Homebrew PCBs

While drilling Many small holes in PCBS--or any plastic or plexiglass for that
matter--it seems that the bit will become coated with plastics. 
Either it just accumulates, or it can melt on the bit no matter what the
right speed is.  So, how can this be handled?  Is there something which
can be done to have the bit come up clean and not have the accumulation
or coating interfere with the drilling?  I've thought of eleborate cooling
mechanisms combined ith vacuuums to both cool the bit as it eats its way
through the day, and also suck the debris immediately away.  Sounds
convoluted.

Thanks
Charles

On Sun, 13 Jun 2004 11:54:35 -0400 (EDT), <dg140@...> 
wrote:

> While drilling Many small holes in PCBS--or any plastic or plexiglass 
> for that
> matter--it seems that the bit will become coated with plastics.
> Either it just accumulates, or it can melt on the bit no matter what the
> right speed is.  So, how can this be handled?  Is there something which
> can be done to have the bit come up clean and not have the accumulation
> or coating interfere with the drilling?  I've thought of eleborate 
> cooling
> mechanisms combined ith vacuuums to both cool the bit as it eats its way
> through the day, and also suck the debris immediately away.  Sounds
> convoluted.
>
> Thanks
> Charles
>

I don't run into that problem with FR4, which material do you use?
I guess compressed air might cool it enough.

st

In a message dated 6/13/2004 12:13:09 PM Central Standard Time, 
dg140@freenet.carleton.ca writes:
While drilling Many small holes in PCBS--or any plastic or plexiglass for that
matter--it seems that the bit will become coated with plastics. 

Charles:  No.  The material does NOT do this.  Of course, the bits must be 
clean and sharp at the outset, but a good sharp carbide bit will not accumulate 
either copper nor glass-epoxy, perhaps partly as the two are not MISCIBLE.

You should find a "local PCB house" and get invited to come see their 
Excellon (or whichever) CNC PCB-drill going at it!  It will blow you away!   And they 
can show you their NEW bit-inventory and the USED-BUT-STILL-USEABLE 
bit-inventory, and discuss with you whether they sharpen ("recondition") or just throw 
OUT the used bits (Some GOOD houses do BOTH!).

If you watch for goodies, you MIGHT discover, as I did, that they TRASH 
anything 4" and narrower.  I got enough FR-4 between 4.25" and 3.8" to last ME for 
a long, long time in my home-brew stuff, last time I visited the local 
"house"!  Of course, most of it is only ½-oz., but it's still good enough for 
tinkering!

Jan Rowland


[Non-text portions of this message have been removed]

Thanks, Jan.  I must be doing something wrong.  Then gain, the bit is not
for plexiglass or plastics, and ths speed might be too high.  The
particular board which needs drilling is actually for the mechanical part
of the project.  It has Thousands of holes, several hundred per square
inch.  I've never been to a PC=drilling operation.  How fast do they 
drill out the boards?  I'm looking at buying some kind of CNC machine
sistem for light work: something like the stuff from Taig Tools or Prazi.

Charles

---

>Charles:  No.  The material does NOT do this.  Of course, the bits must
be 

>clean and sharp at the outset, but a good sharp carbide bit will not accumu=
>late=20
>either copper nor glass-epoxy, perhaps partly as the two are not MISCIBLE.
>
>You should find a "local PCB house" and get invited to come see their=20
>Excellon (or whichever) CNC PCB-drill going at it!  It will blow you away! =
>  And they=20
>can show you their NEW bit-inventory and the USED-BUT-STILL-USEABLE=20
>bit-inventory, and discuss with you whether they sharpen ("recondition") or=
> just throw=20
>OUT the used bits (Some GOOD houses do BOTH!).
>
>If you watch for goodies, you MIGHT discover, as I did, that they TRASH=20
>anything 4" and narrower.  I got enough FR-4 between 4.25" and 3.8" to last=
> ME for=20
>a long, long time in my home-brew stuff, last time I visited the local=20
>"house"!  Of course, most of it is only =BD-oz., but it's still good enough=
> for=20
>tinkering!
>
>Jan Rowland
>
>
>[Non-text portions of this message have been removed]
>
>
>
>------------------------ Yahoo! Groups Sponsor --------------------~-->=20
>Make a clean sweep of pop-up ads. Yahoo! Companion Toolbar.
>Now with Pop-Up Blocker. Get it for free!
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>
>Be sure to visit the group home and check for new Bookmarks and files:
>http://groups.yahoo.com/group/Homebrew_PCBs=20
>Yahoo! Groups Links
>
>
>
>=20
>
>
>

