Are the Zapp 3NM steppers good with their PM-752 drivers?

[Jonathan]

I've been waiting for money to transfer to my bank account from paypal. I didn't pay with paypal directly as I don't think it's fair to make a website pay paypal fees when I can pay using a debit card. Now I've just found that the stepper drivers have gone up from £44 to £50 today :( Now I've not got enough pocket money...

How much difference will getting the PM542 and running the lower voltage make?

[Gary]

The price has gone up because of the exchange rate, out of my control im affraid.
have a look at the torque curve in the datasheet, and this will give you an indication of the difference in power.

[Jonathan]

My mum lent me £20 so I was able to buy them on Friday :).
Order was dispatched on Monday and arrived yesterday - excellent service, thanks!

Been doing some testing...
I've not got round to making pulleys for a 1:1 ratio, so for the moment the closest I can get is 22T on motor, and 42T on screw.
The motor stalls above 1250rpm (no load), yet it still has enough torque to drive the X-axis at 25mm/s (1150rpm). Trying higher feed-rates than this gets a bit dicey.
I think this means that if I put a 1:1 ratio, then above 25mm/s is almost certainly attainable since the motor will only have to run at 600rpm to get the 25mm/s. Having said this the current speed is pretty scary! I had to put a lot of tension in on the belt to stop it slipping.

Currently I'm using 1/4 microstepping. I've tried 1/8 but it doesn't seem to make much difference. What do you recommend I use? The computer I'm using is only 1.4ghz, this might be a limiting factor? I'm using Mach3 at the moment, I intend to change to EMC.
Also, I've set the port frequency setting in Mach3 to 25Khz. I tried 35Khz but it seemed worse, should one be better than the other? I've set the pulse width to 5us, is there any reason to change this? I guess not unless I start using 10000pulse/rev...

Thanks for all the advice so far.

[Jonathan]

Oh one thing I forgot to mention...I measured the current into one driver (using both an ammeter and a shunt resistor) and when idle it's about 0.3 amps. It goes up a bit when the motors running, but either way that seems a bit low to me? I've got the driver set to 4.09A peak, I take it this is correct for these motors in bipolar parallel? The motor is only a little warm, nowhere near 80°C.

I'm currently using a 225VA toroid for just the one motor. There's no perceivable temperature rise on it so maybe I can run more than one motor from this transformer?