Re: [Emc-users] EDM Small Hole Drilling

[TJoseph Powderly]

good point
i was an applications engineer
and i used that trick
sometimes you have to think well tho

(it dont always work like you think)

i always akin it to 'smoke goes up the chimney'
and
'dont blow down the chimney'

often the heat rise will aid the upwards flow and the swarf contained in 
the fluid
sometimes there's just too much stuff clogging the chimney ( the space 
between the tool and the cavity)
and sometimes the dirt is formed too deep for natural convection to clean
so
use flush, use jump, use ultrasonic vibration to loosen and keep the 
dirt in suspension
sometimes thicker oils sometimes thinner

sometimes upside down is good,
did you know the hydrogen gas bubbles would rise into the now inverted 
cavity?
gues what hapens when you spark into hydrogen ;-)
(oil is a hydrocarbon, the electrical energy _cracks_ it,  the carbon 
(you see 'dirt') and the hydrogen (you see smoke )

one method is not suitable to all cuts

so, form a picture of whats happening, test that picture every day
tomp tjtr33

On 02/12/17 11:43, Ralph Stirling wrote:
> I've got a question for you, TomP.  Why aren't sinker edm systems operated in 
> an inverted fashion, with the work facing down and the electrode underneath 
> facing upward?  I would think gravity could then help clear debris out of the 
> hole.
>
> -- Ralph
>
> On Feb 11, 2017 2:35 AM, TJoseph Powderly  wrote:
>
>
> On 02/11/17 17:15, Andy Pugh wrote:
>>> On 10 Feb 2017, at 22:42, Jim Craig  wrote:
>>>
>>> Seriously though, lasers are expensive. I actually considered lasers
>>> first and went back to a regular spindle.
>> Also, going back to something else mentioned here, ECM might work. It might 
>> be especially effective if the geometry allows several holes to be made at 
>> the same time.
> true, less burr also
> less volts, more amps
> kind of like de-plating
> use carbide tube ( you can get a round hole by rotating or using carbide
> tubes ---old skool rule )
> a jig plate could do several at once. so the precision can be quite high
> still requires gap-width controller
> tomp
>
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Re: [Emc-users] EDM Small Hole Drilling

[Ralph Stirling]

I've got a question for you, TomP.  Why aren't sinker edm systems operated in 
an inverted fashion, with the work facing down and the electrode underneath 
facing upward?  I would think gravity could then help clear debris out of the 
hole.

-- Ralph

On Feb 11, 2017 2:35 AM, TJoseph Powderly  wrote:


On 02/11/17 17:15, Andy Pugh wrote:
>
>> On 10 Feb 2017, at 22:42, Jim Craig  wrote:
>>
>> Seriously though, lasers are expensive. I actually considered lasers
>> first and went back to a regular spindle.
> Also, going back to something else mentioned here, ECM might work. It might 
> be especially effective if the geometry allows several holes to be made at 
> the same time.
true, less burr also
less volts, more amps
kind of like de-plating
use carbide tube ( you can get a round hole by rotating or using carbide
tubes ---old skool rule )
a jig plate could do several at once. so the precision can be quite high
still requires gap-width controller
tomp

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[Emc-users] EDM Small Hole Drilling

[Roland Jollivet]

You don't say how many holes to drill/hr, how many holes per part,
orientation of adjacent holes. (parallel, orthogonal)
It may be practical to have a setup with multiple heads that EDM drills all
the holes at once.