On Sun, 13 Jun 2004 18:19:57 -0400 (EDT), <dg140@...> 
wrote:

> Thanks, Jan.  I must be doing something wrong.  Then gain, the bit is not
> for plexiglass or plastics, and ths speed might be too high.  The
> particular board which needs drilling is actually for the mechanical part
> of the project.  It has Thousands of holes, several hundred per square
> inch.  I've never been to a PC=drilling operation.  How fast do they
> drill out the boards?  I'm looking at buying some kind of CNC machine
> sistem for light work: something like the stuff from Taig Tools or Prazi.
>
> Charles

other materials than pcb will of course clog up the drill.
pcbs don't because the material is relatively heat-resistant.

plexi is a pain to drill, some kinds seem better than others.
use liquid cooling/lubrication.

cnc feedrates are adjustable, ask the material manufacturer on how to drill
it best.

I try to avoid acrylic glass / plexi whenever possible, going for PP or 
ABS instead.

ST

In a message dated 6/13/2004 5:20:21 PM Central Standard Time, 
dg140@freenet.carleton.ca writes:
Then gain, the bit is not for plexiglass or plastics, and ths speed might be 
too high.<<
AH!  Lexan or Acrylic.  Then the "feed" must be right, and the "pull-up" must 
be suitably fast, as "PC-board drilling-speeds" CAN melt that kinda plastic!  
Particularly if the bit is not NEW-sharp!
  The particular board which needs drilling is actually for the mechanical 
part of the project.  It has Thousands of holes, several hundred per square 
inch.<<
I did a little thing like that with MY (Home-brew CNC PCB drill) and did 
holes on 0.05" centers in acrylic.  It was very clean; no melting.  I think the 
little piece of plastic was about 0.03" thick.  I stuck it down with "Wallsaver" 
poster tape (double-sided stickum by 3M).  My machine would do about one hole 
per 1.25 seconds, including fairly near traverse.  
  I've never been to a PC=drilling operation.  How fast do they drill out the 
boards?  I'm looking at buying some kind of CNC machine sistem for light 
work: something like the stuff from Taig Tools or Prazi.<<
The machine I saw had four "quills" turning at about 100,000 RPM (the 
"motors" run on compressed air and literally SCREAM as they spin!), and the "peck 
rate" is 4 to 5 holes PER SECOND! (for 0.1" IC-pin-rows; more for "scattered" 
holes).  These have "stacks" of one to seven "blanks" under each quill.  If a bit 
breaks, that quill will stop and ask the operator if the others should 
continue, or shall the one with the busted bit "go get a new bit" and all continue.  
All automatic.  The danger here would be that the busted-off piece would be 
still in the way, so a new bit would possibly get busted, too.  It is wild to 
see four quills all in a row stop, go back to the "start point", "dump"their 
bits in the original holders, move over, "grab" new ones, and whiz back to work, 
loosing maybe 5 seconds in all.  Bang, bang, bang, at a rate of 4-5 "pecks" 
per second.  Machines like that cost over $100,000, yet pay for themselves 
amazingly soon!  Now, this was over ten years ago.  That machine used 5¼" 
black-cover floppies to transfer the programs from the "office" out to the machine.  
Today, I don't know.  Perhaps 3½" floppies the customers bring-in?  And, 
drill-schedules "from the office", if still done that way, surely via LAN!  I have 
not had reason to "visit" there in 20-25 years, so I have NO clue if they even 
still operate.  At ONE point during these years I have "been gone", their 
front office called to inform that they "now did multilayer", so I could bring my 
work to them!  Hadda tell the lady I once did ONLY 2-sided PTH boards with NO 
silk-screening, no solder-mask (which they LOVE to do, as there is MORE profit 
in those "nice details" than the boards themselves!).  So, maybe they are 
still going strong.  

