Ok, background - 60w Chinesium laser. First 12m of life all it did was engrave. Started using it to cut ply and MDF.
3mm Birch Ply - 10mm/s, 62.5% power
4mm MDF - 7.5mm/s, 67.5% power
These settings worked for ages. Then, after moving the laser, they didn’t. I think it had a knock, and after much deliberation I figured mirror 2 was slightly out and mirror 3 was also out. Cut like a champ again, but slowly and surely this has seemed to fade. I have put this down to a few things, firstly maybe material… secondly maybe humidity and temp, thirdly maybe premature tube failure.
But, then I run a test card. And my 4mm MDF cuts at 10mm/s - 40% power! A fluke, so I try it again, no issue, then I do some text at 10/40 and it cuts…
So - is it possible to be using TOO much power?
Is this a thing? I’m going to be testing and working on this further tomorrow when my new mirrors arrive, but I’d like to know - is it possible that too much power = fail?
That is very slow…
The Ruida controller has a ‘start speed’ for each axes. In the machine settings…
At or below the start speed you will only get minimum power…
Didn’t mention min power.
I didn’t - I knew I would forget an important bit of info!
I used to set min power 5-10% lower than max but the results above are the same even with the max set to the same power level.
Sure. You are ‘machining’ a part, the cutting tool being the laser beam. How fast a tool cuts and how well is related to power/speed. There is a sweet spot.
But, I don’t think that’s the issue here…
What’s the difference between the test card and the artwork?
Well, none, as even cutting a circle, square, hexagon at 70%+ seems to just burn and burn more and more… then when I ran the circle at 40% it cut through.
I used to be a metal worker and we had the phenomenon known as work hardening, and it made me think - Before I tested more tomorrow I just wondered if there was a known issue mainly with say Medite MDF, does too much power cause glue bonding or charring rather than cutting? My assumption was that if 40% cuts then 100% also cuts…
It is important that you know your laser setup precisely. The CO2 laser power curve is not linear and the effect actually drops at approx. 70%
The question you mention, about too much power, I have only observed with acrylic. But here the material welds together again due to too high a temperature and/or typically too slow a cut.
MDF and HDF do not have this property, too high laser power just brings more temperature into the material around the cut, with charring as a result.
With my 60Watt tube I use 20mm/s x 55%(14mA) for 3.6mm MDF and 27.5mm/s x 50%(13mA). I work a lot with MDF and HDF and find that these values suit my tube best. Over time, however, the values must be checked again as the tube becomes weaker.
Other thing to consider when you are cutting, is that not all material is created equal. If one sheet cuts at a particular speed and power, another may not due to the glue content and other unknowns.
@HalfNormal, it’s correct what you say, but @cninja is a bit too far from the appropriate settings in my opinion (if, his tube and focus are ok)
To avoid the problem you mention, I make a new setting test from each new delivery. In my experience and with my supplier, I don’t have much variety with MDF and HDF, but actually more with plywood.
It should cut in both instances.
Anyone that’s used a table saw knows you best cut is between where it burns and where it gouges out material. You can feel it as you push the material through.
Can you cut it slower (slower feed), sure, but it will generate excessive heat, resulting in burning of the tool or saw blade and wood… you shove it through fast, it will take large chunks out and damage the nearby wood.
Somewhere in that range of power/feed is the ‘right’ ‘settings’ for your laser and that material. I have a microscope which is very enlightening when you look at the damage.
I can tell you this about your problem, assuming you haven’t bent the frame …
- laser tube is functioning properly
- optical path is clean and properly aligned, including m3.
- it is properly focused
If you have these three, they work… you need to determine which of these are missing in your machines operation.
This needs to be checked with the actual co2 beam. Don’t know if I asked or was stated, but how are you checking the alignment?
I have checked the alignment recently using tape, mirror 2 and 3 needed adjusting as it was hitting the cone slightly. The difference there was huge and instant. I have also checked where the beam is exiting the cone and it is dead centre at all points. I have noticed a slight crack in Mirror 2 and will be replacing that shortly, the crack is on the very outer edge though and I dont think that it is causing too much issue, although it may be why I had to re-align M2 and M3.
After reading responses, I did some testing and essentially running at a lower power, and slightly faster speed has helped. Items are less charred.
3mm Birch Ply, 30% Power - 15mm/s
4mm MDF, 35% Power - 10mm/s
I have spent so much time running at a higher, what seems unnecessary power level, and had serious inconsistency in cuts, with issues having a clean drop out for so long, this seems like a revelation!
My thought process previously was - “this job has to be perfect - add more power!” and in 9/10 cases it was not cutting through. This post has been informational for me guys, thank you for your help.
I will continue to test and hopefully improve once I get my mirrors replaced. Am I best to replace all 3 do you think? I have 3x Si mirrors ready to go but it looks as tho the ones in the machine are MO, can I mix/match?
I am glad that you are on the right track.
I don’t think it’s a problem to mix the mirrors and I only change the mirrors and lenses that need to be changed, i.e. are either broken or can no longer be cleaned perfectly.