Interesting point, about flexing at the entry material!

What if the drill flexes at each layer of copper (just theorizing)and
the largest "flex" would occur at the top copper layers of the panel,
would a composite entry be the most forgiving to the carbide?  Consider
a .010 diameter drill at 100k rpm. If the drill does indeed flex, then
it has a back and forth wiggle that cycles at 100k. It probably rubs
around and around the entry material hole.  Does the carbide prefer to
do the 100k wiggle against pure aluminum, a little bit of aluminum
(clad) or no aluminum at all?  I guess that carbide holds up better
without doing battle against a hunk of aluminum.  If only the melamine
guys would lower their prices we could get serious about using it.  My
experience is very low breakage with one type of melamine composite, and
also excellent exit side registration.  But alas, it is far too
expensive.
George Lubbecke wrote:
> 
> These are the areas you can try in your testing:
> 
> 1. Entry material.  Try 9 mil composite aluminum.  Keeps smaller bits
> (.012 - .020) from flexing and reduces breakage.
> 
> 2. Try different infeed rates on your drills.  Try chip loads .8 - 1
> mil.
> 
> 3.  Try different drill bit constructions.  Some vendors have thicker
> webs that stiffen the bit.  There are trade-offs though with less
> room for chip evacuation with thicker webs.
> 
> 4.  Clean collets (every shift) and check spindle run-outs often (200
> machine hours).
> 
> 5.  Make sure that your coordinate measuring system gets calibrated
> often so you get accurate measurements.  Also make sure you use
> double-sided tape when checking hole locations.
> 
> Hope this puts you down the right road............
> 
> > <[log in to unmask]>  5/1/97, 11:17am >>>
> What are the factors that contribute to drill wander?  We are
> planning to
> improve the amount of drill wander we get.  If anyone has any ideas
> of
> possible techniques for improvement, I will be very appreciative.
> 
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