Re: [CAD_CAM_EDM_DRO] OOPS! Need bigger stepper motors

Gary,

Thanks for the URL. I think he spells it "Hans Wedemeyer". That works
on a search, I thought I recognized it!

On the motor ratings, If his drivers are like other chopper motor
drivers, Much higher voltages are useful (did Mariss say 20x?), so going
up to about 34v (not ALL the way to 40), will give you an increase in
power. Motor "ratings" of a few volts and a few amps, I.E. 3.6V, 2A are
often driven with 34 (or more) volts! This is for "chopper drives", of
which the L297/L298 combo usually are. The other (old design) is to
again use higher voltage, but limit the current. So an L/R drive will
have a resistor in series with the motor windings to limit the current.
The net effect, simply stated, is that the motor coils attempt to
"charge" up to a higher voltage, so they get up to their max current
much faster. Are your motors/power supply rated at 12V? Too much
current, on the other hand, CAN de-magnetize the motor! What are the
motors on now? Look at the motors that Smithy recommends (if they do),
or a similar sized mill or lathe (3 in 1), and see what motors and
timing belt drive ratio's they use. There are some users here on the
list that can probably give you a better recommendation.

Oh yeah! Here's the "bucket of sand" torque meter! You might clamp a
rod to your Smithy's crank, and see what it takes to move the
carrage/ways!

Alan KM6VV



Gary wrote:

>
> Alan was gracious enough to suggest bigger stepper motors than 100
> oz/in. I still need a source for something along the line of 300
> oz/in, 12 or higher VDC (40 volts max). Anyone got any ideas? Alan
> the URL to Hans' home page is: http://hans-w.com/. I have run the
> system using small stepper motors and DANCAM and I am very happy with
> the performance, especially considering the total cost has been around
> $100.oo for everything needed to run 4 axis CNC. Except the motors
> and machine mods, of course. Hans' boards use L297 and L298 chipsets
> and the boards are capable of 4+ amps per motor and almost 45 VDC per
> motor. Overall I am very happy with Hnas' boards and would suggest
> them to anyone just getting involved in CNC. Just need a source of
> useful motors. Anyone have any experience with running steppers at
> voltages higher than their ratings?