Re: [Emc-users] Dedicated Processor hardware for LinuxCNC

[Rafael Skodlar]

On 2/18/19 5:00 PM, Greg Bentzinger via Emc-users wrote:

( Greg )
Every kid would love to ask for a pony, if they thought they could get it they 
would ask for a unicorn. Reality however usually proves this to be impractical 
to impossible.
Everything is changing today at a hyper accelerated pace. Back in the day Motorola produced the 68000 CPU, it was used in all sorts of equipment from 

^^ not true for everything.

Apple PC's to Okuma machine controls. I would guess that that CPU was 
still being used to manufacture products 20 years after debut.

Today PC cpu and chip sets are what a 3-5 year life cycle before going OOP. 
Same with many ARM CPU. Look at the Arduino and how many generations have come 
down the road. Most new version have moved to 3.3V and are no longer compatible 
with 5V shields.
Even if someone did come up with a backplane card rack for most of the interface cards, 
that main CPU board would have to be updated nearly constantly because key components 
would become un-obtainable. Todays global manufacturing tries to run as close to true JIT 
as it can.(JIT="Just in Time") companies want as little space and capitol tied 
up in inventory. When I worked an Apple PC assembly line they were so JIT focused they 
only kept 4-6 HOURS worth of components in the facility. This meant that trucks were 
delivering Mem, HDD's ect. were being unloaded every few hours and being reloaded with 
boxed product ready for market.


Good to know. I love computer history.


Several Chinese machine tool builders have offered LinuxCNC as the control to 
reduce the overhead of building the machine. I believe it would be used more if 
tool builders were sure they could not be held liable for a system they sold 
that had been modified by the buyer.
GRBL has come along way - and it was a project to fit a stripped version of the 
early EMC/LinuxCNC into cheap Arduino hardware. the current v1.1 IIRC had to 
strip down the boot loader and some other items to still be able to squeeze the 
optimized assembly code into the Atmega328p chip. What did GRBL have to give up 
to fit in an Arduino? Tool table capability {G43}, Tool radius comp {G41-G42}, 
Minimal look ahead buffer, No program storage - its all drip feed via serial, 
no program editing, X-Y-Z only no additional axis, no spindle feedback 
(tapping), requires second device to stream G-code and operate the control. Now 
I like GRBL and it has the honor of being the founding code which virtually all 
extruder type 3D printers is based. I hope someday there is a port for a rotary 
axis, I would love to use it to engrave on cylinders using X-A-Z.
For now though, the movement towards SSerial and interface from control PC via 
Ethernet allows all sorts of flexibility.
As for HP-GL, I had to work with HPGL for tool paths for several years and it was a complete disaster. Mathematically a "line" has no physical width, not exactly so in HPGL so you will have gaps, broken chains, lines intersecting not at there endpoints and all arcs are output as splines. While at the scale for a HP pen plotter this worked out, for CNC use it was a dismal failure of epic man hours wasted trying to get each file into a usable state. I hope HPGL 


HPGL was not designed for CNC work if we assume that plotter is not a 
CNC machine. However, the reason I brought it up was in it's simplicity 
of writing raw code for it be that in Basic in HP-85 for example, or 
whatever else. It's easier to remember PA (Plot Absolute), PR (Plot 
Relative), PT (Pen Thickness), SC (Scale), etc. than G-code.

http://paulbourke.net/dataformats/hpgl
For 3D somebody would need to come up with language extensions.

is banished from the face of the earth long before G-code begins to 
fade. I agree that G-code is far from perfect, but there is no other 
method out there that even comes close. Early AutoCAD had the same sort 
of dysfunction issues by the use of the "polyline" construct.

Lastly - May I ask the status of LCNC v2.8? Is there any potential release date 
on the horizon?
Thanks ( /Greg )


G-code is like Latin used by doctors 50 years ago. How is that working out?
Just because your implementation did not work for you HP-GL is not bad. 
Repeatability and accuracy on HP plotters was very good even for pens in 
my experience. With a bit of adjustment for a CNC environment HP-GL 
would be at least as good ad G-code in 2 dimensional space. Code is just 
a code. One is easier to read than the other but it has nothing to do 
with machine accuracy.


It was only used by engineers not a crowd that only knows how to insert 
paper into inkjet printing machine. I've seen some very impressive IC 
layout designs plotted with HP-GL on HP plotters that I maintained or 
repaired in the past.


--
Rafael
Exclusive Linux user since Feb 1994


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Re: [Emc-users] Easy use of a 2 line URL [Was: Re: DIY CNC builder dilemma, open request for comments

[Erik Christiansen]

On 18.02.19 22:47, Gene Heskett wrote:
> >
> Already set true here Erik. Next? ;-)

And it didn't take the lumpy URL when pasted whack in the middle of the
screen? (Dunno that I have any other magic settings. That one works
here.)

Erik


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Re: [Emc-users] Easy use of a 2 line URL [Was: Re: DIY CNC builder dilemma, open request for comments

[Gene Heskett]

On Monday 18 February 2019 21:55:06 Erik Christiansen wrote:

> On 18.02.19 16:52, Gene Heskett wrote:
> > unforch, John, you did not surround this link with a pair of<> which
> > would have preserved its validity even if it had been 2k chars long,
> > but alibaba, rather than leaving half of it displayed so we can
> > manually copy/paste the rest of it, has to be cute and replace it
> > all with their custom 404 message. And even after I fixed it, it
> > still goes to a google listing. And none of them goto that
> > particular machine.
>
> On 18.02.19 14:39, John Dammeyer wrote:
> > I still had to edit the text into one line
> > However if you google this: " ? alibaba Low-cost-New-Product-3Axis->
> > 4Axis " it will bring up the link.
>
> The original two-chunk URL works fine for me on iceweasel (so firefox
> too), just by highlighting the two lines and pasting anywhere in the
> browser window. To do that, just:
>
> Put about:config in the URL box, scroll to 
> middlemouse.contentLoadURL, and click to toggle it to true. Now a URL
> highlighted in an xterm can be pasted to firefox (and opened) with one
> middlemouse click - even if it has a spurious space/line-break in it.
>
> That's miniscule effort for endless ease henceforth. It's the very
> best tweak my browser has had, saving a pile of sweat over the years.
> (Picked it up from John L. Fjellstad - can't remember which list.)
>
> Erik
>
Already set true here Erik. Next? ;-)
>
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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 



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Re: [Emc-users] New problem, how best to solve?

