ULS Versal VL200 acrylic boxs

[Darin Drossel]

I am looking for a little help with my laser. I recently purchased a VL200 and finally have it setup. I am trying to make some acrylic boxes with tabs and want it to be a friction fit.
I have tried a few different programs for creating the boxes and wasted a small pile of acrylic. I just can't get the joints tight enough. I have done all the basics and tried different cut with setting/kerf settings. I manually focus to the material.

Any insight is greatly appreciated.

[Kev Williams]

I'm assuming you're mating tabs to tabs?

Part of your problem may be that your cuts aren't perfectly vertical due to light refraction, and/or the beam may not be firing perfectly straight. Still, you should be able to get a snug fit--

Do you know how to use Corel's contour tool? If so, and assuming your original vector art is actual size, you should take your art sections and run an outside contour of the original @ plus .002", this will add .004" inch overall to the perimeter of the cut, which is roughly the width of your laser's beam. If your actual beam width is wider or your cuts have 'straight' issues, the tabs may still be too loose. If so, then re-run the contour @ plus .003", which will compensate for .006" of beam width...keep this up until you're just right, or too tight--

If too tight, be aware that you can enter to 4 decimals in Corel, as in .0025", for fine-tuning. Corel will display .003", but it WILL use your actual entry measurement.

Use cardboard or posterboard, etc, to do test fitting before chewing thru more plastic

[Scott Shepherd]

Good luck with every making friction fits on acrylic. Acrylic sheet has a thickness tolerance of about 10%. It not only varies from sheet to sheet, but it varies a lot across the sheet. I've seen a .010" of an inch difference over 1 ft of 1/8" thick acrylic. I've seen the specs from the manufacturers. It's very loose. Friction fitting might work for one box, if you measure carefully, but it's not possible to do production with it.

[Lee DeRaud]

I manually focus to the material.

That may be part of your problem: are you sure your manual focus tool is properly set? They have a setscrew that holds the base to the post so the post height can be adjusted. Mine is 1.90" from the base to the middle of the registration bevel.

That said, I'd trust the autofocus unless there's a reason you think it's out of calibration...and if it is out of calibration, stop everything until that gets done.

1/8" acrylic is too flimsy to support friction-fit joints in any case, just too easy to break the tabs during assembly if they're tight enough to hold. Otherwise, Kev's suggestions will do the trick for 1/4", and you can use 1/4" MDF to practice with.

[Lee DeRaud]

If too tight, be aware that you can enter to 4 decimals in Corel, as in .0025", for fine-tuning. Corel will display .003", but it WILL use your actual entry measurement.

The display precision can be set to 4 or 5 places, no problem, at least in any version newer than 11. It's under Tools/Options/Workspace/Edit -> Drawing Precision. (Yes, that's really the display precision: Corel uses floating-point internally.)

[Kev Williams]

Thanks for that Lee, now I'm down to only 4,322 things I don't know about Corel!

--I wonder if EZcad has that option, it's a PITB to tweak the size parameters when the mm displays only to 2 decimal points (but accepts to 3...)

[Lee DeRaud]

Good luck with every making friction fits on acrylic. Acrylic sheet has a thickness tolerance of about 10%. It not only varies from sheet to sheet, but it varies a lot across the sheet. I've seen a .010" of an inch difference over 1 ft of 1/8" thick acrylic. I've seen the specs from the manufacturers. It's very loose. Friction fitting might work for one box, if you measure carefully, but it's not possible to do production with it.

(scratches head) I'm not clear what thickness variation has to do with friction fit of a laser-cut tab in a laser-cut slot, since both of those are in the plane of the sheet.

[Scott Shepherd]

(scratches head) I'm not clear what thickness variation has to do with friction fit of a laser-cut tab in a laser-cut slot, since both of those are in the plane of the sheet.

Depends what you mean by friction fit. If you have a sheet of acrylic that varies .010" across a 8" sheet and it's ranging from .112-.122, what size slot are you going to cut? Trust me, I've been cutting a lot of acrylic for a long time and I've been through the whole "friction fit" acrylic request so many times I can't count them all. I had a customer that wanted to make a T shaped divider for a product one time. Just cutting a slot in 2 pieces and slipped them together to make a T, like you'd see in a cardboard box divider. After explaining it to them about 5 times, I finally shrugged my shoulders and cut them. When they went to use them, they said "Hey, some of these are loose and some are tight". I said "Remember the multiple discussions we had about acrylic sheet varying in thickness?". They said "Yes". I said "that's why I told you this wouldn't work. What you are complaining about is exactly what I told you was going to happen".

[Lee DeRaud]

Depends what you mean by friction fit.

For the purposes of this thread (i.e. boxes), I mean finger joints. Like I said, in that situation, the critical dimensions are both dependent on the laser cuts, not the material thickness.

And yes, I'm familiar with the problems of cross-slot T-fittings: I'm the guy who posted the macro that would go through a drawing and adjust all the slots for a desired material thickness. Trust me, you're not the only one here who's been cutting a lot of acrylic for a long time.

[Scott Shepherd]

For the purposes of this thread (i.e. boxes), I mean finger joints. Like I said, in that situation, the critical dimensions are both dependent on the laser cuts, not the material thickness.

And yes, I'm familiar with the problems of cross-slot T-fittings: I'm the guy who posted the macro that would go through a drawing and adjust all the slots for a desired material thickness. Trust me, you're not the only one here who's been cutting a lot of acrylic for a long time.

True, finger joints work but things like Raspberry Pi cases don't.

[Doug Fisher]

Lee, I did a quick search trying to find your post about the macro but could not find it. Can you please post a link? Thanks.

[Lee DeRaud]

Lee, I did a quick search trying to find your post about the macro but could not find it. Can you please post a link? Thanks.

Try searching for "resize circles". Some one had posted that one, which I modified so it could find circles within groups...the "resize slot" was just a quick mod of that.

I'll look for the macro file itself when I can get to the upstairs computer, it's not on this one.

[Lee DeRaud]

Here ya go:
Resize.zip
The slot one assumes the slots are Corel rectangle shapes, so if you drew them using line segments you're out of luck. But it handles rotated ones as well in case you had slots at an angle.

[Glen Monaghan]

for which version(s) of CD were those macros written?

[Lee DeRaud]

for which version(s) of CD were those macros written?

Don't recall offhand. I did the mods when I had X4 IIRC, but the original macro they're based on was older than that. They worked in X6, haven't used them in quite awhile so I'm not sure about X7. But off the top of my head, there's nothing version-specific in there, just basic object manipulation stuff.