Cut is not 90 degrees to the surface of material

[Mayo Pardo]

I'm just making some Halloween decorations trying to learn the machine and any adjustments to mirrors are probably not dialed in. I'm not even sure this problem is a mirror alignment problem.
Maybe it's a focus problem? The acrylic cut pretty good with nice polished edges. If anything it may have been just a bit too hot.

I cut a small acrylic piece that is going to fit into a slot on another piece of acrylic so that it stands vertically. When I insert the piece into the slot, it's a snug fit and there is no slop or play however the piece which should be straight up (90 degrees) is on an angle.

The acrylic I cut was about 0.097 inch in thickness.
The angle of the piece is about 8 or 9 degrees away from 90. On thicker material this would be more of a problem.

The slot was cut going in the Y direction on an oval shaped piece and unfortunately I don't know if the cuts are angled to the X positive direction or the X negative direction.
My red dot pointer shows up where I expect it to at 0,0 when I start out. But I do notice it doesn't stay at that spot when the bed is lowered.

Could the bed itself be out of alignment? It seems to move smoothly with no grinding or hesitation.

Is there a default test pattern that Trotec has built into the machine for checking and adjusting this angled cut problem? I'm planning on calling tech support on Monday but thought I'd ask here first. The Job Control ver. 9.4.2.7 manual and the Speedy 300 machine manual doesn't go into this.

[matthew knott]

Sounds like the laser is not aligned through you cutting lens correctly, you need to go through an alignment procedure, especially the cutting nozzle part.

[Joe Pelonio]

That's normal, the "shape" of the beam from a CO2 laser is hourglass, with the hottest spot being the narrow center. This results in the angled cut and yes, it's worse on thicker material. For the kind of job you are doing it can be frustrating, because for precision fits you must run it through a router or sander to get the edge perpendicular. I have fabricated without "fixing" the edge using the Weldon cement which actually melts the acrylic but have to use a miniature framing square to true-up each piece while it sets.

[Mayo Pardo]

I understand the concept of the hourglass causing a variation but if a rectangular slot is cut, wouldn't you then expect the opposite sides to have different (opposite) angles? Wouldn't this have a cancelling out effect as far as the slant is concerned? This is not the case on my cut pieces. For reference, this is only 2.75" tall.

Acrylic1.jpg Acrylic2.jpg

[matthew knott]

Fire the laser into a thickish block of clear acrylic , you should get a nice parallel hole, if it look at an angle then is defiantly your cutting lens alignment !

[Michael Hunter]

Fairly easy way to check and roughly adjust the beam alignment :

Bring the table up to the focus position and mark where the red do hits the table.
Now take the table down to its lowest position - how far is the red dot from the mark that you made?

By adjusting the mirror(s), you can get the beam to hit the centre of the lens and then the red dot won't wander off.
It may take several incremental adjustments to get the alignment right with this method.

Note that this depends on the red dot itself being accurately aligned to the laser beam. On my machine the dot is off slightly, but I have learnt where it should hit the lens.

[Mike Null]

Mayo

I agree that you need to align your mirrors to get a more vertical cut. I doubt that you'll ever get to a real perpendicular though.

when you do that you'll probably find that your engraving quality improves as well.