Help me riddle this, alignment issues

Community Laser Talk
1

Couple of days ago i successfully aligned the mirrors from scratch, or so i thought. Russ’s methods were used.

Went to cut something big today (900x600 bed) and noticed bad cuts in one corner.

Recheck:
Mirror 1 to 2 beam is dead center and parallel with Y motion.
Mirror 2 to 3 beam is also dead center and parallel to X motion on far end.
However, if i move Y all the way back my beam is HIGH ? How ?

If i turn mirror down where its high, its going to be low on near end.

Doing my head in.

Y rails not parallel to each other ? Spot on on near end, low on far end ?

Am i making sense ?

2

Have you measured the height from bed to laser head and/or focus lens at all 4 corners? it seem your laser bed plane is not parallel to gantry x/y plane.

3

Yes i have, all good. Thats why its a riddle.
Its not the focus distance that changes, its beam veering off in ONE corner.

I cant turn mirrors, as if i do it will be low on the other end.

According the Russ method, my tube is parallel to X at one Y end (far from tube) and not parallel at near end (away from tube).

aiming
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4

So it looks like the back end of the right hand Y rail is a little low and needs shimming or some other form of adjustment.

1 Like
5

Thanks for confirmation that i’m not crazy. Moved back of rail up - problem gone without touching mirrors. Brilliant. Learned someting new, thanks.

6

Now that the rails are level with each other you should check the distance from the nozzle to the bed in all 4 corners and center to make sure your focus distance doesn’t vary across the table.

7

Thats the idea. However i’m in a process of ordering flat steel table cut as i cannot trust honeycomb with this one bit. I always had trouble with focusing properly throughout the size of my HC.

Nozzle to table subframe seems to be ok, but honeycomb over it - focus is all over the place. Not sure how to “level” honeycomb for it to be consistent at all places. Ideas ?

8
9

Its not the corners that are the problem, its bits in between. I can measure well on subframe, but honeycomb is -~2mm at places.

10

Yeah, my honeycomb is amazingly un-flat. I have a special place for it leaning up against a wall where it can do no harm. I hate the thing.

11

Immediate use now is PETG cutting. Its thin, its floppy - honeycomb is a must.
In near future i expect to cut leather, which is also asking for honeycomb use.
Just trying to figure out how to flatten it properly.

But yeah, i see how people dont like honeycomb. Havent got enough experience lasering to rant on about that yet. Just trying to make damn thing flat. :smiley:

12

Well if you find a good technique for flattening the thing let me know.
About the only thing I use it for now is the occasional rubber stamp. The stamps usually only cover a few square inches so “flat” doesn’t matter much.

13

When i had to cut a rolled rubber sheet I used a double sided tape and sticked it flat on a 4mm poplar plywood.

14

Curious about your shimming method. I have the same problem with drifting spot and I’m sure I need to raise my right rail to create a plane. What material/ technique did you use to get it right at every single screw hole along the rail?