Re: Electronic Lead Screw & Power Cross Feed | Poor Man's CNC ?

Right Bob,
You've got it right.
about two weeks ago I've post the same thread on electronic gear,
but was turn down with the same "hook up a computer and you have a
full cnc controller."
I have a old south bend clone missing gears,and this would be
perfect for it.
I don't want to have a full cnc lathe, if I can cut threads it
would be fine.
As you mention there is a lot more than just hook up motors and get
a computer to run it, after that done you still have to replace the
leadscrews, learn how to programm fight with software control and
have a big controller box and find a place to put it.
Here is a nice and compact exemple:
Atmel at90s2313
Lcd
a stepper drive based on a3977 from allegro.
I make a stepper controller board based on the allegro microchip
with galvanic opto isolated inputs and it's about 5 1/2 x 4 inches
size could be smaller if I don't want it opto isolated.
Get a code into the at90s2313 chip, and you'll have a box about 8 x 8
inches that will do the job without a computer and costs less than
$150 bucks.

Fogassa.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Vaso" <borpe2001@y...> wrote:
>
> Bob:
>
> You've done an excellent review of the entire issue. Full CNC is
> clearly far more complex than electronic lead screw - and requires
far
> more learning time. CNC leads to a different lathe machine
altogether
> - where "machining" is replaced by "programming" - even for simple
> one-off pieces. I understand - once converted to CNC - a "CNC lathe"
> cannot be a good "hands-on" manual lathe - except maybe with
expensive
> electronic handwheels.
>
> My thinking so far is to do a CNC conversion of my Super X3 Mill -
> because, in a mill, full CNC has overwhelming advantages. In a
simple
> bench lathe, however, electronic lead screw is all I really need -
for
> control of threading ratios and traverse speeds - with perhaps an
> extension to electronic cross feed.
>
> Full CNC does have the large advantage - as you point out - that
much
> of the R&D work has already been done. Would a few people be
> interested in setting up a Yahoo Group devoted exclusively to
> developing a generic and adaptable Electronic Lead Screw design -
with
> perhaps SIEG's C6B as a test bed ? Once developed as an "Open
Source"
> design, electronic lead screw implementations should be very cheap
> compared to full CNC.
>
>
> ---"BobWarfield" <bob@t...> wrote:
> > I think the CNC setup is actually considerably more complex than
> > what is contemplated in the strictest sense of an electronic
> > leadscrew and I'll tell you why. It all sounds like a case
of "Gee,
> > if I have to hook up a stepping motor anyway, why not just go
CNC?"
> > However, let's look at a couple of different reasons why that is
not
> > really the case.
> >
> > First, we have to make sure we are doing an apples to apples
> > comparison. It is certainly true that there are no electronic
> > leadscrews to be bought off the shelf today unless you want to
count
> > the short-lived Frog CNC. I will therefore readily admit that
the
> > development of an e-leadscrew from scratch will certainly be more
> > complex than to piece together a CNC system from off-the-shelf
> > components. So let's assume the e-leadscrew exists. Not so far
> > fetched, BTW. As was pointed out, there is the Frog CNC and also
> > this conversation keeps coming up on all sorts of boards.
Clearly
> > there is demand or interest, and someone is going to get around
to
> > building one. Heck I heard Cletus Berkeley say he was going to
look
> > into it over on another board, and there is a fellow on the Home
> > Shop Machinist board that has built an electronic gearbox for a
gear
> > hobbing machine, so someone WILL do it!
> >
> > So what would this new animal be like? Well, it's going to be
very
> > simple because it doesn't have to do much. Again, if you have
ever
> > seen a Frog CNC, there is nothing to it. It's a tiny little
circuit
> > card with a membrane keyboard and LED readout that's built around
a
> > PIC controller. It's got a stepper driver on board and takes a
> > spindle encoder signal in.
> >
> > Let's imagine something very similar to the Frog CNC will work.
In
> > fact, I think it will be very similar to the Shumatech DRO in
terms
> > of the complexities involved (hence a thread about this on that
> > board too). Lots of folks manage to get one of those DRO's up
and
> > running for around $150 plus the cost of the scales. Picture
> > something similar here. You order the blank PC card from a
> > Shumatech-like entity, buy your parts to populate it, solder it
> > together, and $150 plus a little time later, you are ready to
plug
> > it into your spindle encoder and leadscrew stepper motor you got
on
> > eBay.
> >
> > Which brings me to my second point. If that solution existed
today,
> > it's a lot simpler than full CNC. If I can really build the
thing
> > for $150, buy a surplus stepper from eBay, and hook together a
few
> > parts for a spindle encoder, it is hard for me to regard that as
> > even approaching the complexity of CNC.
