On Tuesday 16 April 2019 14:34:15 Gene Heskett wrote:

> Greetings all;
> While adding a couple timedelays and a couple or2's to my hal file,
> basically to prove that I can pulse the spindle for the nominally 200
> msecs used to spin the nut on/off to release the collet and supposedly
> drop the tool, or just drop it all, I came up against a designed in
> problem.  This vfd has a pid in it that will no doubt wind up if the
> speed command is present for any great amount of time, so its possible
> I might have to cobble up a set of PID params to essentially disable
> that. Because I think I am going to need to have the speed present at
> the VI1 input before I enable the fwd or reverse commands for the
> timed 200 millisecs to drop or pick up the tool during the change. The
> wind up in that case might be advantageous in that it might jerk the
> nut loose, or tighten it tighter before the carousel puts the real
> tighten on it. But likely difficult to control too.
> But I find its not possible to send this speed request before the
> run/dir signals. I can mux2 the spindle speed inputs to the 7i76, and
> have the as yet unwritten tool changer code issue the speed and
> timings.
> Is that the choice?
> A secondary problem if I do the 3d printed tool holders inside the
> collet sockets, like the orange pieces in one of the videos on
> hack-a-day, depending on the tool to drop free when the nut backs out
> the collet, is that the tool does not always come free, and this looks
> like a showstopper problem that puts me back to buying a handfull of
> nuts and collets so I can drop it all and then reposition the carousel
> to pick up the next tool/nut/collet as an assembly. Either way, it
> seems like I'll unavoidably need an automatic TLO setting to complete
> the change.

Some more along the lines of finding out how much force I can figure on 
as being available to tighten or loosen the collet nut. I can get, for 
under a tenner, 4 ea 50Kg load cells and a processor board that converts 
the very low level diffs of a wheatstone bridge made out the these, 
things, and which give a serial output to 12 or more bits.  So all I 
have to do is place the cell kit between a frame and the carriage and 
give it a squeeze to get a measurement.  These are the same as used in 
digital bathroom scales.

Has someone made up a serial protocol for a Mesa board that could collect 
this data, and show me in pounds or kg, how much force I can get out of 
this machine before a motor slips s "cog", which in turn determines how 
big around the carousel has to be to adequately tighten, and of course 
loosen it too.  The module needs a clock, one output on a 7i76D, and one 
data input, so all we need to do is toggle the output line with the 
servo-thread, and read the bit with an input line. A bit bang receiver 
IOW.  Do we already have such a blob of code?

Thanks for any comments on my hair brained ideas.

> I figure on a bigger
> carousel than shown in the videos. That thought is driven by the
> difficulties I've had with the hand tightened (with a pair of 12 to
> 16" wrenches) on the ER32's on the G0704.
> I've wrecked parts and broken tools because they'll walk out of the
> collet, dig too deep and finally break off.  That bit of history has
> cost me several hundred in tools so far. :(
Thanks for any wisdom shared. URL's etc.

Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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