On 10 February 2017 at 23:59, Jim Craig  wrote:

> I am working on a project at work where we are designing a new CNC
> machine for a particular application. Up to this point I have been
> planning on using a standard machine spindle.
>
> The more I think about the actual process and needs of the machine I am
> thinking that a small hole EDM drilling head would be better for this
> application.
>
> The application required drilling small 0.050" diameter holes through
> .135" thick stainless steel. The back side of these holes are in an
> annular space that cannot be easily reached for deburring.
>
> The reason I am contemplating the small hole EDM process is three fold.
> First it is difficult to drill these tiny holes in stainless and the
> drill bits frequently break. Secondly the back side of the hole needs to
> be burr free but is difficult to get to with conventional tools. Third
> the machine could be lighter and simpler if I use EDM vs a standard
> milling head.
>
> So my questions are as follows. What type of power supply would I need
> to use for doing small hole EDM drilling? Can I use a tig welder as the
> power supply and control pulsing with LinuxCNC driving an external IGBT?
> Could I use the Mesa THC to control gap of the electrode to the workpiece?
>
> It appears that spindles don't need to rotate very fast. What type of
> rpm do the spindles typically run at?
>
> That is all for now. I am sure I will have more to come.
>
> Thanks,
>
> Jim
>
>
> 
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Re: [Emc-users] EDM Small Hole Drilling

[TJoseph Powderly]

thats hot! 1mm dia.
tomp

On 02/12/17 04:52, Ken Strauss wrote:
> A local shop uses the larger version of these to deburr holes drilled in
> tubing. They claim to be usable in 0.040 holes and there is a Swiss company
> that I can't recall the name of that makes really small ones.
>
> http://www.ezburr.com/products/micro_series.php
>


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Re: [Emc-users] EDM Small Hole Drilling

[TJoseph Powderly]

Jim hello
again let me stress the word 'scale'
most google hits will claim edm has 'no burr'
thats a damn-lie (tm) invented by sales-people
i can feel it with my finger tip
IF it was done fast on a cheap machine
so there is a sliding scale of burr height from nanometers to tens of 
microns

the burr height is related to current at entry/exit (not solely 
dependant, bit its a biggie in the picture)
so you can get less burr if you reduce the power at entry and exit

http://bit.ly/2l6hvkx

the url shows edm hole burrs, it uses SEM photos ( scale again :-)

my discussion before was cheap taiwanes hopops
if you use an sophisticated(read expensive) machine
( say sarix or sodick or hitachi )
you will get control over the entry and exit power
and hopefully control over the control method at exit

changing from gap control to feed control at exit helps
because
when you exit the hole, there aint no gap, theres nothing in front of 
the tool tip
at that time the gap width control fails and the control begins to bang 
into that last tiny bit of stock hanging on the edge of the cave exit
and you get some nasty micro short circuits and some scraggy exit edges

if the control system is bad enuf, you actually push the remaining stock 
out!

again, its magnitude/scale,
so take a sample part to a jockey (aka applications engineer) and see 
what result you get
thats a good feasibility/reality test



On 02/12/17 01:27, Jim Craig wrote:
> On 2/10/2017 9:01 PM, TJoseph Powderly wrote:
>>> The reason I am contemplating the small hole EDM process is three fold.
>>> First it is difficult to drill these tiny holes in stainless and the
>>> drill bits frequently break. Secondly the back side of the hole needs to
>>> be burr free but is difficult to get to with conventional tools.
>> scale again... 'burr free'
>> well edm produces a burr, its small a few thou to 10 thou depending on
>> energy at breakthru and the system ability to control position well
>> ( hammering thru with bang bang control has larger burr )
>> to get almost no burr, use a sacrificial plate and burn thru the SS and
>> into the sacrifice
> I will have to reconsider if it does not make a burr free hole without a
> backer. I was under the impression it did. I guess what I was reading
> was with a backer or a stack of parts. I am not sure if the client would
> consider a 10thou burr acceptable.
10thou is large and the size can be controlled at the expense of time
( small burr needs small current. small current = larger time )
Afaik there will always be some burr, but i'm talking tiny.
> This is a spherical part where we are drilling through the spherical
> shell into the hollow center. Some holes are off center again benefiting
> from the EDM process.
yes drilling off center on a ball is something the hole drill edm can do
it requires a bit of control work , its like riding a horse down hill on 
gravel
a lot of this is the driver/jockey controlling the machine, picking the 
right adjustments and having a good machine.
> We could possibly have fluid (water) in the core of the sphere would
> that help reduce the burr?
yes it will help, drilling from wet to dry will aggravate it
so 'help' is what it will do, it will not 'fix' the exit problem

