Laser cutter safe operating procedure

The rules

• Ask an instructor for permission before using the laser cutter. An instructor must be present in the lab any time you are using the machine.
• You must be alive, awake, alert, and enthusiastic in order to operate any machine safely. If you are sleepy, distracted, or intoxicated, come back another time when you are up to the task.
• Cut only the approved materials listed in the table below. Talk to an instructor before cutting if you make significant changes to the settings in the material library.
• Never attempt to defeat the cutter's safety interlocks.
• Remain at the cutter and keep an attentive eye on the work for the entire duration of the machining operation. No exceptions.
• 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.
• 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.

Permitted materials

Polymers	Things made from trees	Natural fibers	Metal	Other
Acrylic Laser grade rubber	Paper Cardboard Matboard Cork Solid maple Solid oak Solid walnut	Cotton Denim Felt (wool)	Anodized aluminum That's it. Seriously. No other metal.	Vegetable tanned leather Glass

Cutting procedure

1. Turn the cutter on. The power switch is located at the bottom, right, rear of the machine.
2. Ensure that the exhaust damper is open.
3. Tidy up. The area around the cutter must be free of clutter.
4. Clean any debris from cutter's workspace. Debris from previous operations can cause or accelerate a fire.
5. Make sure the lens is clean. Notify an instructor if it needs attention.
6. Focus the cutter using the spacer puck.
   • Ensure that the dovetail seats properly when you tighten the thumbscrew.
   • Properly focusing will increase the quality of your cut and reduce the risk of fire.
7. Load your stock.
8. Use the Import button on the web interface to load your design files.
   • The Run Perimeter button on the web interface can help you verify correct positioning.
9. Use the Start button on the web interface to send your job to the cutter.
10. Plan ahead. The cutter calculates and displays the duration of your job on the touch screen. If you cannot stay until the job finishes, don't start it.
11. Answer the safety questions on the touch screen. Double-click the silver button to start the job.
12. Remain at the cutter and keep an attentive eye on the work for the entire duration of the machining operation
    • 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.
    • If you need a short break, use the Pause button. The cut will resume where you left off when you continue.
    • Press Stop on the touchscreen and notify an instructor if a fire starts or anything else unusual happens.
    • There should be no odor. A smoke smell indicates there is something out of sorts with the exhaust system. Stop the job and get an instructor if you smell smoke.
13. After the job completes, wait 30 seconds or so for the fumes to clear before lifting the lid.
14. Be polite to the next user: remove offcuts and debris from the workspace.

Fire safety

It is essential that you remain at the cutter and monitor its operation. Small fires are trivial to handle; large fires are not. A large fire is equal to a small fire plus time.

A candle-sized flame is normal when cutting materials such as acrylic. If a sustained flame larger than a candle flame develops, act promptly but do not panic.

A fire requires fuel, heat and oxygen. Removing any one of these ingredients will stop a fire. The laser is a heat source, and the exhaust system draws more oxygen into the workspace. So here is what to do If a fire breaks out:

Take action while the fire is small:

1. Press the STOP button on the LCD control panel (to remove the heat source).
2. close the exhaust damper (to reduce available oxygen).

Whew. The fire is probably out now. But in some cases, the material may be able to sustain a fire on its own. If this happens, notify an instructor immediately. Do not lift the lid of the cutter. Doing so will increase oxygen available to the fire.

Alert an instructor on duty if a fire starts. The instructor will help rectify the problem that caused the fire by changing some combination of material, cutting parameters, or program.

Things that increase the likelihood of a fire:

• Cutting flammable materials.
• Cutting thin stock (including paper or tape affixed to thick materials).
• Dirty or poorly focused optics.
• Inappropriate settings for the material.
• Patterns that have lots of cut lines close together.
• Cutting (versus engraving).

Laser and eye safety

There are two lasers inside the cutter. One is a powerful death ray that does the actual cutting. The other laser is more-or-less the same as a laser pointer.

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 infrared cutting laser beam is invisible. 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 is transparent to visible light, the infrared cutting beam cannot penetrate it. The designers of the cutter essentially eliminated the risk that the cutting beam can escape the confines of the machine by including a safety interlock that shuts off the cutting beam when the lid is open. When the lid of the cutter is closed, the cutting beam is contained inside the shell of the cutter where it can't hurt you.

There is really only one thing you need to do to avoid a laser injury: Never attempt to defeat the safety interlock.

Sometimes the light generated by cutting process is pretty bright. Never stare at a bright light. If the glow from the is uncomfortably bright, monitor the process by taking short glances instead of staring.

Fun facts about lasers

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.

Operating manual

The complete operating manual for the Dremel LC40 laser cutter is available here.