At my local hackerspace, we have an older K40 laser. The electronics have been replaced with an AWC608, and the 18mm Air Assist head, both from LightObjects. LaserCad, of course, is the software we’re having to use, and it’s not the greatest.
The laser tube, mirrors, and lens have all been replaced, and recently one of our members figured out the bed was too high, and the focal point of the laser was wrong. It’s been re-aligned several times, as well. This improved things, but the K40 is still not performing anywhere close to what I see in this group.
Example: I cut some 3mm cedar planking today. Did some etching, and cut out some circles. At 75mm/s, at 80% power, it took 3 passes.
I then attempted to cut some 3mm acrylic. It took 6+ passes, starting at 75 / 80% and going all the way to 8 / 95%. And it still didn’t cut all the way through. We drastically lose power at the front right corner of the bed.
What can we do to fix this? From what I’m seeing in the group, I should be able to cut 3mm plywood at far lower power in a single pass, and acrylic should be even easier?
it’s important everything is square. it’s not the laser setting (mirrors) to correct frame/bed twist. position of the unit on the table resting straight flat.
laser alignement should be one the same plane (no vertical compensation) tube mirror1 mirror2
the working bed should be parallel to the plane and at focus height
Power issue:
4) clean lens and 3 mirrors (also check tube output)
5) check if head’s lens is well orientated.
75mm/s may be the reason you’re having to do multiple passes on the 3mm wood. On my end, cutting 3mm ply takes about 10mA power (~40% of full potential) @ 10mm/s @ 3 passes. Albeit, my settings may be off a bit & could probably do with a realignment sometime in the near future. But 75mm/s definitely seems fast (in my opinion) to be able to cut anything in one pass.
In addition to the above suggestions; I recently worked with a user whose objective lens was installed incorrectly in the LO air assist head was crooked and loose. The lens mounts inside the threaded ring and may need a spacer ring to hold it in place.
Its not unusual especially if your laser is not parallel to the gantry for the beam going through the LO head to hit the inside of the small exit hole. Take it apart and check lens fit, stability and look closely for scoring from the laser on the side walls.
You can quickly check for this condition by tape-ing a target to the bed, firing and lowering the bed. If the spot moves position it may be that the beam is not exiting the last mirror perpendicular to the bed. BTW it assumes that when you lower the bed, the bed itself is not moving out of position.
The bed in our K40 is a fixed one - to change the Z it involved making new spacers. An adjustable Z is on the list of things I’d like to add. I’ll take a look at all the things suggested, and see if that helps.
@Noel_Bundy another way to check to insure the beam is not interposed with the body of the LO assist cowling is to shoot a target, with and without the cowling installed and look for differences.
Indications might be:
…More than one spot (reflection)
…Change in size or shape
…Reduction in apparent power
To the OP. I believe the speed is too fast. 5mm ply on mine is… 8ma, 2 passes at 300mm/min. Like I mentioned before on this group, I believe the key is to find what is the slowest speed you can cut without flare ups, and then work from there and up. And the first pass always needs to be slower than the second pass, and not the other way around.
The 75/80% thing was because someone had written it down, and I was testing. Usually for cuts I do 8mm at 95%, and it still takes 2 or more passes. I think I need to dedicate an evening to working with the cutter, just to see if I can get it tuned better. Doesn’t help that lasercad at times will take 45+ minutes to upload a file. Probably a network thing.
I really want to switch the printer over to using laserweb, but that’s after I get the rest of it working properly
The person who broke it took responsibility, and they did have good intentions, I’m just a bit tired of working with something that could be so much better. So I’ll get my own K40, and start modding it as I go. I have an ArduinoCNC board kicking around, so that’ll get me started with a GRBL-based system. And as soon as I can afford it, I’ll get the Cohesion3D board. The nice thing is that I have 3D printers, so I can easily fab parts I need. I just gotta sort out funding - it’s a bit expensive being in Canada, and converting to Metric Dollars makes things a lot more pricy.
I think I need to dedicate an evening to working with the cutter, just to see if I can get it tuned better. Doesn’t help that lasercad at times will take 45+ minutes to upload a file. Probably a network thing.
I just gotta sort out funding - it’s a bit expensive being in Canada, and converting to Metric Dollars makes things a lot more pricy.