[Gene Heskett]

On Monday 18 February 2019 20:50:10 Ken Strauss wrote:

> > -Original Message-
> > From: Gene Heskett [mailto:ghesk...@shentel.net]
> > Sent: Monday, February 18, 2019 7:20 PM
> > To: emc-users@lists.sourceforge.net
> > Subject: Re: [Emc-users] New problem, how best to solve?
> >
> > On Monday 18 February 2019 16:56:38 jrmitchellj wrote:
> > > Hey Gene, If you were so inclined to make your own touch probe,
> > > there is an article in the winter 2011 edition of Digital
> > > Machinist that describes a construction project.
> > > If interested, send your email address to me, and I will send more
> > > information.
> > >
> > > --J. Ray Mitchell Jr.
> > > jrmitche...@gmail.com
> >
> > Its the from line above, if it survives the list
> > else try ghesk...@shentel.net.  I'd be interested in anything thats
> > half the size of a renishaw.
> >
> > Thanks J. Ray.
>
> I haven't been following this discussion closely. What are your size
> restrictions? I'd have to go to the shop to measure exactly but a
> Renishaw MP3 is about 3.25 inch in diameter and 2.5 inch in Z-height.
>
Generally, thats to big. And I'd have doubts I could put it in an er-11 
collet. The el-cheepo I just bought has a 1/4" top stud, 2.1" diameter, 
and with the default probe, a hair over 4" tall.  And that will eat much 
of the z height of this machine. I should know for sure by this time 
next week as it ships from stateside. Maybe the dual mister will be here 
by then, but its promised the 27th soonest. The 2nd air valve? Middle of 
March...
>
>
>
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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 



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[Emc-users] Easy use of a 2 line URL [Was: Re: DIY CNC builder dilemma, open request for comments

[Erik Christiansen]

On 18.02.19 16:52, Gene Heskett wrote:
> unforch, John, you did not surround this link with a pair of<> which 
> would have preserved its validity even if it had been 2k chars long, but 
> alibaba, rather than leaving half of it displayed so we can manually 
> copy/paste the rest of it, has to be cute and replace it all with their 
> custom 404 message. And even after I fixed it, it still goes to a google 
> listing. And none of them goto that particular machine.

On 18.02.19 14:39, John Dammeyer wrote:
> I still had to edit the text into one line 
> However if you google this: " ? alibaba Low-cost-New-Product-3Axis-> 4Axis "
> it will bring up the link.

The original two-chunk URL works fine for me on iceweasel (so firefox
too), just by highlighting the two lines and pasting anywhere in the
browser window. To do that, just:

Put about:config in the URL box, scroll to  middlemouse.contentLoadURL, and
click to toggle it to true. Now a URL highlighted in an xterm can be pasted
to firefox (and opened) with one middlemouse click - even if it has a
spurious space/line-break in it.

That's miniscule effort for endless ease henceforth. It's the very best
tweak my browser has had, saving a pile of sweat over the years. (Picked
it up from John L. Fjellstad - can't remember which list.)

Erik


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Re: [Emc-users] Dedicated Processor hardware for LinuxCNC

[Gene Heskett]

On Monday 18 February 2019 20:00:21 Greg Bentzinger via Emc-users wrote:

> ( Greg )
> Every kid would love to ask for a pony, if they thought they could get
> it they would ask for a unicorn. Reality however usually proves this
> to be impractical to impossible. Everything is changing today at a
> hyper accelerated pace. Back in the day Motorola produced the 68000
> CPU, it was used in all sorts of equipment from Apple PC's to Okuma
> machine controls. I would guess that that CPU was still being used to
> manufacture products 20 years after debut. Today PC cpu and chip sets
> are what a 3-5 year life cycle before going OOP. Same with many ARM
> CPU. Look at the Arduino and how many generations have come down the
> road. Most new version have moved to 3.3V and are no longer compatible
> with 5V shields. Even if someone did come up with a backplane card
> rack for most of the interface cards, that main CPU board would have
> to be updated nearly constantly because key components would become
> un-obtainable. Todays global manufacturing tries to run as close to
> true JIT as it can.(JIT="Just in Time") companies want as little space
> and capitol tied up in inventory. When I worked an Apple PC assembly
> line they were so JIT focused they only kept 4-6 HOURS worth of
> components in the facility. This meant that trucks were delivering
> Mem, HDD's ect. were being unloaded every few hours and being reloaded
> with boxed product ready for market. Several Chinese machine tool
> builders have offered LinuxCNC as the control to reduce the overhead
> of building the machine. I believe it would be used more if tool
> builders were sure they could not be held liable for a system they
> sold that had been modified by the buyer. GRBL has come along way -
> and it was a project to fit a stripped version of the early
> EMC/LinuxCNC into cheap Arduino hardware. the current v1.1 IIRC had to
> strip down the boot loader and some other items to still be able to
> squeeze the optimized assembly code into the Atmega328p chip. What did
> GRBL have to give up to fit in an Arduino? Tool table capability
> {G43}, Tool radius comp {G41-G42}, Minimal look ahead buffer, No
> program storage - its all drip feed via serial, no program editing,
> X-Y-Z only no additional axis, no spindle feedback (tapping), requires
> second device to stream G-code and operate the control. Now I like
> GRBL and it has the honor of being the founding code which virtually
> all extruder type 3D printers is based. I hope someday there is a port
> for a rotary axis, I would love to use it to engrave on cylinders
> using X-A-Z. For now though, the movement towards SSerial and
> interface from control PC via Ethernet allows all sorts of
> flexibility. As for HP-GL, I had to work with HPGL for tool paths for
> several years and it was a complete disaster. Mathematically a "line"
> has no physical width, not exactly so in HPGL so you will have gaps,
> broken chains, lines intersecting not at there endpoints and all arcs
> are output as splines. While at the scale for a HP pen plotter this
> worked out, for CNC use it was a dismal failure of epic man hours
> wasted trying to get each file into a usable state. I hope HPGL is
> banished from the face of the earth long before G-code begins to fade.
> I agree that G-code is far from perfect, but there is no other method
> out there that even comes close. Early AutoCAD had the same sort of
> dysfunction issues by the use of the "polyline" construct. Lastly -
> May I ask the status of LCNC v2.8? Is there any potential release date
> on the horizon? Thanks ( /Greg )
>
Don't know Greg. I'm running master on all my stuff, and except for a 
rare minor upset tummy because I didn't get the memo, its just worked. 
Breakage has been minimal, and fixed with the next build.
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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 



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Re: [Emc-users] DIY CNC builder dilemma, open request for comments

[Gene Heskett]

On Monday 18 February 2019 17:07:14 John Dammeyer wrote:

> Let's try this then.
>
> Then there is the Far East solutions like the one in this link.
> is_603 43603384.html?spm=a2700.7724857.normalList.37.3701292eTmjk5p>
>
> John Dammeyer
>
>
Somewhere in the path is a line-wrapper thats ignoreing the <> 
convention. Normally the <> around a link protects it from such 
destruction. IOW it still isn't working.

