Defective methacrylate cut (dentate)

[gnumax (Luis Méndez)]

Hi,

Until yesterday I have been cutting and engraving 3mm methacrylate without problems with 60% power and 9 speed in a 60Watts laser.

Today trying to cut a box I have observed that the vectors come out jagged, that is, as if they were saws and the design sent is clean, with few nodes and well defined as you can see in the attached LightBurn capture.

The machine apparently is fine, the mirrors I think fine and the height of the cutting table the usual for this material.

Someone could tell me what I might be doing wrong?

Concerned

Thank you very much for your wise advice.

[bernd.dk (Bernd)]

… are you sure it’s not polypropylene or polyethylene ?, if you do a test in plywood or wood, the lines are just as uneven? (is it the laser that runs so strangely or is it the material that deforms when cut?)

[gnumax (Luis Méndez)]

Hi @bernd.dk

According to the manufacturer it is Acrylic (PMMA). In that same material yesterday I made cuts with the same parameters without problems.

I will try other designs and other materials to see.

Thanks for responding.

[Grumpy_Old_Man (Anthony Bolgar)]

That looks like polycarbonate the way it cut.

[gnumax (Luis Méndez)]

Hi,

I tried with another similar methacrylate (PMMA) that yesterday I cut perfect and today the circles and all the cut comes out disastrous.

From yesterday to today nothing has changed on the machine that I know of.

Dirty lenses?

Thanks for any advice you can give me.

[Hank (Hank Morgan)]

I’m going to go with “something is loose and jiggling around”.
Lens loose in holder, mirror loose on mount, carriage loose on gantry, etc.

[gnumax (Luis Méndez)]

Hi @Hank

I’ve checked mirrors (I see them a little dirty but I’m still not sure how to clean them without damaging them, sorry), I’ve tightened a couple of nuts (just in case) and I haven’t seen anything that moves.

I do not know what is “carriage loose on gantry” forgive my ignorance, I learn every day, after watching many videos and reading many threads in this forum, thanks.

[Hank (Hank Morgan)]

The gantry would be the long rail that moves in the Y direction (highlighted in green) and the carriage is the part that moves along the gantry in the X direction and has the laser head and lens attached (in blue)

[joel1 (Joel)]

I had a similar issue a while back, for me, it was a loose mirror. It was one of the first things I checked and thought all were good. Went back another day and found one.

It takes very little movement to do that. I put on latex gloves so I could touch the mirrors and try to wiggle them. My holders have a hole on the back side, so made pinching the mirrors and try to wiggle them easier.

[bernd.dk (Bernd)]

A cotton swab and some technical alcohol, that’s what I use. I do not usually disassemble my mirrors and lens.

[gnumax (Luis Méndez)]

Hi,

Thank you for your answers.

I bought a lens cleaning kit and I will take advantage of a video where it explains very well the cleaning and calibration https://youtu.be/T9p-1AZKCVg and I will perform the process to see if the lenses return to their previous state.

I’ll tell you all about it!

Thanks for your help.