Homebrew PCBs

When milling a circuit board on a CNC, I can see two possible 
approaches...

1) Using a 'V' shaped bit to outline the traces. This leaves a lot 
of the copper on the board.

2) Using a flat bottom milling cutter and cut away all of the unused 
copper.  

As I have never done this before, is one method preferrred over the 
other, or perhaps even another way of doing it?


Chris

Also, what happended to all the discussion on building a CNC machine 
for this purpose?  There was a bunch of talk, then it all seemed to 
dissappear - did it get moved to a different group?

We're still here; either waiting for another member to move along on his
driver design, waiting on parts or workin on the structure for the most
part.

In the meantime,  I'm stocking parts in 2 versions: lightweight material for
the drilling station, and heavy-duty for the CNC machine.

Just got my hands on 3/4" 10TPI long screws today for the CNC, and I have my
eye on 3/4" pillow blocks (more to come on that).  I'm also waiting for 20mm
precision rods and linear bearings to come in as well.  I'm most likely
going to be using 3/8" 16TPI screws for the drill with polished 1/2"
aluminium rods (quick and dirt).  I'll probably fabricate teflon or plastic
bushings to slide on the rods.


V outlining VS flat milling all copper:

- I see nothing wrong with leaving 'all that copper', I use it as my
negative and helps to reduce noise (<--- total newb here, so please feel
free to add on this).  Leaving it on also helps keep the etchant clean and
takes less time to machine.

My intention is to use the drilling station for V-scoring and drilling PCBs
as well as drilling faceplates.  As already mentionned, we already have all
the coordinates for the holes in the DRILL file.

I did think of another feature I will include on my drilling station; a
small camera for quality control.  I already have 2 cams ready to connect on
a PCI card.  I will be able to switch Windows to supervise the work from my
PC and check the quality of the work in progress.  Check EBay for small
cameras.  Don't bother with wireless and you'll get them dirt cheap.

The last thing I'm still researching is how to process track pins on the
drilling station (plugging vias).

Robert
:)



-----Message d'origine-----
De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
la part de lcdpublishing
Envoyé : juin 10 2005 10:09
À : Homebrew_PCBs@yahoogroups.com
Objet : [Homebrew_PCBs] Milling circuit boards with CNC?


When milling a circuit board on a CNC, I can see two possible 
approaches...

1) Using a 'V' shaped bit to outline the traces. This leaves a lot 
of the copper on the board.

2) Using a flat bottom milling cutter and cut away all of the unused 
copper.  

As I have never done this before, is one method preferrred over the 
other, or perhaps even another way of doing it?


Chris

Also, what happended to all the discussion on building a CNC machine 
for this purpose?  There was a bunch of talk, then it all seemed to 
dissappear - did it get moved to a different group?








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Excellent source of pillow blocks:

<http://stores.ebay.com/VXB-Bearings-Skateboard-and-Slotcar_Other_W0QQcolZ4Q
QdirZ1QQfclZ3QQftidZ2QQtZkm>

I ordered 1/2" units for my drilling station and 3/4" for the CNC machine.
These units also have 2 small screws to hold the long screw in place, no
need to 'sandwich' the inner bearing runner with 2 bolts (like I thought I'd
have to do so now I've got extra bolts to go along with my loose screw  :D
)

I would have taken smaller blocks for the driller, but they only have 1/2",
3/4" and 1" sizes.  Since I already had 1/2" screws on hand and just got
3/4" screws today, my choices were easy.  I can't get anything at a better
price locally anyways.

I also ordered my precision rods and bearings at VXD (forgot if I mentionned
their site already, I expect a $100 commission on each sale I generate from
this group  :D  yeah right...).

Robert
:)



-----Message d'origine-----
De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
la part de Robert Hedan
Envoyé : juin 10 2005 22:04
À : Homebrew_PCBs@yahoogroups.com
Objet : RE : [Homebrew_PCBs] Milling circuit boards with CNC?


...

Just got my hands on 3/4" 10TPI long screws today for the CNC, and I have my
eye on 3/4" pillow blocks (more to come on that).

...

Robert
:)



 







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On Sat, 11 Jun 2005 04:03:42 +0200, Robert Hedan  
<robert.hedan@...> wrote:

> We're still here; either waiting for another member to move along on his
> driver design, waiting on parts or workin on the structure for the most
> part.


