Homebrew PCBs

Hi,

I hope I'm not re-asking a worn out question... but here goes. What is 
the best tool to use to route printed circuit boards on an NC mill? I 
have a Sherline mill with the NC kit, Xylotex controller, and Master 5 
as the controller software. I am using Eagle PCB for designing boards. 
I just need to know what the best (meaning least expensive but giving 
good results & life). What does LPKF and the other board router 
devices use? Is Grizzly a good source? Tool steel or carbide? 

Thanks!

Bob

Hi Bob-

I am not an expert on this, and I have no direct experience. I do know
that John Kleinbauer, who designs and sells plans for home built CNC
machines including PCB millers, recommends the bits sold by Think and
Tinker. I believe that carbide is the only way to go since the glass
eats up bits fast. John has an internet forum, but it is only open to
those who buy one of his plans from him. The list was open until
recently and was a good source of experience, knowledge and support
which might well be worth the price of a set of plans. You can see
John's machines/plans at:

http://www.crankorgan.com/

Another source of information, although you have to spend time looking
for it, is at:

http://www.luberth.com/plotter/plotter.htm

and if you are not aware of it you could try the Yahoo group

http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/

Grant

--- In Homebrew_PCBs@yahoogroups.com, "spoothammer" <spoothammer@h...>
wrote:

> 
> Hi,
> 
> I hope I'm not re-asking a worn out question... but here goes. What is 
> the best tool to use to route printed circuit boards on an NC mill? I 
> have a Sherline mill with the NC kit, Xylotex controller, and Master 5 
> as the controller software. I am using Eagle PCB for designing boards. 
> I just need to know what the best (meaning least expensive but giving 
> good results & life). What does LPKF and the other board router 
> devices use? Is Grizzly a good source? Tool steel or carbide? 
> 
> Thanks!
> 
> Bob

In a message dated 5/7/2003 6:36:46 AM Central Standard Time, 
spoothammer@... writes:

> Is Grizzly a good source? Tool steel or carbide? 
> 

Bob:  I have been reading mail from latest-received, on, so I just got to 
your good question:   HSS ("tool steel") drill-bits will last perhaps a dozen 
holes in G-10 or FR-4 (glass-fiber-reinforced PCB material) before they are 
so dull they will not work anymore.  IF you could find some tiny "mill-bits" 
sufficiently small for pattern-routing/milling, I am sure they would go dull 
so fast that you'd soon assume they "CAME dull from the source"!

The ONLY thing that works sufficiently well on "glass epoxy" (the light-green 
PCB-stuff) is TUNGSTEN-CARBIDE.  Professional PCB drill-bits from, what, #80 
up to perhaps 1/4" dia. all have 1/8" shanks so that the auto-load PCB-drill 
machines can handle all kinds of drill-sizes efficiently (i.e., "fast!").  

I have seen solid-carbide "router bits" in various mail-order catalogs, but 
never having used them continuously every day, just buying a few "to have on 
hand if ever needed", I can't now tell you from whence!  Check catalogs of 
MPJA, JDR Microdevices, Enco, Harbor Freight, and of course, those I have 
forgotten at the moment!

I have seen TWO forms of these bits for PCB-work for EDGE-milling:  The 
"fluted" kind, similar to those used for metal-machining, with two, three, or 
four flutes, some parallel, and some "spiral", both "up-cut" and "down-cut".  
And a second kind, the "rotating file surface" kind, that is, with a kind of 
"knurled" surface that kinda "abrade" the material away.  I can NOT compare 
the function of the two, as I have never used either for PCB work (well, I 
DID use a two-flute router-bit, once, to mill "key-slots" between the 
gold-plated edge-connector fingers).  I assume you realize this latter kind 
must be rotated at least at 25,000 RPM (better:  100,000 RPM or more!) to be 
effective.  The "feed rate" for the mill-bit type would have to be such that 
the linear move per revolution would be no more than about 0.002".  Thus, for 
any rate at all, you'd have to spin the bit at least 25,000 RPM!   I have no 
clue what kind of TIP-cutting this "file-type" have, if any.  

For the "mill-bit" type, you should use "center-cutting", as the bit will 
very often (mostly!) have to be "plunged" onto the blank, rather than 
"starting from the edge".  It may-well be best to use only "two-flute 
center-cutting"!

Yes, I realize bearings and motor-types for quills become a problem for 
avocational purposes even at that 25K speed!  The price of good air-motors is 
outrageous, and high-frequency AC (electric) motors cost fortunes, when the 
400 Hz or whatever power-source is considered.  (I did that in '84, and it 
works (still!) wonderfully, but "never again"!)   A "laminate trimmer router" 
by Hitachi or Milwaukee is a possibility, using a 1/8" collet-adapter, but 
such a machine is somewhat cumbersome to change bits rapidly and carefully as 
required by delicate carbide drill-bits!  Also, the EMI generated by one of 
those "universal motors" would probably be a serious problem for 
computer-controlled stepper-motor drives!  UGH!

