Re: [Emc-users] EDM forms?

[Gene Heskett]

On Thursday 01 August 2019 13:01:25 andy pugh wrote:

> On Thu, 1 Aug 2019 at 16:47, Gene Heskett 
> wrote:
>
> Did that got g3 error, usual recipe, converted it back to g17, lcnc
>
> > bought it but back plot shows the arc as a straight line???
>
That turned out to be a missing F in the G2/3 lines.  So I have it 
working, sortof. arcgenm18.py is showing a full 180 degree path, but 
when that code is pasted into an ngc file, I am getting only the bottom 
90 degrees in the backplot.

> At this point I would give up and use R-format arcs.

Its getting tempting.

Here is the code:
%
( for a woodruff key, .750 long, .1885 wide, depth about 170 thou )
( from arcgenm18.py, z curve offset starting point for arc )
G20 (use inches)
#<_x_offset>= -0.3750
#<_y_center>=- 0.
#<_x_end>   = -#<_x_offset>
( Z motion from X#<_x_offset )
( G3 X0.3750 Y0. I0.3750 J-0. )
( translate to G18  y becomes z, j becomes k)
( G3 X0.3750 Z0. I0.3750 K-0. )
( comeing back )
( G2 X-0.3750 Y0. I-0.3750 J-0. )
(Translated to G18)
( G2 X-0.3750 Z0. I-0.3750 K-0. )
#<_z_tmp_start> = .3750
(intialize z-tmp)
#<_z_tmp>   = #<_z_tmp_start>
( tool is carbide, .125 diameter dull 2 flute mill )
(key is .1885 wide so)
#<_key_wobble>  = [[ .18855 -.125] / 2.]
#<_z_inc>   =   .001 (burn 1 thou per pass)
S300 m4 (run it backwards)

o50 WHILE [#<_z_tmp> gt 0.000]

G1 F10 x#<_x_offset> y[#<_y_center> + #<_key_wobble>]
G1 F10 z#<_z_tmp>
G18 G2 F1 X0.3750 I0.375000 K#<_z_tmp_start>
G17
G1 F5 y[-#<_key_wobble>]
G18 G3 F1 X-0.3750 I-0.375000 K#<_z_tmp_start>
G17
G1 F.2 y[#<_y_center> - #<_key_wobble>]
#<_z_tmp> = [#<_z_tmp> - #<_z_inc>]

o50 ENDWHILE
G17
m5
g0z5
M2
%

If you can see why I'm only seeing a 90 degree arc in the backplot, teach 
me what is wrong.

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)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] EDM forms?

[andy pugh]

On Thu, 1 Aug 2019 at 16:47, Gene Heskett  wrote:

Did that got g3 error, usual recipe, converted it back to g17, lcnc
> bought it but back plot shows the arc as a straight line???
>

At this point I would give up and use R-format arcs.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is designed
for the especial use of mechanical geniuses, daredevils and lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] EDM forms?

[Gene Heskett]

On Thursday 01 August 2019 05:52:06 Gene Heskett wrote:

> On Thursday 01 August 2019 02:59:37 andy pugh wrote:
> > On Thu, 1 Aug 2019 at 04:36, Gene Heskett 
> > wrote:
> >
> > output of arcgenm18.py is assumeing G17. not G18.  So I need to
> >
> > > translate the ijk into what it would be for G18 motion. Is there a
> > > rule of thumb for that?
> >
> > G17 XY IJ
> > G18 XZ IK
> > G19 YZ JK
>
> Thanks Andy. It would be very helpfull if that was added to the docs.
>
> > So to change a G17 arc to a G18 change Y to Z and J to K.
> >
Did that got g3 error, usual recipe, converted it back to g17, lcnc 
bought it but back plot shows the arc as a straight line???

Now clarify please. I have a #<_z_tmp>, which the gcode sets to=.1875
This equals the radius of the arc and also represents the depth as the 
while [#<_z_tmp> gt 0.], meaning that if no erosion on the carbide, 
the final pass, decrementing at -0.0005 per pass, the last pass will be 
a few thou over the depth the key sits in the slot. or it will be 
shallow if the carbide has seriously eroded.  The only y  motions are 
those that move to work the width of the key, ostensively to make the 
groove .1890" wide. those motions take place at the ends of the g2 or g3 
moves so that from above the tool is
  _
 ||
=$64K-Question=
Now in order to maintain the shape of the half circle, while effectively 
moving it to an ever increasing depth and running in G18 anything 
referencing z must have the z_tmp added so the center point decrements 
with z_tmp. Right?