Jan Rowland


[Non-text portions of this message have been removed]

How does ABS and PP handle the heat generated by drilling?  I have to also
mill some ABS.

--

>other materials than pcb will of course clog up the drill.
>pcbs don't because the material is relatively heat-resistant.
>
>plexi is a pain to drill, some kinds seem better than others.
>use liquid cooling/lubrication.
>
>cnc feedrates are adjustable, ask the material manufacturer on how to drill
>it best.
>
>I try to avoid acrylic glass / plexi whenever possible, going for PP or 
>ABS instead.
>
>ST
>
>
>
>Be sure to visit the group home and check for new Bookmarks and files:
>http://groups.yahoo.com/group/Homebrew_PCBs 
>Yahoo! Groups Links
>
>
>
> 
>
>
>

Hi Jan.  How did you account for backlash in your homebrew CNC rig?  What
about those PCB drilling machines, what do they do for backlash and other
error components?

---

>Particularly if the bit is not NEW-sharp!
>  The particular board which needs drilling is actually for the mechanical=
>=20
>part of the project.  It has Thousands of holes, several hundred per square=
>=20
>inch.<<
>I did a little thing like that with MY (Home-brew CNC PCB drill) and did=20
>holes on 0.05" centers in acrylic.  It was very clean; no melting.  I think=
> the=20
>little piece of plastic was about 0.03" thick.  I stuck it down with "Walls=
>aver"=20
>poster tape (double-sided stickum by 3M).  My machine would do about one ho=
>le=20
>per 1.25 seconds, including fairly near traverse.=20=20
>  I've never been to a PC=3Ddrilling operation.  How fast do they drill out=
> the=20
>boards?  I'm looking at buying some kind of CNC machine sistem for light=20
>work: something like the stuff from Taig Tools or Prazi.<<
>The machine I saw had four "quills" turning at about 100,000 RPM (the=20
>"motors" run on compressed air and literally SCREAM as they spin!), and the=
> "peck=20
>rate" is 4 to 5 holes PER SECOND! (for 0.1" IC-pin-rows; more for "scattere=
>d"=20
>holes).  These have "stacks" of one to seven "blanks" under each quill.  If=
> a bit=20
>breaks, that quill will stop and ask the operator if the others should=20
>continue, or shall the one with the busted bit "go get a new bit" and all c=
>ontinue.=20=20
>All automatic.  The danger here would be that the busted-off piece would be=
>=20
>still in the way, so a new bit would possibly get busted, too.  It is wild =
>to=20
>see four quills all in a row stop, go back to the "start point", "dump"thei=
>r=20
>bits in the original holders, move over, "grab" new ones, and whiz back to =
>work,=20
>loosing maybe 5 seconds in all.  Bang, bang, bang, at a rate of 4-5 "pecks"=
>=20
>per second.  Machines like that cost over $100,000, yet pay for themselves=
>=20
>amazingly soon!  Now, this was over ten years ago.  That machine used 5=BC"=
>=20
>black-cover floppies to transfer the programs from the "office" out to the =
>machine.=20=20
>Today, I don't know.  Perhaps 3=BD" floppies the customers bring-in?  And,=
>=20
>drill-schedules "from the office", if still done that way, surely via LAN! =
> I have=20
>not had reason to "visit" there in 20-25 years, so I have NO clue if they e=
>ven=20
>still operate.  At ONE point during these years I have "been gone", their=20
>front office called to inform that they "now did multilayer", so I could br=
>ing my=20
>work to them!  Hadda tell the lady I once did ONLY 2-sided PTH boards with =
>NO=20
>silk-screening, no solder-mask (which they LOVE to do, as there is MORE pro=
>fit=20
>in those "nice details" than the boards themselves!).  So, maybe they are=20
>still going strong.=20=20
>
>Jan Rowland
>
>
>[Non-text portions of this message have been removed]
>
>
>
>------------------------ Yahoo! Groups Sponsor --------------------~-->=20
>Make a clean sweep of pop-up ads. Yahoo! Companion Toolbar.
>Now with Pop-Up Blocker. Get it for free!
>http://us.click.yahoo.com/L5YrjA/eSIIAA/yQLSAA/bGYolB/TM
>--------------------------------------------------------------------~->=20
>
>Be sure to visit the group home and check for new Bookmarks and files:
>http://groups.yahoo.com/group/Homebrew_PCBs=20
>Yahoo! Groups Links
>
>
>
>=20
>
>
>