> Snip
>> sorry i gets carried away with edm stuff
>> tomp tjtr33
> No reason to apologize. You have provided lots of good information here.
>
> Thanks a bunch,
>
> Jim
>
thank you
tomp tjtr33
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Re: [Emc-users] EDM Small Hole Drilling

[Jim Craig]

On 2/11/2017 3:52 PM, Ken Strauss wrote:
> A local shop uses the larger version of these to deburr holes drilled in
> tubing. They claim to be usable in 0.040 holes and there is a Swiss company
> that I can't recall the name of that makes really small ones.
>
> http://www.ezburr.com/products/micro_series.php
>
>
Ken,

That looks like it just might work. Seems like EDM was going to get 
nearly as expensive as lasers (and sharks). For a good power supply 
spindle pump etc. . .

I will keep proceeding with the standard milling spindle for now. I may 
experiment with EDM on om own. Just for kicks. Because I don't have 
enough to do anyway.

Thanks all,

Jim

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Re: [Emc-users] EDM Small Hole Drilling

[Ken Strauss]

A local shop uses the larger version of these to deburr holes drilled in
tubing. They claim to be usable in 0.040 holes and there is a Swiss company
that I can't recall the name of that makes really small ones.

http://www.ezburr.com/products/micro_series.php


> -Original Message-
> From: dave [mailto:dengv...@charter.net]
> Sent: Saturday, February 11, 2017 3:14 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] EDM Small Hole Drilling
>
> ECM can be good stuff but often slow. LOTS of current at low voltage.
> NaCl or NaOH as electrolyte. Byproducts may not be soluble and therefore a
> mess especially if you make ferric hydroxide; a mess to filter. I thought
about
> doing this in salt water. That is use water out of the bay. Not an option
for very
> many users.
> ECM is slow because it is electrochemistry. One equivalent wt of
> metal/coulomb.
>
> On another tack. Drill with carbide and then deburr by electropolishing.
> I've also seen some spring loaded tooling that will deburr both sides of a
hole.
>
> Some things are simply not easy unless you have unlimited $$$ to throw at
the
> problem.
>
> Dave
>
> On 02/11/2017 02:35 AM, TJoseph Powderly wrote:
> >
> > On 02/11/17 17:15, Andy Pugh wrote:
> >>> On 10 Feb 2017, at 22:42, Jim Craig <jimcraig5...@windstream.net>
> wrote:
> >>>
> >>> Seriously though, lasers are expensive. I actually considered lasers
> >>> first and went back to a regular spindle.
> >> Also, going back to something else mentioned here, ECM might work. It
> might be especially effective if the geometry allows several holes to be
made
> at the same time.
> > true, less burr also
> > less volts, more amps
> > kind of like de-plating
> > use carbide tube ( you can get a round hole by rotating or using
> > carbide tubes ---old skool rule ) a jig plate could do several at
> > once. so the precision can be quite high still requires gap-width
> > controller tomp
> >
> >> -
> >> - Check out the vibrant tech community on one of the world's
> >> most engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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>
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Re: [Emc-users] EDM Small Hole Drilling

[dave]

ECM can be good stuff but often slow. LOTS of current at low voltage. 
NaCl or NaOH as electrolyte. Byproducts may not be soluble and therefore 
a mess especially if you make ferric hydroxide; a mess to filter. I 
thought about doing
this in salt water. That is use water out of the bay. Not an option for 
very many users.
ECM is slow because it is electrochemistry. One equivalent wt of 
metal/coulomb.

On another tack. Drill with carbide and then deburr by electropolishing. 
I've also seen some spring loaded tooling that will deburr both sides of 
a hole.

Some things are simply not easy unless you have unlimited $$$ to throw 
at the problem.