So as I step thru the code, watch it get to setting the starting height, 
but instead of raising z to 0.1875, it stops at about .070" So x and y 
seem to be running  in inches, but z is maybe running in mm but showing 
inches. But thats just a theory at this  point. Different problem but 
this is 2.9 master too... I need to find that too

I noted the shaft was showing a teeny bit of rust from sitting in the 
distilled water over night, and that the blocks I had positioned and 
gooped to prop it into alignment hadn't stuck to the poly tray, so I 
dumped everything and cleaned up the shaft, and now have a 1x2 by 9 
piece of white ash gooped to the bottom of the water tray sitting out in 
the sun so maybe it will stick better. Thick enough the shaft can be 
laid lengthwise w/o the tray pushing on the ends.

So while all that glue is setting, I can work on duff code.
And maybe look around in my junk box for another useable capacitor. This 
sort of pulsing will kill an electrolytic in a short time, not to 
mention it can't deliver the amps to make a destructive spark like an 
oil/paper or mylar can.
 
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)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] EDM forms?

[Gene Heskett]

On Thursday 01 August 2019 02:59:37 andy pugh wrote:

> On Thu, 1 Aug 2019 at 04:36, Gene Heskett 
> wrote:
>
> output of arcgenm18.py is assumeing G17. not G18.  So I need to
>
> > translate the ijk into what it would be for G18 motion. Is there a
> > rule of thumb for that?
>
> G17 XY IJ
> G18 XZ IK
> G19 YZ JK

Thanks Andy. It would be very helpfull if that was added to the docs.

> So to change a G17 arc to a G18 change Y to Z and J to K.
>
> You won't get a true segment of a cylinder with a cylindrical tool.
> Which was why I suggested a rotating disc that looks like an actual
> Woodruff cutter.


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)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] EDM forms?

[Gene Heskett]

On Thursday 01 August 2019 02:59:37 andy pugh wrote:

> On Thu, 1 Aug 2019 at 04:36, Gene Heskett 
> wrote:
>
> output of arcgenm18.py is assumeing G17. not G18.  So I need to
>
> > translate the ijk into what it would be for G18 motion. Is there a
> > rule of thumb for that?
>
> G17 XY IJ
> G18 XZ IK
> G19 YZ JK
>
Thank you.

> So to change a G17 arc to a G18 change Y to Z and J to K.
>
> You won't get a true segment of a cylinder with a cylindrical tool.
> Which was why I suggested a rotating disc that looks like an actual
> Woodruff cutter.

Of no concern, the back of the key has a flat area, something like the 
rear .075"  is removed from a key that would be if a full 3/4" circle, 
such that the key is only .3" deep, not .375". So the flat spot in the 
middle that a cylindrical tool cutting on the end of it while doing a 
180 degree circle's run in G18 mode is actually fitting the key better 
than a regular key cutter. If in cuttable steel useing a key mill, one 
would have to cut straight in to needed depth, then advance the cutter 
lengthwise by at least 3/8" in order to duplicate the shape of the key.

With the lack of working room, and the need to figure out how to keep the 
key from tipping when its entering the groove in the pulley, its a right 
cast iron bitch to fit.  So IF I can locate another capacitor (the guy 
in Bulgaria that has all the soviet surplus is out of pocket till late 
August, caps like this have not been made in any great qty since there 
was a run on them  when it became sick bird to use pcb's over here, 
about 30 years back. It cost the station around $20K to get rid of most 
of what we had by having Westinghouse send a truck to pick it up and 
burn it at nearly 7000F, pcb's are dambed hard to destroy) This now 
failed one was spared the fire by not having a pyranol on its label at 
the time. Modern plastic caps to replace it are $100+ and probably only 
available as 30 yo NOS.

So, since that pulley now has a taperlock, I think I'll just make sure 
its pulled up as well as I can get it, relying on the taperlock to 
freeze it on the shaft. This new shaft, being unworn, fits the hub of 
that pulley with a lot less rattle room, and the twin grub screws can 
probably be adjusted to reduce the runout if I can get a dial to it to 
measure it.

But I need to find something ASAP or the shaft will start rusting sitting 
there in the water...

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)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] EDM forms?

[andy pugh]

On Thu, 1 Aug 2019 at 04:36, Gene Heskett  wrote:

output of arcgenm18.py is assumeing G17. not G18.  So I need to
> translate the ijk into what it would be for G18 motion. Is there a rule
> of thumb for that?
>

G17 XY IJ
G18 XZ IK
G19 YZ JK

So to change a G17 arc to a G18 change Y to Z and J to K.

You won't get a true segment of a cylinder with a cylindrical tool. Which
was why I suggested a rotating disc that looks like an actual Woodruff
cutter.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is designed
for the especial use of mechanical geniuses, daredevils and lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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