[catahoula]

Hi,

Looking for feedback on my fixed gantry router build. Goal: machining aluminum molds with high precision (+/- .002"), and trimming carbon composites at high RPM (hence router not mill). This design is heavily influenced by earlier discussion on this forum, but just want to check in before I proceed further.

frame
24" x 24" x 3" granite surface plate base
8" x 6" x 1/2" steel gantry tube, machined, epoxy aggregate filled
5" x 2" x 3/8" gantry supports- welded, stress relieved, machined, epoxy aggregate filled
16" x 14" x 1" cast aluminum plate for table

linear motion
20mm medium preload linear rails - not hiwin but best quality chinese, fairly spendy
1204 ballscrews driven 2:1 with GT5 belts
Nema 34 steppers (leaving room for servo upgrade in the future if needed)

Controller
buildbotics control system

Spindle
yet to be determined, likely the spindle stocked by Avid CNC


Have priced out every component and it should come in well south of $5K.

Specific questions:

-What about replacing the 1" thick z-plate with 10x2.25x1/2" aluminum C channel? Would add much rigidity and bring spindle closer to gantry. Do I have any hope in hell at machining the web of a C-channel flat and it staying that way?

-Any drawbacks to 12 mm ballscrews? Screws are short so whip is not a problem here

-Have 0.5 mm clearance over ballscrew mounting blocks. Clearance is clearance, right?

-The y-axis table rails are mounted on ground flat aluminum bar. I'd prefer to mount the rails directly to the surface plate and put the spacers between the carriage blocks and the table as this would elimate issues of flatness with the ground bar. But elevating the rails would keep them from the water that will collect a bit on the plate (will drill drainage holes anyways). Pros and cons?


Thanks so much!