The laser is making strange things (for me)

Community Laser Talk
1

Hello,
I’m using a Ruida-based laser cutter, and I’m consistently getting dimensional inaccuracies when cutting box outlines (e.g. cardboard packaging). The weird part is that it’s always the same deviation pattern, regardless of the file I use.
My machine working area is (X)1250 x (Y)2500mm
The problem is mostly on Y.

For example, I have a rectangular shape with the following expected side lengths:

  • Side 1: 102 mm → cuts correctly
  • Side 2: 104 mm → gets cut as 105 mm (+1 mm)
  • Side 3: 102 mm → cuts correctly
  • Side 4: 104 mm → gets cut as 103 mm (−1 mm)

So sides 1 and 3 are correct, but 2 and 4 are consistently off, and always in the same way across multiple different files. This tells me it’s not a mechanical issue (like backlash or slop), because in that case the errors would appear randomly depending on the direction or the geometry.

2

When I look into the crystal ball :smirk:, I see a mechanical error, take a look here:

3

Тhank you for reply.
But why does it do it on the same principle on different files? I even did tests on different ends of the machine - the situation is the same. If it’s a mechanical problem, wouldn’t it do it in different places - unevenly?

I forgot to mention that I am cutting at low speed (2mm/s).

4

The sizes you list strongly suggest a mechanical problem in the axis parallel to the 104 mm sides, so the motion is too long in one direction and too short in the other. The machinery is pushed to one side by the travel move to the start of the previous (perpendicular) side, then affects the motion along the parallel axis.

The loose part(s) may be in the laser head, rather than the drive train. Look for loose screws, stripped threads, and wobbly optics.

The visible symptoms depend on the path taken to the current point and the speeds / accelerations along that path, so they may appear random, but they’re surprisingly deterministic.

Another possibility is a beam problem due to:

  • A failing tube producing a non-uniform beam
  • Dirty / damaged mirrors or focus lens
  • Laser head misalignment

Scale this test pattern to fill the platform, lay down a sheet of cardboard, set the speed as high as it’ll go with the power set to mark the cardboard, and run it:

GrundTest.lbrn2

Any differences between the intended path and the actual results will help diagnose the problem. Upload good pictures of the results to let us look over your shoulder.

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5

I don’t know if I explained the problem correctly.
I’m attaching a simple picture so you can get an idea of ​​the machine and what I mean.

14959bd91a2cc10b742f5e07aa964edf37545650-02
14959bd91a2cc10b742f5e07aa964edf37545650-021522×1437 135 KB

1 Like
6

That picture definitely helps.

Running the test pattern I suggested and showing a picture of the result will add more evidence and move the diagnosis toward the goal.

1 Like