Homebrew PCBs

>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