Hi!

My name is Andreas and I'm toying around with the idea to build a CNC for ages. I've worked with CNCs in the past (old machines with SD floppy drives built in to transfer data) but I've never built or designed one.

Naturally I'd like to build a machine that does everything, but due to monetary restrictions (e.g. I'm not Trump) I'd like to start it kind of simple but keep it flexible to upgrade.

My biggest problem is that I'm frightened about all the calculations about steppersizes, screws, etc., so I'd like to have some help, please.


What I've got in mind:

So one citeria is the size of plywood sheats from my local building supplies store. Another one is my targeted materials I'd like to work with, which would be mostly wood and wood products (plywood, particle board, etc).

I've read many articles in the last weeks which recommends these ballscrews and these steppers, but in the end, without calculations it'll be just guestimation.


Long story short, this would be a description of my CNC:
Workable area: 2600 x 1500 x 750 mm
X- and Y-Axis: linear rails, rack and pinion drive
Z-Axis: linear rails, ACME screw
Bottom construction: steel, partly welded and screwed together for disassembly in case of moving, 50 x 50 x 3 mm box tubing
Top construction: aluminium system profiles, 160 x 40 mm
Axis: 3 + 1 at the beginning, in the end 5 + 1
Spinde: chinese 2.2 kW watercooled spindle
Targeted materials (ltr prioritized): wood, plastics, non-ferrous metals, steel


Now a few of my minds about these specs:

Workable area: Full plywood sheats in my local building store are about 2500 x 1250 mm, standard building height to code is about 2500 mm, so I'd be able to route entire sides of a wardrobe at once.
Rack and pinion drive: Due to the lenght of the axis (x and y) I think it would suite best. I think a screw this long would introduce wobble or would sag.
ACME screw: I've read that an acme screw would be more likely to hold the weight of the axis in case of a power loss.
Steel subframe: cheaper
number of axis: what I've read, a slave drive for the long axis would be necessary. For the beginning 3 axis (maybe a fourth one on the table) would be sufficient, but in the end I'd like to build a 5 axis machine with an additional on the table.
system profiles: got 4 + 2 near perfect slots where I could mount the rack, linear rails and a dust cover.
spindle: I'll take a risk for a cheap one, I can upgrade later
materials: steel would be nice to work, but is entirely optional. If it wouldn't work out with steel to route, I would probably replace the top with a water bed and try to use the cnc as a plasma cutter for steel if needed.


Summary:
I'd appreciate your input about my targeted specifications and also your help to calculate what steppers, rails, racks and screws I'd need. I'd estimate roughly the ganty to about 75 kg without stepers, rails and rack. Side plates of the gantry are calculated with 20mm aluminium. The system profiles have about 8.7 kg/m.

Thank you in advance
Andreas