Thought I'd start mesel' a Build Log, so when I have a bunch of stupid questions, there's something to refer to. Although this is in the Router Logs forum, I currently live in hope that it'll be able to do a bit of aluminium.
Some specs first, partly because I currently don't have a machine running SketchUp.
Cutting area: about A3 (420mmx297mm) and around 200mm of Z axis travel.
Outside dimensions: I really want to make it so that it can be packed away into a 146L Really Useful Box after use, with minimal work (hopefully just lowering the Z-axis and lifting it in). That means 700mmx545mmx400mm, which affects a lot of design decisions.
Steppers and drivers: Zapp's 3-Axis 3Nm kit.
Y-axis: dual leadscrews, driven by pulleys from 1 stepper, moving a gantry mounted on supported round rails (20mm?)
X-axis: on the gantry, single leadscrew driven by a pulley from the stepper. Not sure if the round rails will be supported or unsupported, again 20mm.
Z-axis: single leadscrew driven by - you guessed - a pulley. The rails and leadscrew mounted on the router mount, and the bearings/nut attached to the X-axis. Unsupported rails, 20mm.
The machine frame is mostly to be aluminium profile.
Can't think of much more to add at the moment ...
I'm not greatly experienced in CNC, but I also bought a 3 axis 3Nm CNC kit from Zapp a few years ago and have since discovered that I could have bought the same parts much cheaper direct from China via eBay sellers. For example:
NEMA23 Stepper Motor CNC Driver 2M542 Controller | eBay
3Nm Stepper motor - for CNC Milling machine / router | eBay (this is from Zapp, but cheaper!)
480W High Power CNC Stepper/Servo Motor Driver Switching Power Supply 48V10A PSU | eBay
5 Axis CNC Breakout Board for Stepper Motor Driver with DB25 Cable | eBay
3 x Stepper Drives @ £23.88 each = £71.64
3 x 3Nm stepper motors @ £28 each = £84
1 x 48V 10A PSU = £57.29
1 x 5 axis Breakout board = £8.33
TOTAL COST: £221.26
Regarding lead screws (I assume you're going to use ballscrews from Chai?) I'd try to minimise the use of belts as they might introduce backlash. Go for direct drive Oldham couplings wherever possible.
Last edited by birchy; 31-08-2013 at 06:54 PM.