The reason I'm curious is that I'm in the middle of making a 6040 work 
with LinuxCNC.  And its being difficult regarding the vfd. Mach only 
turns it on and off, apparently from wide open.. That wasn't the first 
problem though, it had only a 24 volt motor psu, which when the 4th axis 
was plugged in, folded back to about 14 volts.  So its now being moved 
by the 28 volt rig I took off the broken HF mill. So I'm in the process 
of building a 2nd interface similar to the one I put on the g0704, which 
has a 5i25, driving a 7i76 so I now have enough I/O to actually run the 
g0704.

And before I can run the spindle on the 6040, I need the spindle hardware 
in the 7i76. Chicken v egg. I did manage to get a usable back panel for 
all the I/0 connectors carved for the g0704 version, but even with the 
spindle down below 5 grand, I had to stop and clean the melted alu out 
of the tool 4 times. And burnt my fingers on the panel despite its 
swimming in cutting oil. Smoking cutting oil.

So I've got misting coolant stuff on order before I try to run another 
duplicate panel for the 6040 but with bigger connectors.

Rounding up enough other stuff to put coolant/mist under control, home 
switches & some other "gingerbread-ish" stuff on it. I'd like to figure 
out how to make an encoder work, but at 24k revs wide open, that will 
take a relatively course encoder. Or a d/a put to work in the 7i76 if I 
can figure out where to hijack the rpms it displays on the vfd panel and 
pipe it back to LCNC. That might take some rs485 monkey business. The 
book mentions it, but the rj45 socket pattern on its pcb is empty.

The software book on this vfd, a 120 volt model, in Chinese, translated 
well in google translate, up to about the 40th page, but there's nearly 
70 pages, and it was just getting good when google decided that's all 
you get for free. :(

FWIW, I tend to agree with 99% of your rant. Seems like we should have a 
stretch based x86 installer by now.

Take care, John.

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 



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Re: [Emc-users] New problem, how best to solve?

[Ken Strauss]

> -Original Message-
> From: Gene Heskett [mailto:ghesk...@shentel.net]
> Sent: Monday, February 18, 2019 7:20 PM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] New problem, how best to solve?
>
> On Monday 18 February 2019 16:56:38 jrmitchellj wrote:
>
> > Hey Gene, If you were so inclined to make your own touch probe, there
> > is an article in the winter 2011 edition of Digital Machinist that
> > describes a construction project.
> > If interested, send your email address to me, and I will send more
> > information.
> >
> > --J. Ray Mitchell Jr.
> > jrmitche...@gmail.com
> >
> Its the from line above, if it survives the list
> else try ghesk...@shentel.net.  I'd be interested in anything thats half
> the size of a renishaw.
>
> Thanks J. Ray.

I haven't been following this discussion closely. What are your size
restrictions? I'd have to go to the shop to measure exactly but a Renishaw
MP3 is about 3.25 inch in diameter and 2.5 inch in Z-height.




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[Emc-users] Dedicated Processor hardware for LinuxCNC

[Greg Bentzinger via Emc-users]

( Greg )
Every kid would love to ask for a pony, if they thought they could get it they 
would ask for a unicorn. Reality however usually proves this to be impractical 
to impossible.
Everything is changing today at a hyper accelerated pace. Back in the day 
Motorola produced the 68000 CPU, it was used in all sorts of equipment from 
Apple PC's to Okuma machine controls. I would guess that that CPU was still 
being used to manufacture products 20 years after debut.
Today PC cpu and chip sets are what a 3-5 year life cycle before going OOP. 
Same with many ARM CPU. Look at the Arduino and how many generations have come 
down the road. Most new version have moved to 3.3V and are no longer compatible 
with 5V shields.
Even if someone did come up with a backplane card rack for most of the 
interface cards, that main CPU board would have to be updated nearly constantly 
because key components would become un-obtainable. Todays global manufacturing 
tries to run as close to true JIT as it can.(JIT="Just in Time") companies want 
as little space and capitol tied up in inventory. When I worked an Apple PC 
assembly line they were so JIT focused they only kept 4-6 HOURS worth of 
components in the facility. This meant that trucks were delivering Mem, HDD's 
ect. were being unloaded every few hours and being reloaded with boxed product 
ready for market.
Several Chinese machine tool builders have offered LinuxCNC as the control to 
reduce the overhead of building the machine. I believe it would be used more if 
tool builders were sure they could not be held liable for a system they sold 
that had been modified by the buyer.
GRBL has come along way - and it was a project to fit a stripped version of the 
early EMC/LinuxCNC into cheap Arduino hardware. the current v1.1 IIRC had to 
strip down the boot loader and some other items to still be able to squeeze the 
optimized assembly code into the Atmega328p chip. What did GRBL have to give up 
to fit in an Arduino? Tool table capability {G43}, Tool radius comp {G41-G42}, 
Minimal look ahead buffer, No program storage - its all drip feed via serial, 
no program editing, X-Y-Z only no additional axis, no spindle feedback 
(tapping), requires second device to stream G-code and operate the control. Now 
I like GRBL and it has the honor of being the founding code which virtually all 
extruder type 3D printers is based. I hope someday there is a port for a rotary 
axis, I would love to use it to engrave on cylinders using X-A-Z.
For now though, the movement towards SSerial and interface from control PC via 
Ethernet allows all sorts of flexibility.
As for HP-GL, I had to work with HPGL for tool paths for several years and it 
was a complete disaster. Mathematically a "line" has no physical width, not 
exactly so in HPGL so you will have gaps, broken chains, lines intersecting not 
at there endpoints and all arcs are output as splines. While at the scale for a 
HP pen plotter this worked out, for CNC use it was a dismal failure of epic man 
hours wasted trying to get each file into a usable state. I hope HPGL is 
banished from the face of the earth long before G-code begins to fade. I agree 
that G-code is far from perfect, but there is no other method out there that 
even comes close. Early AutoCAD had the same sort of dysfunction issues by the 
use of the "polyline" construct.
Lastly - May I ask the status of LCNC v2.8? Is there any potential release date 
on the horizon?
Thanks ( /Greg )

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Re: [Emc-users] New problem, how best to solve?

