On Sun, 3 Feb 2013, John Kasunich wrote:

> Date: Sun, 03 Feb 2013 17:08:37 -0500
> From: John Kasunich <jmkasun...@fastmail.fm>
> Reply-To: EMC developers <emc-developers@lists.sourceforge.net>
> To: EMC developers <emc-developers@lists.sourceforge.net>
> Subject: Re: [Emc-developers] custom EDM configuration questions
> 
>
>
> On Sun, Feb 3, 2013, at 03:59 PM, EBo wrote:
>
>>
>> possibly, but a more principled hack would be to interface it at the
>> point where it calls the low lever Catmull-Rom spline, and just evaluate
>> it in reverse.  I do not know how difficult that would be, but it would
>> require the ability to move in the negitive direction.  I have written
>> things like this for moving along splines with custom code, but I would
>> have to look into how to do this in EMC-s low level motion planning.
>> Probably the easiest thing to do would be to set up a "reverse-motion"
>> pin in HAL, and then evaluate it internally, or modify the adaptive move
>> command to allow positive/negitive feedback voltage which would imply
>> forward/reverse of motion.  Anyway that is my thought off the cuff.
>>
>
> Where things get ugly is when you try to do this in a general way.  For
> example, what happens if you ask for negative feed while in a spindle
> synchronized move (single-point threading or rigid tapping)?  Actually,
> that issue must have already been dealt with - adaptive feed would
> cause the problems in that case even for positive scale factors.  But
> that was just an example.  What about probing moves?  What about
> the blend between successive non-co-linear straight lines?  What about
> a profile that consists of many 0.002" long lines?  Can you back up
> more than 0.002"?
>
> Sure, you can say "an EDM will never make a spindle synchronized
> move", but changes to the motion module need to do sane things
> regardless of what kind of a machine is being controlled.
>
>

What about different motion modules optimized  different classes of 
applications?

>
>
> --
>  John Kasunich
>  jmkasun...@fastmail.fm
>
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Peter Wallace
Mesa Electronics

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