Re: [CAD_CAM_EDM_DRO] Re: Backlash effect on Part accuracy

shadi_salhab_78 wrote:

>Hi Jon,
>
>What is climb mill and what is it's advantage?
>
>

When milling with the side of the cutter, there are two ways to feed the
material into the cutter. One way is called "conventional milling" and the
rotation of the cutter is against the feeding of the work. This is safest
for the machine, as the cutting force holds the table against the leadscrew
backlash. But, the tool tends to dig into the work, and the progress of the
workpiece into the cutter causes the cutting teeth to start with a very thin
chip, making the tool skate across the material before digging in. This
leaves
a poor surface finish, welding chips onto the just-cut surface,
especially with
aluminum. You get reduced cutting tool life, too.

The opposite direction is called climb milling, as the cutter tends to
climb up
onto the work surface. The real problem with old machines is that the feed
direction is WITH the cutter rotation, and the cutter will tend to PULL the
work into the cutter. When this cutting force equals the friction on
the table,
the work will suddenly be "sucked" into the cutter for a distance equal
to the
backlash. This can cause broken cutters, loss of machine alignment, and
possibly
having workpieces thrown violently across the room! So, on sloppy machines,
climb milling is dangerous. This is too bad, because improved surface
finish
and tool life are substantial benefits of this cutting direction. I do
almost all
my work in the climb milling direction.

(I hope this isn't too far off topic, but it is a major consideration
in the ballscrew
or Acme decision.

Jon