Re: Reality Check for CNC mill

The FET4 isn't a bad board but I am not sure it can hack the stepper
motors you are talking about. Maybe the FETS can take the current
but what about the rest of the circuit board? The traces on there
are not that large.

Also my calcs show you need 80 watt (min) resistors on both size
motors.

Download my current limiting resistor calculator software at
http://www.e-zflight.com/files/stepcalc102.zip

It's for calculating resistors for unipolar motors.

I am afraid you will need to go with gecko's (which isn't a bad
thing) to handle that kind of current. You COULD email Russ at
stepperworld and see what he thinks.

Eric



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "amoss70" <a-jmoss@a...>
wrote:

> I'm looking to build a CNC mill and am currently in the design

phase

> and would like a reality check on my design. Any assistance or
> opinions on my design choices you can provide would be great.
>
> I did use MicroKinetics CNC Express as a sort of base idea.
>
> Thanks
>
> Base machine:
> Enco or Rong Fu bench top mill converted to ball screw on the
> X and Y axis.
>
> Stepper package:
> Stepper World FET-4 with the MOSFET upgrade. Uni-Polar Drive.
>
> Stepper Motors:
> X & Y axis NEMA 34's 344-610-DU 610oz 3.9v motors connected

via

> toothed belt at a 2:1 ratio.
> Z axis NEMA 23 233-180-SU 180oz 2.7v motor connected via

toothed

> belt to the fine down-feed at a 2:1 ratio.
> 6 in Rotary table NEMA 34 344-304-SU 304oz 2.5v motors

connected

> via toothed belt at a 2:1 ratio.
>
> Power Supply:
> 24v 60A unregulated. It's actually an old UPS and by
> connecting across the positive and negative terminals I figure I
> could get at least 60 amps plus a beautiful 3400-mAH reserve. I of
> course clamp it with zeners for surge protection.
>
> Current Limiting: (this is where I'm the weakest)
> X & Y axis NEMA 34's 344-610-DU 610oz 3.9v motors will
> be connected in series with 5 ohm 50 watt power resisters. (Not

wire

> wound)
> Motor: .97 ohm
> Power Resistor: 5 ohm
> Circuit total: 5.97 ohm
> Voltage 24v/ 5.97 ohm = 4.02 amps
>
> Z-axis NEMA 23 233-180-SU 180oz 2.7v motors will be connected

in

> series with 5 ohm and a 2 ohm 50 watt power resisters. (Not wire
> wound)
> Motor: .9 ohm
> Power Resistors: 7 ohm
> Circuit total: 7.9 ohm
> Voltage 24v/ 7.9 ohm = 3.03 amps
>
> Rotary table NEMA 34 344-304-SU 304oz 2.5v motors will be
> connected in series with 5 ohm 50 watt power resisters. (Not wire
> wound)
> Motor: .62 ohm
> Power Resistors: 5 ohm
> Circuit total: 5.62 ohm
> Voltage 24v/ 5.62 ohm = 4.27 amps
>
>
> CNC controller:
> Pentium 400+ something running Win 2000 or Win XP
> CNC controller software:
> MACH 1 and upgrade to MACH 2 when available.
> CAD/CAM:
> BobCad v18 upgraded to v19 when available.