It's time to talk safety again.  A member on one of the laser forums I follow posted this picture of there shed recently (I hope it's just there shed).  They left there laser (k40) unattended for a moment and something went terribly wrong.  Everyone is ok but they did spend some time in the hospital.

Anyway the point is that lasers and cnc machines are dangerous.  Not just in the lose your eye sort of danger but fire and plenty of other risks.  This is not something to goof around with.  You need to treat it like the scariest saw in the shop.  In fact it is far worse than that because it is automated and will continue to cut or burn long after something goes wrong.

• Always stay close to your machines when they are running. You should be able to smell the smoke, or hear the broken bit as soon as it happened.  Don't rely on a baby monitor or camera to monitor, and never leave things unattended even for a moment.
• Be wary of anything on the machine that can detach and become embedded under the laser or cutting tool.  This includes air assist nozzles. My design bolts to the laser head, I would not want to risk a friction fit.
• Don't push the machine too hard, loosing steps can lead to tools being trapped in the work.  In fact anytime the laser or cutter is in continuous contact with any object you are at a high risk for fire.
• Always wear safety gear.  A laser light can bounce off of anything and even an unfocused light can start a fire or blind you.  Your ears, eyes and mouth all need protection at all times.
• Don't ever power up the laser when it is just resting on the table.  It is too easy to accidentally bump it and have it spin around.  The laser should be well secured at all times.
• Make sure your machine is properly maintained with all cables tied up and everything well secured.

Safety is no joke.  You need to use your brains when building this machine.  It is not my job or anyone elses to keep you safe, that falls squarely on your shoulders.  And it goes without saying but my instructions above are only a guide to how I build my machine, I am not responsible for any harm you may cause to yourself, others, or your property.  Keep safe!