Re: 5th & 6th axis

[Jon Elson <jmelson-at-artsci.wustl.edu>]

Till Franitza wrote:

> Hi,
> has anybody an Idea, why my 5th and 6th stepper axes dont work?
> I am very happy to have 6 Axes in my yemc Display now and when I switch to
> joint variables I can moce axis 1..4. But my last 2 Axes do not work and
> there are no pulses coming from Pin 1, which should give the pulses for Axis
> 5.

No surprise there.  Yemc is a 4-axis user interface.  The other 2 axes are
'leftovers' from using the quasi-6 axis version of the motion routines, which
move the 6 links of a hexapod machine, but commanded only by 3 degrees
of freedom (XYZ, but no tilting of the platform).  Yemc is a hack to get
one additional axis, but doesn't change the kinematics routines that really
need to be overhauled to completely free them up for more general motion
programming.  This IS being worked on, but there are substantial areas
of the lower level EMC (especially the interpreter) code that were written
for 3 degrees only.  With Yemc, you can manually jog the 4th axis, but you
can't program it from MDI or move it in auto from a program.  But, that
will come.  Since the kinematics for a basic machine tool are very simple
(axis in => axis out) this shouldn't be a big change.  Programming 3 rotation
axes as well as 3 cartesian axes on the Stuart platform (hexapod) is going
to be the tough one.  If you want crash protection of an arbitrary machining
head against an arbitrary fixture profile, you might end up at the funny farm!

>
> Is it possible that it has something to do with the control-lines of the
> lpt? Axis 1..4 are cabled with data-lines and they work. the rest is on
> control-lines and they are electrically different. They are open collector.
> How can I find out if they are damaged? Why does the testppt program don
> work on my system? It is impossible to set or clear output-bits.

No, very unlikely there is any harm done.

Jon