Another Wood Question

Hardwoods are where you get the best cuts with a minimum of "clean up" sanding at the end. Oak, Hard Maple are where I've had my best results. Pine leaves a messy result that takes some cleaning. Poplar seems to be somewhere in the middle. Oak and Maple are available at most big box stores. Softwoods will work ok depending on your product, for example a lettered sign can be perfectly fine in softwood since the majority of the wood is uncarved and only the lettering is cut. I recommend adding a blur to your drawing (photoshop, gimp, etc work as editing programs) to give the edges more of a rounding, it avoids the up/down motion somewhat and allows the bit to ease into the wood rather than plunge down.

I concur with all the above observations about hardwoods having the least burrs and less sanding required. When dealing with fuzzy pine one way I found to get rid of the fuzz was a propane torch, then you have to selectively sand your work to get the proper highlights against the lightly scorched wood. Unfortunately I prefer the natural pine look to the burned-in look.

While you are exploring you machine's capabilities here are other materials other than wood you can experiment with:
MDF or PARTICLE BOARD = even cuts with no grain to worry about, however not too asthetic and does not weather well outdoors
LAMINATE PANELS - lettering can be cut thru the laminate into the base particle board, can fill letters with paint for contrast and sealing & wipe excess of laminate surface
CORK = cuts clean and fast - e.g. to make custom coasters for drinks, or nice logos etc
PLASTIC DECK BOARD = cuts evenly, weatherproof, watch for buildup of melted material on bit occasionally during the run
PLEXIGLAS or LEXAN = cut with "invert" image and also transform horizontally left to right on GIMP or Photoshop to give you a lithophane (note that melted plastic buildup can be an issue as well). Can make good signs such as for rooms in your doctor's office.
INSULATION FOAM = foam cuts fast - can be painted with latex paint and is good way to quickly make images or text (or a mold if you reverse the image).

...Andrew

I use:
...DOW CavityMate blue foam - 2'x8'x2.5" or 1"
...OWENS-CORNING Foamular C200 pink foam - 2'x'8' in 1/2" or 1" thickness -- is a bit finer than the blue foam and I like the best.
...White cellular foam bead type - not so great as it cuts coarsely and isn't strong enough for molds - just cheap signs. The Blue & Pink foams from Lowes or Home Depot aren't cheap but are strong enough to retain detail and flexible enough to strip off the finished cement. You can get 3 uses with care (must clean and sometimes recoat each time).

1. Cut your relief mold (moderate to heavy blur on image to facilitate release) about 1/2" depth or whatever you want. You can experiment and see the limit of detail you can get away with without having it stick to the mold.
2. Brush the foam every which way to clean burrs and fuzz. Then rub it with your fingers to roll off more fuzz and smooth it further.
3. Coat the foam with latex paint, or better yet, smear with acrylic silicone caulking (can dilute a bit with water on your fingers).
4. Make a 4 sided plywood box. Include a bottom.
5. Run a bead of caulking around all edges of foam and the corners and smooth by hand - to seal gaps.
6. Spray inside mold surfaces and sides with silicone spray.
7. Fill with concrete (I like premixed sand topping mix - have made some custom mixes of crush stone & sand but stone sometimes doesn't settle into mold detail so well - need more practice). Use a shaker table (look up ideas on youtube) or a vibrating palm sander held underneath the mold for a minute or so until you see it flow & "liquify" the mix and you start to see bubbles rise to the surface. This vibration is necessary to release and float the bubbles off the mold face (otherwise you will have voids and bubbles on your image).

You can do two colour pours also - I have been making Canadian flags the past couple days to sell at market. Do the first colour in the desired depressions and vibrate as above, let sit for 30-40 minutes, then carefully deposit 2nd colour (or plain) concrete in and vibrate a 2nd time.
...Andrew McC.