Machining plywood that has pockets filled with epoxy resin?

[MJ]

Hi:

I am a newbie to CNC and Shopbot. I'm currently working with the 3-axis ShopBot CNC PRSAlpha, 96" by 48" by 6" at http://www.makerlabs.ca in Vancouver BC. I'm really enjoying learning how to use this machine.

I have machined a piece of 3/8" Birch plywood that has a number of large pockets that I intend to fill with coloured epoxy resin.

Once the resin has cured I would like to flip this piece over and then remove the bottom (unpocketed) wood layer so as to allow the resin to be seen from both sides.

I imagine that a thin layer of epoxy will be removed along with the wood to get an even surface so my question is it possible to machine epoxy resin on the Shopbot?

Will this damage my bit? Am I crazy even thinking about doing this?

Cheers

Mark

[MogulTx]

You can machine epoxy, however you will have machining marks in the epoxy. The marks characteristics will depend on what size bit you use, what type, and what speeds you use for spindle and travel...

I do not know if this is of concern to you and your project. What might help if this is a concern, is to pocket all the way through and place wax paper or plastic wrap or some other easily released material under the panel and fill the pockets. You may have to do what ever finish you will want on the second side and then use modeling clay to create a small dam around the pockets and then press it firmly back to the table to ensure no leakage.

[myxpykalix]

Another way to do this without milling the epoxy is to create your epoxy circle in a seperate mold. Then cut the same size corresponding hole in the plywood only the bottom of the hole might be an 1/8th inch smaller which would give you a backer to hold the epoxy puck into the plywood, kind of like a picture frame with a dado in the back of it...if that makes sense...

[Ger21]

The epoxy will most likely cut far easier than the surrounding wood. Not an issue at all.

[MJ]

Thanks everyone for your comments and suggestions.

I will give this approach a try and see how it turns out.

I thought about the wax paper/plastic wrap but there are a lot of pockets so I thought I'd try wood pockets first then remove the wood later.

Jack. Interesting idea! I would need to create molds for each of my pockets. I'll keep that in mind for another project. The pockets are not circles so mold making would be a bit more involved.

[myxpykalix]

Actually it wouldn't be any more difficult...you just take the same circle, elipse, square, whatever shape that you are going to cut into the plywood and use that shape to pocket out your shape in a separate piece of wood you would use as your mold.
Pour your epoxy into that shape then insert the resulting puck into the corresponding shaped hole in the plywood.

[zeykr]

If you can get the right colors of plexiglass, inserting cut plexi shapes in a stepped pocket in the ply might work well.

[Burkhardt]

I think the original cast epoxy idea should work just fine and be the simplest way (pocket or through holes with the bottom covered).

There will of course be tool marks but hitting it with a sander will remove them in no time. I made a table surface with inlays where large void areas were filled with table top epoxy a little higher than the wood. I could not even CNC the surface because it was too big but used a coarse grit belt sander to flatten and up to 220 grit on ROS to prepare for a high gloss varnish. Alternatively it could be sanded even finer and the resin polished.