On Sun, 13 Jun 2004 19:47:09 -0400 (EDT), <dg140@...> 
wrote:

> How does ABS and PP handle the heat generated by drilling?  I have to 
> also
> mill some ABS.
>

my main problem with plexi is:
melting -> binding -> shattering
when drilling larger holes.

not sure about small drills and abs, might break the drill which is no 
issue with big ones.

but generally the material is nicer to work on.

st

For larger holes in plexi, drilling a pilot or starter hole works well;
speeds at about 500-600 RPM,; and the plexiglass bit with its appropriate
flutes and sharpness.

---

>my main problem with plexi is:
>melting -> binding -> shattering
>when drilling larger holes.
>
>not sure about small drills and abs, might break the drill which is no 
>issue with big ones.
>
>but generally the material is nicer to work on.
>
>st
>
>
>
>Be sure to visit the group home and check for new Bookmarks and files:
>http://groups.yahoo.com/group/Homebrew_PCBs 
>Yahoo! Groups Links
>
>
>
> 
>
>
>

In a message dated 6/13/2004 7:52:33 PM Central Standard Time, 
dg140@... writes:
How did you account for backlash in your homebrew CNC rig?<<

You DID see the photo in the PHOTO section under "Jan Rowland"?  

I built that in '84, and was feeling CHEAP, so I did NOT spring for the 
preloaded Turcite nuts sold by Ball Screws and Actuators, San Jose, CA.  I bought 
the "Single" Turcite nuts which have a 15/16"-16 threaded end for fastening 
into the carriage or flange or whatever.  I then carefully bored/tapped a hole 
for 6-32 cap-screws through one side, and then I band-sawed through that one 
side with the screw-hole so that inserting and tightening the screw would 
"reduce" the I.D.  This would tighten-up on the screw nicely, and obviously a "feel" 
for HOW-tight was necessary.  It worked, and has not been a problem needing 
re-adjustment.  These nuts are also more than twice as compact as the (spring-) 
preloaded nuts, and MUCH less expensive.  These screws are 7/16" dia. 
1/8"-pitch, 4-start.  Thus, one turn = 1/2" movement.  So each step of the axis 
steppers is 0.0025".  Thus, I had to write my "Coordinate recording program" to 
round-off each X and Y typed in to the nearest 0.0025" (not 0.001").  I realized 
how cumbersome this would be (got USED to it!), but wanted the 1/2" lead for 
SPEED of operation between holes. 
  What about those PCB drilling machines, what do they do for backlash and 
other error components?<<
Of course, all lead-screws on such professional CNC $100,000 machines are 
covered with bellows ("way-covers", etc.), so they are not viewable by a visitor 
not willing to exhibit violence.  I am however POSITIVE they are preloaded 
ball-screws!  AND, the screws are surely "precision ground", not the ROLLED type 
also available.  

"Other error components?"  There are MORE?  Uh . . .  I'd guess MUCH care and 
careful workmanship by folks who can READ (if you get what I mean!).


[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> On Sun, 13 Jun 2004 19:47:09 -0400 (EDT), <dg140@f...> 
> wrote:
> 
> > How does ABS and PP handle the heat generated by drilling?  I 
have to 
> > also
> > mill some ABS.
> >
> 
> my main problem with plexi is:
> melting -> binding -> shattering
> when drilling larger holes.
> 
> not sure about small drills and abs, might break the drill which is 
no 
> issue with big ones.
> 
> but generally the material is nicer to work on.
> 
> st

heat is the killer on plastics.

also clearing chips is vital.  if a chip gets between the cutter and 
the stock being cut, it acts like a slippeery wafer and the sliding 
generates bucnhes of heat.  if you can use compressed air to blow 
away the chips as they are being created it will do a lot to keep 
things cool.

also, if you are cutting out a perimiter  ie: all the way thru, leave 
a place for the chips to fall out.   if you put a board under and not 
space, the chips will bind.

