Runaway is something i was worried about, and I still havnt determined the
culprit of why the Y ran off that last day the machine was in service in the
shop it was in. So far I know that the A and B signals from the encoder are
good, havnt tested the z, znot, anot and bnot yet, and I have to solder a
couple wires into the tach because one of the cats got to it and thought it
was tasty enough to chew in half.
I was hoping that if I limit the commanded voltage to the amp and turn the
gain down enough, I could keep it from turning fast enough to miss counts,
but im not sure how safe this would be. the last time this machine crashed,
it had a tool changer arm there to help it decel. When(if) I do get EMC
connected up to the amps this way, it'll go through considerable testing
on the bench before putting the motors back on the machine. I'm just
hoping to be making some chips before I have saved enough to buy the mesa,
but dont want to see how hard i can smack the end of a ballscrew or the hard
stops. not sure if the tach's signal could somehow be used, to switch the
estop on if the voltage gets over a certain point.
for the tooling and the spindle, im pretty sure its CAT 40. I've always
just heard it refered to as '40 taper' and it's the same holders (minus
pullstuds) that the fadals and the haas VF2,4, and 5 use at the shop.
the motors and amps are sanyo denki BL-super
>From the machine's manual the motor and amp combinations are..
X motor 20BM090MXP42 amp 27BA030FTH1 torque cont./stall 90/200 kg-cm
Y motor 20BM090MXP41 amp 27BA030FTH1 torque cont./stall 90/200 kg-cm
Z motor 20BM220MBP41 amp 27BA050FXTH2 torque cont./stall 200/340 kg-cm
all max 1500 RPM, overspeed detection speed at 2400 rpm
I've googled around but couldnt find any info on these, i have what looks
like a datasheet, but it's in japanese, so i sure cant make anything of it.
If anyone happens across some docs i'd love to see them.
On Sun, Aug 10, 2008 at 10:11 AM, Peter C. Wallace <[EMAIL PROTECTED]> wrote:
> On Sun, 10 Aug 2008, Jim Coleman wrote:
> SNIP___________________________________________________________________
> >>
> >>> Also, what do I need to add in the hal and everything to enable an
> >>> index on the encoders? I'm thinking I can see if it is missing counts
> >>> if I have an index to reference.
> >>
> >> I think you would need to write a custom component that reads the
> >> software decoder counter on the first index trigger and then compares
> >> that with subsequent counts on index to see if they happen on multiples
> >> of encoder counts per rev. I wouldn't mind seeing more background error
> >> checking of hardware subsystems.
>
>
> This brings up a real hazard here: If you get going so fast you miss counts
> with your software encoder counter, you can lose control of your servo.
> Index
> pulses tend to be short so they may disappear at the same time. Normally I
> would expect this set of circumstances to throw a FE, but I would not trust
> my
> life or even a small appendage to this always happening.
>
> Servo runaway can also happen with hardware failure in ways that will not
> throw a FE ( say a broken encoder wire+ an integral term in the PID
> loop...),
> so I think its good to have some kind of excessive drive detection (maybe
> as
> simple as detecting full drive for 20 or so samples in a row)
>
>
>
>
> >>
> >>> I hope all of this makes sense, its been a long day and I'm excited
> >>> I've actually made a little progress.
> >>>
> >>> Thanks guys,
>
> >>> Jim Coleman
> >>
> >> Are you doing more than one project? I thought you where well along on a
> >> mill conversion. Could you give us a summary of what you are doing?
> >>
> >> --
> >> Kirk Wallace (California, USA
> >> http://www.wallacecompany.com/machine_shop/
> >> Hardinge HNC/EMC CNC lathe,
> >> Bridgeport mill conversion, doing XY now,
> >> Zubal lathe conversion pending
> >> Craftsman AA 109 restoration
> >> Shizuoka ST-N/EMC CNC)
> >>
> >>
> >>
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>
> Peter Wallace
> Mesa Electronics
>
> (\__/)
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