I work at a summer camp, and we are cutting laser projects for the kids to put together. During work hours 9-5, I have the CNC with the laser running almost constantly. I am cutting tempered hardboard 3mm, which I have found usually cuts well at 100% power, 40 IPM. There is always a slight inconsistency between each sheet of material, so during the beginning of each job I adjust the feed rate plus or minus 3%. I’ve been running it like this for the past 2 weeks with no issues, however, day to day I’ve noticed inconsistency between the feed rate that is required to cut through the material. Today, I’ve had to run all the jobs at 80% feed rate to get the same results as I was yesterday at 106% feed rate. I have a 3 phase air dryer setup, and I am cleaning the laser lens as soon as there is any sign of charring or a wider than normal kerf. This morning there was a significant amount of charring around the laser cuts, so I cleaned the lens, and now there is no charring and the laser cuts look like they are back to normal but I am running jobs at only 80% IPM of what I am used to.
Is it normal to need to run the laser at different feed rates day to day?
Is laser meant to be run 8 hours a day every day?
Am I supposed to be doing some kind of maintenance on the laser that I am missing?
You shouldn’t get inconsistency from day to day. The biggest factors I’ve noticed are #1 to make sure you get a consistent, optimized focus height setting, #2, make sure the lens stays clean, #3 correct airflow (which will also determine if your lenses stay clean very long), and then material variation (hardboard can be pretty different sheet to sheet due to the glue content and other processing factors). And make sure your air nozzle is never misaligned or on too far as to block some of the beam.
When the laser is at 100%, the PWM signal is just “on” all the time, so there isn’t anything to vary there. Yes, that laser should last a long time and can run all day long. If it does degrade, it will stay degraded (i.e. a diode may burn out, but it won’t just start working the next day).
I generally don’t run my feed rate to the hairy edge when cutting because I hate it when little pieces hang on and don’t cut off clean, so I usually run a little slower just to make sure I always cut through, but then I’m not running through that much material like you, so I can afford to run a little slower just so I always get more consistency, so I probably wouldn’t notice the variation as much as you.