Hey all,

Planning on building a fixed gantry build designed to cut plastic/wood/aluminum with reasonable precision in a relatively small form factor, and at a price point around $1500. At this stage I have a basic plan laid out, and am looking for feedback, but this thread will serve as the "build thread" for the project as well.

THE DESIGN
The base of the machine is a 24" x 24" Cast Iron surface plate, that I got on a good deal in the local classifieds. The plate has the usual light scratching, but the previous scraping marks are still easily visible, with no discernible warpage as measured with a precision straight edge and one thou feeler gauge. I know granite is very popular for higher end DIY builds, and isn't susceptible to corrosion and has better vibration characteristics, but the plate was super cheap, and I can readily drill/tap it without the need for special bits/inserts. I'd estimate the weight in the 150-160 lb range, and it should be plenty sturdy enough for the things I plan to machine. In addition I believe the CI plates are a bit more thermally stable.

The X gantry is 3" x 6" 8020 extrusion that I plan on filling with epoxy granite. I debated going with HSS, but decided that trying to get it machined around here would be tough with limited options, and it would be relatively easy to swap out for something else in the future is need be. The gantry will sit on 2" x 4" rectangular HSS. I haven't decided on a wall thickness, but probably something between 1/4" and 3/8". On the top will be a 3/8" plate that the extrusion will sit on along with support brackets (not pictured) on either side as well as the back. I had to get a bit creative on the mounting to the surface plate, and I'm afraid this will be the weak link if I encounter any serious vibration/deflection issues. It again will be 3/8" plate, fastened on both the top and side surfaces. I'll likely extend the plate in the Y axis to improve longitudinal stability. Although only one bolt is pictured I plan on securing it with 4 7/16" grade 8 bolts on either side, and once I get everything exactly where I want it I may consider pinning it with some dowels.

All of the rails are offshore 20mm HIWIN clones, and while I know there are better options out there it's just not in the budget. These should provide a reasonable amount of rigidity, and for the moment will get me in the game. The X axis will be 750mm (600mm rails in the model at the moment) which should allow for just over 600 mm of travel. The Y axis are 500mm, and though shorter than the plate would allow the machining table I plan on using is 12" x 24" x 1/2" aluminum plate, and 500mm rails net me over 300mm of travel. The Z axis is loosely laid out in the model, but I'm considering purchasing a premade axis off of ebay that uses 15mm rails, and looks to have decent machine work.

As for motion control the X and Y axes are setup with 16mm dia. 10mm pitch ballscrews. the consensus seems to be that this is a solid middle ground between resolution and movement speed. The Z axis is setup for a 5mm pitch ballscrew, as movement speed isn't as critical in this axis. For motors I've gone with offshore 2.2 Nm NEMA23 steppers driven by generic stepper drivers and a 12.5 amp 48 V power supply with shielded cable throughout. I've gone with MACH3 as the control software and have a super cheap USB breakout board for now just to play with. It doesn't have much in the way of I/O and I plan on using inductive limit switches, and will require I/O for the cooling and spindle so a final board will be decided in the future. I've already purchased the basic electronic setup, and have successfully tested all 3 motors in MACH3.

The spindle will be a generic Chinese 2.2Kw unit unless a used or new old stock unit falls in my lap. For the time being this is on the back burner until I get some axes in motion.

For the moment I've made a few purchases of parts that so far includes:
Stepper motors
Drivers
Power supplies (24V and 48V)
USB breakout board
Shielded cable
X, Y, and Z axis rails
X, Y, and Z axis ball screws
Surface plate

Any and all feedback is appreciated. I have a large amount of experience in CAD (Catia, SW, SE, Fusion360) but very little experience in the CNC world. 99% of the CNC I've done has been waterjet cutting on OMAX's and a little bit of 3D printing. This has thus far been a daunting, but rewarding learning experience, and I'm excited to make my first chips!