Re: [CAD_CAM_EDM_DRO] Bridgeport CNC Mill???

>
> The vast majority of new tools, today, are cnc tools. Purpose of this group.
> Of those, maybe 1% have inverse kinematics. At most.

Of course lathes, 3 axis cartesian machines and 3 axis + rotary don't
need it. That covers most of the machines out there. However once you
get into 5 axis then kinematics are needed. Actually kinematics are very
useful for hobby machines as well. My lathe for instance has a worn bed.
This means that the diameter is dependent to a small degree on the Z
axis position. Kinematics can be used to compensate for this.

My little Orac lathe running Mach3 tends to turn tapers. As I can't
compensate mechanically or in kinematics I have to do it in code which
can get rather messy.

> The vast majority of lathes in the world, today, maybe 99%, DO NOT have
> DROs.

I assume you are talking about manual lathes. Manual lathes are dying
out fast. Walk into any machine shop producing turned parts. You will
almost always find mostly CNC with maybe a manual hidden in a corner for
odd jobs. Hell, a lot of modern operators don't even know how to use a
manual.

> And for a (quite) small subset of users they can certainly enhance their
> effectiveness a great deal.
> No-one has ever disputed the desirability of certain features.
> Desirability "is not eq" necessity.

Take that to it's ultimate conclusion. How many hobbyists NEED a CNC? In
reality very few. That still doesn't stop thousands of hobbyists from
owning one.

> Now ..
> as regards proper position feedback, if you mean by that that machine
> shave dro´s that is one thing, and that new CNC machine use servos which
> have a tolerance within which they move, that is certainly correct and
> desirable.
> Nevertheless this ignores the fact that it was not always so, even for
> industrial machines.
>
> Now, from the point of view of a user, for most it is immaterial how
> closely they servo tracks, as long as they make parts to tolerance.

Knowing the following error of a servo is of no real use to a user. That
is purely for the guy setting it up in the first place. What I am
talking about is the fact that the control always knows exactly where
the machine is. Mach or any other control running step/direction only
knows where the machine should be. If you estop for instance the
machine's actual position may not correspond to the control's prediction.

> This is one of the very, very good features of EMC2, that you can often
> analyse this (I have no idea whether this is possible with most advanced
> hw, and I believe generally you cannot do this [w. avd hw that is]).
> I believe that with most advanced servo cards/hw, you cannot see how
> closely the servo tracks during programs execution.

This is true for step/direction servo cards. Systems using true closed
loop will know the following error at all times and if you get into
their configuration functions you will be able to see the error. However
as I said before this is purely for the guy setting the machine up. Once
set up the following error when cutting should be considerably less than
other mechanical errors such as flex.

Les