It almost seems that some "ol' boy out there" in the machine-manufacturing 
business might do well to design/offer a neat little 100-W. air-motor with 
air-bearings, a 1/8" collet, and a design-RPM of, what, 100,000 RPM, running 
on 90 PSI, 4 CFM "shop air" for $100 each, not including compressor!    (is 
90 PSI @ 4 CFM about equal to 100 Watt????)

Discuss?    Jan Rowland



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

Bob,

We always used "diamond cut fishtail" router bits for profiling 
boards on Excellon Automation CNC routers. Almost every job was 
routed using .093" diameter bits. We would stack the boards two or 
three deep depending on the required accuracy. The spindles were 
started at 25,000 rpm and then the operator would manually tweak the 
speed until everything sounded right. If the spindle speed and table 
feedrate was not just right the bits could make a loud screeching 
noise. The table feedrate was set to around 50 inches per minute and 
was also adjusted by the operator for best performance.

Sometimes .062" router bits were used and these were operated at 
about 45,000 rpm but at a slower table feedrate with a maximum stack 
of two .062 thick panels.

The biggest mistake made with these router bits is to use them past 
their service life. I don't remember how long they would last before 
becoming dull but I think it was only about 400 or so inches. When 
the bits are new and sharp they will leave almost no dust in the 
routed path. When they start getting dull the dust will pack into the 
ends of the cuts especially on internally routed slots.

Another mistake is to set the plastic ring too far away from the tip 
of the tool. Excellon specifies .810" from the ring to the tool tip 
for drills but only .680" when using router bits. Many machine 
operators make this mistake and the extra flute length leaves the bit 
subject to oscillation. This problem can really affect the accuracy 
of the finished parts and break bits as well.

For "etch cutting" patterns directly into copper clad panels we used 
small size broken drill bits. It's easy to use a small diamond wheel 
to dress a broken carbide bit into a very effective cutting tool.

If I remember correctly we paid about $1.80 each for .093" router 
bits and purchased most of these bits from Tulon Corp. Hope this 
information helps.

Tom 

--- In Homebrew_PCBs@yahoogroups.com, "spoothammer" 
<spoothammer@h...> wrote:
> 
> Hi,
> 
> I hope I'm not re-asking a worn out question... but here goes. What 
is 
> the best tool to use to route printed circuit boards on an NC mill? 
I 
> have a Sherline mill with the NC kit, Xylotex controller, and 
Master 5 
> as the controller software. I am using Eagle PCB for designing 
boards. 
> I just need to know what the best (meaning least expensive but 
giving 

> good results & life). What does LPKF and the other board router 
> devices use? Is Grizzly a good source? Tool steel or carbide? 
> 
> Thanks!
> 
> Bob

--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
-snip-
> I have seen solid-carbide "router bits" in various mail-order
catalogs, but 
> never having used them continuously every day, just buying a few "to
have on 
> hand if ever needed", I can't now tell you from whence!  Check
catalogs of 
> MPJA, JDR Microdevices, Enco, Harbor Freight, and of course, those I
have 
> forgotten at the moment!

Don't forget to check the Links section of the list, and if you have a
good supplier please add their website in the appropriate folder.

-snip-
> It almost seems that some "ol' boy out there" in the
machine-manufacturing 
> business might do well to design/offer a neat little 100-W.
air-motor with 
> air-bearings, a 1/8" collet, and a design-RPM of, what, 100,000 RPM,
running 
> on 90 PSI, 4 CFM "shop air" for $100 each, not including compressor!
   (is 
> 90 PSI @ 4 CFM about equal to 100 Watt????)

Don Lancaster suggested dental turbines as cheap (about $14)
disposable cutting tools. Something I've wanted to try. Also called a
"Dental Handpiece".

http://63.140.207.28/musev.pdf/hack76.pdf

With a suitably sharp bit, one of these on a very flexible airhose,
and a heck of a vacuuming system, these may work on something like HP
flatbed plotters. Maybe have to stick with 1 oz or 1/2 oz copper. I
have no idea what the runout is on these little turbines. It should be
pretty low, as any vibration while carving up teeth is -highly-
undesirable.

Here's his page on what he calles "flutterwumpers", ie, hack and grind
plotters:
http://www.tinaja.com/flut01.asp

Has anyone done any more investigation on using John Kleinbauer's
Scratch 'N Etch idea? For those that weren't here then:

Spray PCB with Layout Fluid (Dykem brand was suggested) with a thin
even coat.

Place modified pen in plotter- it has a carbide tip in place of the
pen tip.

Plot PCB pattern onto board. It scratches off a thin line of the
layout fluid.

Etch and drill.

