Prototype Rack-n-Pinion 4'x8'

Have been cleaning my home shop for a few months just enough to work out of it again. That really means finally building my very own CNC machine. It is a full cut capacity 4x8 frame built from OpenBuilds parts and other custom components.

The table is handmade from Sande-Ply plywood from Home Depot. It will have an 18mm Baltic Birch plywood top skin with a plenum grid cut in, then sealed with epoxy. The hold down comes from a Rigid 6hp shop vacuum.

The gantry assembly is mostly standard OB stock with re-worked Y-legs from an older build, and newly made X-parts (still in progress). The Z axis is all slightly modified OB components and will use a Bosch or DeWalt router for cutting for now.

Unlike most DIY machines, this build features a custom rack and pinion drive on the X/Y axis. The gear racks are 20* pressure angle/20 pitch, and were CNC cut at my day job from Delrin. The (NEMA 23) pinion/pulley system comes from AVIDCNC.com. I have been testing and developing this drive setup for most of the year on other builds at work, with good results. This build will help round out the drive design.

I'm not great at writing these things out, so I'll post as many pictures as possible through the rest of the build and will answer all questions as best I can.

Design Specs;

- Max Travel (cut capacity) - 50" X axis, 100" Y axis, 4" Z axis
- Mac Footprint - 62" x 110"
- Motors - 4 NEMA 24 (439 oz-in) 3.5 amp. Stepper online #24HS34-3504D
- Power supply - 36 volt meanwell (buildbotics controller, 24 volt meanwell OP blackbox)
- Control box - Buildbotics (also tested with OB blackbox)
- Drive - Rack and Pinion X/Y axis, OB leadscrew Z axis
- Cutting Head - Bosch Colt trim router/Dewalt 611
- Frame - OB C-Beam and V-slot, wheels and hardware, custom phenolic xx components
- Table - 3/4" Sande-Ply plywood with baltic birch top.
- Vac Hold Down - 6.5hp Ridgid, cannister shop vacuum

**UPDATE** This build is complete and is well into testing the gear racks.

*****UPDATE***** Please visit my new post, bor 454-D for new info!!!



Here is a vid of the first cut project on the new build. The filming and editing suck,sorry.




** Finally finished the vacuum hold down table for the prototype last week. Pics added below.
Here is a vid of the plenum being cut;