[Gene Heskett]

On Monday 18 February 2019 16:56:38 jrmitchellj wrote:

> Hey Gene, If you were so inclined to make your own touch probe, there
> is an article in the winter 2011 edition of Digital Machinist that
> describes a construction project.
> If interested, send your email address to me, and I will send more
> information.
>
> --J. Ray Mitchell Jr.
> jrmitche...@gmail.com
>
Its the from line above, if it survives the list
else try ghesk...@shentel.net.  I'd be interested in anything thats half 
the size of a renishaw.

Thanks J. Ray.
>
> "No problem can be solved from the same level of consciousness that
> created it"Albert Einstein
>
> On Mon, Feb 18, 2019 at 9:57 AM Gene Heskett  
wrote:
> > On Monday 18 February 2019 05:53:31 Gene Heskett wrote:
> > > On Monday 18 February 2019 02:31:46 jrmitchellj wrote:
> > > > Perhaps victims of the Trump tariffs!
> > > >
> > > > --J. Ray Mitchell Jr.
> > > > jrmitche...@gmail.com
> >
> > I've not seen anything thats blaming that BS yet...
> >
> >  But I did note that one opto based proximity detector on ebay just
> > now, no real specs listed but $0.99 copy. But shipping from the
> > Russian Federation was $30, and delivery estimates were 90 days. If
> > you needed 10,000 next year, maybe, but 10 yesterday?
> >
> > Most of the proximity stuff is designed to work with ferrous,
> > worthless for locating an alu workpiece. But it sure seems to me
> > that the market for a $5 sensor, accurate to .001" or better is wide
> > open, and whoever comes up with such a device will own the market.
> > It exists of course, called a switch, but would have to be designed
> > for that specific job. Its not something that you could just turn a
> > G38.2 loose on without some preliminary fumbling to find the target.
> >  Looking for the edge of an anodized alu panel 70 thou thick is not
> > an easy job w/o some sort of machine vision. Electrical contact
> > detection in the presence of the anodic coating only becomes
> > practical when you've a kilovolt to puncture that coating, or enough
> > mechanical force to damage it and I've neither. That leaves
> > something resembling a Renishaw. Or machining a pallet locked to the
> > table for alignment for every part you make, which except for pcb's
> > you are going to mechanically etch 100's of, has proven to be a huge
> > waste of time. IMO anyway. This machine with its target being
> > engraving, may be fast enough that it won't starve the operator.
> >
> > Up till now I've always been so limited in feed speeds by the
> > available spindle rpms that making a pcb resembled watching grass
> > grow in the time of a drought. With 10x the revs, I ought to be able
> > to carve a pcb at 30 ipm. There will no doubt be other limits found
> > long before getting to a 30 ipm average speed. Because the moving
> > parts are lighter than a conventional mills table, I expect accel's
> > can be pushed some. But thats something I haven't yet explored,
> > waiting till its moving on all-mesa i/o, so far its still on a
> > parport and moving 10x faster than the older HF, with the same
> > driver kit, stolen from it.  Same BoB too.
> >
> > And I haven't seen an obit for Murphy yet. He must be immortal... :)
> >
> > 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 
> >
> >
> >
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>
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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 



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Re: [Emc-users] DIY CNC builder dilemma, open request for comments

[Bruce Layne]

I'm glad there are fully integrated CNC control packages for those who
want to go that route, but I greatly prefer LinuxCNC for two major reasons.

1)  I control the entire design, making the design choices that make
sense for me on each machine.  I generally prefer to spend a few more
dollars on high quality PC components that will be reliable - a solid
power supple, name brand motherboard, solid state drive, etc.  I usually
prefer inexpensive motion control components, often stepper motor and
driver packages from Chinese manufacturers.  They're a great value and
they've been reliable.  I usually buy a set with one more axis than I
need so I have a spare motor and driver.  (Pro Tip:  It's worth buying
high quality shaft couplings and good bearings for the motion control
components.)  I'll usually get the largest LCD I can fit on the machine
and a Logitech wireless keyboard and touchpad that doubles as a pendant
when jogging and zeroing the axes.  No vendor can offer the exact
hardware I want on each machine.  There are too many variables and every
pre-configured package will have compromises, and they're usually fairly
severe.

2)  I built the entire system so it's much easier for me to repair.  A
heavily integrated CNC control system, particularly if the computer and
the motion control are on the same board, is both more likely to be
damaged and less likely to be repaired.  Repair is often by
replacement.  A comparable problem on my system might only require
swapping a stepper driver (and I have a spare already on hand).  For the
same reason, LinuxCNC is great for replacing antiquated high dollar CNC
controls on commercial equipment.  Toss the 1990s Fanuc controls,
replace them with LinuxCNC for a very small amount of money, and breathe
new life into an old machine where the controls were dead but the iron
still has a lot of life left in it.



On 2/18/19 5:39 PM, John Dammeyer wrote:
> I still had to edit the text into one line 
> However if you google this: " ? alibaba Low-cost-New-Product-3Axis-> 4Axis "
> it will bring up the link.
>
> Point is that for $1500 you get a CNC controller ready to go.
>
> For $800 Alibaba lists "Cheap 3 axis CNC milling center CNC controller"  The
> drawing shows the outputs going to 3 drives and motors.
>
> But for $50 for a used dual core PC and either parallel port and BoB or and
> enhanced control card from Mesa and the rest is the same.  3 drives and
> motors.
>
> I don't believe that it's currently, in today's market, to compete with a
> far east by making a custom board. 
>
> John
>
>
>> -Original Message-
>> From: John Dammeyer [mailto:jo...@autoartisans.com]
>> Sent: February-18-19 2:07 PM
>> To: 'Enhanced Machine Controller (EMC)'
>> Subject: Re: [Emc-users] DIY CNC builder dilemma, open request for
>> comments
>>
>> Let's try this then.
>>
>> Then there is the Far East solutions like the one in this link.
>> > 4Axis_60343603384.html?spm=a2700.7724857.normalList.37.3701292eTmjk5
>> p>
>>
>>
>> John Dammeyer
>>
>>
>>
>>
>> ___
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>> https://lists.sourceforge.net/lists/listinfo/emc-users
>
>
> ___
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>




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Re: [Emc-users] DIY CNC builder dilemma, open request for comments

[John Dammeyer]

I still had to edit the text into one line 
However if you google this: " ? alibaba Low-cost-New-Product-3Axis-> 4Axis "
it will bring up the link.

