 and is still one of the most useful. Carbon dioxide lasers are the highest-power continuous wave lasers that are currently available. They are also quite efficient: the ratio of output power to pump power can be as large as 20%. The CO2 laser produces a beam of infrared light with the principal wavelength bands centering on 9.4 and 10.6 micrometers (μm).
Moderate and high-power lasers are potentially hazardous because they can burn the retina of the eye or even the skin. To control the risk of injury, various specifications like 21 Code of Federal Regulations (CFR) Part 1040 define "classes" of lasers depending on their power and wavelength. These regulations impose upon manufacturers required safety measures, such as labeling lasers with specific warnings, and wearing laser safety goggles when operating lasers.
Consensus standards, such as American National Standards Institute (ANSI) Z136, provide users with control measures for laser hazards, as well as various tables helpful in calculating maximum permissible exposure (MPE) limits and accessible exposures limits (AELs).
Thermal effects are the predominant cause of laser radiation injury, but photochemical effects can also be of concern for specific wavelengths of laser radiation. Even moderately powered lasers can cause injury to the eye. High power lasers can also burn the skin. Some lasers are so powerful that even the diffuse reflection from a surface can be hazardous to the eye.
The coherence and low divergence angle of laser light, aided by focusing from the lens of an eye, can cause laser radiation to be concentrated into an extremely small spot on the retina. A transient increase of only 10 °C can destroy retinal photoreceptor cells. If the laser is sufficiently powerful, permanent damage can occur within a fraction of a second, literally faster than the blink of an eye. Exposure to laser radiation are largely absorbed by the cornea and lens, leading to the development of cataracts or burn injuries.
Infrared lasers are particularly hazardous, since the body's protective glare aversion response, also referred to as the "blink reflex," is triggered only by visible light. People exposed to invisible laser radiation may not feel pain or notice immediate damage to their eyesight. A pop or click noise emanating from the eyeball may be the only indication that retinal damage has occurred i.e. the retina was heated to over 100 °C resulting in localized explosive boiling accompanied by the immediate creation of a permanent blind spot.
Lasers can cause damage to biological tissues, both to the eye and to the skin, due to several mechanisms. Thermal damage, or burn, occurs when tissues are heated to the point where denaturation of proteins occurs. Another mechanism is photochemical damage, where light triggers chemical reactions in tissue. Photochemical damage occurs over the course of hours. Laser pulses shorter than about 1 μs can cause a rapid rise in temperature, resulting in explosive boiling of water. The shock wave from the explosion can subsequently cause damage relatively far away from the point of impact. Ultrashort pulses can also exhibit self-focusing in the transparent parts of the eye, leading to an increase of the damage potential compared to longer pulses with the same energy.
Users need to be properly trained on the potential hazards, control measures, lab and manufacturer’s operating procedures, use of personal protective equipment (PPE), emergency procedures, and safety precautions for operating the engraver. The required PPE includes safety glasses to protect eyes from radiations, particles, debris, etc., proper skin protection to reduce burns, and hearing protection (if necessary).
The acrylic laser safety viewing windows installed in the US made laser engravers like ULS, Epilog, etc... in combination with safety interlocks do provide adequate protection and conform to published safety standards. The orange windows in the K40 lasers are largely considered to be adequate and they may be but, given the lack of quality control and cloning by the Chinese laser markets, I'm not sure I would trust my eyesight to them. Remember the "fake" eclipse glasses debacle of 2017?
Eye protection suitable to the laser should be worn within the laser control area if there is a potential for exceeding the MPE limit if the beam is viewed. Protective eyewear may include goggles, face shields, spectacles or prescription eyewear using special filter materials or reflective coatings.
It is easy to become confused by laser goggles if you are not used to all of the terminology associated with laser safety. If you are ordering laser safety goggles from a company, it is a good idea to ask them any questions you may have. It is certainly a good idea to be absolutely certain you know that you’re getting the right laser safety goggles before you order them. If you make a mistake with laser safety, it could be the difference between keeping or losing your vision.
