I have been messing around today with trying to burn some patterns in paper and having some issues.
I have a pair of OD 6+ glasses so I can watch the laser and where its burning very easily.
I also have a digital readout inline on my laser so that when the PWM is sent to the laser I get a digital readout of exactly what power level its burning at.
When burning these patterns on to paper I have an issues that a lot of the lines its trying to burn do not burn at all, at these times even though the digital readout shows me that the laser is at 85% power continuously the laser dot is a light yellow looking and the second it starts actually burning it turns a very distinguishable orange.
To make it worse this will happen at what seems like random spots. So I end up with a half cut pattern.
I thought it was related to some other post I read here where the laser starts moving and before the laser can actually kick in its already moving causing the similar issue.
I do not believe this is the same issue because for example it will be cutting a 4 inch line and at the beginning it will start moving and the laser dot reflection looks yellow and it may get 1 to 2 inches in to burning the line at a speed of 500 mm/min and 85% power before all of a sudden the laser dot reflection will turn orange and start cutting right through the paper and I end up with half a line cut or less. I dont think its the laser or its controller because I have burned probably 100 ceramic tiles and they came out as expected with no missing areas that did not get burned.
I can probably do a video of what I am seeing through the OD 6+ glasses if more clarity on the issue is needed.
I am using a Neje 20W (5.5) laser.
Anyone have any idea what could be causing this?
Laser is brand new, and they tout 20,000 hrs on the one I have. Of course I doubt that is 100% true but even a 100hrs on it would not cause this problem.
In any case as usual right after I posted this I solved my own issue. It was the paper. Something to do with the white paper and certain areas had I guess a more reflective surface than other parts of the paper.
I ran the same test on a piece of red construction paper and it cut it out 100% with out any changes to my original design that failed on the white printer paper.
I am going to leave this here in the event anyone else runs across the same issue.
Is the paper white? White paper reflects most of the energy from a visible light diode laser, so it’s not uncommon at all for them to have difficulty with it.
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Yea it is white, I was testing with plain old printer paper. Weird part is it cut perfectly fine in the majority of the areas of the paper and some it would not even mark the paper at all.
Hi.
Does this missing burning happened at the lines which are near angles? If yes, that is the problem of dynamic laser power. At such angles, CNC decrease speed to change direction of laser. If CNC does not decrease speed than should happened somekind of crashes etc. However, this decrease of speed on full laser power will cause overburn. Therefore you have to check minimal “spindle” (laser) speed and play a little around this parameter. CNC calculate laser power by speed of traveling laser and max and min “spindle” speed.
Br,
No it was doing it on a straight line that was 4 inches long, first inch and a half or so would not burn then all of a sudden it would finish the line just fine. I am positive it is the paper cause every other color paper I burn it works 100%. Something funky with standard printer paper.
If you’re using a diode laser, they use visible light, which white paper reflects very well. Until the paper heats up enough to burn and change color, nothing happens. As soon as it gets hot and starts to darken, the darker color absorbs more of the light energy, and the effect cascades. Once it’s burning, it will stay burning, but until then, it’s hard to start it. That’s why it only happens on white paper.