On Saturday 09 March 2019 08:50:19 grumpy--- via Emc-users wrote:

> On Sat, 9 Mar 2019, Gene Heskett wrote:
> > On Saturday 09 March 2019 07:53:05 Nicklas Karlsson wrote:
> >>> On Sat, 9 Mar 2019 at 11:59, Nicklas Karlsson
> >>>
> >>> <nicklas.karlsso...@gmail.com> wrote:
> >>>> I think CPU Cortex-M4 is a lot slower than arduino
> >>>
> >>> Really? That isn't my experience. Given that the M4 is running at
> >>> 120MHz and the Arduino is 8MHz and both are running the same code?
> >>
> >> No I got it wrong and mixed it with raspberry, I think.
> >
> > The pi's huge, glaring slow i/o problem is that internal usb-2 hub.
> > AIUI, only the wifi and gpio bypass that huge bottleneck.
> maybe this would help
> https://geekworm.com/collections/raspberry-pi-hats/products/x820-v3-0-
Looked this over but I don't see it solving the biggest problem of the 
pi, the fact that the video data has to get to the hdmi circuitry thru 
the internal usb2 hub. That precludes doing a full screen video update 
rate of more that about 6 or 7 frames a second.  And if the pi gets 
busy, way less than a frame a second, which was the condition when I 
made the mistake in calculating K for a g76 operation. The result was 
that any movement (jog) button took over a second to get from the 
keyboard to start moving the machine, it moved at the commanded speed 
for a minimum of a second, and it was 3 cycles of screen updates at 
about 1.5 seconds each before the screen was fully updated.  The 
onscreen backplot was showing a deeper than normal depth of cut which 
was my clue to recheck my math. The math error was caused by the 
document section describing G76 NOT saying that K is a factor from P, so 
it took k=.466 as inches, not k=[p/0.866].

And because the 3 cornered thread cutting chips are so gawdawfull 
expen$ive, and fragile I tend to fix the g76 anchor point off the end of 
the thread, and define #<_Ze> as [p * -number of threads] as I can add 
one thread at a time while cutting air until the end of the last thread 
just clears the ER-42 collet. That way I can also adjust my off the end 
of the work z starting point in p increments without screwing up a 
partially cut thread. The one thing I wish I could do is teach G76 to 
cut so as to compensate for the works flexing as I get threads a couple 
thou bigger on the end vs at the chuck. I need, for small work, another 
variable to make it cut the teeniest of tapers, a thou, maybe 2 small at 
the start.  Extreme amounts of H do not fix that for small bolts of 
under 1/4"/6mm.

I should make a tool holder die carrier, but then you're stuck with the 
die makers fit unless you buy split adjustable dies. And must use a 
g33.1, which has its own problems when the spindle is doing lots of 
overtravel, so much I wrote some hal code and some pyvcp.xml to display 
it.  Its helped me to not break so many taps from hitting the bottom of 
the holes. If I use the data it shows me, I can rigid tap at 250 revs 
wearing a 40 lb chuck that makes the belts yelp during the end of stroke 
reversal.  Belts need replaced, I have some powerstroke stuff but can't 
figure out how to assemble them in the room allowed by the adjustments. 
So the spindle or the lower pulleys have to be removed, the belt 
assembled, and the shaft re-inserted.

A long tedious job since the lower dual sheeve that used to have a 
woodruff key now has a shop made (on TLM) taperlock hub. It was 
installed wrong side to by someone in the past, and their attempt to 
tighten the setscrews without the locking key tore up the sheeves bore 
and scored the shaft, so my best fix was to make a taperlock hub for it 
and pull the bronze bushings putting in the torrington needle cages 
called for in the parts list. It turned out that the majority of the 
400F heat I was measureing with an IR thermometer was the friction of 
the setscrews slipping on the shaft.

Moving the drive screws to Jack that apart and remove the upper shaft is 
a major pita, no room to swing the allen wrench w/o driving the 
shaft/pulley 20 degrees back and forth at the same time. I should have 
replaced the belts then but didn't have them. Now I do, but dread the 
job. And I'd need to grow at least one more arm since there's not room 
for 2 people under there. Did I mention it will be a PIMyBack?

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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