I would have been done with my driver design by now, but sadly i have lost  
my HDs and all the nice files and PCB layouts are lost. Why don't you make  
your own driver, it is not that hard? Divide it in two sections, control  
and power, this way you can accomodate additional or different motors  
easily (no. of phase etc..).

The brain can be whatever you like, i suggest a CPLD like the ones from  
xilinx. they are easier to programm than a micro, and are ideal to do many  
things at the same time (you can easily run 5 axes with one cpld). Should  
you not be familiar with CPLDs, they are basically chips with many pins  
where you can programm in whatever logic you want.
But you could also use microprocessors or even simple 74xx logic to make  
the brain.

The power modules would have the driver transistors, and also comparators  
to form closed loop control of the current in the winding. That means  
you'd supply them with a voltage, like 0-5V, and the drivers would  
translate it into 0-5A or whatever on their own. The brain does not need  
to get feedback in this case, which makes things much easier.
To make microstepping you simply programm two coils with different  
percentages of the full voltage.
When the power modules do all the chopping, it is very easy to have them  
show a ideal current rise-time (full on as long as current has not reached  
set value), for fast speeds.


ST

Stefan, I was talking about Alan.  :D

I'm not in any panic mode either, as I said, I'm waiting for parts to come
in.  Once I have all my hardware, then I'll have all the measurements and
space requirements for the components.  That should help fabrication of the
chassis a much easier thing to do.

I'm going to use my el-cheapo SP-57B unipolar 24V steppers for the drilling
station.  I'm looking at the Xylotex 4-axis DIY driver circuit/power
supply/fan, not bad looking and quick to get up and running, or is that
stalling?

Later, when Alan finishes his work, I'll be using his design on the CNC
station.  By the way he describes it, I assume his system will be more
robust than the Xylotex DIY system.  I'll most likely order the new NEMA 23
269oz stepper motors from Zylotex; that should be plenty strong for my CNC
requirements.

I wish I could design my own basic driver system, but I lack the hardware
knowledge.  I can program a PIC just fine and there are plenty of sources of
information on them (I use PIC 'cause I have everything required for this
system).  It's the part that comes after that I have no knowledge of
fabrication.  Alan has already mulled this over for years now so I don't
mind waiting for him.

I've found this simple circuit over at AaronCake, but as I said, I lack the
experience to determine if I'd just be wasting my time with it. Darn, it
looks like Aaron finally got around to shutting both his tutorials and his
forum.   :(
<http://www.aaroncake.net/circuits/index.asp>

Ok, I've uploaded the material here.  Good thing I kept a copy just in case.
:)
<http://www.xavierkamial.com/Videos/Stepper%20Motor%20Controller.htm>

Comments on that design please?  I see how to control direction and steps,
but what about speed?  Is it a matter of just sending the pulses quicker
from the PIC?

Robert
:)



-----Message d'origine-----
De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
la part de Stefan Trethan
Envoyé : juin 11 2005 03:50
À : Homebrew_PCBs@yahoogroups.com
Objet : Re: RE : [Homebrew_PCBs] Milling circuit boards with CNC?

I would have been done with my driver design by now, but sadly i have lost  
my HDs and all the nice files and PCB layouts are lost. Why don't you make  
your own driver, it is not that hard? Divide it in two sections, control  
and power, this way you can accomodate additional or different motors  
easily (no. of phase etc..).

...


ST



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

If Files or Photos are running short of space, post them here:
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On Sat, 11 Jun 2005 12:25:44 +0200, Robert Hedan  
<robert.hedan@...> wrote:

> Comments on that design please?  I see how to control direction and  
> steps,
> but what about speed?  Is it a matter of just sending the pulses quicker
> from the PIC?
> Robert
>


It's really simple, and not for microstepping, but that's fine for small  
machines like a drill.
I do want to have a chopper driver however, 'cause with threaded rod you  
need every RPM you can possibly get, and when you have a chopper already  
it is too easy to include microstepping not to do it.

Usually you have two inputs to a stepper motor controller, step and  
direction. If the frequency on step is increased it turns faster. Those  
two signals come out of the PC parallel port (in simple systems).


ST