Sculpfun S9 (upgraded to 10W) appears to loose power after engraving


usually my machine cuts 3mm MDF at 600mm/min and 85% in 3 passes without any problems. Yesterday I had a bit larger project going on that involded first engraving some pictures and then cutting them out from MDF. The engraving was running for about 4 hours at 2000mm/min and 50%. After that the cutting did not work anymore with the settings mentioned at the beginning. Just for fun I tested how many passes I would need and ended up with 14(!) passes. This morning I tried again and was able to cut in 3 passes again.

Can this be a kind of overheating effect due to the long engraving time? Any ideas are welcome :slight_smile:

Best, Ben

diode laser output power is very temperature dependent. See, for example:

Moreover, laser life is significantly shortened when working at higher temperatures.
(different diodes, but same principle).
IMO high power diode laser heads should be water cooled for proper operation, but then they would be too expensive and cumbersome for practical use.


thanks a lot for the information. So overheating is an option. The question then is if my experience is common behaviour of laser cutters so it would be normal to wait for a certain time between engraving and cutting. I have never read something like this to be honest

Best, Ben

AFAIK, this is the normal behavior. With constant current (or, roughly, constant electrical power), the optical output decreases as the diode temperature increases and viceversa. Starting at ambient temperature, the laser will get warmer while working, and its optical power will decrease accordingly - until it will (hopefully) come to a point of equilibrium. Anyway, the laser efficiency will degrade with time, so it will cut less than before. The degradation rate will grow dramatically when approaching the maximum operating temperature (say, 60-65 deg. C on the diode case).

I have had a problem similar to this too. To solve the problem, I installed a PC power supply to power the laser machine. I am cutting 1/4" oak and it was taking 12 passes. Then it was starting to take more passes to cut through. Once the PC power supply was installed, it now takes me 7 passes to cut through the wood. I would highly recommend getting a better power supply for your machine. Also, make sure you have a air supply on the nozzle to help keep the laser lens clean.

My 2 cents worth after all that engraving your lens is going to be smoky no matter how good your air assist is. After about 2 cuts plus a little engraving taking 1/2 an hour each the cutting was not cutting all the way though so I cleaned the lens and cutting back to normal…3mm MDF 250/85 x 2 passes.
So now I clean before a cut every time, a hassle I know but bigger hassles if you don’t…

Have fun Merlin…

In 90% of the cases, the lens is not clean anymore. This is very crucial, and it should be cleaned regularly. Here is a guide on how to: Guide to mechanical adjustments and maintenance
As the others mentioned, power supply could also be the reason as well as corrupted firmware settings (all are mentioned in the article).
If you use an air assist, it is also essential not to put the pump into the housing / close to the laser. It should never suck in dirty air.

I have cleaned the lens a couple of times with a Q-Tip and Isoprop but no improvement. I also had the idea of changing the power supply as I had a spare PC power supply around but that does not fix the issue as well. Then I had another look at the lens. This time I have removed the construction where the lens is in so I could investigate it against a light source. It turned out that I had for some reason some kind of moisture on the inside/backside of the lens that was of course not removed with doing a quick clean.

I will investigate this a bit further. I also ordered a couple of replacement lenses. Also I can acknowledge that the lens gets dirty very very fast. I have air assist installed using a Aqua Forte V-60 pump that is active only while cutting.

Ben just my 2 cents for what it’s worth, run your Air Assist while engraving as well as cutting the amount of smoke I get from engraving is bad on my lens…

Short update: I got the replacement lenses yesterday and now the cutting performance is almost back to normal. Only almost as my piece of MDF I used for testing takes 1-2 passes more than used to but that may be the air humidity it was exposed to the last 2 weeks.

Regarding running the Air Assist wihle engraving as well: I used to normally read the recommendation to leave it off due to quality issues of the engraving result. I never compared it myself but I will do so.

EDIT: I did the test: having Air Assist on while engraving (right) makes a huge difference regarding quality.

But I really like the idea of Air Assist possibly helping to keep the lens a bit cleaner. Is this a situation where a adjustable air pump would be beneficial? I always wondered what the advantage would be of using a adjustable one…

Best, Ben