Homebrew PCBs

> We obviously have different 
> standards of right and wrong - I can back my statements up with 
> machine tool design in industrial applications, you cannot.

I'd be a fool to even try since these homebrew projects were never 
intended to be industrial applications? Maybe you should add "fool" 
somewhere in the subject line.

--- In Homebrew_PCBs@yahoogroups.com, "lcdpublishing" 
<lcdpublishing@y...> wrote:
> Again, as I have stated before, using software backlash 
compensation 
> is not an excuse for poor machine design and construction.  I agree 
> completly that a small circuit board drill would not move the 
table, 
> however, the larger the drill, the greater the problems.  I really 
> don't care to debate this with you. We obviously have different 
> standards of right and wrong - I can back my statements up with 
> machine tool design in industrial applications, you cannot.
> 
> 
> 
> 
> --- 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