Dave

On 02/11/2017 02:35 AM, TJoseph Powderly wrote:
>
> On 02/11/17 17:15, Andy Pugh wrote:
>>> On 10 Feb 2017, at 22:42, Jim Craig  wrote:
>>>
>>> Seriously though, lasers are expensive. I actually considered lasers
>>> first and went back to a regular spindle.
>> Also, going back to something else mentioned here, ECM might work. It might 
>> be especially effective if the geometry allows several holes to be made at 
>> the same time.
> true, less burr also
> less volts, more amps
> kind of like de-plating
> use carbide tube ( you can get a round hole by rotating or using carbide
> tubes ---old skool rule )
> a jig plate could do several at once. so the precision can be quite high
> still requires gap-width controller
> tomp
>
>> --
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>> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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Re: [Emc-users] EDM Small Hole Drilling

[Jim Craig]

On 2/10/2017 9:01 PM, TJoseph Powderly wrote:
>> The reason I am contemplating the small hole EDM process is three fold.
>> First it is difficult to drill these tiny holes in stainless and the
>> drill bits frequently break. Secondly the back side of the hole needs to
>> be burr free but is difficult to get to with conventional tools.
> scale again... 'burr free'
> well edm produces a burr, its small a few thou to 10 thou depending on
> energy at breakthru and the system ability to control position well
> ( hammering thru with bang bang control has larger burr )
> to get almost no burr, use a sacrificial plate and burn thru the SS and
> into the sacrifice

I will have to reconsider if it does not make a burr free hole without a 
backer. I was under the impression it did. I guess what I was reading 
was with a backer or a stack of parts. I am not sure if the client would 
consider a 10thou burr acceptable.

This is a spherical part where we are drilling through the spherical 
shell into the hollow center. Some holes are off center again benefiting 
from the EDM process.

We could possibly have fluid (water) in the core of the sphere would 
that help reduce the burr?

Snip
> sorry i gets carried away with edm stuff
> tomp tjtr33

No reason to apologize. You have provided lots of good information here.

Thanks a bunch,

Jim


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Re: [Emc-users] EDM Small Hole Drilling

[Jim Craig]

> The problem is EDM is very slow.  Your holes would take at
> the least, several minutes each.  But, they'd be pretty clean.
> You ought to get in touch with Ben Fleming, he demoed a
> pulser EDM system at some of the CNC workshops in Ann Arbor
> a few years ago.
>
> http://www.homebuiltedmmachines.com/build-a-pulse-edm/
>
> He has a book and a circuit board, and you can build it in a
> couple weekends.  It was VERY cool to watch it work!
>
> Jon
>
I found Ben's website. I will probably buy his book and circuit board to 
at least play with the concept.

Thanks,

Jim

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Re: [Emc-users] EDM Small Hole Drilling

[Nicklas Karlsson]

> >> Seriously though, lasers are expensive. I actually considered lasers
> >> first and went back to a regular spindle.
> > Also, going back to something else mentioned here, ECM might work. It might 
> > be especially effective if the geometry allows several holes to be made at 
> > the same time.
> true, less burr also
> less volts, more amps
> kind of like de-plating
> use carbide tube ( you can get a round hole by rotating or using carbide 
> tubes ---old skool rule )

Something different than round for example square or like a cogg wheel rotating 
to get good removal of debri?

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Re: [Emc-users] EDM Small Hole Drilling

[TJoseph Powderly]

On 02/11/17 17:15, Andy Pugh wrote:
>
>> On 10 Feb 2017, at 22:42, Jim Craig  wrote:
>>
>> Seriously though, lasers are expensive. I actually considered lasers
>> first and went back to a regular spindle.
> Also, going back to something else mentioned here, ECM might work. It might 
> be especially effective if the geometry allows several holes to be made at 
> the same time.
true, less burr also
less volts, more amps
kind of like de-plating
use carbide tube ( you can get a round hole by rotating or using carbide 
tubes ---old skool rule )
a jig plate could do several at once. so the precision can be quite high
still requires gap-width controller
tomp

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Re: [Emc-users] EDM Small Hole Drilling

[Andy Pugh]

> On 10 Feb 2017, at 22:42, Jim Craig  wrote:
> 
> Seriously though, lasers are expensive. I actually considered lasers 
> first and went back to a regular spindle.

