re: backlash comp
Posted by
Tony Jeffree
on 2000-11-09 04:40:04 UTC
At 06:51 09/11/00 +0000, you wrote:
appreciated is that it is not only a change in direction of movement that
may require compensation to be applied. If the toolpaths you have defined
result in a change from climb milling to conventional milling (or
vice-versa), then, for the axes that were resisting the cutting forces
before the change, the direction in which the compensation is applied needs
to be changed to maintain accurate positioning, as the cutting forces may
be large enough to cause the backlash to be taken up in the other direction
on those axes. If the software you are using to generate/execute the
toolpath is not capable of analysing whether you are climb milling or not,
and applying compensation accordingly, you had better define your toolpaths
so that they consistently mill conventionally only, or climb mill only. If
the cutting force being applied to an axis is comparable to the force
needed to move that axis, then you had better not use climb milling at all,
as there will always be some uncertainty as to where that axis is actually
located - i.e., positioning could be out by up to the backlash value for
that axis.
Regards,
Tony
>There are some things programmers writing controls can do to improveOne potential problem with software compensation that is not always
>the "real world" functionality of backlash comp, but it is usually
>implemented by "math" instead of logic. :-)
appreciated is that it is not only a change in direction of movement that
may require compensation to be applied. If the toolpaths you have defined
result in a change from climb milling to conventional milling (or
vice-versa), then, for the axes that were resisting the cutting forces
before the change, the direction in which the compensation is applied needs
to be changed to maintain accurate positioning, as the cutting forces may
be large enough to cause the backlash to be taken up in the other direction
on those axes. If the software you are using to generate/execute the
toolpath is not capable of analysing whether you are climb milling or not,
and applying compensation accordingly, you had better define your toolpaths
so that they consistently mill conventionally only, or climb mill only. If
the cutting force being applied to an axis is comparable to the force
needed to move that axis, then you had better not use climb milling at all,
as there will always be some uncertainty as to where that axis is actually
located - i.e., positioning could be out by up to the backlash value for
that axis.
Regards,
Tony