Re:[CAD_CAM_EDM_DRO] Re: Newbi needs advise on torch table. - now THC(oops)

> Sorry about the double post here, I accidentaly hit
> send before I was done. Please disregard my first
> post.
>
> I think that the system that you are using has some
> very strong merits for most people. Eventually I will
> probably go that route or something similar. I have
> two problems with it though.
>
> 1. I can't control a oxy/acetylene torch with
> this system. Which probably is not a very big deal,
> though I would like the ability to cut larger pieces
> of steal then what plasma will pierce. Ideally I
> would like to have the ability to cut some thick
> chunks of steal up to say six inches. Obviously I
> will need to make multiple passes no matter what I cut
> with.
> 2. Second and not so important I have to use
> Windows to run the system. I have no problem with
> Windows, it just is not my preferred choice.
>
> Will
>
>
> --- caudlet <info@t...> wrote:
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com,
> > "turbulatordude"
> > <davemucha@j...> wrote:
> > > > MACH2 is cheap, well written, constantly being
> > improved and the
> > THC
> > > > is real and working. I cut for 4 hours today
> > using it.
> > >
> > >
> > > Hi Tom, and all,
> > >
> > > I am not totally clear on the THC problem.
> > >
> > > it seems that the table requies an X/Y to move the
> > head, but the Z
> > > can be independant. lower to part, start cutting,
> > let it be
> > > independant of the rest of the CNC software and
> > just keep it's
> > > location based on voltage.
> > >
> > > Then just wing that sucker around the table as
> > needed.
> > >
> > > why is it so critical to have the CNC software
> > keep track of the
> > > head ?
> > >
> > > a command up with an end switch prior to any
> > non-cutting moves, and
> > a
> > > start cutting with a resultant 'go' from the
> > independant head
> > control
> > > seems like a simple approach.
> > >
> > > After all, don't a log of guys just ignore THC all
> > together ?
> > >
> > > My EDM is similar in that the electrode postioning
> > in seperate from
> > > X/Y and even total feed is not counted as
> > electrode wear has a huge
> > > effect on distance.
> > >
> > > I 'home' to home, then re-zero on the first spark,
> > then burn to
> > depth
> > > figuring no electrode wear, then home again, then
> > back to the
> > > starting zero and then measure the electrode wear.
> > From that I can
> > > caluclate wear in that part and how much farther I
> > need to go.
> > > Mind you none if this is critical, I'm still
> > setting things up.
> > >
> > > Dave
> > Dave: You are correct. You can run the Z totally
> > independent of the
> > XY. There are several commercial products ($$$$)
> > available to do
> > that. In essence they use an external micro chip to
> > measure the gap
> > voltage and adjust the torch height using DC motors.
> > That has been
> > the conventional way it has been done for a long
> > time.
> >
> > As an Engineer I started looking for a THC solution
> > as I was building
> > my table. I could not afford the commercial units
> > and the nearest
> > thing was a RUTEX kit that was about 500 bucks and
> > required a
> > bewildering array of sensors that had to be
> > constructed and provided
> > by the "Builder" (me). Since I had already planned
> > on making the Z
> > axis a full Step and Direction design so my table
> > could also be used
> > for other stuff, I felt is was redundant to design
> > and build some
> > sort of electronic "switchover" so that the motors
> > could be
> > controlled by the THC rather than the
> > computer.....if only I could
> > find a piece of software that could do the "logic"
> > part as well as
> > the XY control then all I had to design was the
> > sensing and measuring
> > hardware. Art of Master5/MACH1 fame agreed to
> > modify his software to
> > my specs and I set out to build a real cost
> > effective solution.
> >
> > Once you get out of the manual control or the
> > set-it-and-let-it-cut
> > approach (both which I tried), then you face several
> > issues:
> >
> > 1. You need to be able to control the pierce cycle.
> > You need to be
> > able to find the material surface, move the head
> > down to a specified
> > pierce point, and start the arc.
> >
> > 2. You need to wait a variable length of time until
> > the arc has been
> > established, lower the head into the cut then
> > release and start the
> > XY moves.
> >
> > 3. Dynamically adjust the head during the cut to
> > account for material
> > unevenness and warpage.
> >
> > 4. Do that cycle each time, for each cut, because
> > the position of the
> > head is not known after it starts adjusting UP and
> > Down
> >
> > The reason the commercial units cost so much is that
> > they have to
> > provide all of that logic in the unit. My reasoning
> > was that if I
> > could use the power of the controller PC and the
> > software logic then
> > I could do several things.
> >
> > 1. The sensing (surface zero) could be done and
> > maintained as
> > a "referencing" move in a g-code.
> >
> > 2. The pierce cycle could be integrated with the
> > controller to
> > provide XY hold and the sequence could be simple
> > g-code and added to
> > my CAM post processor.
> >
> > 3. The controller software would adjust the Z height
> > on the fly and
> > it would "know" where the absolute position of the
> > head was so you
> > could skip the re-zero move on every individual cut.
> > That would also
> > provide a know distance to start the pierce and
> > lower the head for
> > cutting.
> >
> > 4. You could set limits in the software to prevent
> > the head for over
> > compensating (max and Min adjustments).
> >
> > The cost then becomes just the external sensing
> > components.
> >
> >
> > We were able to do all of those things so that now
> > cutting material
> > is a smooth operation and I trust my machine enough
> > to load a piece,
> > hit RUN and walk off to work on cleaning up the
> > previous piece I just
> > unloaded. My CAM software POST puts in all of the
> > g-codes so now I
> > just draw the design, run it through CAM to define
> > the cut vectors
> > and lead-ins, and load it on the machine. The whole
> > process takes
> > minutes.
> >
> > Can you live without a THC....yep. You can use a
> > drag tip and
> > floating head and do a lot of stuff but that has
> > issues as well.
> > If you cut very much material though, you will
> > quickly decide it (THC)
> > is a neccessity rather than a luxury. Could you use
> > a different
> > approach? Sure, but you would be giving up some
> > features that are
> > real nice to have. I find my consummables (tip &
> > electrode) costs
> > are almost double when I don't do things in the
> > right sequence and
> > use the THC. If you cut 3 pieces a week then NBD,
> > but if you cut 20
> > a day like I do sometimes then I go through a LOT of
> > tips.
> >
> > Tom C
> >
> >
> >
> >
> > Addresses:
> > FAQ: http://www.ktmarketing.com/faq.html
> > FILES:
> > http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> >
> === message truncated ===
>
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