Weird laser cutting issue (not cutting properly)

[Dan Hintz]

I'm with you, Richard. This suggestion may be a holdover to other equipment such as lathes where leveling the entire system is done to prevent twist in the ways, etc. On larger machines this may still be a good idea, but on smaller systems it's really not that critical. Make sure the bed is level with the carriage on a grid of points on the table and be done with it.

[Richard Rumancik]

. . . Richard, I used the laser level to first level the gantry on both X and Y axis and then leveled the table.. Ill grab a dail micrometer and atache it to the head of the laser at some point and check to make sure the work surface doesnt vary from the gantry (just like tramming a mill I guess) I know one of the problems is the poor quality of the honeycomb table.. Now I just need to find a better solution to that and it should all be good. . .

Phil: Well, if that's the case, then what you are doing is not wrong; I'm just surprised that there is a vertical adjustment on your gantry/rails. I have never felt it mattered if the gantry was running at a slight angle. Whatever the angle actually is, I just want my table to follow suit.

I suppose I am just accustomed to the "conventional" systems with rails secured tight to the frame. I would not really think of trying to adjust (shim) them on mine.

I will admit that a larger frame could twist as Dan suggests; in such a case I would probably shim the offending wheels (or use the screw levellers if supplied) and make it permanently immobile like a machine tool.

[Rodne Gold]

If the table is out with respect to the head/lens plane , the easiest fix is to cut a nice flat sheet of 3 or 5mm anodised aluminium and shim it up atop the original table.
Honeycombs are a big problem in respect of maintaining exact focus , over time they sag and often the frames are out
When focus is critical , I would rather use the table and use blocks to elevate when and if cutting. The anodising of the ally (even when the table is true , we still use a thin sheet atop the table) actually sort of acts as a backstop to stop any flashback. If you use black , its easy to make templates , cos all you do is run the outline of the object and it comes out white..
Of course there are times when you HAVE to use the honeycomb ..but we try avoid it if we can..

[Richard Rumancik]

Rodne, you are right about honeycomb; by its nature it has no torsional strength and a simple aluminum frame won't hold it from twisting. And it is easy for it to get a sag or bulge in the center.

I haven't actually used my factory honeycomb for some time - what I use is an aluminum grid that I picked up surplus - I think it was some kind of grille for HVAC (heating/ventillating). Although it is more rugged than honeycomb it will still twist. I used it on a wooden frame clamped to the tabletop. I lose z-clearance but I don't need much clearance for sheet. The wooden frame has rail supports for the grid along two edges with 4 jackscrews for quick leveling of a job with a screwdriver.

[Phil Horne]

All is good!!! I cut a templet today with the same settings I was using the other day and it cut just fine!

[Wes Moore]

I have had this happen several times. A couple of things that I identified
follow:

1 The material was near the maximum thickness that the laser could cut.
When starting first run the laser has enough power to punch through but
as it warms the output power decreases and is unable to cut all the away
through on a single pass.

2 Cleanliness is next to perfect work. If cutting material near the speced
maximum thickness and my lenses/mirrors have any leftover smoke from a
previous cut then this sort of thing will happen.

YMMV and this may not be your problem, but these two items have bitten
me a couple of time. Hope this helps.

[Richard Rumancik]

All is good!!! I cut a templet today with the same settings I was using the other day and it cut just fine!

So what did you do differently, or what do you attribute the problem to?