For clear acrylic coasters without a cork or felt backing, the reverse etch is my preferred method. Did a pile of them for a submariner’s reunion this summer with the boat’s logo. Etching from the back keeps condensation from pooling in the etch and if it’s a complex etch the glass may get wobbles depending on where the glass is placed on it.
I did Challenge Coins as well with the same design (2" dia vs 4" for the coasters) but etched from the front - provides more tactile feedback for someone playing with it in their pocket like a worry stone.
Always good to consider how a user will actually use the things we make
I guess what I really am is envious. My drink coasters, without benefit of laser cutter/engraver or mill took a day and a half and they are not quite finished. You finished the design and GF work in a morning? That is so cool what you did for your friend. Hey, you want to be my friend? - Rich
The base is cut out of 1/4" plywood and it just notches together, no glue needed. It took me a couple of tries to get the sizes of the notches just right, but the final one has a tight fit that makes it surprisingly sturdy.
This is one of the things that worries me. I’ve been trying to utilize parametrics in all of my designs, at least when dealing with material thickness (and therefore the notches), but I can just imagine that all of my designs are off by .1mm or something and then I have to redesign everything! Not very confident in my parametric design abilities.
If you know what material you’re planning on making your project out of, then you can do a quick test-cut to measure the kerf before designing all of your slots Deferring to the awesome @smcgathyfay for her words of wisdom:
maybe, some of our regulars with access to lasers and experience would be able to work with you and do a SMALL test for you to make sure your parametrics are working correctly. That way, if it works out, you can rest assured that your more complex file will be good to go. And if it doesn’t work out right, you have time now to change them up.
I bet that @smcgathyfay can just look at your design and tell you how to fix it, or if it is good to go.
Most of my very first projects are just going to be engraving on things that I’m building, but once I start cutting things out, I’ll have LOTS more questions.
She’s already done one of them - the acrylic light bulb thing…I hate to get greedy!
And Martin did the sheep trivet. (So I’ve probably gotten my share.)
Reverse etch or engrave for glass is also good if doing glass (clear) plates. I’ve sand blast engraved plates (reverse on the bottom) and that way they can also be used as well as decorative. Also if it is a coaster, you you added color to the etching ( rub n buff or some other fill) , it won’t get affected by any water or spills.
One of my first plates
genuinely curious question, if you are etching or sandblasting an image without words on it, is there really a “reverse” to it? It’s just an image and it would change which direction it’s pointing, but I thought words were the only thing that would really need to be “reverse” etched.
This one needs to be a collaboration, since the file needs to be prepared in F360 for the specific material, in order to test the parametric side of things in the file. (The ones I have on hand are too complex, I’m going to put together something smaller and easier to cut for the testing. If it works out okay in the testing, it will work in more complex designs, and she won’t have to use up $20 worth of materials.)
I’m going to take @smcgathyfay up on her offer to cut a small test case. I’ll need to get a couple of actual measurements from her (actual material thicknesses and the kerf for the laser that she is using), then I’ll create the file for her to cut, and she should be able to do it quickly without making any further adjustments.
If things go as I expect they will, the parts are going to force fit together with zero leeway, and the treatment of kerf will need to be adjusted a bit…real life generally just isn’t that accurate.
Then, after we get the kerf treatment worked out, I’ll have her cut it out of a different material, get some new measurements, send her a new file, and we’ll see if that one works as well.
But it needs to be a little 2 inch sized file…just a few tabs. (I worked up a quickie last night but built it off the wrong face, so I need to rework it this morning.)
Anyway, stand by @smcgathyfay …test file coming soon. (You might regret volunteering for this girlfriend! ROFL!)
I’m up for the challenge…
I can visually tell if it will work by checking the file, so more complex is fine too.
You can start with the baltic birch ply
.124" thickness
.006 kerf
- Rich
Deferring to the awesome 
