Reasons for poor laser cutting

Some reasons your laser cutter might be cutting poorly, from most probable to least probable:

1. Dirty lens. Clean with care, never touch the lens with your fingers.
2. Dirty mirrors. The #3 and #2 mirrors get dirty - the #1 mirror almost never does.
3. Scratches or other flaws on mirrors and lens. Probably due to mishandling, excessive cleaning or insufficient cleaning.
4. Poor focus. For acrylic, focus onto the top surface of the material, for other materials, focus halfway through the material. Warped material or a poorly leveled bed can also cause this.
5. Bad alignment resulting in the beam clipping the edge of the nozzle tip. This causes the nozzle to get insanely hot - which is a good clue that it's happening. Running with bad alignment can trash your lens within minutes - so don't do that!
6. Poor smoke removal. Smoke in the path of the laser attenuates it. A puff of smoke should leave your machine within a couple of seconds. Your smoke extraction system should pull the smoke AWAY from the path of the laser, not towards it.
7. Mis-adjusted laser power supply delivering too little beam current. You can measure this with an ammeter - but be VERY careful - the laser power supply produces enough voltage to kill you...even when it's unplugged...and it can generate 3" long sparks!
8. Inadequate air-assist. Lack of good air-assist airflow reduces the depth of cut - and it also allows smoke to get onto the underside of the lens.
9. Ineffective water chilling resulting in the tube overheating. Did you clean out the air filters on your water chiller recently?
10. Water condensation on the lens - possibly due to air-assist issues.
11. Aging laser tube. Expect your tube to last for 3,000 to 5,000 hours of operation and to gradually degrade in power over that time.