Re: Knee / Quill interaction?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "jmkasunich"
<jmkasunich@y...> wrote:

>
> I posted a Shoptask specific version of this question earlier,
> but the core issues apply to many machines.
>
> How does CNC deal with two axis that are parellel to each other,
> like the quill and knee of a Bridgeport?
>
> I know the simple answer is to only motorize one of them. But
> there are pros and cons to each, and some benefits to controlling
> both. For example, the quill weighs much less, is easier to
> move, and is more accurate. But it has limited travel. On the
> other hand, the knee has lots of travel, but is very heavy, and
> on a worn machine may cause errors unless it is locked.
>
> It seems that a good solution would be to motorize both. Use
> the knee to adjust for large differences in tool length, like
> an end mill in a collet vs. a long drill bit in a drill chuck.
> Then lock the knee and use the quill for the actual machining.
> (The same thing can be done with a manual knee - adjust the
> knee manually when you do a tool change.)
>
> The question is, how does the control deal with the changing
> position of the knee?
>
> John Kasunich

Depends on your Software, a Axes that runs parallel to "Z" is
usually called "W".
Industrial controller Software on expensive machinery often
has a automatic W/Z relational Compensation function wich allows
W and Z to stay syncronised.
Meaning the Operator can manualy reposition ether Axes and the
other will ajust automaticly to the new positional relationship.
None of the Pc controller Software I have seen will do this,
to complicated, they will simply position each axes as directed
by numeric controll.
It is up to the Progammer to ensure that his driving instructions
fall within the limits of travel for all axeses.
Good Luck