On Wednesday 17 April 2019 07:12:53 andy pugh wrote:

> On Wed, 17 Apr 2019 at 06:57, Gene Heskett <ghesk...@shentel.net> 
wrote:
> > 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
>
> Why not set your torque wrench to the correct torque for your nuts and
> then see how far down the handle you have to be to trip the wrench?
>
> That tells you what radius of action you need to get the right torque.
>
> There is no question that your machine can produce the torque, given
> the classical "sufficiently long lever"

And that is the final question as to whether or not the idea is actually 
practical. It assuredly is not if the xy motors are so weak it needs a 
carousel more then 18" in radius to the circle of sockets just to 
tighten a tool well enough to dig off .010" of an alu chip without 
slippage of tool in the collet.  Even that isn't going to be practical 
but it does serve to outline exactly why the 3" radii carousels we are 
seeing in the videos will turn out to be an obvious disproof of concept.  
The videos of it going thru the motions on hackaday would certainly have 
to suffer from the loose tools syndrome if actually put to work on a 
usable thickness of alu stock, say .03125" thick. Putting bigger motors 
on it would be one option, but even 470 oz nema 23's, might not be 
enough, and most certainly could/would bend the frame or bearing rods. I 
have the motors from the broken HF I can move, and probably will as that 
would at least double the power, but just haven't found the round tuit 
yet. Among other things they have dampers on them. But I'll have to 
change the A motor again, putting a 435oz on it. I already changed the 
90 for a 230, so a 435 can't fail to be even better at holding work. 
That would leave the pair of 235's for XY, and would leave the longer Y 
to be moved to Z duties. 

The 1600oz nema 34 supplied as Z motor in the kit for a G0704, which was 
a too slow disaster on the G0704, often stalling at 29 ipm, but was 
strong enough to stretch the bolts anchoring the nut carrier to the z 
sled, causing those to need replacement quite early, but now moves at 90 
ipm with a 940oz motor that has not further damaged those replacement 
bolts, would be a prime example of overkill. However I reused that motor 
as Z drive on the Sheldon, where it has no weight to lift, works well at 
75 ipm on the Sheldon with the same driver I took out of the G0704. I 
put in the $180 AC powered drive to spin that 940oz on the GO704. Dead 
smooth and 20 db quieter. The DM860H drive is a noisy drive, so noisy I 
had to install miniature quarter round on the keyboard shelf edges to 
keep stuff on it, including the keyboard and mouse. The 860 has very 
very poor step vs amps in coils calibration, so there is no nice quiet 
all steps in the microstep mapping regardless of the current setting. 
The thing you notice most is that a /8 setting actually does 7 steps 
because one of them is way too small.

But thats not solving this measurement problem. Since this $7 kit, needs 
an external clock, it seems like that could be done by siggen, for a 500 
baud baud rate, and a software uart could do the rest. But the packet 
length is unk until I have such a kit in my hot little hands. The 
fleabay adv's don't say.

Thanks Andy.

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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