[Catmandu13]

Hey guys,

I'm drawing up plans for a CNC, first time(of course!). I've got a few parts, , but before i commit to the big purchase of the electronics I wanted to see if my cart is satisfactory.

The main use of the CNC is to cut signs out of 1/4"-1/2" wood panels, and possibly aluminum , but only up to 1/4" probably, and a random chance use of <1/4" plexi/lexan. Currently looking only for 3 Axis, possibly 4th for turning legs in the future, but not likely.

Currently will run on 1 start 1/2"-10 acme rods. and 12mm bearing shafts. (with intentions of being upgraded later)

MY router : Porter-Cable 895PK 12 Amp 2-1/4-HP
(might downsize there to something more disposable)


I was thinking vendor-wise to go with buildyourcnc.com, as they had a relativity nice electronic kit. Which they have a nice site, but too far many bad reviews to risk. I've read about Keling, now Automation Technology Inc...and they seem to have a similar type components for about the same price with favorable reviews.

This is on my seriously considering list via Auto Tech Inc:
3x NEMA23 425oz/in 2.8A Stepper Motor ¼” Dual shaft (KL23H286-20-8B)
3x KL-4030 Bipolar Stepper Motor Driver, 40VDC/3A
1x 24V/8.3A Switching CNC Power Supply (KL-201-24)
1x Breakout, not sure which yet.

(3X2.8A = 8.4A...PSU too small?)

I've also seen a few all in one breckout/driver type guys out there like the one from Sainsmart: SainSmart CNC TB6560 4 Axis Stepper Motor Controller

But I'm a little leery there, I'd rather spend an extra $50 and get 3 proven drivers.

Anything here seem out of place? I'm just trying to make sure I'm headed in the right direction without too much of a hard learned lesson.

Thanks

-Cat

[ger21]

About the worst possible choices you can make are the combination of 1/2-10 acme, 425oz motors, and 24V power supply.

With 1/2-10 acme, you'd get better performance with 270oz motors.

How big is this machine?
Are the 12mm shafts unsuppported? (supported at only the ends?) If so, you'll probably see a tremendous amount of flexing.

If you want advice, here it is:
1) Don't use 1/2-10 single start acme. At the minimum, I'd get 1/2-8 2 start. If the screws need to be longer than 42", then get 1/2-8 4 start, or 1/2-10 5 start.
2) Don't buy a TB6560 from anyone.
3) Don't buy 425oz motors from anyone. In order to get better performance from 425oz motors, you need to spend 2-3x more on drives that can actually use them to their potential.
4) Electronics should not be the first thing you buy. Most people that buy electronics first end up buying them twice.
5) If you definitely have plans for a 4th axis, then save up and get a Gecko G540, and then get the 381oz motors. It'll cost a bit more, but you'll get 2-3 times the performance you'd get from what you were thinking of buying. Four of KL-4030's are about $165, and a G540 is $250, but you don't need a breakout board, so that narrows the gap a bit more. There's your $50 more.

[Catmandu13]

Thanks! Not the response i was expecting, but exactly what I was looking for.

The machine will be 3'x4'

Having checked out the G540, that is a real nice package for the price. I was thinking gecko was out of my price range(using the individual drivers), but I must have missed that all in one guy(which is apparently 4 G250's under the hood).

The acme rods and the 12mm shafts are some freebies, The 12mm would be supported about every foot(it's tapped on one side of the length).

I'll see about sourcing some 4-5 start rods and new rails...12mm does seem a bit small for the application. I have some "H"-style extrusion I was considering running V-bearings on, it may be a little stiffer...moreso if I put supports throughout the upper and lower openings

And with the G540 controller with the 381oz.in motors. At 3.5Amps per motor, X 4 motors X 0.67 comes to 10Amps(worst case) for a powersupply, correct?

-Cat

[ger21]

Yes, 10 amps is plenty.