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Author Topic: PCB Isolation Routing - Very Nice Results  (Read 20607 times)
airnocker
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« on: May 19, 2011, 15:00:35 pm »

CamBam is so versatile.  Couldn't be more pleased.

Here is a simple PCB I created recently using CB to create the circuit pads, traces and G-code.  Open Offset in 098i is perfect for this. 

The copper-clad board is 1oz. copper on an epoxy/fiber reinforced substrate .062" thick.  Board in photo measures 1.4" x 3.0".  I used a 60deg. 2flute V-cutter w/.125" shank from PreciseBits.  DOC was .001" for traces, .005" for pilot holes, at 10,000 RPM and 10 IPM, using Mach3 v3.043.022.

We don't need no Eagle software to do PCBs  Shocked





* 556 Dimmer-2c.JPG (283.48 KB, 1599x858 - viewed 2104 times.)
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airnocker

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lloydsp
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« Reply #1 on: May 19, 2011, 16:22:17 pm »

That's just FINE, and what I tried to describe to another poster who wanted to mill away all the ground land.

For low-frequency work, or DC, it makes no sense to remove all that unused copper.

Now, if you get into microvolt amps or high-frequency stuff, you really have to watch out for inter-lead capacitances and ground coupling effects -- so then, you might need to switch to an end-cutting mill and mill away some copper here and there to comply with the needs of the circuit.  But not the WHOLE land, no.

Nice work!

LLoyd
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« Reply #2 on: May 19, 2011, 16:48:42 pm »

So much easier than the way my dad used to do PCBs ages ago.  Draw the circuit on the board with some kind of marker.  Drop it in a pan of acid.  Take it out much later.  Ick.  If he still wants to do it that way I guess we could use the mini mill to draw the circuit.  LOL. 

Very nice work by the way. 
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If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
airnocker
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« Reply #3 on: May 19, 2011, 19:20:41 pm »

Thanks Lloyd and Bob for the kind remarks.  Lloyd, right on, we are on the same page.

Yeah, acid bath etching is not fun, been there done that. But this is a breeze compared to some 4-layer 6502 CPU boards I developed, laid out and paid to have 4x art done 3 decades ago.  They were acid etched also, but in a proper shop (actually whether the shop was proper was debatable)  bonded together, drilled on a commercial mini CNC machine, silk-screened etc.  This was all back in the mid-80's.

Picked up some Harbor Freight 1/8" shank, tungsten carbide mini drills sets this morning so, this board is the last one I have to use my drill press on.  Nice assortment, marked in mm and inches, $7US for 20.


* 556 Dimmer-4c.JPG (152.13 KB, 628x1193 - viewed 1325 times.)
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airnocker

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Dragonfly
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« Reply #4 on: June 07, 2011, 21:12:26 pm »

@airnocker
What file format did you use to export the PCB? Or did in CB itself?
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airnocker
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« Reply #5 on: June 07, 2011, 22:18:40 pm »

I created the PCB traces all with CamBam 0.9.8i.

Here is the basic technique I used:

1.  I used circles for the pads, single-line polylines for the connections between pads centers and points for the pad center hole locations.

2.  Then, to create the trace widths I selected the single-line polylines and did an Open Offset with a value of .020".

3.  I made a copy & pasted of everything created in steps 2 & 3 into a separate "route engraving" layer

4.  Hide the first "layout" layer

5.  On the "route engraving layer" I deleted all of the single-polylines leaving behind their respective open offset poly "slots".

6.  Associated pads and poly slots where jointly selected and a Break at Intersections was done.

7.  All the tiny bits not needed for each pad and trace outline were then deleted leaving the partial pad circle and the slot trace touching it.  These were then "Joined" with .001" distance value so that each trace or pad was a closed polyline.

8.  An Engraving MOP was defined for each trace outline using a 60 deg. 2 flute V-cutter, -.001" DOC, and .001" as the bit diameter.

9.  A drill MOP was defined to make "pilot divots" at hole centers using the same V-cutter, with a DOC of -.005", and .001" as the bit diameter.

10.  The board outline was then cut using the save v-cutter with a DOC of -.06", in .02" increments, using holding tabs half the thickness of the board, as well.