Also, going back to something else mentioned here, ECM might work. It might be 
especially effective if the geometry allows several holes to be made at the 
same time. 
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Re: [Emc-users] EDM Small Hole Drilling

[Gregg Eshelman]

Some googling turned up info on first drilling through with an undersize tool 
then making a grinding pass to finished size.
http://link.springer.com/article/10.1007/s12541-012-0123-2


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Re: [Emc-users] EDM Small Hole Drilling

[Gregg Eshelman]

Small  hole  EDM  (electrical  discharge  machining)  drilling,  also  known  
as  fast  
hole EDM drilling, hole popper, and start hole EDM drilling, was once relegated 
to a “last resort” method of drilling holes. Now, small hole EDM drilling is 
used 
for production work. Drilling speeds have been achieved of up to two inches per 
minute.  Holes  can  be  drilled  in  any  electrical  conductive  material,  
whether  hard  
or soft, including carbide. See Figure 14:1 for various small hole EDM machines.
http://www.reliableedm.com/Complete%20EDM%20Handbook/Complete%20EDM%20Handbook_14.pdf
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Re: [Emc-users] EDM Small Hole Drilling

[TJoseph Powderly]

i was surprised how much off the shelf stuff exists
its not impossible to reverse engineer the connections
but a working experience is handy
maybe you know an edm service engineer cum hacker?
the mechanical stuff ( motors spindles pumps ) are too cheap to mess 
with diy
the guides wont be a diy project, drilling holes thru ruby & ceramic 
aint easy )

save up for 1 1kva trafo!
tomp tjtr33
( i _think_ these teeny jpgs will pass the size restrictions on this list )

On 02/11/17 05:58, Comcast wrote:

The laser drilling was the first thing I thought of too.  Pratt & Whitney uses 
this process to drill similar size holes in the turbine blades.  The keep the slag 
out of the holes they fill the interior of the blade with epoxy:  Upon burn through 
the epoxy virtually explodes, blowing and slag or burr-like recast out of the hole.

N. Christopher




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Re: [Emc-users] EDM Small Hole Drilling

[Gene Heskett]

On Friday 10 February 2017 21:54:45 Jon Elson wrote:

> On 02/10/2017 03:59 PM, Jim Craig wrote:
> > So my questions are as follows. What type of power supply would I
> > need to use for doing small hole EDM drilling? Can I use a tig
> > welder as the power supply and control pulsing with LinuxCNC driving
> > an external IGBT?
>
> TIG is constant current, and generally way more than you
> need. IGBTs are good for 400+ Volts, MOSFETs make more sense
> below that.
>
> > Could I use the Mesa THC to control gap of the electrode to the
> > workpiece?
> >
> > It appears that spindles don't need to rotate very fast. What type
> > of rpm do the spindles typically run at?

What I've done is A, rank amateur, and B, at 150 to 200 rpms so as not to 
be pitching the dielectric fluid, usually distilled water, all over.  
But whats the hole diameter and depth again?  If the hole is deep 
compared to the diameter, you'll be going down less than the hole 
diameter before the sludge shorts you out, so figure on doing a peck 
cycle, and figuring out how to flush the hole clean before putting the 
electrode back in the hole. If you can figure out how to feed dielectric 
into the right sized hypo needle, that would keep the hole flushed and 
would cut lots faster. But I've not managed to come up with a workable 
idea for that, I'm usually done by the time I've noodled out an idea I 
could do with what I had on hand. Best idea so far as do a peck, going 
about a thou deeper per peck, and doing the peck at a high enough speed 
to keep the mix well agitated so the sludge would be squirted out on the 
downstroke, and the upstroke would bring fresh water to dilute the 
sludge, in at a high enough speed to keep it well stirred.  Fast its not 
going to be.

