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

Jon Elson wrote:

>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
>
>

That's good to know. As long as we're on this topic, what can I do to
reduce backash on the mill I just got? It already has ballscrews but my
guess is that they're pretty worn out, 10 thousandths in Y and 3 in X.
Can I buy oversize balls, adjust something, get new screws, or what?
Michael