How to configure PWM?
I finally got my K40 laser up and running and have been trying to cut 3mm acrylic and after multiple passes, it still does not go all the way through in a single pass even at 100% power through LightBurn. My ma gauge reads 16-17ma at 100% power and ~12ma at 75%. I even removed the POT to see if that was the issue and the reading is still the same 🙁
Please help!
TIA for taking the time to read and comment on my post.
The max power of a K40 is about 15 to 19 mA depending on weather and laser tube water cooling temperature. Max power goes down with higher temperature. So I think your laser is working as it should, however I suspect that you have either the focus incorrectly set or the travel speed set to fast.
On my K40, typical settings for 3 mm clear acrylic are 90% power and ~5 to 7 mm/sec travel. In gerbil that would be a power setting of ~230 (max 255) and speed setting of 300 mm/min. These settings are not optimized but should cut 3 mm clear acrylic in a single pass. If this doesn't work for you make sure you have the focus set correctly.
Colored acrylic settings will be slightly different. Black takes a bit less and orange or yellow transparent acrylic a bit more.
Another possibility is the mirrors are not aligned correctly, but if you are seeing the material doing some cutting, it is probably okay. Just make sure your beam is in the middle of the final mirror, and not just catching an edge.
Hope this helps.
Speeds are very slow. I have been running at 180-300mm/min at 75% and need 2-3 passes to cut through 3mm acrylic. I have tried black and clear and the black needed the 1 extra pass to cut through. I have taken the K40 apart and made sure everything is square and level as much as possible. I DID notice there is a dark spot on my 1st mirror but not sure if that is the issue or not as they are new :/ I run a makerspace so most things currently seem to be coming out of pocket. ????
Have you checked your focus? If you try to cut a piece of cardboard (say from a cereal box), does the cut kerf appear very narrow?
You can use a slightly tapered piece of wood placed on your deck and run a cut down the length of it. Use say 30% power and 600 mm/min speed. You are not trying to actually cut the wedge, just mark it. The point of the cut with the narrowest kerf is the best focus. Adjust your material so that the top of it is at this distance from the bed. When you look at your wood wedge you should see the kerf go from wide, to narrow, then wide again. Note, focusing at the top of the material is not necessarily the best for maximum penetration, but for 3 mm acrylic and similar materials, it should be fine.
On my machine, I have installed a perforated steel sheet on the spacers that held the original deck/clamp. On top of that I use 1/4" magnets (~6mm) then place my material. Luckily, this puts the material in pretty good focus. On the material I use additional magnets to mate with the ones holding up the material to keep the material in place. The magnets also place the material above the deck so that material can drop down when it is cut. Also, it helps minimize artifacts on the back side of the material.
BWT, do you have an air assist? If not, you should explore getting one. It minimizes fire, keeps your lens cleaner, and gives you better and deeper cuts. The nozzle should be just above the material for best results.
Good luck.