re:Re: lathe arcs

Carey,

Can you break your arcs down into a series of short straight line
segments? Not the best way to do the turning, but might get you out
of trouble until you find the cause of the problem. Keep the
segments short and you won't notice the difference between continuous
arcs.

Sometimes I have to do the same thing on an older Emco production
machine with steppers. Emco limited the programmable arc radius to
something in the 5" range to eliminate possible stair steps on the
part due to machine resolution.

BTW, what are the rollers for? I turn special rolls for my power
beading machine once in a while.

Doug

--- In CAD_CAM_EDM_DRO@y..., "Carey L. Culpepper" <mr.c@b...> wrote:
> Ballendo: The machine still makes the original "angular" rollers
perfectly. Actually it will do the roughing passes on the parts
> with arcs until it goes for the finish pass. Then it goes nuts.
Everything looks good until it hits the code for an arc. Sometimes
> it just keeps going straight. Other settings did a chamfer instead
of an arc.Nothing resembling an arc.
> I did cheat the system by using the CNCPro driver and reconfigured
to use x-y axis (easy to do with cncpro-tis in the setup,no
> changing wires) and did use G18. Same bad stuff but I had to try
it. Doug emailed me back and recommended trying relative
> coordinates. Then it followed an arc but didn't cut the part the
same as the drawing. I found trying to use relative coordinates
> difficult to set up where to set the tool to start to wind up with
the correct diameter. I did take some time and made up a
> penholder that is held in a magnetic base to draw the part on paper
so I would get a hard copy of where the machine was going. I
> have tried a lot of things -drawing in different quadrants-changing
axis direction-cutting direction. I have tried so many things
> that I am probably duplicating attempts. It will probably be a
driver setting that is the problem. I sent Don a screen print of the
> driver setup and the roughing finishing setup windows. Waiting to
hear back . He had to work till noon today. I am about ready for
> the looney bin at this point. Thanks,Carey
>
> ballendo@y... wrote:
>
> > Hi Carey,
> >
> > Don's probably got ya covered, but just in case...
> >
> > First, Can you correctly make the "previous" rollers now!? Using
> > whatever means you used before? If so, then you know there is no
> > change in the system functionality. If NOT, then you know to look
at
> > ANY changes made since they last ran correctly. I would keep
trying
> > to run them until they are cutting correctly; THEN go to the "new"
> > stuff.
> >
> > Don mentioned G18. You could also use g17 (xy plane for arcs)
> > and "cheat" by changing the cables to the motors.
> >
> > Sorry I can't do more than this. I have mentioned in the past
that I
> > have experienced some "strange" output from CncPRO... usually
> > excessive Z motion. Would this correlate to your problem? I.E.,
the
> > arcs are ellipses or worse, jagged ellipses?
> >
> > Hope this helps.
> >
> > Ballendo
> >
> > --- In CAD_CAM_EDM_DRO@y..., "Carey L. Culpepper" <mr.c@b...>
wrote:
> > > I am in need of some help. I am doing lathe work on my cnc
converted
> > > Hardinge hlv-h lathe. I am making forming rollers for
specialized
> > sheet
> > > metal shapes. The first sets of rollers were strictly angular
flats
> > and
> > > angles. The next stages require arcs (fillets). I cannot get my
> > machine
> > > to cut the arcs. It machines all of the flats and angles
perfectly
> > but
> > > does weird things when it gets to the arcs. The drawings and
gcodes
> > are
> > > Vector 8.2 generated. I even went back and altered a previous
BobCad
> > > drawing(which was used to make the previous rollers without
problem)
> > > with some fillets. Same type of problem. I have been working on
> > this for
> > > several long frustrating days. I have talked with Fred and tried
> > some
> > > things and emailed Doug and tried doing it with relative
coordinates
> > > which did result in some arcs but still not accurate to the
> > drawing. I
> > > am using CNCPro as a control program. I have tried drawing in
> > different
> > > quadrants, all manner of different things- all wrong. This is
> > probably
> > > something really simple as far as setup(to the experienced
> > operator) but
> > > I just haven't found it yet. I made up a pen holder to draw the
tool
> > > path on the lathe and have gotten some rather unusual shapes.
Fred
> > and
> > > Doug have been very helpful but it is the weekend and I am
> > desperate.
> >
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