> >
> > Let's just break it down. I have to have a PC for CNC. What if
I
> > don't have a spare sitting around? Even a cheap obsolete PC
costs
> > as much as the DRO. I have to configure it properly for my
> > software. TurboCNC doesn't want to run on Windows XP, so I gotta
go
> > deal with that. Mach will run on XP, but the software costs as
much
> > as my PIC controller for the leadscrew and its just one piece of
the
> > solution. I need a Gecko drive, which is another $100. It's
very
> > possible my PIC-based project can deal with driving one stepper
> > right on the card for its $150 cost as we already saw with the
Frog
> > CNC device. What about backlash? The CNC crowd certainly spends
a
> > lot of time talking about it and going on about ballscrews to
avoid
> > it or various other solutions. Ballscrews are big bucks. The e-
> > leadscrew doesn't care about backlash because the operator deals
> > with it as a matter of course. How about a breakout card so my
PC
> > can talk to my Gecko drive? Campbell designs makes a great one,
and
> > oh by the way it too costs as much as a Shumatech DRO. Maybe I'd
> > like a nice pendant, because I really don't care to type on the
> > keyboard and click the mouse, I want to work on my lathe for
crying
> > out loud! www.lowcostcncretrofits.com has one that plugs into my
> > USB port (hope I didn't buy an old 486 machine to save money!).
> > Guess what, it too costs about what that darned Shumatech DRO
would!
> >
> > Now just about every component in the CNC system has cost as much
as
> > the e-leadscrew electronics, each and every one of them has a
> > learning curve before I can get it to work at all, and we haven't
> > even gotten on to the real learning curve associated with the
fact
> > that your machinist may know full well how to make parts with his
> > lathe but not know the first thing about CNC, or care to learn.
> > He's just tired of digging around in the swarf to find the right
set
> > of gears to cut a thread he needs or change the feed speed to get
> > rid of some chatter.
> >
> > It's all fine and well to argue CNC is better, but its really
better
> > at solving a completely different problem and it is far from
being
> > simpler or "you might as well go for CNC if you are going to go
to
> > all this trouble anyway."
> >
> > BTW, the clever thing about the Frog CNC is you can use it as an
> > electronic leadscrew AND as a breakout box + stepper driver.
This
> > way you get both CNC if you hook up all the extra components and
a
> > vastly improved manual lathe if you want to focus on one-off
parts.
> > That too would be a nice attribute for the e-leadscrew when it is
> > available.
> > BW
> >
> > ---"Paul Kelly" <tech@c...> wrote:
> >> This thread crops up with some regularity.
> >> Yep, you could make a setup, as described, work. Or you could
> >> add one more motor. And use simpler, off the shelf electronics
> >> (or simpler, 'you build em', electronics) and have a CNC setup.
> >> Typically the proponents of the electronic gearing systems feel
> >> that, because you can do so much more with it, a CNC setup must
be
> >> more complex. In fact, this is not the case. Vaso alludes to the
> >> reality of the situation. The issue is mostly about stepping out
> >> of your comfort zone and learning a new thing...
> >> PK
> >>
> >> -----Original Message-----
> >> From: On Behalf Of Vaso
> >> Sent: Sunday, 4 December 2005 5:54 PM
> >> Subject: Re: Electronic Lead Screw & Power Cross Feed |
> >> Poor Man's CNC ?
> >>
> >> I've done machining for several years, but I'm new to CNC. I'm an
> >> electronics engineer, so an electronic approach to gearing -
> >> rather than mechanical gears - appeals. This PLL (Phase Lock
> >> Loop)method is well-known in electronics.
> >>
> >> Maybe electronic gearing could be called the "Poor Man's CNC".
I'm
> >> less interested in full programmable CNC right now than I am in
> >> correcting some deficiencies in the SIEG C6B lathe I just
bought.
> >> The C6B has variable spindle speed, but fixed saddle traverse -
so
> >> feed rate is either 0.1mm/rev or 0.2mm/rev and switching between
> >> the two is awkward. There is no Quick Change Gear Box, so
> >> threading requires manual gear substitutions. There is no Power
> >> Cross Feed, and there is no taper attachment. Seems to me PLL
> >> control of the lead screw, as described in this article, with the
> >> enhancement of microprocessor control of speed ratios, could give
> >> practically unlimited threading and traverse speeds. Power cross
> >> feed could also be arranged by this method. If Power Cross feed
> >> linked to lead screw speed, then this is effectively an
electronic
> >> taper attachment. Several tricks short of full CNC could be
> >> microprocessor-controlled.
> >>
> >> Am I missing something ?
>