Re: [CAD_CAM_EDM_DRO] Spindle RPM control

Guys, I know this is an idea exchange and that's fine, but controlling
speed via an axis o/p seems to be getting awfully complicated to
implement both in hardware and software (g-code). I for one really like
the KIRSS principle (keep it "relatively" simple...).

I have a Hitatchi SJ100 VFD on my BP clone - I've found that for 99% of
my routine metal munching, I only use two speeds out of my VFD: fast
(for a BP spindle) at 4800RPM and moderate, around 2500RPM. I just use
one output line from my flashcut controller to select speed and another
to select on or off. Then I programmed the VFD to watch two of its 5
input lines accordingly. In my flashcut config, I created two M codes
(I arbitrarily chose M50 for low speed and M51 for high speed) which my
CAM software can also generate, based on programmed speed. Later I may
assign another i/o line and M52 & M53 to get a total of 4 programmable
speeds - if the need arises.

Question: Has anyone fitted external braking resistors to an SJ100 VFD?
I find that I can turn the spindle faster than 4800RPM but above 4800,
I get E07 errors due to overvoltage generation when decellerating the
spindle motor. i.e. I need to brake the motor faster - to prevent the
error.

Cheers, Peter

Dave Lantz wrote:

>im thinking im missing something... aren't most hobby cnc retro's using some
>form of step'n'direction signal? from a parport? is there an existing
>circuit to control the vfd from step/direction?--dave l.
>
>-----Original Message-----
>From: Jerry Kimberlin [mailto:kimberln@...]
>Sent: Friday, September 27, 2002 1:27 PM
>To: CAD_CAM_EDM_DRO@yahoogroups.com
>Subject: Re: [CAD_CAM_EDM_DRO] Spindle RPM control
>
>
>Dave Lantz wrote:
>
>>if someone where to make some of these, i, for one would be interested in
>>purchasing! if i understand it right, it would be like a gecko 3XX for a
>>spindle, right? (but controlling rpm instead of position)--dave l.
>>
>
>Plenty of them out there already. If you have a 3 phase motor
>running 220v, you can just use a VFD. These things can be
>totally computer controlled as to speed, speed-up rate, slow-down
>rate, forward, reverse, etc. You really need a 3 phase motor to
>adequately adjust speed anyway, so I don't see why some VFD like
>a Hitachi SJ100 couldn't be used.
>
>Maybe using a VFD has already been discounted by those who know
>better. I don't know better as yet.... :-).
>
>JerryK
>
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