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Gentlemen,
Drill wander is the byproduct of one of the following factors:
1. If you are using an extremely "hard" entry material, ie.
phenolic
or melamine, the drill can have a tendency to "skate" on the entry prior
to
penetration. This will usually cause excessive drill wander and have
detrimental
effects on front to back registration for obvious reasons. If you are
using
on of these types of entries, try using LCOA EO+ ( an aluminum clad
cellulose
core material) or 7 to 8 mil virgin aluminum foil. The EO+ seems to work
better
in suppressing drill wander.
2. If the flute to diameter ratio is too great ( greater than
20:1) than this
can be a contributor to drill wander. The first thing that you should do
is call
your drill vender and have them analyze your situation. Many times they
can
offer a tool that better fits you particular application. If they don
have any
standard product for you to test, see if they will design a tool that
better fits your needs. If your drill vender cannot build a
special...get a new drill vender!!!
3. If the spindle runout is excessive, it can have an effect on
drill wander.
Contact your drill machine supplier and find out what their
specifications are
for spindle runout ( most are between .0002" to .0005"). Try to perform
a runout check at least once per week. A fairly good barometer, should any spindle have excessive runout, is drill breakage, however, depending
on the diameter of the tool you
are using, this is not always the case.
4. Lastly, tool geometry and carbide selection can have an effect
on
drill wander. Designing cutting tools is a constant game of trade-offs.
If you want
a stronger tool that will have better resistance to breakage and
deflection, the trade-
off is usually a decline in hole quality. if you want a tool that will
produce excellent
hole quality, you can bet that you will have more breakage, increased
drill wander,
and reduced stack heights. The task of the drill room process engineer
is to find
the happy medium that will share the best of both worlds, however, it
behooves
the engineer to involve their machine and tool suppliers to assist in
this endeavor.
I wish you success in this project.
Regards,
Mark R. Ford, North East Application Engineer - Megatool
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