The last time I was working in a deep hole, I was burning the center web 
out of a couple broken off in the hole 6-32 taps. IIRC it was much of a 
day for each broken tap cleared out of the hole.  But it still beat 
starting all over by $25 worth of steel and 3 days putzing around to 
make it again.

> The problem is EDM is very slow.  Your holes would take at
> the least, several minutes each.  But, they'd be pretty clean.
> You ought to get in touch with Ben Fleming, he demoed a
> pulser EDM system at some of the CNC workshops in Ann Arbor
> a few years ago.
>
> http://www.homebuiltedmmachines.com/build-a-pulse-edm/
>
> He has a book and a circuit board, and you can build it in a
> couple weekends.  It was VERY cool to watch it work!
>
> Jon
>
> --
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> most engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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 soap, ballot, jury, and ammo. Please use in that order."
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Re: [Emc-users] EDM Small Hole Drilling

[TJoseph Powderly]

wow, i gotta look into that epoxy idea,
we just pressurized the cavity with water
and that was a complex jig already!
thx tomp

On 02/11/17 05:58, Comcast wrote:
> The laser drilling was the first thing I thought of too.  Pratt & Whitney 
> uses this process to drill similar size holes in the turbine blades.  The 
> keep the slag out of the holes they fill the interior of the blade with 
> epoxy:  Upon burn through the epoxy virtually explodes, blowing and slag or 
> burr-like recast out of the hole.
>
> N. Christopher
>
>> On Feb 10, 2017, at 5:16 PM, andy pugh  wrote:
>>
>>> On 10 February 2017 at 21:59, Jim Craig  wrote:
>>> The more I think about the actual process and needs of the machine I am
>>> thinking that a small hole EDM drilling head would be better for this
>>> application.
>>
>> Maybe consider lasers (and sharks?) too:
>> https://www.oxfordlasers.com/laser-micromachining/applications/fuel-injector-production/
>>
>>
>> -- 
>> 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
>>
>> --
>> Check out the vibrant tech community on one of the world's most
>> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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>
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Re: [Emc-users] EDM Small Hole Drilling

[TJoseph Powderly]

re: other technogies...
if you can drill it, it'll be faster
a good applications engineer from a good company
can read your specs and give you tools and tooling that will do the job
it may be expensive but its pretty guaranteed and even proven on your 
test parts
tomp

On 02/11/17 05:42, Jim Craig wrote:
> On 2/10/2017 4:16 PM, andy pugh wrote:
>> On 10 February 2017 at 21:59, Jim Craig  wrote:
>>> The more I think about the actual process and needs of the machine I am
>>> thinking that a small hole EDM drilling head would be better for this
>>> application.
>> Maybe consider lasers (and sharks?) too:
>> https://www.oxfordlasers.com/laser-micromachining/applications/fuel-injector-production/
>>
>>
> But that would cost 1 million dollars.
>
> Seriously though, lasers are expensive. I actually considered lasers
> first and went back to a regular spindle.
>
> Thanks Andy,
>
> Jim
>
>
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Re: [Emc-users] EDM Small Hole Drilling

[TJoseph Powderly]

Jim hello
I have worked with a lot of taiwanese hole drills ( hopops for short )

On 02/11/17 04:59, Jim Craig wrote:
> I am working on a project at work where we are designing a new CNC
> machine for a particular application. Up to this point I have been
> planning on using a standard machine spindle.
>
> The more I think about the actual process and needs of the machine I am
> thinking that a small hole EDM drilling head would be better for this
> application.
>
> The application required drilling small 0.050" diameter holes through
> .135" thick stainless steel. The back side of these holes are in an
> annular space that cannot be easily reached for deburring.
ok scale & magnitude in this conversation...
  you say 'small hole' and...
.050 is almost optimum size ( 1mm dia is pretty the optimum for the 
technology)
2mm is difficult, .006 is difficult ( for std cheapo (<20k$) hopops )
> The reason I am contemplating the small hole EDM process is three fold.
> First it is difficult to drill these tiny holes in stainless and the
> drill bits frequently break. Secondly the back side of the hole needs to
> be burr free but is difficult to get to with conventional tools.
scale again... 'burr free'
well edm produces a burr, its small a few thou to 10 thou depending on
energy at breakthru and the system ability to control position well
( hammering thru with bang bang control has larger burr )
to get almost no burr, use a sacrificial plate and burn thru the SS and 
into the sacrifice

