Homebrew PCBs

All you are doing is quoting the specs for the **better** CNC 
machines out there. Something any idiot can do by going to the 
manufacturer's websites. It's like quoting the specs on Benzs, BMWs 
etc. and then giving the impression that these are the only cars that 
exist.

If a manual mill can have a backlash of .100" (I certainly wouldn't 
want to have one such as this but these are your words) and the owner 
was satisfied with it then why wouldn't he be satisfied after 
converting to CNC with backlash compensation in software? Why would 
his products suddenly be any worse?

Now here is where you're really foolish...Didn't you say this;

"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 small amount of backlash .001" or less usually. Beyond 
that and it is time to correct the mechanical problems."

Great! So you've used some of the better CNC systems out there. But 
you seem also to be suggesting that if any of us have backlash 
over .001" then it's a poor design.... How many in this group even 
have the capacity to measure .001" backlash? When drilling PCBs using 
a home setup, at least one reference point has to be arrived at 
manually, who the hell can do that with .001" accuracy? Do you even 
know the size of a typical PCB pad? Trust me, most of the guys here 
will be happy if the bit hits the pad...ANYWHERE!!! LOL!


--- In Homebrew_PCBs@yahoogroups.com, "lcdpublishing" 
<lcdpublishing@y...> wrote:
> Okay, Now you are just talking stupid.  The reason you would bet 
the 
> farm that you don't have to bet, is that you don't know what you 
are 
> talking about. Manual mills may have upwards of .100" backlash.  
> 
> Industrial CNC machines (and most hobbiest CNC machines) that use 
ball 
> screws have less than .002" backlash on the screws.  An even 
greater 
> majority of precision metalworking machinery (industrial machine 
> tools) have less than .0006" of backlash.  Most machine tools using 
> ball screws go so far as to even put two nuts on with a tab between 
> them to further eliminate backlash to near zero (usually .0002" or 
> less).  When a machine tool get's excesive mechanical backlash, you 
> would adjust the two ball nuts to remove it, the software 
compensation 
> is only there to take care of .0003" or so.
> 
> Now drop this discussion and quit demonstrating your ignorance on 
the 
> subject mater.
> 
> 
> 
> 
> 
> 
>  
> > I'm willing to bet the farm (if I had one) that more than 50% of 
all 
> > industrial CNC setups have backlash > 10 thou. Either because 
> greater 
> > accuracy was never required or due to lack of maintenance. 
Whatever, 
> > provided the end product isn't being impacted, nobody cares. 
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