Fully enclosed and interlocked laser cutters are normally low-risk, Class 1 lasers in accordance with ANSI Z136.1 Safe Use of Lasers. These devices are safe when used as designed, without manipulating the safety features, and are exempt from UW laser registration and other control measures.
HOWEVER, the lasers embedded inside the enclosed system are often Class 3B or Class 4 lasers, which emit high energy laser beams capable of causing serious eye and skin injury if the beam is not contained within the device. Therefore, safety interlocks should never be bypassed.
THE K40 LASER ENGRAVER SHOULD BE CONSIDERED A CLASS 4 DEVICE SINCE IT HAS NO INTERLOCK SYSTEMS. There are interlock mods available for this unit which will be addressed in future Knowledgebase Articles.
Users need to be properly trained on the potential hazards, control measures, lab and manufacturer’s operating procedures, use of personal protective equipment (PPE), emergency procedures, and safety precautions for operating the engraver. The high-intensity laser beam can produce extremely high temperatures and significant amounts of heat as the substrate material is burned away while cutting.
Some materials can catch fire during cutting operations creating fumes and smoke inside the device. Dirt and debris may cause fire and a poor quality cut or mechanical component failure. It is important that users remain with the laser during operation to ensure that any flare-ups/flame are properly contained and extinguished. Obtain the Material Safety Data Sheet (MSDS) from the material’s manufacturer when handling or processing the materials.
Although laser machines can process a broad range of materials, certain types of material should not be lased because of their chemical make-up. Laser processing these materials creates dangerous gases or dust. Some are so corrosive they will literally eat your machine!
Here is a list of materials that are not laserable:
Leather and artificial leather that contains chromium (VI)
Carbon fibers (Carbon)
Polyvinyl chloride (PVC)
Polyvinyl butyral (PVB)
Polytetrafluoroethylenes (PTFE /Teflon)
Any materials containing halogens (fluorine, chlorine, bromine, iodine, and astatine)
Epoxy or phenolic resins
Additionally, extreme care must be used when attempting to lase Manganese, Chromium, Nickel, Cobalt, Copper, & Lead.
A K40 Low Voltage Power Supply (LPS) has an integral HIGH VOLTAGE FLYBACK TRANSFORMER (HVT) capable of producing up to 20,000 VDC. This transformer supplies sufficient voltage to the laser tube to trigger the laser via ionization. The wires going to the laser tube, as well as the related terminals and electronics can seriously injure you. High Voltage behaves very differently (the skin effect) and can grab a hold of you before you know it. Since the K40 has no safety interlocks you should NEVER open the units access panels when it is on, operating, or even plugged in! Extreme care must be taken when working with the hi-voltage section of this engraver.
Routine and preventive maintenance optimize the safety and performance of your laser. It requires just a few minutes of regular maintenance to prolong the service life of your machine and to optimize its performance.
US brand laser engraver manufacturers publish recommended maintenance schedules so I won't reinvent the wheel here. Keeping the unit clean, tight, lubricated, and aligned should be a continuous process.
The frequency and duration of these processes will be dependant on your particular usage. You can find links to more detailed maintenance information in the resources below.
7. MORE RESOURCES
Below are links to more information and resources related to the topics in this Knowledgebase Article. As always, you need to do your homework and develop safety guidelines specific to your equipment and needs. It is also important to adhere to a preventative inspection and maintenance schedule to maintain the safety and reliability of your systems. The provided links will open in a new window or tab.
OSHA TECH MANUAL - LASER HAZARDS
CLASS 4 LASER SAFETY REQUIREMENTS - PHILLIPS SAFETY PRODUCTS
MATERIAL SAFETY AND YOUR LASER - EPILOG
SYSTEM MAINTENANCE - EPILOG LASER (PDF DOWNLOAD)