>   Third
> the machine could be lighter and simpler if I use EDM vs a standard
> milling head.
the time to burn .050 hole thru 0.1" SS should be near 45seconds
go to a shop to verify, or take a test pc to a sales house

>
> So my questions are as follows. What type of power supply would I need
> to use for doing small hole EDM drilling? Can I use a tig welder as the
> power supply and control pulsing with LinuxCNC driving an external IGBT?
igbt's are not popular/common in commerical units
igbt's have not been driven on and off as clean as individual fets, esp 
the irf series
(its the clean off drop that marks a low wear unit)
irf 540s and up are very very common ( theres a high-v spike due to 
overall system wiring,
things like wire wrapped resistors, cable length etc add capacitance and 
inductance)

the power should be , in _very_ general description...
100V open volts, 0-32 amperes supply in short circuit
the polarity will be negative to tool and the tool will be brass tubing
the on time will be 10 to 50uS and duty cycle 1-50%

since linuxcnc's ability to do stuff quick is limited by thread speed
you wont get better than your fastest thread as a time quantum for spark 
timing
( a 1ms thread period gets you 1ms time divisions, or 2ms with any 
jitter overages )
so plan on a pic ( very common ) or an arduino (fairly easy to hack)

the medium will be tap water, deionizing is not a _large_ benefit
submersing the part will aid in breakthru and less burrs

oh, a 'soft start' at lower current for a couple seconds will reduce 
entry burr.

the tool will be a tube with a .01ish hole thru it
a special feed thru chuck with a rubber seal is used
the rubber seal is pressed by water pressure onto a flange in the 
albrecht like chuck
the water pressure is 900-1500psi but delivered by a simple air driven pump
the pump has a large bore (4-8") and the piston is on a rod that goes 
thru both ends of chamber
this piston cycles back and forth thru the pressure chamber, driven by 
shop air (8bar+)
the cycle is controlled with 2 prox switches sensing a ferrous slug on 
the piston.
the ENDs of this shaft enter small bores at each end of the large bore 
and the ENDs are pistons themselves!
the small ends are sealed for the small bore and in the small bore is water!
this size ratio is the pressure amplification, 100psi in, 1500 psi out, 
stupid and simple
VERY low volume though, we only have a .01 hole to pass thru.
the system is controlled by the 2 prox swxs, so it the piston just 
cycles back and forth,
pumping tiny spoonfuls of hipressure water thru the tiny hole. a leading 
air pressure unit
(drying and pressure regulator) will controll the maximum value, a gauge 
on output leg
can show operator the value. it goes chug chug chug all day long.

After this high pressure water makes it thru all the plumbing restrictions
it isn't strong enuf to do more than dimple your fingertip. any line break
will immediately reduce to water at less that shop air pressure.

oh the thru hole water is neccesary, and as soon as you break thru, its 
LOST.
so the back up plate helps a lot, the submerging helps to a lesser degree

  
Could I use the Mesa THC to control gap of the electrode to the workpiece?

i got a mesa thc but used a hal component and a window comparator myself 
for sink edm
i did not build a hopop supply yet. got lotsa parts tho

the windo comp used a preliminary voltage divider to reduce 100V to 5V
the windo comp had 2 setpoints ( pot adjusted)
the 

Re: [Emc-users] EDM Small Hole Drilling

[Jon Elson]

