Milling PCBs and Circuit Board Evolution

I've been dabbling in electronics for years. Most of the time this involves starting on a breadboard and then transferring your finished circuit onto stripboard.

More often than not I'm trying to squeeze far too much stuff into a tiny space, for example in my Zippo Burglar Alarm.
Which means that the resulting boards are an awful mess of wires and massive solder lumps.

For this post I'm going to use my Hellboy Corpse Locator light board as an example, because it's been through a fair few revisions.
It's a fairly simple piece, I needed a board to fit under the dial of my corpse locator prop, and make the dome light up red. A simple task electronically, but mechanically it's difficult to get everything to fit.

I started by using a tank cutter to cut disks out of stripboard.

I was surprised by how well this worked, it made it easier, not having to shape each board by hand, but each one still took about 10 minutes.

I wanted to use surface mount LEDs, they were on the copper side, meaning everything else was on the reverse side. Which left me trying to find a way to create a second battery contact on the reverse side of the board.

The most reliable solution I could come up with was stitching a grid with copper wire.

Again, at the time, I was proud of my little inovation, conductive paint had too much resistance, glueing foil to the board had been problematic, this wasn't perfect (some wide copper tape would have been good) but working with materials at hand it did the job.

Once everything else was attached, the board looked like this. 

After making about 10 of these I managed to get them quite neat. But it was very labour intensive, each one probably took over 3 hours of quite fiddly work. 

And due to the nature of cutting out the boards, each one was slightly different, in where the LEDs went and where the wires were routed.

Many months later, the dawn of my CNC machine, and obviously one of the first things I wanted to have a go at was milling PCBs. I drew up the design in Vectorworks (EagleCAD* is the proper tool) and bought some copper clad board and was very easily able to cut out a simple PCB.

Milled PCBs are different to proper manufactured PCBs, you start with a solid layer of copper and simply mill away 'isolation paths' to create your tracks.

The one on the left is my very first attempt, I just used a cheap V bit that I had and the result was some very rough looking paths, but an entirely functional board.
My second attempt (using a 0.8mm ball nose) was much neater, but after my PCB milling bits arrived from China I was able to cut really neat boards. These are 0.2mm isolation paths, so potentially I can mill some really complex boards with lots of tiny surface mount parts.

Designing for CNC always affects your design. For example I wanted to take advantage of the fact that the copper layer could act as my other battery contact (no more stitching) so that meant the board was flipped and everything was soldered on the back. 

This also meant I had to switch to normal 3mm LEDs and mount them upside down (poking through the board) I originally use smt LEDs to keep the board thin, but the limiting factor is always the battery thickness so this works out fine, and the 3mm leds are brighter.

The boards look really cool now, very neat and I can do cool stuff like engrave labels and my logo. But the main thing that makes these far better than their predecessors is the time they take to produce. Each one probably takes about 20 minutes of milling, because it requires several tool changes. But then only about 10 minutes of soldering and it's finished.

Also each one is identical, which means I can add matching screw holes to my plastic corpse locator parts. rather than the tedious task of lining up and drilling each individual part to match it's specific board.



* Eagle is a program which allows you to draw up circuit diagrams, as well as layout circuit board designs for sending off to have fabricated. With the proper add on you can also create Gcode to send to a CNC machine. It sounds like a fantastic tool, but when I had a go there was a lot to learn and, for such a simple circuit, with mostly through hole components it was just slowing me down.

Hellboy Corpse Locator - First Finished Piece

The original item was cast up in polyester resin, gilded with Rub 'n Buff and weathered with pigmented plaster. Leaving me with my first finished piece.

Completed: 10-Feb-2012

I was very happy with my first attempt but over the coming months I made almost 15 of these and I'd like to think each one was a little better.

The following posts are an amalgamation of various different build ups, logically ordered. Most of it is written as a tutorial.

The Build Up 

Originally posted: 25-Jun-2012

This is one full kit of parts

The main pieces are cast in polyurethane resin, and the dome cast in a clear polyester resin.





First up is pretty standard clean up, removing flash and filling in lil' bubbles.

Occasionally one or two of the tiny thorns won't be properly formed, so they'll need fixing. This is much less of a problem with new kits, since I changed the mould.
You can use bondo, but given how small they are I prefer to use milliput, which is how I sculpted the original.

Also the side of the compass at the top of the mould is prone to sub surface bubbles, you can just paint over them but, for a long lasting paint job, I prefer to open them up and fill them with bondo. 

When cleaning up the seam on the lid don't go overboard sanding it completely smooth, there is supposed to be a linear texture running round the edge, so don't go taking it all off.

The same can be said for building this up in general. Don't go OTT trying to smooth things out like you might on other builds. Any texture you leave looks great when you dry brush it with gold, and just looks a bit off and fake if you try to make it perfectly smooth.

