Has anyone seen any good design ideas for an adjustable height cnc table? I'm building a solid frame (steel) to make a 4x5 shapeoko 3. I have a couple ideas about how to approach this, but I'd love to see how others might have accomplished the same thing. I'm thinking along the lines of 6-8 points on my table with large bolts running into the frame. Screw one direction, table raises, screw another direction, it drops. I imagine I'd end up linking them with sprockets and adding power (maybe even add arduino support and be able to set programmable heights). I'd probably use additional nuts to lock it in position once it's where I want it. I'd need to make sure the table fully takes advantage of the rigidity of the frame. Although I'm making the table with 1/4" carbon steel plate and 1" square tubing reinforcing it, so maybe with a large enough bolt my concerns about table vs frame movement would be moot. Not really sure. Anyway, I'd love to hear from anyone who has tackled something like this, or be pointed towards any designs or photos that touch on the subject. I'm mostly going to be doing large wood pieces 1-2" thick, but I'd like the ability to do the edge of some pieces. Like ornamentation on the side of a guitar or similar. Not really certain how I'd end up using it in the long run, but I like the idea of the flexibility. Thanks!
It sounds like what you really want is extra Z-clearance on part of your table rather than an adjustable height table. Given that, it seems like a much simpler design would be to either: (1) Design your table so that some portion of the cutting area is off the table on one side. Then if you have convenient mounting points on your table, you could mount a jig to hold a guitar or any other piece at the end of the table for cutting. (2) Design your table with a removable 'leaf' spoilerboard in the middle. Just like the leaf of a dining room table, make a separate spoilboard in the center. You can then have a few bolts to keep the spoilboard in place securely that can be removed to lift or slide it out of the table. At that point, you can place a guitar or other tall item in that spot. The disadvantage is that you wouldn't be able to get that extra Z-clearance on your whole table at once. So if you wanted to engrave the top of a thick slab of wood you might not be able to. But for most 'deep' work, you generally only need to carve on a small portion of your table.
I should add one more thing. If you do come up with an adjustable height table, especially one that is controlled by steppers, then you should probably get rid of the Z-axis on your CNC router and replace it with the table-based Z-axis. Including the Z-axis on the cutting head reduces rigidity substantially. It is one more set of plastic wheels that will deform under pressure and makes the distance between the cutting tool head and the gantry support plate longer, thus acting as a lever given the forces involved.
