>discussing milling or drilling.
That should have been milling or routing.
--- In
Homebrew_PCBs@yahoogroups.com, "derekhawkins"
<derekhawkins@y...> wrote:
> >A 40 pound table would not move, the drill
> >bit would break.
>
> LOL! Where is the force trying to move the drill bit coming from?
> Assuming such a force existed, why would this force suddenly
> disappear with a perfect zero backlash setup and not break the bit
> then also? Both a 40 pound table and a zero backlash setup would
have
> the same thing in common "THE TABLE WON'T MOVE".
>
> Any slop would be manifested as spurious ∗∗movement of the table∗∗
in
> the backlash dead zone since the X and Y screws are "fixed" at
drill
> time by the holding torque of the motor. You seem to be confusing
> drilling and milling in the same random thought.
>
> >There will be others here that will be using dremels and will be
> >using very lightweight tables with loose construction.
>
> With the right size hole the bit will be piloted to some extent in
a
> lightweight setup just as in manual drilling. Most of us are alrady
> familiar with that trick. Long story short....You're making a
> mountain out of a mole hill. However, I would agree with you 100%
if
> discussing milling or drilling.
>
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "lcdpublishing"
> <lcdpublishing@y...> wrote:
> > Considering that most of the drill bits used for circuit boards
are
> > so small, they probably would bend or break before they cause the
> > table and part to move. A 40 pound table would not move, the
drill
> > bit would break.
> >
> > There will be others here that will be using dremels and will be
> > using very lightweight tables with loose construction. So, while
> > you may not agree, fact is fact, software backlash compensation
is
> > not the "Solution" to poor machine design and construction.
> > However, sometimes you can get away with it.
> >
> > Furthermore, you make the statement "If you know what you are
> > doing", well, considering that most of the people considering
> making
> > a CNC machine will be their first CNC (and probably machine),
it's
> a
> > bad assumption. Again, "trickery", is not a good solution to
poor
> > machine design and construction.
> >
> >
> >
> >
> >
> > --- In Homebrew_PCBs@yahoogroups.com, "derekhawkins"
> > <derekhawkins@y...> wrote:
> > > >When drilling, the position will be off and the
> > > >holes will not be on size.
> > >
> > > I don't agree with this. Perhaps with a light table and a high
> > runout
> > > drill such as the ubiquitous Dremel one may have an issue. With
a
> > > heavy table (the X axis and saddle in my setup weighs over 40
> lbs)
> > > and a low runout drill this is not an issue. Backlash
> compensation
> > in
> > > software is very effective when it comes to precision drilling
> IMO
> > > provided you know what you're doing. Milling and routing is
> > another
> > > story.
> > >
> > > --- In Homebrew_PCBs@yahoogroups.com, "lcdpublishing"
> > > <lcdpublishing@y...> wrote:
> > > > While I don't fully know the exact details, I can tell you
> right
> > > > away, you cannot rely on software to eliminate the backlash
> > within
> > > a
> > > > CNC system. For basic positioning, perhaps a little, but in
> > > > practice, no.
> > > >
> > > > While software can compensate for the static deviation
between
> > > where
> > > > it told the motor to position and where it really is based on
> > > > encoder feedback, the "Slop" is still there. During cutting,
> > the
> > > > dynamic cutting forces will cause the axes to move around
> within
> > > the
> > > > mechanical slop. When drilling, the position will be off and
> > the
> > > > holes will not be on size. When milling, all sorts of
> > dimensional
> > > > problems pop up and in the end, you will have wished you took
> > the
> > > > time the eliminate the mechancial backlash.
> > > >
> > > > While there is backlash compensation within all CNC systems I
> > have
> > > > used in the industrial world, it is primarily only used to
> > > > compensate for a very samll amount of backlash .001" or less
> > > > usually. Beyond that and it is time to correct the mechanical
> > > > problems.
> > > >
> > > > So, don't waste your time or effort in thinking of a software
> > > > solution to backlash - backlash is a mechanical problem and
> must
> > be
> > > > designed out of the system for even the most basic of machine
> > > > performance.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > --- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
> > > > <stefan_trethan@g...> wrote:
> > > > > On Tue, 28 Jun 2005 08:36:23 +0200, mikegw20
<mikegw20@h...>
> > > wrote:
> > > > >
> > > > > > Now I have never built a CNC anything and I am not overly
> > > > mechanical.
> > > > > > Right that is my qualifications out of the way...
> > > > > > I was thinking about high torque motors to drive a linear
> > > thread
> > > > and I
> > > > > > thought about those really cheap cordless drills. That
is
> > idea
> > > > pt1.
> > > > > > Now of course you need some sort of feedback for the
> > position,
> > > > the
> > > > > > normal way would be to put a shaft encoder on the drive.
> My
> > > > thinking
> > > > > > is that if you used a linear encoder then you would get
> > absoulte
> > > > > > positioning thereby negating the need for backlash
> > > > compensation. Now a
> > > > > > quick look around ebay reveals that linear encoders are
not
> > > > cheap. So
> > > > > > has anyone used optical mice for a linear encoder? (idea
pt
> > b)
> > > > > > Here endith todays musings.
> > > > > > Mike
> > > > >
> > > > >
> > > > > cordless drills usually use a motor what the model-vehicle
> > > > builders would
> > > > > call similar to a "speed 600".
> > > > > Not a bad motor, and you can get replacements really cheap
as
> > > well
> > > > as
> > > > > better motors the same size.
> > > > >
> > > > > I would try to find drills with metal gears for this
purpose.
> > I
> > > > recently
> > > > > bought a very cheap one with plastic gears, it is still
> > working,
> > > > but i'm
> > > > > always expecting it to fail any time. It was cheaper than a
> > > > replacement
> > > > > battery for a better drill.
> > > > > There are often ebay lots of many drills.
> > > > >
> > > > >
> > > > > As for linear encoder, there are those striped plastic
strips
> > in
> > > > printers,
> > > > > but a much easier solution would be to use digital calipers
> > and
> > > > use the
> > > > > data-out, 'cause you would get absolute position not only
> > > > relative.
> > > > > Probably more expensive than shaft encoders and certainly
> more
> > > > expensive
> > > > > than steppers.
> > > > >
> > > > >
> > > > > ST