Point is that for $1500 you get a CNC controller ready to go.

For $800 Alibaba lists "Cheap 3 axis CNC milling center CNC controller"  The
drawing shows the outputs going to 3 drives and motors.

But for $50 for a used dual core PC and either parallel port and BoB or and
enhanced control card from Mesa and the rest is the same.  3 drives and
motors.

I don't believe that it's currently, in today's market, to compete with a
far east by making a custom board. 

John


> -Original Message-
> From: John Dammeyer [mailto:jo...@autoartisans.com]
> Sent: February-18-19 2:07 PM
> To: 'Enhanced Machine Controller (EMC)'
> Subject: Re: [Emc-users] DIY CNC builder dilemma, open request for
> comments
> 
> Let's try this then.
> 
> Then there is the Far East solutions like the one in this link.
>  4Axis_60343603384.html?spm=a2700.7724857.normalList.37.3701292eTmjk5
> p>
> 
> 
> John Dammeyer
> 
> 
> 
> 
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Re: [Emc-users] DIY CNC builder dilemma, open request for comments

[John Dammeyer]

Let's try this then.

Then there is the Far East solutions like the one in this link.


John Dammeyer




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Re: [Emc-users] New problem, how best to solve?

[jrmitchellj]

Hey Gene, If you were so inclined to make your own touch probe, there is an
article in the winter 2011 edition of Digital Machinist that describes a
construction project.
If interested, send your email address to me, and I will send more
information.

--J. Ray Mitchell Jr.
jrmitche...@gmail.com



"No problem can be solved from the same level of consciousness that created
it"Albert Einstein


On Mon, Feb 18, 2019 at 9:57 AM Gene Heskett  wrote:

> On Monday 18 February 2019 05:53:31 Gene Heskett wrote:
>
> > On Monday 18 February 2019 02:31:46 jrmitchellj wrote:
> > > Perhaps victims of the Trump tariffs!
> > >
> > > --J. Ray Mitchell Jr.
> > > jrmitche...@gmail.com
>
> I've not seen anything thats blaming that BS yet...
>
>  But I did note that one opto based proximity detector on ebay just now,
> no real specs listed but $0.99 copy. But shipping from the Russian
> Federation was $30, and delivery estimates were 90 days. If you needed
> 10,000 next year, maybe, but 10 yesterday?
>
> Most of the proximity stuff is designed to work with ferrous, worthless
> for locating an alu workpiece. But it sure seems to me that the market
> for a $5 sensor, accurate to .001" or better is wide open, and whoever
> comes up with such a device will own the market. It exists of course,
> called a switch, but would have to be designed for that specific job.
> Its not something that you could just turn a G38.2 loose on without some
> preliminary fumbling to find the target.  Looking for the edge of an
> anodized alu panel 70 thou thick is not an easy job w/o some sort of
> machine vision. Electrical contact detection in the presence of the
> anodic coating only becomes practical when you've a kilovolt to puncture
> that coating, or enough mechanical force to damage it and I've neither.
> That leaves something resembling a Renishaw. Or machining a pallet
> locked to the table for alignment for every part you make, which except
> for pcb's you are going to mechanically etch 100's of, has proven to be
> a huge waste of time. IMO anyway. This machine with its target being
> engraving, may be fast enough that it won't starve the operator.
>
> Up till now I've always been so limited in feed speeds by the available
> spindle rpms that making a pcb resembled watching grass grow in the time
> of a drought. With 10x the revs, I ought to be able to carve a pcb at 30
> ipm. There will no doubt be other limits found long before getting to a
> 30 ipm average speed. Because the moving parts are lighter than a
> conventional mills table, I expect accel's can be pushed some. But thats
> something I haven't yet explored, waiting till its moving on all-mesa
> i/o, so far its still on a parport and moving 10x faster than the older
> HF, with the same driver kit, stolen from it.  Same BoB too.
>
> And I haven't seen an obit for Murphy yet. He must be immortal... :)
>
> 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 
>
>
>
> ___
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> https://lists.sourceforge.net/lists/listinfo/emc-users
>

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Re: [Emc-users] DIY CNC builder dilemma, open request for comments

[Gene Heskett]

On Monday 18 February 2019 14:11:38 John Dammeyer wrote:

