Re: Max stepper speed (Sherline)

Hi Al, others,

My power supply is 24VAC output transformer, producing 33VDC at the
bridge rectifier, 3 separate 4700uF 50V capacitor feeding the motors
via individual wires via fuses. Wonder if it make any difference to
have a single large capacitor or it the individual capacitors can be
interconnected to act as one (connection in parallel or something).
Come to think of it, when all three capacitors have common terminals
at the bridge rectifier, isn't that already connecting the capacitors
in parallel?

Peter

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "alenz2002" <alenz@b...>
wrote:

> Peter,
> I have a similiar setup on my Sherline 5400 mill. Sherline steppers
> wired using half winding, 2A Camtronics driver in half-step mode, a
> homebrew power supply consisting of a 24VAC center tapped xformer

and

> a 10,000MFD cap which runs about 36VDC output. Am using the

Sherline

> CNC stepper kit, CNCPro software and a 133mhz box. The motors will
> sing right along at 60 in/min in all three axis. (Not that you

would

> want to, I usually keep the max velocity at around 20 in/min).
> Contact me off list and we can walk through our systems and see

what

> we can do. The problem is NOT your steppers or driver. I started
> with a 12VDC power supply and got about what you are reporting, the
> higher voltage made the difference.
> Good luck,
> al
> PS After reading some of the other posts, I got to wondering if my
> memory was failing, actually it is :), so just did a quick check.
> The x and y easily went 60 in/min but the +Z stalled out at 50. Had
> to put a drop of oil on the Z leadscrew, then it was OK at 60 also.

I

> have the handwheels, so can use them to confirm that it comes back

to

> zero, and used a stopwatch to verify timing, ie, 2 inches in 2 sec,

3

> inches in 3 sec etc.
> al
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "forumtvm" <forumtvm@y...>
> wrote:
> > "IMService" <imserv@v...> wrote:
> > Check out this chart:
> >
>
>http://www.empiremagnetics.com/global_pages/torque_charts/calc_st_tor
> > q_U21.htm
> > >
> > > They have graphed the torque curves for a stepper motor at
> various
> > > supply voltages. Note on the top chart (2 amp motor), curve

#2.

> > At 5 rps (revolutions per second)
> > > the torque drops from over 50 to around 17.
> >
> > "Daniel J. Statman" <titanium@c...> in Sherline group wrote: "I

am

> > using TurboCNC with a 75 MHz Pentium 1 computer running DOS. I

have

> a
> > 26VDC power supply connected to a Xylotex drive running NEMA 23

180

> > oz-in stepper motors (200 step per revolution) running in 1/8th
> step
> > microstepping mode."
> >
> > I am using the Sherline 9.7 kg-cm (134 oz-in) stepper, camtronics
> 2A
> > driver, 36VDC supply, and steppers stalling badly at 16-18 ipm,

and

> > greedy for more.
> >
> > Hope Statman is reading this post. Is the 180 oz-in stepper a
> triple
> > stack? A 180 oz-in stepper is only a 34% improvement over my 134

oz-

> > in, which proportionately will be 24 ipm, so there must be
> something
> > I can do to improve the performance.
> >
> > What can I do to get the Statman kind of performance?
> >
> > Peter