Anybody here from Midlands?

**kingcreaky** · 02-10-2012

Hi Jonathion

excellant. thanks for the nudge. that supplier has just what im looking for...

evil laugh

ebay: 250482515891

Think il buy that? recon its up to it?

I have the steppers (bought for another project) can you recommend power supply / breakout board / stepper controllers etc?

im in Stoney Stanton...

Matt

**Jonathan** · 02-10-2012

Nonooo.. too early to buy things! You should get the design done and do a lot of research first to avoid mistakes.

That set is very mismatched. The lengths of the rails implies it is intended for a machine with, roughly, 1000x1550 travel however only the Z-axis ballscrew is the most optimal size. The problem is the critical speed of the screw, which is the rotational speed at which the screw will start whipping/vibrating excessively, imposes a lower limit on the diameter of ballscrew you can use for a given length. Short answer is up to about 600mm use RM1605 and up to 1500mm use RM1610. The reason for that is using the 10mm pitch screw instead of 5mm means the rpm for a given feedrate is halved, so if you are limited by the critical speed, this doubles the possible feedrate.

**kingcreaky** · 03-10-2012

Your right. Il get some drawings of my intentions done, and take it from there. Ready your comments it appears I have a lot to learn, and shouldnt rush in.

I should perhaps start an actual build thread rather than continue this one also. Il do this when I have some drawings

In response to martin (and anybody else who can make any recommendations on drivers / breakouts / power supplies the steppers Ive bought are as follows

Nema23 3.1Nm High torque Stepper Motor 1.8 Deg, Dual shaft

full spec sheet http://cnc4you.co.uk/resources/60BYGH301B.PDF

**Jonathan** · 03-10-2012

The 3Nm stepper motors are used on most builds as they are good value for money, so that's a good buy. Did you get 3 or 4 motors? For the size of machine you're planning on 4 would be best so you can have two ballscrews on the axis that moves the gantry, or you can link the axes with a long timing belt so that only one motor is required.

The torque from a stepper motor is proportional to the phase current. Therefore the torque reduces as the motor speed increases since the inductance of the coils limits how high the current can reach before the next step. To combat this you need to run the motors on a higher voltage, since this increases the rate of change of current. The motors you have chosen can be run on up to about 75V, so it's best to choose drivers rated for at least that. Currently there's plenty of 80V drivers available on eBay, such as these:
Cnc 7.8A,80V,256 Mirco digital Nema34 step motor driver | eBay
CNC Micro-Stepping Stepper Motor Driver 2M982 24~80V 7.8A Controller | eBay

I bought quite a few of the DQ860MA and found them to be a little better than the m752's I have.

Next question will probably be what power supply do you need? Getting a toroidal transformer and making it yourself is the best option and there's a few discussions in other threads about how to do this and why. Or I can show you...