> > However, I started to wonder last year what's the future of
> > LinuxCNC? What concerns me most is the computing part mainly based
> > on silly old PC architecture from the 80's. Using PCs for that
> > purpose made sense in the early 1990s to about 2010 but now it's
> > time to move on IMO. I don't see much usable discussions on this
> > mailing list, sorry guys.
>
> I'm still in the middle of my CNC conversion.  I'm far enough along
> that the motors are mounted and now I'm working on the power supply
> cabinet. Control has aleready been done with MachineKit on a BBB.
> Here's a video of two axis control published last year in May. I'm not
>  much further along other than the third axis(X)  now has a motor
> mount and I've created motion on all three axis using a surplus PC on
> which I've booted both MACH3 and LinuxCNC.  I have a new dual parallel
> port BoB for it. The interface board I was using for the Beagle
> expected NO limit switches and I'm uncomfortable with that concept for
> machine control.  Anyway here's a link to the BBB with MachineKit
> short video.
> https://youtu.be/9GF709ZfLRQ
>
> This weekend I'm working on the power supply cabinet and a place to
> mount the PC screen, keyboard and mouse.  There's a pull out drawer
> for a surplus PC or I suppose a BeagleBone.  Haven't decided
> ultimately what I will use. During the last year I also acquired a
> harmonic drive and STMBL servo controller but I still need to cast the
> mount which means I still need to finish the 15 lb crucible all for a
> fourth axis. There's no end to projects to make the project.
>
> I won't get into the Linux verses Windows  religious discussion.  I
> use windows because my job requires I use development tools that
> aren't available on Linux.  So there's no discussion really.
>
> Dedicated hardware is an interesting question.   I designed and built
> an controller for old lathes that were missing gears.  Called an
> Electronic Lead Screw (E-Leadscrew group on Yahoo) it uses a small
> PIC18F series processor, has 2 line LCD display, MPG knob and 35 key
> buttons.  And before the stepper driver devices  became really
> expensive also a 3A 48V micro-stepper driver for the Z axis
> (carriage).  Single pulse per revolution sensing means that it needs a
> very stable spindle speed.  The user interface is less CNC like and
> more manual lathe like.  I use it on my 1942 South Bend with only
> single axis control and can cut both metric and imperial threads and
> safely bore a hole to depth without hovering over the half nut.
>
> I mention the ELS only because it's a dedicated machine controller and
> there have been requests to improve it.  And there's the problem.  I
> could use a BeagleBone with Machine Kit and build a new interface.  I
> could use a PIC32 mounted on a small carrier board to plug in and
> replace the PIC18F 40 pin DIP processor.  I even started down that
> road with modifications to my Gingery home built lathe.  I've 3D
> printed mounts for 3 sensors and a slotted tooth sensor for the Beagle
> to better capture spindle speed and position.  But like the CNC
> conversion of my mill these projects have all been stalled due to lack
> of time.
>
> The problem, and sorry  to take so long to describing this, is that
> the market has pretty well dried up.  Those who have CNC on their
> mills are using it.   Those who don't may dream of it and some do
> upgrade but very few now.   If someone has a working conversion in
> their shop running MAHC3 on a WIN-XP single core processor why change
> just for the sake of change. Especially if their desire it to make
> parts, not play with PCs.   There are probably thousands if not 10s of
> thousands using MACH3 (not the newer MACH4) for their CNC routers in
> their home shop.
>
> Similarly if someone is running LInuxCNC on working hardware, why
> change. Why upgrade?  To what end?
>
> Then there is the Far East solutions like the one in this link.



unforch, John, you did not surround this link with a pair of<> which 
would have preserved its validity even if it had been 2k chars long, but 
alibaba, rather than leaving half of it displayed so we can manually 
copy/paste the rest of it, has to be cute and replace it all with their 
custom 404 message. And even after I fixed it, it still goes to a google 
listing. And none of them goto that particular machine.

> As I understand it there are lots of systems like this out there.  I
> suspect, that like my ELS, the _time_investment_ to make a LinuxCNC
> something on dedicated hardware only slightly better just isn't
> available anymore.  If I spent another 1000 hours redeveloping my ELS
> with a 32 bit custom processor or ported BBB MachineKit to make a
> better ELS the question is how many more would I sell to recover the
> 

Re: [Emc-users] DIY CNC builder dilemma, open request for comments

[John Dammeyer]

> However, I started to wonder last year what's the future of LinuxCNC?
> What concerns me most is the computing part mainly based on silly old PC
> architecture from the 80's. Using PCs for that purpose made sense in the
> early 1990s to about 2010 but now it's time to move on IMO. I don't see
> much usable discussions on this mailing list, sorry guys.

I'm still in the middle of my CNC conversion.  I'm far enough along that the
motors are mounted and now I'm working on the power supply cabinet. Control
has aleready been done with MachineKit on a BBB.
Here's a video of two axis control published last year in May. I'm not  much
further along other than the third axis(X)  now has a motor mount and I've
created motion on all three axis using a surplus PC on which I've booted
both MACH3 and LinuxCNC.  I have a new dual parallel port BoB for it. The
interface board I was using for the Beagle expected NO limit switches and
I'm uncomfortable with that concept for machine control.  Anyway here's a
link to the BBB with MachineKit short video.
https://youtu.be/9GF709ZfLRQ

This weekend I'm working on the power supply cabinet and a place to mount
the PC screen, keyboard and mouse.  There's a pull out drawer for a surplus
PC or I suppose a BeagleBone.  Haven't decided ultimately what I will use.
During the last year I also acquired a harmonic drive and STMBL servo
controller but I still need to cast the mount which means I still need to
finish the 15 lb crucible all for a fourth axis. There's no end to projects
to make the project.
  
I won't get into the Linux verses Windows  religious discussion.  I use
windows because my job requires I use development tools that aren't
available on Linux.  So there's no discussion really.  

Dedicated hardware is an interesting question.   I designed and built an
controller for old lathes that were missing gears.  Called an Electronic
Lead Screw (E-Leadscrew group on Yahoo) it uses a small PIC18F series
processor, has 2 line LCD display, MPG knob and 35 key buttons.  And before
the stepper driver devices  became really expensive also a 3A 48V
micro-stepper driver for the Z axis (carriage).  Single pulse per revolution
sensing means that it needs a very stable spindle speed.  The user interface
is less CNC like and more manual lathe like.  I use it on my 1942 South Bend
with only single axis control and can cut both metric and imperial threads
and safely bore a hole to depth without hovering over the half nut.

I mention the ELS only because it's a dedicated machine controller and there
have been requests to improve it.  And there's the problem.  I could use a
BeagleBone with Machine Kit and build a new interface.  I could use a PIC32
mounted on a small carrier board to plug in and replace the PIC18F 40 pin
DIP processor.  I even started down that road with modifications to my
Gingery home built lathe.  I've 3D printed mounts for 3 sensors and a
slotted tooth sensor for the Beagle to better capture spindle speed and
position.  But like the CNC conversion of my mill these projects have all
been stalled due to lack of time.

The problem, and sorry  to take so long to describing this, is that the
market has pretty well dried up.  Those who have CNC on their mills are
using it.   Those who don't may dream of it and some do upgrade but very few
now.   If someone has a working conversion in their shop running MAHC3 on a
WIN-XP single core processor why change just for the sake of change.
Especially if their desire it to make parts, not play with PCs.   There are
probably thousands if not 10s of thousands using MACH3 (not the newer MACH4)
for their CNC routers in their home shop.

Similarly if someone is running LInuxCNC on working hardware, why change.
Why upgrade?  To what end?  

Then there is the Far East solutions like the one in this link.
https://www.alibaba.com/product-detail/Low-cost-New-Product-3Axis-4Axis_6034
3603384.html?spm=a2700.7724857.normalList.37.3701292eTmjk5p

As I understand it there are lots of systems like this out there.  I
suspect, that like my ELS, the _time_investment_ to make a LinuxCNC
something on dedicated hardware only slightly better just isn't available
anymore.  If I spent another 1000 hours redeveloping my ELS with a 32 bit
custom processor or ported BBB MachineKit to make a better ELS the question
is how many more would I sell to recover the say 1000hr * $100 per hour
consulting R costs?