Denny did a couple of tests by hand, here are the archived messages:
http://groups.yahoo.com/group/Homebrew_PCBs/message/281
http://groups.yahoo.com/group/Homebrew_PCBs/message/286

I've modified a pen and bought an HP plotter just for this, even have
a spray can of layout fluid. Just have had way too much to do.

Steve Greenfield

the scratch and etch is a very nice idea.

knows anyone how i may obtain a plotter file (hpgl1) which contains the information needed to plot the 
outline of a layout?
i think this should work with the software used for milling pcbs. (anyone knews which is free available 
and good?) i have gerber out, and printing to any other format in positive image.

i find the software most difficult to get right also with positive plotting, i simply can't get a 
plotter file (plotting with carbide tip and staedtler ink - very good quality results) which has the 
drill holes open as a guide for drilling.

but the scratch method would be very fine for those who don't have carbide pens (expensive) and it also 
would only make the isolation etched, this would save the etchant...

if it may be possible to get the drill holes open with the scratch method?

but first i have to get a software which generates this files, if anybody knows where to find please 
post.
i read commercial pcb mills interpret the gerber files directly. there should be a workaround for hpgl 1 
plotters??

regards
st



08.05.2003 18:48:08, "Steve" <alienrelics@...> wrote:

>--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
>-snip-
>> I have seen solid-carbide "router bits" in various mail-order
>catalogs, but 
>> never having used them continuously every day, just buying a few "to
>have on 
>> hand if ever needed", I can't now tell you from whence!  Check
>catalogs of 
>> MPJA, JDR Microdevices, Enco, Harbor Freight, and of course, those I
>have 
>> forgotten at the moment!
>
>Don't forget to check the Links section of the list, and if you have a
>good supplier please add their website in the appropriate folder.
>
>-snip-
>> It almost seems that some "ol' boy out there" in the
>machine-manufacturing 
>> business might do well to design/offer a neat little 100-W.
>air-motor with 
>> air-bearings, a 1/8" collet, and a design-RPM of, what, 100,000 RPM,
>running 
>> on 90 PSI, 4 CFM "shop air" for $100 each, not including compressor!
>   (is 
>> 90 PSI @ 4 CFM about equal to 100 Watt????)
>
>Don Lancaster suggested dental turbines as cheap (about $14)
>disposable cutting tools. Something I've wanted to try. Also called a
>"Dental Handpiece".
>
>http://63.140.207.28/musev.pdf/hack76.pdf
>
>With a suitably sharp bit, one of these on a very flexible airhose,
>and a heck of a vacuuming system, these may work on something like HP
>flatbed plotters. Maybe have to stick with 1 oz or 1/2 oz copper. I
>have no idea what the runout is on these little turbines. It should be
>pretty low, as any vibration while carving up teeth is -highly-
>undesirable.
>
>Here's his page on what he calles "flutterwumpers", ie, hack and grind
>plotters:
>http://www.tinaja.com/flut01.asp
>
>Has anyone done any more investigation on using John Kleinbauer's
>Scratch 'N Etch idea? For those that weren't here then:
>
>Spray PCB with Layout Fluid (Dykem brand was suggested) with a thin
>even coat.
>
>Place modified pen in plotter- it has a carbide tip in place of the
>pen tip.
>
>Plot PCB pattern onto board. It scratches off a thin line of the
>layout fluid.
>
>Etch and drill.
>
>Denny did a couple of tests by hand, here are the archived messages:
>http://groups.yahoo.com/group/Homebrew_PCBs/message/281
>http://groups.yahoo.com/group/Homebrew_PCBs/message/286
>
>I've modified a pen and bought an HP plotter just for this, even have
>a spray can of layout fluid. Just have had way too much to do.
>
>Steve Greenfield
>
>
>
>Be sure to visit the group home and check for new Bookmarks and files:
>http://groups.yahoo.com/group/Homebrew_PCBs
>
>To unsubscribe from this group, send an email to:
>Homebrew_PCBs-unsubscribe@yahoogroups.com
>
> 
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 
>
>
>

Carbide will last a lot longer and give you better results (definition). It
is more expensive than tool steel, but in the long run, it will be less
expensive because it lasts longer.

-Mike

----- Original Message -----

From: "spoothammer" <spoothammer@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, May 07, 2003 4:34 AM
Subject: [Homebrew_PCBs] what's the best tool for etching pcb's


>
> Hi,
>
> I hope I'm not re-asking a worn out question... but here goes. What is
> the best tool to use to route printed circuit boards on an NC mill? I
> have a Sherline mill with the NC kit, Xylotex controller, and Master 5
> as the controller software. I am using Eagle PCB for designing boards.
> I just need to know what the best (meaning least expensive but giving
> good results & life). What does LPKF and the other board router
> devices use? Is Grizzly a good source? Tool steel or carbide?
>
> Thanks!
>
> Bob
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> To unsubscribe from this group, send an email to:
> Homebrew_PCBs-unsubscribe@yahoogroups.com
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>