Re: EMC2 Screw Cutting Problem

Steve.
Thanks for a most helpful reply - it's allowed me to get the carriage
moving with the spindle - something I couldn't do in 2 days. You are
a star.

It seems like the configuration wizard in EMC2 is faulty as it
consistantly set up my machine with the wrong parameters for
successful threading despite my best efforts.

The one small fly in the ointment is that the Z axis surges instead
of moving smoothly in time with the spindle. Does anyone know what
might be causing that to happen? Any help is much appreciated.
Thanks again, Martin.

> The way EMC2 does threading is basically by electronically gearing

axis

> motion to the position of the spindle. That's a little different

from

> the way the other controls do it - I think they use estimated

velocity

> to more or less do feed rate scaling.
>
> It's not clear to me that you have loaded an encoder counter to

read the

> spindle feedback. When using Halscope, were you looking at the

parallel

> port pins? I'll assume that the two bits are connected to parallel

port

> pins 11 and 12 - you'll need to edit those to whatever is

appropriate

> for your machine. Lines that begin with "#" are comments, and may

be

> left out or included (they'll be ignored).
>
> Here is what you'll need to add to one of your HAL files:
>
> #--- START HERE
> # load the software encoder counting module
> loadrt encoder num_chan=1
>
> # we need counter mode, since this isn't a quadrature encoder
> setp encoder.0.counter-mode 1
>
> # 48 slots = 48 counts per revolution
> setp encoder.0.position-scale 48
>
> # reading the parallel port needs to be done in the fast thread
> addf encoder.update-counters base-thread
>
> # updating position output can be done at a slower rate
> addf encoder.capture-position servo-thread
>
> # connect the two parallel port input pins to the encoder counter
> # change the numbers to suit your setup
> net count_bit encoder.0.phase-A parport.0.pin-11-in
> net index_bit encoder.0.phase-Z parport.0.pin-12-in
>
> # connect the encoder counter output to the motion controller
> net spindle_pos encoder.0.position motion.spindle-revs
>
> # connect the encoder velocity output to the motion controller, for

CSS

> and FPR modes
> net spindle-vel encoder.0.velocity motion.spindle-speed-in
>
> # and allow the motion controller to tell the encoder counter when

to

> reset the count
> net spindle-index motion.spindle-index-enable encoder.0.index-enable
> # --- END HERE
>
> It looks complex, but it's not that bad, really :)
> You may want some filtering on the spindle velocity output. If so,

take

> a look at the sample config sim/lathe - it has everything set up

for

> threading, CSS, FPR, nice on-screen readouts, etc.
>
> Side note: there aren't too many EMC2 users on this list. For

specific

> configuration information, it may be better to ask on the emc-users
> list. You can subscribe here:
> <https://lists.sourceforge.net/lists/listinfo/emc-users>, or just

mail

> to the list here: <emc-users@...>
>
> Hope this helps
> - Steve
>