RE: Freqmod problems

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

we have the remains of one (the old cybermation control) sitting in the back
of our building. I don't miss not being involved in trying to keep one of
those running. The y-axis sounds kind of like and old Heath machine (they
were one of several absorbed by esab)

Our plasma machines routinely run at cut speeds of 500 to 300 IPM with rapid
moves at 600 IPM (we have played with 1200 ipm but it doesn't make
production all that much faster - you still have to accelerate and
decelerate..) We have 1500 watt drives on each end and the y-axis and we
still have to careful of the tuning to keep the cut quality where customers
want it.

To stiffen your machine I would recommend putting a second drive on the
other end of the X axis and connect the stepper driver in parallel with the
existing X drive. As long as you are running steppers that should cause no
problem as long as both ends can keep up. That may also help reduce
following errors it would take a lot of the flex out of the beam and rail
system. Also check out the linears - when they are new, clean and tight they
work great, but a bit (or a lot) of wear and they can really bog down. They
can be hard to keep clean and the bearings will tend to slide rather than
roll. We use an 8" hardened wheel to support the machine and ball bearings
on either side of the master rail (rail is rectangular) and then run a piece
of 1/4" brass plate on top of the rail with a low pressure air stream to
help blow the dirt away. Plasma & Oxy/fuel present some of the same problems
that wood & plastic dust present - it gets everywhere, put a little pressure
on it and it will stick and stay put unless moving would cause more problems
and then it will migrate to the place where it can cause the most problem.
Wood dust though can burn, and does attract moisture helping things rust.
>
> Pete,
> it is a gantry machine, with the ball bearing type
> linear bearing on the master rail, cam follower on the other end.
> Single axis drive. rail is approx 16" from top of table, with 8" of
> clearance. y axis uses a carriage with 3 sets of bearings at
> +_45 degrees to the rails top and bottom, this machine was
> originally a cybermation cnc router, with the usual pdp-8 controller.
> it ran in the 150-300 ipm range. From what I understand, cybermation
> bought the tables from esab and added a bunch of controls to them.
> I've spoken with someone who routinely retros these and uses 23 frame
> triple stacks, a linear bearing on the cam follower end of the gantry,
> and can get 400+ ipm, BUT you have to rebearing, and everything has
> to be perfect, and stay that way. Not realistic in a sign
> shop, where we
> have
> dust from routing, overspray, etc. i'd be happy with 200 ipm
> and a 1 -2 mil
> step size, as we route primarily aluminum, brass and wood/foam.
> any help or suggestions you can give are greatly appreciated, as
> when I have this one running reliably, my plan is to build a 5x10 for
> more detailed work.
>
> 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 10:48 AM
> Subject: RE: Freqmod problems
>
>
> >
> > 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
> > > > >
> > > >
> > > >
> > > >
> > >
> > >
> >
> >
> >
>
>