Homebrew PCBs

A milling table is just a dovetail cross slide positioner. However, 
because there're designed for milling they tend to be large in mass 
and heavy. But this actually works in your favor when it comes to 
light drilling since due to the weight, drill motor vibrations do not 
cause spurious movement in the backlash dead zone. 

Spurious movement in the backlash dead zone is what makes backlash 
(or the lack thereof) so critical in milling and routing operations 
due to side forces on the cutting bit. This is far less of an issue 
when drilling provided your software offers backlash compensation. 
Also, optimizing the Excellon to G-code drill cycle conversion so 
that one axis never reverses means zero backlash on that axis.

Naturally, you have to match the increased weight/friction of a 
milling table with the necessary torque from your drives for any 
desired speed. And this is where one has to be careful when using 
steppers, you may end up losing steps without knowing it if your 
desired speed is to ambitious. Not so with a step compatible servo 
setup, it will fault immediately when the drive cannot keep up with 
the step frequency.

--- In Homebrew_PCBs@yahoogroups.com, "mycroft2152" 
<mycroft2152@y...> wrote:
> Derek,
> 
> DETAILS. DETAILS!
> 
> I was told by this learned group that this was impossible to do. 
You 
> proved them wrong. $70 for the mill table with a 12" x 5"  work 
area 
> is great.
> 
> I'll buy one for manually drilling my pcbs.
> 
> Myc
> 
> 
> 
> --- In Homebrew_PCBs@yahoogroups.com, "derekhawkins" 
> <derekhawkins@y...> wrote:
> > I bought a milling table from Enco (US) and modified it for 
> minimal 
> > backlash and CNC on X and Y axis. Modified the drill press for 
CNC 
> on 
> > the Z axis. Using DC geardhead motors retrofitted with encoders, 
a 
> > servo setup....TurboCNC is the software. Yes, there are photos.
> > 
> > --- In Homebrew_PCBs@yahoogroups.com, Mycroft2152 
> <mycroft2152@y...> 
> > wrote:
> > > HI Derek,
> > > 
> > > what design for the driller did you use? Any photos?
> > > 
> > > I am told that some laser printers will shrink the
> > > design slightly in one direction. Haven't had that
> > > problem yet, still designing my machine.
> > > 
> > > Myc
> > > 
> > > --- derekhawkins <derekhawkins@y...> wrote:
> > > 
> > > > Hi,
> > > > 
> > > > Just finished putting together a CNC drilling
> > > > machine and have now 
> > > > stumbled on a problem that I never
> > > > anticipated....The drilling machine 
> > > > appears to be more accurate than the printer used
> > > > for the PCB 
> > > > artwork....Tried both a HP2420 (laser) and Epson
> > > > 2200 (Inkjet) and the 
> > > > results were similar. Is this a known issue with CNC
> > > > setups?
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > > 
> > > 
> > > 
> > > 
> > > 		
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