Hello,
BTW, in PCB's there is an effect call epoxy smear, which DOES cause
havoc with platethrough holes. Anything you read in depth about PCB's
will mention it... Epoxy is a thermoset, not a thermoplastic, but it
still can smear the inside of the hole. When it does so in a multi
layer board the "smear" covers the inner layers, and the PTH doesn't
connect to that hole. It's part of the reason we can buy cheap PCB
bits. A board house CANNOT afford to use anything but SHARP bits.
The Excellon machines Jan described are still used my many PCB shops
today. Look for the signature green and orange paint scheme. And they
still use the old floppies and even older controls.
Sneakernet is still widely used. (which kinda makes sense when you
consider that the boards layers themselves are stacked
and "assembled" for drilling by hand. (Remember, board houses drill
FIRST.)
As for the construction and backlash etc. in the PCB drills, these
machines are built on and with huge Granite slabs, using air bearings
and precision ground ballscrews with preloaded nuts. The 4 spindle
type is pretty much an industry standard. You can usually find
pictures of one of these on ebay, as they sell rather frequently.
Use "excellon" in a search...
It's actually pretty surprising to see how "old" most PCB houses
appear in their techniques and machinery. Living near silicon Valley,
I've seen a few...
PCB ASSEMBLY houses, on the other hand, almost always have the latest
and greatest... Nowadays they have to. Pick and place, reflow ovens,
vison systems and xrays for BGA, etc. ..
Hope this helps,
Ballendo
--- In Homebrew_PCBs@yahoogroups.com, dg140@f... wrote:
> Hi Jan. How did you account for backlash in your homebrew CNC
rig? What
> about those PCB drilling machines, what do they do for backlash and
other
> error components?
>
> ---
>
> >Particularly if the bit is not NEW-sharp!
> > The particular board which needs drilling is actually for the
mechanical=