http://www.instructables.com/id/CNC-Plasma-Table/
The belt drive is probably ok for a very small table, but when we scaled it up there was so much slop in the belt drive that the thing was worthless.
I put turnbuckles on the belt to try and tighten it more but ended up just bending stuff and it never got any better. The other issue I had with this design was the plate the torch mounted to had tons of slop, it was just bad all the way around.
This is it with the belt drive and all before we put the water table and supports in
This is how it sits now. We got rid of the belt drive and modified the rack and pinion drive that http://www.cncrouterparts.com/ sells
I rebuilt the Z axis with some 8020 extrusion and used my 3d printer to make the torch holder and shaft coupler.
for my z axis, the coupler is 3d printed, the part attached to the motor uses a set screw to hold it to the motor shaft, then to make sure the "Fingers" dont break off there is a 10-32 screw down each one. For the coupler attached to the acme screw, the coupler piece is threaded to screw onto the acme rod then I printed a jam nut to keep it from spinning. I didnt have much luck with a set screw there, the jam nut works perfectly.
In the red "bearing block" I have a small piece that threads onto the acme rod, that is just loctited into place. It fits inside the bearing block with the "lid" held on by zip ties. That holds the acme rod up.
The lower torch holder piece is threaded to accept the acme rod, that's what drives the z up and down. I have a bit of tig wire hose clamped to the torch and bent down to act as the ohmic probe. The next modifications will be to build a floating Z into the torch holder, the ohmic works great using the shield with the 45a consumables, but the 30a require the probe rod which bends out of the way pretty easily and requires a very watchful eye to keep from breaking things.
We were able to use the table with the belt drive to cut the pieces we needed to change over to the rack and pinion. We had to make new holders for the square steel tube because we needed it held at a different angle, the 1/4'" thick plates that hold the cncrouterparts carriages together were also cut with the belt drive. They all took a ton of hand fitting with grinders, etc to make work. the long belts had probably 0.050" worth of backlash, the short belt had probably 0.030".
I'm using the $25 sainsmart break out boards off amazon, $25 nema23 motors also from amazon. The stepper drivers are cheapo's off ebay. I'm also using a proma thc150. I'm also using a russian ohmic sensor, I originally had it wired directly to the break out board, but after frying a few I figured we needed something to protect the board from the plasma voltage.
http://www.ebay.com/itm/321846429622?_t ... EBIDX%3AIT
Currently I'm using mach3 with a uc100 motion controller, but that will be changed over to a UC400eth and UCCNC next week so that I'll have enough inputs to wire in all the homing switches and limit switches.
This is my first experience with anything along these lines. We pretty much went into this knowing absolutely nothing about linear motion, cnc controls, any of it. My shop is a high performance auto shop, this was built so that we could bring some of our production in house and make custom parts quicker.
