Difference between revisions of "Laser cutter safe operating procedure"

Revision as of 15:12, 27 September 2019

General safety

• 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.
• 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.

The rules

1. Never cut an unidentified on unapproved material.
2. Clean the cutter's workspace before you load your stock. Debris from previous operations can cause or accelerate a fire.
3. Ensure that the area around the laser cutter is free of clutter.
4. Ensure that the exhaust damper is open before you start your job.

• • Things will get stinky fast if the exhaust is closed.
  • Notify an instructor if you notice anything wrong with the exhaust system.

1. Ensure that the lens is clean.

• • If the lens needs cleaning, notify an instructor.

1. You must 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.
  • It is possible for a fire to start no matter how careful you are, and regardless of what material you are cutting.
  • There are no exceptions to this rule. Violating this rule will result in the severest of sanctions.
  • Plan ahead. The cutter calculates and displays the duration of each job. If you cannot stay until the job finishes, don't start it.

1. Never attempt to defeat the machine's safety interlocks.
2. After your cut completes, wait for the smoke to clear from the workspace before lifting the lid.
3. Clean offcuts and debris from the workspace after the operation finishes.

Rule number 6 is paramount for the following reason: small fires are trivial to handle. Large fires are not. This is the reason why it is imperative to monitor the entire cutting operation: a large fire is a small fire plus time. If a fire starts, do not panic. Act promptly. Take action while it is small. A candle-sized flame is normal when cutting materials such as acrylic. If a sustained flame larger than a candle flame develops, stop a large fire from developing as directed below. A fire requires fuel, heat and oxygen. Removing any one of these ingredients will stop a fire.

If a fire breaks out:

1. Remove the heat source: press the STOP button on the LCD control panel.
2. Reduce the oxygen supply: close the exhaust damper.

• • The exhaust system will "fan the flames" of a self-sustaining fire.

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.

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 and lots of cut lines close together.
• Cutting is more likely to start a fire than engraving.

Always alert the instructor on duty if a fire starts. An instructor will help rectify the problem that caused the fire by changing some combination material, cutting parameters, or program.

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.