View Full Version : BUILD LOG: CNC In A Box

31-08-2013, 06:45 PM
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 ...


31-08-2013, 07:28 PM
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 (http://www.ebay.co.uk/itm/140749152634)
3Nm Stepper motor - for CNC Milling machine / router | eBay (http://www.ebay.co.uk/itm/321036123392) (this is from Zapp, but cheaper!)
480W High Power CNC Stepper/Servo Motor Driver Switching Power Supply 48V10A PSU | eBay (http://www.ebay.co.uk/itm/360723730236)
5 Axis CNC Breakout Board for Stepper Motor Driver with DB25 Cable | eBay (http://www.ebay.co.uk/itm/310657023006)

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 (http://www.ebay.co.uk/sch/linearmotionbearings2008/m.html)?) I'd try to minimise the use of belts as they might introduce backlash (http://www.mycncuk.com/forums/linear-rotary-motion/6118-best-timing-belt-pulleys-type-minimum-backlash.html). Go for direct drive Oldham couplings (http://uk.farnell.com/oldham-couplings) wherever possible.