Problem: substituting small stepper motor with a larger one

[overture]

udn2917eb cnc

Haven't done anything yet. Just had been thinking if this is possible. An existing system is being driven by a stepper of the following characterstics :

Type: 4-phases / 96-pole / HB type stepping motor
Drive Voltage : 42 VDC ± 5% (The voltage applied to the driver)
Coil resistance : 10 W ± 10% (at 25° C per 1 phase
Connection : Bipolar
Excitation mode : 2-2 phase, 1-2 phase, W1-2 phase constant current drive
Minimum step : 1/720 inch / step (2-2 phase drive)

The motor is being driven by an Allegro driver IC UDN2917EB
(data shett for the IC can be seen here h**p://www.datasheetcatalog.com/datasheets_pdf/U/D/N/2/UDN2917EB.shtml

It does microstepping depending on the reference voltage provided on pins 25 and 44. Thus the linear resolution is achived upto 1/720 inch/step.

So far so good. But I want to modify the whole mechanical system using a larger stepper motor of higher torque driving a different leadscrew and slide assembly than the original. Somewhere around 6 Amps. Can the output from UDN2917EB used directly to drive another set of stepper drivers?

Also, another problem shall arise when I'll change the mechanical portion. I'll be driving a leadscrew. The new leadscrew has a different lead/inch. But I still need to maintain that 1/720 inch/step linear resolution. Can the ratio be varied electronically so that I can adjust the final value by trial and error?

 

[artem]

udn2917eb stepper motor

1. The ds says 1.5 A continuous and 1.75 A max at 20 usec time. That seems impossible.

2. Regardless linear resolution it can be done if

Lold/(360/Nold) == K * Lnew/(360/Nnew)

where

Nold is step angle of your current motor,
Nnew is step angle of your new motor
Lold is lead of your current leadscrew
Lnew is lead of your new leadscrew then
K is any integer number from 1 to infinite)

 

[overture]

2-2 phase step motor driver circuit

Thanks for the reply. Well, it wouldn't exactly replace a screw. In the original machine it was a roller platen, that I want to change into a sliding table using leadscrew. Didn't say all this in the first post to reduce confusion by proving too many things.

Anyway, if it is possible to change the ratio electronically then I can probably set it up by trial and error. In the original circuit the driver IC inputs are being provided by a gate array. It gets it's Phse control signal and phase data and reference voltage for microstepping all from that gate array. May be I can connect the inputs of the driver IC to the inputs of a H-Bridge to drive it? But still that resolution thing is on the way. Is there something like almost infinitely variable microsteping?

 

[artem]

hiwin motordata

The step angle of step motor is fixed and you can not change, it is specified in step motor data sheet. you can try replace step motor with servomotor but that will change completely your drives and mechanical design (suppose you will need gearbox) encoder and driver circuit.

OFFTOPIC :
I am going to make one and looking to prefabricated parts . There is ready to use linear modules or screwballs from Hiwin, aluminum profiles from Bosch Rexroth , step motors from Oriental motors and linear optical encoders. But what i afraid is that final price will be one third of original CNC.)
For todays quote request i just got price for step motor Vexta PK268 - about 120 euros each.