Then cutting a pocket, getting the chips out with air or liquid is 
important.

Dave

--- In Homebrew_PCBs@yahoogroups.com, dg140@f... wrote:
> For larger holes in plexi, drilling a pilot or starter hole works 
well;
> speeds at about 500-600 RPM,; and the plexiglass bit with its 
appropriate
> flutes and sharpness.
>

The key to drilling plastics is to drill with a flat bottom drill.  
the normal taper drill will remove a lot of plastic and as it exits, 
the area of contact suddenly gets much smaller and before you know 
it, the flutes will grab and push thry, often cracking the part.

a flat bottom drill, like an end-mill will not suffer the same exit 
problems.

Dave

On Mon, 14 Jun 2004 07:13:07 -0000, Dave Mucha <dave_mucha@...> 
wrote:

> --- In Homebrew_PCBs@yahoogroups.com, dg140@f... wrote:
>> For larger holes in plexi, drilling a pilot or starter hole works
> well;
>> speeds at about 500-600 RPM,; and the plexiglass bit with its
> appropriate
>> flutes and sharpness.
>>
>
> The key to drilling plastics is to drill with a flat bottom drill.
> the normal taper drill will remove a lot of plastic and as it exits,
> the area of contact suddenly gets much smaller and before you know
> it, the flutes will grab and push thry, often cracking the part.
>
> a flat bottom drill, like an end-mill will not suffer the same exit
> problems.
>
> Dave
>

i see... thanks, that's goin to be helpful.

st

--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> In a message dated 6/13/2004 7:52:33 PM Central Standard Time, 
> dg140@f... writes:
> How did you account for backlash in your homebrew CNC rig?<<
> 
> You DID see the photo in the PHOTO section under "Jan Rowland"?  
> 

Look in Files for a larger version:

<http://groups.yahoo.com/group/Homebrew_PCBs/files/Homemade%20PCB%20equipment/>

Note what computer he had controlling it (until it died).

Steve

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> On Mon, 14 Jun 2004 07:13:07 -0000, Dave Mucha <dave_mucha@y...> 
> wrote:
> 
> > --- In Homebrew_PCBs@yahoogroups.com, dg140@f... wrote:
> >> For larger holes in plexi, drilling a pilot or starter hole works
> > well;
> >> speeds at about 500-600 RPM,; and the plexiglass bit with its
> > appropriate
> >> flutes and sharpness.
> >>
> >
> > The key to drilling plastics is to drill with a flat bottom drill.
> > the normal taper drill will remove a lot of plastic and as it 
exits,
> > the area of contact suddenly gets much smaller and before you know
> > it, the flutes will grab and push thry, often cracking the part.
> >
> > a flat bottom drill, like an end-mill will not suffer the same 
exit
> > problems.
> >
> > Dave
> >
> 
> i see... thanks, that's goin to be helpful.
> 
> st


Another way to drill plexiglass is to use a second sheet as a backing 
plate.  and take a piece of wood to hold it down on your drill 
press.  The wood should hold the plexi down very close to the hole so 
the top sheet does not lift up when the standard drill goes thru.  
This way, the drill has full contact as it goes thru the top sheet 
and you get a great hole.

I wish I had link to the site that explained this in great detail.  
it was a link from a drill sharpening manufacture that had done 
research on the best ways to sharpen drills for sheet metal and 
plastics and such.

Dave

> Another way to drill plexiglass is to use a second sheet as a backing
> plate.  and take a piece of wood to hold it down on your drill
> press.  The wood should hold the plexi down very close to the hole so
> the top sheet does not lift up when the standard drill goes thru.
> This way, the drill has full contact as it goes thru the top sheet
> and you get a great hole.
>
> Dave
>

makes sense, then the flutes can't dig in and break everything...

I have flat ground drills somewhere for milling slots, next time
i will use one of the suggested methods.