I think the support on this group is awesome.  I suspect though that none of
the members have the time nor interest in re-inventing a wheel that is
already turning.   What does one do with that 4 hours of free time.  Take
their CNC machine apart to try something new?  Or just go out and make
something with what they have and what is familiar?

John Dammeyer




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Re: [Emc-users] New problem, how best to solve?

[Gene Heskett]

On Monday 18 February 2019 05:53:31 Gene Heskett wrote:

> On Monday 18 February 2019 02:31:46 jrmitchellj wrote:
> > Perhaps victims of the Trump tariffs!
> >
> > --J. Ray Mitchell Jr.
> > jrmitche...@gmail.com

I've not seen anything thats blaming that BS yet...

 But I did note that one opto based proximity detector on ebay just now, 
no real specs listed but $0.99 copy. But shipping from the Russian 
Federation was $30, and delivery estimates were 90 days. If you needed 
10,000 next year, maybe, but 10 yesterday?

Most of the proximity stuff is designed to work with ferrous, worthless 
for locating an alu workpiece. But it sure seems to me that the market 
for a $5 sensor, accurate to .001" or better is wide open, and whoever 
comes up with such a device will own the market. It exists of course, 
called a switch, but would have to be designed for that specific job. 
Its not something that you could just turn a G38.2 loose on without some 
preliminary fumbling to find the target.  Looking for the edge of an 
anodized alu panel 70 thou thick is not an easy job w/o some sort of 
machine vision. Electrical contact detection in the presence of the 
anodic coating only becomes practical when you've a kilovolt to puncture 
that coating, or enough mechanical force to damage it and I've neither. 
That leaves something resembling a Renishaw. Or machining a pallet 
locked to the table for alignment for every part you make, which except 
for pcb's you are going to mechanically etch 100's of, has proven to be 
a huge waste of time. IMO anyway. This machine with its target being 
engraving, may be fast enough that it won't starve the operator.

Up till now I've always been so limited in feed speeds by the available 
spindle rpms that making a pcb resembled watching grass grow in the time 
of a drought. With 10x the revs, I ought to be able to carve a pcb at 30 
ipm. There will no doubt be other limits found long before getting to a 
30 ipm average speed. Because the moving parts are lighter than a 
conventional mills table, I expect accel's can be pushed some. But thats 
something I haven't yet explored, waiting till its moving on all-mesa 
i/o, so far its still on a parport and moving 10x faster than the older 
HF, with the same driver kit, stolen from it.  Same BoB too.

And I haven't seen an obit for Murphy yet. He must be immortal... :)

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 



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Re: [Emc-users] DIY CNC builder dilemma, open request for comments

[Jon Elson]

On 02/18/2019 10:58 AM, Rafael Skodlar wrote:



However, I started to wonder last year what's the future 
of LinuxCNC?
What concerns me most is the computing part mainly based 
on silly old PC architecture from the 80's. Using PCs for 
that purpose made sense in the early 1990s to about 2010 
but now it's time to move on IMO. I don't see much usable 
discussions on this mailing list, sorry guys.


I believe LinuxCNC will run on several ARM processors, such 
as Rasberry Pi and Beagle Bone.
Also, the Machinekit fork of LinuxCNC definitely runs on the 
Beagle Bone.


Also, Centroid is selling the Acorn CNC control, which 
appears suspiciously to be a LinuxCNC clone running under 
cover with another GUI.


Jon


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[Emc-users] DIY CNC builder dilemma, open request for comments

[Rafael Skodlar]

Hi everybody,

I'm following this mailing list for a number of years with one year 
interruption during kitchen remodeling and unplanned medical leave last 
year. First annoyance was subscribing again to post to the list. Now I'm 
getting two copies of each email.


Having experience with mechanical computer peripherals I'm not afraid of 
building a CNC machine of some kind. I spend a lot of time researching 
possibilities to achieve my goals:

- convert Grizzly lathe/mill to Linux CNC,
- build a small CNC router for my hobby use (aluminium, plastic)
- build larger CNC router for woodwork use by my relative in EU.

However, I started to wonder last year what's the future of LinuxCNC?
What concerns me most is the computing part mainly based on silly old PC 
architecture from the 80's. Using PCs for that purpose made sense in the 
early 1990s to about 2010 but now it's time to move on IMO. I don't see 
much usable discussions on this mailing list, sorry guys.


There seem to be no major industrial drive to use LinuxCNC as one of 
available software options to more or less "open hardware design". I 
believe there's $$$ to be made with LinuxCNC: system design, 
installation, support, and training for this open source product. OS is 
free but based on my research CNC kits manufacturers do not offer or 
mention it at all.


On the other hand, there is plenty of those that include that other CNC 
thing, Mach??. I wonder why these people are so clueless to design their 
software for the worst mass produced OS in the history of computers and 
never bothered to port their product to much better OS Linux?


One thing that's hard to understand on LinuxCNC side is why is there so 
much emphasis on testing a motherboard to make sure it's going to work 
well with real time kernel on multi-core CPUs with GHz clocks? Let's say 
my relative overseas needs to replace a bad motherboard and all I can do 
is to say 'try different mobos with running timing test'! That's too 
much folks!


Most motherboards are build for computer gamers, entertainment, and 
office work so they are bad choice for CNC use. Besides, there is no 
long term support for motherboards which is critical for industrial use.
What's needed is exact selection of hardware that's easy to find and not 
too expensive.


I worked on a number of industrial applications where Digital PDP-8 had 
enough computing power to handle huge critical tasks in the 80's. In 
other cases PDP-11 was used to control machinery in steel mills, hydro 
power plants, etc. Paper tape, core memory; that was fun. That makes me 
wonder why it's so hard to find a decent low cost computer in $500 range 
that would be good for most CNC applications and will last or be 
supported for 10 years or so?


I bet a plate of sushi that LinuxCNC dependency on PC motherboards is 
preventing many to venture into business of building CNC machines or 
kits on this architecture.


