Re: Freqmod problems

["Shelbyville Design & Signworks" <signworks-at-mcleodusa.net>]

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
> >
>
>
>