ST

Hello,

BTW, in PCB's there is an effect call epoxy smear, which DOES cause 
havoc with platethrough holes. Anything you read in depth about PCB's 
will mention it... Epoxy is a thermoset, not a thermoplastic, but it 
still can smear the inside of the hole. When it does so in a multi 
layer board the "smear" covers the inner layers, and the PTH doesn't 
connect to that hole. It's part of the reason we can buy cheap PCB 
bits. A board house CANNOT afford to use anything but SHARP bits.

The Excellon machines Jan described are still used my many PCB shops 
today. Look for the signature green and orange paint scheme. And they 
still use the old floppies and even older controls. 
Sneakernet is still widely used. (which kinda makes sense when you 
consider that the boards layers themselves are stacked 
and "assembled" for drilling by hand. (Remember, board houses drill 
FIRST.)

As for the construction and backlash etc. in the PCB drills, these 
machines are built on and with huge Granite slabs, using air bearings 
and precision ground ballscrews with preloaded nuts. The 4 spindle 
type is pretty much an industry standard. You can usually find 
pictures of one of these on ebay, as they sell rather frequently. 
Use "excellon" in a search...

It's actually pretty surprising to see how "old" most PCB houses 
appear in their techniques and machinery. Living near silicon Valley, 
I've seen a few...

PCB ASSEMBLY houses, on the other hand, almost always have the latest 
and greatest... Nowadays they have to. Pick and place, reflow ovens, 
vison systems and xrays for BGA, etc. ..  

Hope this helps,

Ballendo 

--- In Homebrew_PCBs@yahoogroups.com, dg140@f... wrote:
> Hi Jan.  How did you account for backlash in your homebrew CNC 
rig?  What
> about those PCB drilling machines, what do they do for backlash and 
other
> error components?
> 
> ---
> 
> >Particularly if the bit is not NEW-sharp!
> >  The particular board which needs drilling is actually for the 
mechanical=

Hello,

It works going the "other way" too. Using much STEEPER angles, then 
the breakthrough is a gradual thinng. Most drill sold fro plastic 
drilling will look like pencils; point wise.

Ballendo

--- In Homebrew_PCBs@yahoogroups.com, "Dave Mucha" <dave_mucha@y...> 
wrote:
> --- In Homebrew_PCBs@yahoogroups.com, dg140@f... wrote:
> > For larger holes in plexi, drilling a pilot or starter hole works 
> well;
> > speeds at about 500-600 RPM,; and the plexiglass bit with its 
> appropriate
> > flutes and sharpness.
> >
> 
> The key to drilling plastics is to drill with a flat bottom drill.  
> the normal taper drill will remove a lot of plastic and as it 
exits, 

> the area of contact suddenly gets much smaller and before you know 
> it, the flutes will grab and push thry, often cracking the part.
> 
> a flat bottom drill, like an end-mill will not suffer the same exit 
> problems.
> 
> Dave

On Mon, 14 Jun 2004 15:58:37 -0000, ballendo <ballendo@...> wrote:

> Hello,
>
> It works going the "other way" too. Using much STEEPER angles, then
> the breakthrough is a gradual thinng. Most drill sold fro plastic
> drilling will look like pencils; point wise.
>
> Ballendo
>

should have asked that topic before... would have saved me a few hours of 
ruined work..

ST

Hi,
Keep in mind when drilling PLEXI, that you build up thermal stress 
into the material and can easily break thereof. If critical parts are 
machined thermal treatment in owen is requiered. Manufacturers of 
plexi can give advise how to do it, also *data* on drilling/milling.
Bengt


--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan 
<stefan_trethan@g...> wrote:
> On Mon, 14 Jun 2004 15:58:37 -0000, ballendo <ballendo@y...> wrote:
> 
> > Hello,
> >
> > It works going the "other way" too. Using much STEEPER angles, 
then
> > the breakthrough is a gradual thinng. Most drill sold fro plastic
> > drilling will look like pencils; point wise.
> >
> > Ballendo
> >
> 
> should have asked that topic before... would have saved me a few 
hours of 

> ruined work..
> 
> ST