On 02/10/2017 03:59 PM, Jim Craig wrote:
> So my questions are as follows. What type of power supply would I need
> to use for doing small hole EDM drilling? Can I use a tig welder as the
> power supply and control pulsing with LinuxCNC driving an external IGBT?
TIG is constant current, and generally way more than you 
need. IGBTs are good for 400+ Volts, MOSFETs make more sense 
below that.
> Could I use the Mesa THC to control gap of the electrode to the workpiece?
>
> It appears that spindles don't need to rotate very fast. What type of
> rpm do the spindles typically run at?
>
>
The problem is EDM is very slow.  Your holes would take at 
the least, several minutes each.  But, they'd be pretty clean.
You ought to get in touch with Ben Fleming, he demoed a 
pulser EDM system at some of the CNC workshops in Ann Arbor 
a few years ago.

http://www.homebuiltedmmachines.com/build-a-pulse-edm/

He has a book and a circuit board, and you can build it in a 
couple weekends.  It was VERY cool to watch it work!

Jon

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Re: [Emc-users] EDM Small Hole Drilling

[Comcast]

The laser drilling was the first thing I thought of too.  Pratt & Whitney uses 
this process to drill similar size holes in the turbine blades.  The keep the 
slag out of the holes they fill the interior of the blade with epoxy:  Upon 
burn through the epoxy virtually explodes, blowing and slag or burr-like recast 
out of the hole.

N. Christopher

> On Feb 10, 2017, at 5:16 PM, andy pugh  wrote:
> 
>> On 10 February 2017 at 21:59, Jim Craig  wrote:
>> The more I think about the actual process and needs of the machine I am
>> thinking that a small hole EDM drilling head would be better for this
>> application.
> 
> 
> Maybe consider lasers (and sharks?) too:
> https://www.oxfordlasers.com/laser-micromachining/applications/fuel-injector-production/
> 
> 
> -- 
> 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
> 
> --
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
> ___
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> https://lists.sourceforge.net/lists/listinfo/emc-users


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Re: [Emc-users] EDM Small Hole Drilling

[Jim Craig]

On 2/10/2017 4:16 PM, andy pugh wrote:
> On 10 February 2017 at 21:59, Jim Craig  wrote:
>> The more I think about the actual process and needs of the machine I am
>> thinking that a small hole EDM drilling head would be better for this
>> application.
>
> Maybe consider lasers (and sharks?) too:
> https://www.oxfordlasers.com/laser-micromachining/applications/fuel-injector-production/
>
>
But that would cost 1 million dollars.

Seriously though, lasers are expensive. I actually considered lasers 
first and went back to a regular spindle.

Thanks Andy,

Jim


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Re: [Emc-users] EDM Small Hole Drilling

[andy pugh]

On 10 February 2017 at 21:59, Jim Craig  wrote:
> The more I think about the actual process and needs of the machine I am
> thinking that a small hole EDM drilling head would be better for this
> application.


Maybe consider lasers (and sharks?) too:
https://www.oxfordlasers.com/laser-micromachining/applications/fuel-injector-production/


-- 
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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[Emc-users] EDM Small Hole Drilling

[Jim Craig]

I am working on a project at work where we are designing a new CNC 
machine for a particular application. Up to this point I have been 
planning on using a standard machine spindle.

The more I think about the actual process and needs of the machine I am 
thinking that a small hole EDM drilling head would be better for this 
application.

The application required drilling small 0.050" diameter holes through 
.135" thick stainless steel. The back side of these holes are in an 
annular space that cannot be easily reached for deburring.

The reason I am contemplating the small hole EDM process is three fold. 
First it is difficult to drill these tiny holes in stainless and the 
drill bits frequently break. Secondly the back side of the hole needs to 
be burr free but is difficult to get to with conventional tools. Third 
the machine could be lighter and simpler if I use EDM vs a standard 
milling head.

So my questions are as follows. What type of power supply would I need 
to use for doing small hole EDM drilling? Can I use a tig welder as the 
power supply and control pulsing with LinuxCNC driving an external IGBT? 
Could I use the Mesa THC to control gap of the electrode to the workpiece?

It appears that spindles don't need to rotate very fast. What type of 
rpm do the spindles typically run at?

That is all for now. I am sure I will have more to come.

Thanks,

Jim


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