I'm going going slightly mad

Hi all,

I’ve been designing doll furniture using Fusion 360 and it’s been quite the journey. My design use a lot of tabs and slots and is quite big once it’s laid out flat, about 3 sheets of medium black acrylic and 1 of medium crystal acrylic.

Now what’s bugging me is that the PG acrylic isn’t consistent… Not within a sheet and not within a batch… So pieces cut sometimes fit perfect, sometimes are too tight and sometimes too loose… All with the same settings in Fusion (material thickness and kerf correction in the CAM module).

Fusion allows to go into great detail but the PG material doesn’t seem to allow for that due to the wide variances… Or am I being too difficult on PG?

Does anybody here have any experience with this hoping I could get some tips / tricks?

Thanks in advance!

What kinda variability are you seeing with calipers?

FWIW, and no - this isn’t Proofgrade, but it kinda gives the idea that their is some variability to be expected…

Edit to add… it’s been rumored Glowforge uses Chemcast as the supplier of Proofgrade acrylic, but I can’t say with any degree of certainty.

That said, this PDF shows the thickness tolerance for Chemcast (page 3):

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Anywhere from 2.75 mm to 3.10 mm… Thing scan vary up to .2 mm within the same sheet and .35 mm between sheets…
I wonder if I’m going to have to learn to live with this and just set everything to an average and hope for the best… The thing is, when I measure in inches, it shows most of the sheets either 15/128 or 1/8 - but that’s a big variance in millimeters…

I’ve never found any acrylic to be perfectly consistent, there is always a slightly thicker area. Slots and tabs can be a bear to design for in acrylic.

Having said that…if you are using Fusion 360, had you given any thought to Parametric design? It is possible to create your files so that you can drop in a couple of parameters like material thickness and have the file adjust the size of the slots and tabs for you. (Really a phenomenal time saver, especially if you prototype in a different thickness material from the end product.)

Cast acrylic has more variation within a sheet than extruded acrylic does. I go for an average of a few measurements and make do with a drop of glue or a pass of an emery board to make things fit.


Hi Jules,

I’ve been using parameters in Fusion but if the acrylic differs between sheets then on a multi-sheet design (my last one is spread across 3.5 sheets of acrylic) then it becomes very difficult even with parameters…
But thanks for the response though, I appreciate it!

I think I’m going to have to do the same and live with it for now - probably no use in fretting about it :wink:

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I thought I was just a bad designer until I started measuring my acrylics each time way back with the pre-release unit. Then I realized that acrylic variation of even the slightest makes a difference because of its rigidity. Gave me an appreciation of minuscule adjustments in tabs and slots and that the Glowforge was capable of these adjustments, but definitely had to measure the material each time if I was going for snap fits.


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