11.  A bit change was done with the desired mini-drill size and a separate drill MOP was then performed for drill-throughs.


All-in-all, really very easy to do
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airnocker

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Dragonfly
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« Reply #6 on: June 07, 2011, 23:25:45 pm »

Yes thanks for sharing. For relatively simple PCB's it's OK. But inspired by your idea I exported a stepper controller layout from DipTrace, which I use, to DXF and CB is currently busy thinking.
I'll post the results when I have some.
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Dragonfly
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« Reply #7 on: June 13, 2011, 11:30:40 am »

Here's my first attempt. Photo not very good as well as the result of the routing, but I guess that
- PCB should be designed with routing in mind, this one comes out fine with photo method
- I need an absolutely level table (currently a tenth of millimeter differenc which must be cleared with the planned update)
- maybe I also need a fine end mill instead of a V-cutter



Uploaded with ImageShack.us

In general, I think there's a potential in my homemade router. The other good thing I discovered is that DipTrace can export to DXF the edges of the tracks and CB interprets it in a nice way. Look how one and the same imported DXF file looks in CB and CorelDraw. In CB I can directly produce an engrave MOP.
Black background is CB, white - CorelDraw


* PCB.jpg (210.83 KB, 800x316 - viewed 1182 times.)
« Last Edit: June 13, 2011, 11:36:14 am by Dragonfly » Logged

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airnocker
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« Reply #8 on: June 13, 2011, 17:34:13 pm »

From what can be seen from your photo, the results of your first try look pretty nice.

XY plane flatness is absolutely crucial to within .001" (in my opinion).  60 deg. 2 flute V-cutters work great, small end mills are often used for clearing out larger voids between traces.

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airnocker

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Jeff_Birt
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« Reply #9 on: June 14, 2011, 14:51:03 pm »

As airnocker said 'V' bits are usually the best idea for the isolation routing, they offer the best combination of strength and minimum width of cut. Really small end mills are much more fragile and much more expensive, a good quality 0.005" carbide stub end mill will run $25~$30USD.

I usually suggest 60 degree V bits as they have a good balance of trace width and are a bit less sensitive to board height variations.
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Dragonfly
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« Reply #10 on: June 14, 2011, 15:30:55 pm »

Thanks guys,
the above was done with a 60 degree V-cutter but with a 0.5 mm tip and I think of buying a 0.2 mm tipped one.
Problem is that there are only single cutting edge types here and IMO due to this the copper is not smoothly cut. I applied some fine sandpaper to the board before taking the photo.
Also I intend to try now using a MDF piece on the table and level it with a large diameter mill first.
And will do some tweaks in the pcb layout itself giving larger clearances to the board rules to see the weak points.

BTW, I'd be grateful if you share your experience on how to remove excess copper.
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airnocker
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« Reply #11 on: June 14, 2011, 15:45:09 pm »

Check out http://www.precisebits.com/products/carbidebits/scoreengrave.asp.  They have excellent quality 2-flute v-cutters for this type of work.  Reasonable prices too.



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airnocker

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Jeff_Birt
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« Reply #12 on: June 15, 2011, 13:42:41 pm »

I was going to suggest the bits from Precisebits as well Smiley

I have been a customer of theirs for several years and now carry their bits on my webiste as well:

http://www.soigeneris.com/PCB_Tools-list.aspx

I can ship by postal service too which often makes international shipments much less expensive.
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Dragonfly
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« Reply #13 on: June 15, 2011, 13:56:26 pm »

Check out http://www.precisebits.com/products/carbidebits/scoreengrave.asp.  They have excellent quality 2-flute v-cutters for this type of work.  Reasonable prices too.
Prices are really reasonable. Only I am afraid they will be the price of gold when delivered from USA to Bulgaria Smiley
The nearest distributor listed is in Turkey, but I couldn't find the bits there, following the link, although I know Turkish to an extent.
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« Reply #14 on: September 19, 2011, 13:54:57 pm »

XY plane flatness is absolutely crucial to within .001" (in my opinion)
I agree - of course you can use the mill itself to create a flat area for the PCB to that tolerance. I put a vacuum table on my mill and then machined the face flat - voila, a flat surface for my pcbs.
« Last Edit: September 20, 2011, 09:55:44 am by bigbigblue » Logged
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