Inexpensive/Budget CNC Plasma Table

Last crawled date: 1 year, 11 months ago

Complete real-world build with simple plasma cut/routed parts, a few easy bends, low unique part count, and common parts/fasteners on scrap/drop 2" steel tube and phenolic resin (lab countertop material). Cutting videos added below (2 years after build).

Update: The first cuts were perfect, and no mechanical changes or adjustments have been made except to increase height of rail supports (increase Z), replace Z plate (to better support the torch cable), (much latter) smaller pulleys for greater acceleration, lower shelf to catch parts and debris, and a water nozzle and solenoid for cooling thin material while cutting. There have been no scrap parts except those caused by CAM or operator error. The torch has yet to contact material while cutting and the "temporary" 3D printed PLA torch mount has survived (so far) without any bruises or scars. There have been no issues with the cheapo NEMA 17, it's sloppy brass-like nut and captive rolled T8 thread rod, or motor damper as the THC makes any vertical Z inaccuracies disappear. Very cold temperatures required reducing rapid speeds by 50%.

Due to the ultra low construction cost, even after going a little overboard on electronics, it has more than paid for itself. Only things I'd change if building again would be to use stainless steel wherever possible, powder coat everything else, not weld slats to the table (I didn't think I'd end up cutting as much as I do...), and make cutting area a little larger. With custom post processor and LinuxCNC/PlasmaC, cutting usually only requires manually jogging to start of a nest, zeroing X and Y, and pressing play.

RM2-2RS ($2.50 eBay) bearings in routed grooves on resin X/Y rails and NSK linear rail (scrap yard) for Z. NEMA 23 ($20 - eBay) with XL pulleys and 3/8" Gates belt (McMaster-Carr) for X and Y. Delrin idler pulleys (OpenBuilds) with 688 bearings (eBay) (latter replaced with identical aluminum idler pulleys). 3D printer grade (ie: junk) NEMA 17 ($22 Amazon) with 8mm captive lead and included brass nut for Z. 12mm PNP inductive sensors ($2 - eBay) for X, Y1/Y2 min, Z max, and floating Z switch.

Motion and control via. Gecko G540, custom ARM/FPGA running LinuxCNC/Plasmac, and a couple of cheap/small touch screens. Acceleration and feed rates all greatly exceed those necessary for plasma cutting. Many of the cables are shielded and there have been no noise issues.

The only critical dimensions are depth of V grooves routed into the rails (other materials could be used), spacers, belt anchor locations (based on selected pulleys/idlers), and bend for the Z nut mount.

Completed machine produces very accurate cuts, awesome holes, with no obvious deflection in any axis. Shortcomings in Z (stacked rails and the low-quality NEMA 17 assembly with brass nut on poorly rolled T8 threads) don't appears in cuts and/or are offset by a good THC and motion control.

Z rail support/stiffener on X gantry is 1" Purebond oak plywood (sealed with poly and then painted) that provides some isolation between X and Z, is light, and possibly results in quieter low speed motion than an earlier resin component.

Torch was originally a Hypertherm PAC120 hand torch and gets fed mostly generic/aftermarket consumables. The best cuts are obtained with Hypertherm 120092 "pipe saddle" nozzles and OEM or generic 120573 electrodes. Standard 020350 "gouging" nozzles work best when their faces have been machined flat but require more frequent cleaning (modified or not) during use than 120092.

STEP and IGES via. F360. DXF (by request) includes unfolded sheet metal parts. Clearances not added in CAD unless noted in part name. Steel parts were cut directly from DXF exports, slowing to 60% for holes and slots, which added enough clearance for assembly. Smaller fasteners could replace all except 3/8" supporting the RM2 bearings. All of the 3/8" fasteners were torqued to 24 ft. lbs.

Final cost was less than $300 USD without electronics.

Videos (after 2 years of use) here at link below:

https://youtu.be/cc8HTh48V4s

https://youtu.be/xRbEficCp3U

https://youtu.be/qcVhlMZEud0