Laser cutting at an angle?

[Brett Winston]

It is very easy to test if the beam is at an angle. Fire the laser to make a dot on some thermal paper (like what receipts are typically made of) that is taped down to the table, then without moving the laser head lower the table as far as you can and fire the laser again. If the dot is centered within the darkened ring made by the second firing then the beam is perpendicular to the table, if not then it is angled.

I used this method (with plain copier paper - all I had) and was able to see the problem. Thank you! I leveled the tube and realigned the mirrors and am getting a straighter cut. Not perfect but better. One issue that is consistent is the beam location when hitting mirror 3. When the head is at the furthest x and y location I have to adjust mirror 2 down to meet the mark made at x=0. It appears this is working at mid-table but is off a bit when returned to x=0. Not sure how to compensate for this.

[Richard DiMaggio]

I have had this problem before too. I built my own system and found that when the beam is not hitting the focus lens in the middle, it would cause it to deflect at an angle. If your X/Y relationship is not 90 degrees, the beam will move across the focus lens as the distances between the mirrors changes too. 2 cents.

[Joseph Shawa]

In my case X/Y was right on in all locations right up to the head where it would enter perfectly horizontally and hit mirror 3.
If the beam lever was at the center of mirror 3 it would not be centered in the tube and lens so would get cut off at the cone.
If the beam was raised so that it would hit the center of mirror 3 then it would get cut off by the head BEFORE it even hit mirror 3. Just bad design of the head or maybe made for a smaller beam. My machine came with a 60 W tube and I replaced it with 150 W.

By machining the top of the entry hole into the head the beam could hit high on mirror 3 and be reflected nearer to the center of tube. Cuts great now. I might have kept the 60 W because I think most of my power issues were due to power loss at the cone tip and I didn't know that I should hit mirror 3 high. Live and learn.