Laser cutter safe operating procedure

General safety

• Let an instructor know you a planning to use the laser cutter. An instructor must be present in the lab any time you are using the machine.
• Questions are the most important safety tool. If you have any questions about how to use the laser cutter or anything else in the lab, ask them before you start.
• To operate any machine safely, you must be alive, awake, alert, and enthusiastic. If you are sleepy or intoxicated, come back another time when you are up to the task.
• If anything out of the ordinary happens during your cut, stop the machine and notify an instructor immediately. Do not attempt to fix the cutter yourself.
• Cut only the approved materials listed on this page. Talk to an instructor if you make significant changes to the settings in the material library.

Fire safety

Before you begin:

• Never cut an unidentified unapproved material.
• Clean the workspace before you load your stock. Debris from previous operations can cause or accelerate a fire.
• Ensure that the area around the laser cutter is free of clutter. There must be nothing flammable in the vicinity of the cutter.
• Proper exhaust helps prevent a fire from starting. Check that the exhaust damper is open before you start your job. Notify an instructor if you notice anything wrong with the exhaust system.

A fire can start at any time during a laser machining operation, no matter how careful you are, and regardless of what material you are cutting. Small fires are easy to deal with — you can blow them out like a candle. Large fires are another matter. A large fire is a small fire plus time. This is why it is essential for you to pay close attention to the machine during the entire job. If a fire starts, don't panic. But act promptly. Put out the fire while it is small.

Here is the most important fire safety rule of all:

• You must remain at the cutter for the entire duration of the job.

Plan ahead. The cutter calculates and displays the duration of each job. If you cannot stay until the job finishes, don't start it.

If a fire starts

Put out the fire while it is small.

It takes three things to sustain a fire: fuel, heat, and oxygen. Once a fire starts in the laser cutter, you can't do much about the fuel. Removing the head and oxygen will put it out.

1. Remove the heat source: press the stop button on the touchscreen. Use the up button to move the cutting head out of the way.
   • Do not turn the laser cutter off. This will prevent you from moving the cutting head out of the way.
   • Most fires go out after you stop the cut. In some cases, the fire may generate enough heat to sustain itself even after the cut has stopped.
   • Moving the cutter will give you a clear view of the stock to assess the situation, provide a clear path for taking further action, if needed, and protect the cutting head.
2. Reduce available oxygen: close the exhaust damper.
3. If there is still a small flame after the previous steps (the size of a candle flame), open the lid and blow it out like a candle.
4. If the flame is larger than a candle flame or you cannot blow it out and it is safe to do so, smother the fire by placing the piece of acrylic kept next to the cutter on top of your stock.
5. If the previous steps do not extinguish the fire, pull the fire alarm. Alert the instructor on duty immediately. If it is safe to do so, the instructor may attempt to put out the fire with the fire extinguisher.

Always alert the instructor on duty if a fire starts. Thin stock, lots of close-together cuts, coated stock (including paper or tape), dirty or poorly focused optics, and improper cutting speed increase the chance of fire. An instructor will help rectify the problem that caused the fire by changing some combination material, cutting parameters, or program.

Laser safety

There are two lasers inside the cutter. One is a powerful death ray that does the actual cutting. The other laser is much less intense. Nonetheless, you should treat even weak lasers with the proper care.

It's probably obvious to you that a laser beam powerful enough to cut through material such as wood, plastic, and even metal has the potential to cause serious injury. The cutting laser will burn, vaporize, or otherwise wreak havoc with any part of your body it comes into contact with. If the beam hits your eye, it can blind you instantly. To make matters worse, the cutting laser emits an invisible infrared beam. You literally won't even see it coming. Human eyeballs are sensitive to light wavelengths between about 400 and 700 nm. The cutting beam has a wavelength of 10,600 nm — far too long to be seen. Even though the lid appears to be transparent, the invisible cutting beam cannot pass through it. The designers of the cutter minimized the risk of the cutting beam escaping by including a safety interlock that shuts off the cutting beam whenever the lid opens. When the lid of the cutter is closed, the cutting beam will be contained inside the shell of the cutter where it can't hurt you. Never attempt to defeat the safety interlock.

The kind of laser that generates the intense cutting beam is based on a glass tube full of carbon dioxide gas. Unsurprisingly, this kind of laser is called a CO₂ laser. The tube is about the size of a small baguette. If the CO₂ laser tube inside the Dremel LC40 laser cutter had appeared as a prop in the 1931 film adaptation of Mary Shelley's novel Frankenstein, it would not have looked out of place. ( Interesting commentary on Frankenstein and technophobia [1].)

The second laser inside the cutter is generated by a diode laser similar to the one that's inside your laser pointer. This alignment laser produces the little red dot that you can see. Although some laser diodes can producing a lot of power, the one inside the LC40 emits only about 5 mW of visible, red light with a wavelength of 635 nm. Even though this is 8,000 times less power than the cutting laser, the alignment laser can still cause harm. (Here is a very interesting case report of an injury caused by a low power, handheld laser pointer.) The basic assumption for visible, low power lasers is that the human reflex to look away from a bright light will cause you to look away before any damage takes place. That said, if you ignore your reflex (as in the case report), even an everyday laser pointer can cause a serious injury. With that in mind, never look into or stare at a laser beam. For that matter, don't stare at any bright light.

Inside the cutter, a special kind of mirror called a dichroic combines the alignment laser beam with the cutting laser beam. Combining the visible and invisible beams makes it possible to visualize the path that the laser takes and where the cutting head is aimed. The lid of the cutter is made out of a material that allows the visible, red light from the alignment beam to pass through, but it blocks the invisible cutting beam. Pretty neat.

Acceptable materials

• Polymers
  • Acrylic
  • Laser grade rubber
• Things made from trees
  • Paper
  • Cardboard
  • Matboard
  • Cork
  • Solid maple
  • Solid oak
  • Solid walnut (but not solid walnuts)
  • Plywood (must be California 93120 Phase 2 & TSCA Title VI compliant for formaldehyde)
• Things made from natural fibers
  • Cotton
  • Denim
  • Felt (wool)
• Metal
  • Anodized aluminum
  • That's it. Seriously. No other metal.
• Things made from sand
  • Glass
• Things made from cows
  • Vegetable tanned leather