Economy CNC Plasma Table

Last crawled date: 1 year, 11 months ago

WIP (casual build during design) - Simple table that someone else is constructing from their/my parts on hand, our junk boxes, and common fasteners. Final work dimensions have not yet been determined (will probably be 50x50 in.).

Hacks: Single start 0.5 in. ACME bored to accept pressed in 5mm NEMA 17 shaft that was TIG welded in place for a cheap/permanent captive lead. Two smooth shaft collars were turned so that each has face that does not contact outer race of an adjacent R8 bearing. 16mm 01 tool steel rails were flame hardened and annealed (probably not necessary) and could be replaced with Asian hardened linear rails.

Hacks (cont.): The junk SCS16UU inserts were replaced with quality Igus DryLin RJ4JP-01-16 linear bearings. The two Z rod support brackets were 3D printed from ABS by the builder. The $2 Asian inductive sensors are not very accurate, but individually produce repeatable results (all I've used or tested) with 24+ volt supply, and don't false trigger (with minimal hardware or software debounce) in a noisy plasma environment.

RM2-2RS v-wheels on phenolic resin rails - which is best/cheapest linear motion scheme I've found for a filthy plasma environment. Plasma cut steel parts (0.075 in.) were designed for easy 90 deg. bends in a manual press or finger brake. NEMA 23, Gates XL belts, SDP timing pulleys, and Openbuilds style Delrin smooth idlers for X and Y.

Inductive sensors home each axis and monitor Z switch (backup for Ohmic sensing). Overly long Z switch travel allows convenient access to plasma consumables while paused and without repositioning Z axis. IMService (eBay/web) Delrin anti-backlash nut (DumpsterCNC copy) for Z.

The steel V wheels a cause shiny glaze to appear on contact surfaces in the phenolic resin V grooves. 2000 build, now with 2 years of near-daily use, hasn't required bearing adjustments and no wear can be felt in the V grooves. New RM2-2RS bearings should be disassembled (remove rubber seals), cleaned, and greased before any use.

Don't buy cheap/no-name XL belting or cheap plastic/Nylon timing pulleys. Larger pulleys provide faster acceleration and keep motor RPM down in the torque bands.

Pros: Cheap. Fast. Accurate. Low maintenance. "Press-Play" operation (LinuxCNC/PlasmaC).

Cons: Asian parts. Upper rail grooves must be kept clear of obstructions (dried bird droppings can cause missed steps).

Photos will be added when I receive them.

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