Re: Why is my feedrate slow with stepper motor

I think the hitch in my data stream is what I need to clean up first
as it could derail any other improvements. I put an old ocilloscope
on the timing puls to the driver and can see the hitch - shows up as
a reversal in the wave pattern every so often.

would a faster computer help? I've tried 133 and 200 Mhz pc's but
maybe these are still to slow to overcome interrupt delays.

Roger N
Akron OH

--- In CAD_CAM_EDM_DRO@y..., "Carol & Jerry Jankura"
<jerry.jankura@s...> wrote:

> I'd like to point out one additional cause of low maximum speeds,

even with

> the chopper motor controllers - any "add on" software such as some

versions

> of EMM386 that steal time during the PC's 18.2 millisecond clock

interrupt.

>
> I encountered one situation with a low end (Zenith Z-Star EX -

486DX2-50

> processor, 8 mbytes ram running Novell DOS-7) where Novell's EMM386

memory

> manager stole enough time during the clock interrupt to make the

step pulse

> train to the motor drivers unsteady enough that the motors would

stall out.

> By eliminating the driver, I was able to increase my max speed from

about

> 900 steps/second to 4000 steps/second.
>
> I agree with Jan, that your immediate problem is most likely the

use of 12

> volts to power the circuit and also with his comments regarding the

chopper

> drivers. I chose the other "vendor" for my machine - Camtronics,

and bought

> Dan's 2 amp kit. It does require assembly (Gecko's are prepackaged

modules)

> but it worked the first time and I'm happy with the results.
>
> -- Carol & Jerry Jankura
> Strongsville, Ohio
> So many toys, so little time....
>
>
> |-----Original Message-----
> |From: JanRwl@A... [mailto:JanRwl@A...]
> |Sent: Saturday, March 23, 2002 12:29 AM
> |To: CAD_CAM_EDM_DRO@y...
> |Subject: Re: [CAD_CAM_EDM_DRO] Why is my feedrate slow with stepper
> |motor
> |
> |
> |In a message dated 22-Mar-02 22:06:14 Central Standard Time,
> |rnichol1@n... writes:
> |
> |
> |> Is this normal for stepper motors? I'm thinking of designing a
> |> current limiting or chopper(?) circuit but do not know

electronics.

> |>
> |> I'm guessing others have been here already. Will a chopper

circuit

> |> work? could the k-cam software be part of the problem (I get
> |> a "stop" for one cycle every rev that gets more pronounced with

speed

> |> rate)
> |>
> |> Any comments / advice?
> |
> |
> |Roger: This is what it's all about! A properly designed stepper-

motor

> |driver of either the "old" L/R type, or the new ("only kind to
> |even consider
> |these days!") "bipolar chopper drive" usually takes-in at least 24
> |VDC, and
> |feeds the motor with "constant current" (well, ideally, anyway).
> |12 VDC is
> |way-low!
> |
> |Why re-invent the wheel? A couple of guys on this group

manufacture/sell

> |bipolar-chopper drives, and MY choice is Mariss' Gecko Drive G210.
> | It does
> |what you want, AND will keep the speed "up", if your DC supply is
> |at least 24
> |volts. Maybe on up to 80! Mariss might comment. HIS advice is

gospel!

> |
> |Jan Rowland