[stuarttaylor00]

Hi all,

After a few years with my Shapeoko 3 XXL, it is time to build myself a more serious machine. I have done considerable reading on here and other sites over the last year or so and though I know what I want to achieve, I would like a bit of input into my design from those more experienced members.

Mechanical:
- Work area minimum 1250x1250mm. More is ok, but must fit a half sheet of plywood
- Z-axis travel 150-250mm – I’d like the clearance to fit taller jobs in
- Able to comfortably mill aluminium. This is always a contentious comment, my Shapeoko *can* mill aluminium, but not comfortably. I don’t expect it to cut like a tormach.
- Steel frame, happy to use Aluminum for brackets & smaller parts.
- Steel parts will all be welded. At this stage Heat treating is not feasible, So will weld 20mm sections evenly around the frame to keep temperatures and hopefully warping to a minimum
- Hiwin linear rails all round - 20mm seems well suited.
- 10mm strips of steel welded to beams on linear rail mounting points. Machined flat.

Steel sizes:
Gantry - 200x100x6mm RHS - 1500mm long - Now 200x200x6mm
Side beams - 150x100x5mm RHS - 1500mm long
Cross supports - 50x50x5mm SHS - 1350mm long
Gantry/bearing plates - 10mm steel plate
Z-Axis(when I get there) will be 16-20mm plate


Electrical:
- DMM 750w servos direct drive to (originally 2010) Now 2525 ballscrews. - Not settled on this setup yet - I’d like to avoid belts or any reduction if possible. Now 3:1 reduction. Not sure what rapid rates I should be targeting, maybe 6000-8000mm/min Now 25m/min with screw @ 1000rpm
- There are substantially cheaper 750w AC servos on Aliexpress, at close to half the cost. Not sure if anyone has any experience with these, obviously DMM are better but I don’t want to blow the budget out
- Centroid Acorn control board. Also now considering Mesa 7I77 and LinuxCNC
- Power supplies yet to be decided
- 3-4kw spindle – yet to be decided


So I started drawing up the below design (first two pictures), I got the basic bed and gantry set up, I’m quite happy with this design so far. It seems quite sturdy and has the added benefit of keeping the rails and ballscrews well away from the bed and the majority of dust.



I then started googling for router designs for some z axis ideas and realised that there are not a huge amount of machines designed like this, and most commercial designs have the linear rails at bed height or below, with a ‘gantry riser’ style of design. This doesn’t feel as rigid as what I have designed, but I whipped up a quick draft of how this might look. Don’t be too harsh it’s just a concept at this stage.

Any thoughts on what might be the better option? I haven’t put a lot of time into the gantry riser design, It needs a lot more support on the ends of the gantry and on the riser-bearing joint. The first design is my preferred option, it just feels a lot more rigid, and the joint from the gantry to the Y rails is very solid.

Thankyou for any input, much appreciated!