On the "PC architecture side" I'm aware of PC-104 but that's very poor 
design. Ever tried to use scope on the middle of 3 boards in PC-104? Now 
we have new crop: RaspberryPi, Beagle Board, Arduino, all very powerful 
compared to computers 40 years ago but all have the same _stupid 
sandwich design_ that requires wires connected to their boards from all 
sides or even somewhere in the middle of the PCB. In addition, 
connectors, data or address lines are not standard as far as their 
location on pins go or their voltage.


People that designed PDP series were much smarter and solved such 
problems long time ago so it would make sense to adopt that kind of 
design but on smaller scale with modern higher density ICs and 
connectors. Unibus standardized address, data, interrupt, and few other 
lines. That opened OEM business for PDP platform.


I hate to see parallel port mentioned for use in CNC IO of any kind. 
That's so 1990s. It would make much more sense using parallel I/O card 
from Mesa Electronics or some such by default. Anybody serious about 
retrofitting an old machine to CNC or just building a new one should not 
mind paying a bit more for a decent CNC computer with standard IO 
interfaces plugged into standard backplane, not PCs.


VME is too expensive for DIY. RaspberryPi, BB, Arduino, or such were 
designed for something else. Where does this leave me? On the sideline 
for now but disappointed over the fact that there's so little progress 
in this field. I also hate to see thousands of hours, that many of you 
guys used for designing and tweaking LinuxCNC over the years, go to waste.


Another disappointment is G_code. It's archaic and "inhumane". HP-GL 
with CNC enhancements would be much easier for use on flat surface jobs 
IMO. In systems administration work we (some of us) transitioned from 
korn shell, awk, sed, and perl to more logical and powerful python. Some 
old things just don't die when they should. G-code with it.


There is new (?) trend in using Arduino and GRBL for entry level CNC. 
That alone 

Re: [Emc-users] New problem, how best to solve?

[Gene Heskett]

On Monday 18 February 2019 02:31:46 jrmitchellj wrote:

> Perhaps victims of the Trump tariffs!
>
> --J. Ray Mitchell Jr.
> jrmitche...@gmail.com
>
>
>
> "No problem can be solved from the same level of consciousness that
> created it"Albert Einstein
>
> On Sun, Feb 17, 2019 at 4:00 PM Gene Heskett  
wrote:
> > On Saturday 16 February 2019 20:01:38 Gene Heskett wrote:
> > > On Saturday 16 February 2019 14:28:33 Chris Albertson wrote:
> > > > Thinking about this as an electrical engineer,  I'd say don't
> > > > use DC. DC current is as you say blocked by paint and oil films.
> > > >Use AC. I think a low radio frequency.   Then the DC
> > > > insulators would act like capacitors and pass AC. even while
> > > > blocking DC.  To detect contact use an AC voltage sensor,
> > > > typically a diode and small capacitor.
> > >
> > > The disadvantage there is the rc charge time. This means among
> > > other things a relatively leasure velocity to the first trip, and
> > > a much slower 2nd approach, where as in using the dc circuit, one
> > > usually uses a rotating with the spindle probe so even  if it has
> > > some runnout, the contact surface is recorded an by the first
> > > contact discharging a .1 ufcapacitor, which takes long enough to
> > > recharge that the contacts logic zero, is captured and reported to
> > > LCNC instantly even if by the time the servo thread actually reads
> > > it, the contact has been lost again for .9 milliseconds. The rf
> > > circuit, cannot possibly respond in that time frame unless the
> > > closing velocities are also very slow. The DC method is inherently
> > > the faster method, but does require a very low ohmage connection
> > > in order to fully discharge the cap  on a 10 microsecond contact. 
> > > And we definitely DON'T have a low resistance circuit on this
> > > machine.
> > >
> > > I have one of this old tony's contacts about 75% made, but out of
> > > a brass tube instead of a steel probe and I'll take the machine
> > > out of it by grounding the workpiece, and wiring the tube straight
> > > to the probe input, using the same old cap for storage. The brass
> > > is long enough it can hit and be bent 1/4" without damage as it
> > > will just spring back.
> > >
> > > But its been a long day today.  I'll figure out something thats
> > > hopefully repeatable.
> >
> > Got that done, almost worked when using brass against the edge of
> > this alu panel, so I thought I'd get fancy, and found a steel sewing
> > pit with the rounded backend sewing pin and soldered it into the tip
> > of the tube. Disaster, I can see it sliding along on jerks as I run
> > it back and forth touching the edge of the alu, but the only place
> > its making actual contact is where the brushed finish is damaged,
> > anyplace else needs a 10lb push with my finger to break thru the
> > aloxide and actually make a contact. Would probably work with most
> > anything metallic except the alu. To do this would need a 1kv
> > supply, limited to 1 microamp so as not to eat up the probe too fast
> > and measure the voltage electrostaticly.
> >
> > Last week there were at least a dozen guys selling imitation
> > Reneshaws for 69$/copy.  But I'll be darned if I can find one on
> > fleabay today.

Finally found one and bought it. They sure are BIG though, 2.1" in 
diameter and 4+" long. And Z motion is certainly limited with that 
installed!  Bought a t.l.o. setter and a big bag of teeny homing 
switches. This thing has blocks of solid cambric for crash stops, looks 
like a 2.5mm thick switch glued in there ought to make a serviceable 
homing switch. Now we sit and wait, bored out of my skull till stuff 
gets here. Sigh.

> > > And I've got to figure what to do Monday as my lady adds another
> > > year to her journey on this ball of rock and water, making it to
> > > her 79nth.
> > >
> > > Something she'll appreciate without any physical effort. With
> > > copd, there's not much of that left.  Sigh...
> > >
> > > That said, I think the DC method can be made to work with a
> > > separately wired probe, with both the ground on the workpiece and
> > > the hot on the probe wired independently from the machine. Run the
> > > probe cable as a shielded wire in the cable chain.  At least this
> > > chain can be opened to add more wire, something none of the other
> > > cable chain I've bought can do.  Nice!
> > >
> > > > I don't know if this is done commercially but the AC method
> > > > should in theory by MUCH more reliable.You can even use very
> > > > long cables if you use strong filters tuned to the frequency.   
> > > >  Notice how well the current passes from an AM radio station to
> > > > your radio even over a miles-long air gap.
> > > >
> > > > My guess is that a 100 KHz signal would go right through paint.
> > > >
> > > > On Sat, Feb 16, 2019 at 9:46 AM Gene Heskett
> > > > 
> > >
> > > wrote:
> > > > > Greetings all;
> > > > >
> > > > > I've just found that because everything it painted before
> > >