RE: Freqmod problems

["Pete Cook" <pete.cook-at-alltracorp.com>]

A couple more questions - is this a gantry or a cantilever machine (1 or 2 X
axis drives)? High rail(30"), mid rail (16") or low rail(8")?

Many of those machines ran fine as Oxy/Fuel machines but they were niether
fast enough or stable enough for plasma speeds. For the machines with a
single X drive it was a fairly routine upgrade to hang a second slave drive
on the other end ot the beam to stiffen them up.

I have seen them run with 80 watt servos, but that was only for oxy/fuel
with 150 watt servos used on a plasma machine to handle the speed. Oxy/fuel
is normally in the speed range of 8 to 20 ipm with plasma 50 to 150 ipm (or
faster on sheet metal).

Also - for plasma & oxy/fuel there is no tooling force like there is with a
router.

Pete
>
> Pete,
> I agree, the design of the gantry is less than desirable,
> rigidity is not
> it's strong point.
> I have no idea why cybermation used these as the basis for
> their router.
> the "bounciness" is the reason why I'm going to a 550 oz-in
> motor on the
> x axis, and will be replacing the cam follower with a linear
> bearing and
> carriage as soon as I can find a few $ the wife doesn't know about.
> the next iteration will more than likely have a 4 x 8 gantry,
> with linear
> bearing at each end,
> I'm hoping to reduce the mass to under 150 lbs.
>
> I bought this machine with a trashed controller, I still have
> the original
> servos, I've considered
> mounting encoders and using G320's to drive it, but I have
> several steppers
> sitting around, so
> I'll play for a little bit. All in all, I have $1000 invested
> into this so
> far, including a water cooled precise spindle,
> I'm willing to trade off convenience for lower initial cost
> as our business
> is only 2 years old and far from
> even thinking about profitability.
>
> erie
> Shelbyville Design & Signworks
> 1309 W. S. 7th Street
> Shelbyville, IL 62565
> (217)774-4444
> visit our website at http://216.43.233.169
>
> ----- Original Message -----
> From: "Pete Cook" <pete.cook-at-alltracorp.com>
> To: "Multiple recipients of list" <emc-at-nist.gov>
> Sent: Tuesday, February 12, 2002 10:00 AM
> Subject: RE: Freqmod problems
>
>
> >
> > Question - Does Freqmod use encoders for feedback?
> > If so what are the PID Parameters?
> >
> > I work on these machines (still as plasma cutters) and am
> familiar with
> them
> > with servos attached. The biggest problem I have seen is
> that most of the
> > drive systems are too small and don't handle the bounce
> that is inherent
> in
> > that type machine. If you try to drive tha machine without
> gearboxes in
> the
> > drive train yopu are going to need a whole lot more torque from your
> motors.
> >
> > Pete
> >
> > >
> > > Erie
> > >
> > > Hey I wonder if the following error problem with freqmod is
> > > related to
> > > the notion that we have explored before that if you run
> at the max,
> > > during accel you pile a few pulses into the following error
> > > buffer that
> > > can't get put back into motion.  You might try setting
> > >
> > > [TRAJ]
> > > ..
> > > MAX_VELOCITY =          1.67
> > >
> > > a little larger than
> > >
> > > [AXIS_0]
> > > ..
> > > MAX_VELOCITY =                  1.2
> > >
> > > for each axis.
> > >
> > > You should also set
> > >
> > > DEFAULT_ACCELERATION =  20.0
> > > MAX_ACCELERATION =      20.0
> > >
> > > much lower than default.
> > >
> > > HTH
> > >
> > > Ray
> > >
> > >
> > >
> > > On Tuesday 12 February 2002 09:11 am, Shelbyville Design
> & Signworks
> > > wrote:
> > > > specifics:
> > > >
> > > > Gantry router, 8' x 12' work area
> > > > rack & pinion drive
> > > > 23 frame stepper approx 200 oz-in or so, running halfstep,
> > > geared 40:1
> > > > with a 24 d.p. 30T pinion
> > > > (step size is about .00025, way to small for routing, but
> > > this project
> > > > started out with a real small
> > > > budget (wife holds the purse strings and we all know how
> > > that goes) and
> > > > the reducers were already on the machine)
> > > > gantry weight is approx 600 lbs +-
> > > >
> > > > (if you've ever seen a Heath/Esab plasma cutter, it's the
> > > same machine)
> > > >
> > > > running the table on Turbocnc I can achieve 150 IPM easily,
> > > > but no contstant contour.
> > > >
> > > > I am going to be removing the gear reduction and going
> to gecko 201
> > > > drives, with a 550 oz-in
> > > > motor on the x axis, dirctly driving a 20T pinion, it will
> > > increase the
> > > > step size to approx .0015, this should
> > > > help with the speed, but the biggest problem is
> inconsistent step
> > > > pulses (scope confirms this)
> > > > with this much inertia, it doesn't take alot to throw
> things out of
> > > > whack.
> > > >
> > > >
> > > > erie patsellis
> > > >
> > > >
> > > >
> > > > Shelbyville Design & Signworks
> > > > 1309 W. S. 7th Street
> > > > Shelbyville, IL 62565
> > > > (217)774-4444
> > > > visit our website at http://216.43.233.169
> > > >
> > > > ----- Original Message -----
> > > > From: "Hugh Currin" <currinh-at-oit.edu>
> > > > To: "Multiple recipients of list" <emc-at-nist.gov>
> > > > Sent: Monday, February 11, 2002 6:23 PM
> > > > Subject: Re: Freqmod problems
> > > >
> > > > > Erie:
> > > > >
> > > > > What type of machine are you using?  i.e. size steppers
> > > and drivers.
> > > > > I'll
> > > >
> > > > bet
> > > >
> > > > > someone on the list has an *.ini file they'd be willing
> > > to send you
> > > > > as a starting point.
> > > > >
> > > > > I have freqmod working with 760 oz-in motors, Camtronic
> > > drivers half
> > > > > stepping, 2:1 reduction timing belts on a bridgeport
> kneemill size
> > > >
> > > > machine.
> > > >
> > > > > Does this come close? It isn't optimum but may be a
> > > starting point.
> > > > > :-)
> > > > >
> > > > > Hugh Currin
> > > > > Klamath Falls, OR
> > > > >
> > > > > On Monday 11 February 2002 04:03 pm, you wrote:
> > > > > > am I the only one who has unsuccessfully tried to use
> > > > > > freqmod with steppers? no amount (I've spent at least 8
> > > > > > hours on this so far) of pid tuning seems to
> eliminate following
> > > > > > errors. Steppermod.o for now.
> > > > > >
> > > > > >
> > > > > > erie patsellis
> > >
> >
> >
> >
>
>