Hellboy Corpse Locator - Weaving with Epoxy Putty

Previously I created the dome, this post shows the creation of the main body, focussing on how the vine details were sculpted.

Originally Posted 18-Feb-2012

The main body was constructed out of layers of grey cardboard, just like before, nothing too complicated.

I tried to add a 1mm step to help me place the detailing later. But it was a bit uneven, that's what comes from designing in a computer. It's only worth designing to a tolerance you can achieve with the tools at hand.

Here you can see the beading added to the underside.

And a close up of the inside detailing, I tried really hard to copy reference for these bits and I'm pretty happy with the way it came out.

This is definitely one of the odder ideas I've ever had. 
Epoxy putty has a 3-4 hour working time so I had to work fast, most of the time was spent trying to roll long, consistent 'sausages', which I did using a sheet of perspex.

I then put all the strands in their starting positions and began to weave, because the rolling had taken a good 90 minutes I actually didn't have too much trouble with the putty trying to stick to itself.

I didn't do stage by stage on the side detailing, but it was a similar process. I sculpted the eyes first then did the vines around those. 
This picture shows it after filling and a quick prime, I quite like the odd ivory/porcelain look of it : )


Long post today, almost done.

In the next post you can see the first finished piece.

Hellboy Corpse Locator - Dome

This post details the creation of the amber dome that will sit in the middle of the dial I created last time.


Originally Posted 17-Feb-2012

Bit of an abstract image , but all these paper circles were laminated together to create the dome shape for the centre of the compass.


The whole thing was then spot filled and wet sanded on a lathe to give this.

I then made a 1 part silicone mould.

And began castings, anyone who has ever tried to cast with clear resin knows how tricky it can be.

First cast, the surface didn't cure and was sticky, I polished it up just to see if it was useable, but all the gunk I cleaned off meant it was about 2mm too small and didn't fit.

Second cast, I pre-heated the mould, the surface did cure, but too fast which meant it pulled away from the surface leaving an odd, crinkly texture.

When I cast another I think it will help to reduce the amount of catalyst used, but for this one I just wet sanded the dome down to 3000 and then hand polished it and it looked really good.

Don't have the dome on it's own but you will see it in the final picture.

All that's left is the main body, where I show more details of how the vines were created and then lots of moulding / casting.

Hellboy Corpse Locator - Centre Dial

Last time I was detailing the lid, now I'm working on the centre dial.

Originally Posted 16-Feb-2012
My original plan was to roughly mock up the centre dial, and then cast it in carving wax so it would be nice and easy to etch out details.

This was my first attempt, layers of card built up with an acrylic top piece to make it smooth.

I moulded it but I couldn't get a usable cast with the carving wax, it's too thick and grainy.


So I scraped that and started again.

This is layers of card with the centre pre cut (left in for now).

I then put an acrylic strip round the edge and filled it with bondo.

I left the plastic strip on till I had sanded the top completely smooth.


I then cut out the centre and started carving in the symbols using a fine Dremel bit.

I used a knife and various needle files to add the edge damage (following reference pics as closely as possible)


The centre wall was then added, just a thin strip of card, it is at a slight angle, so I cut notches & curved the wall inward and smoothed it over with spot filler.

I used the same thin card to add formers for the raised details and triangles that come off of the centre.

I then melted lumps of carving wax up over the little formers and carved them to the proper shape, using a tooth pick.

Final touch was to add in these tiny scratches, again sticking as close as possible to my reference.

gtg now, tomorrow I'll post the creation of the amber dome.

Hellboy Corpse Locator - Lid Detailing

Previously: Intro

Originally Posted 15-Feb-2012

This detailing was done using epoxy putty. I rolled it out into thin strands then proceeded to weave with it.  :D

I don't know if anyone has ever weaved with epoxy putty before but it's not the easiest thing in the world.
It  took so long that I came very close to the workable limit (3-4hours) before it cures too hard.

I documented the vines on the underside much better so you can see those later.

I needed to blend the two elements together, as well as fill in any undercuts so that I could mould it without it getting stuck.

I used polyfilla (plaster based, used for filling cracks in walls, like spackle?)

Generally not good for props but I liked the grainy texture it gives you.

I was fairly free in the way I applied the filler, trying to re-create hundreds of years of dirt that may have lodged themselves in the crevices.

But to keep the smooth top surface I kept wiping the top of the vines with a damp cloth.

Don't think I've got a picture of the underside, but on that last picture you can just make out the beading on the edge, more epoxy putty.

Next to tackle is the centre dial.

Hellboy Corpse Locator - Intro

Just to make things a little less dry, and because it's hard to make the prop out from the movie screenshot here's how the first one turned out.

To be honest I was never really that fussed about the Hellboy films. When ever I thought back on them I could never really remember how the story went or much about the characters. But when I had to make a gift for someone I knew liked Hellboy I gave the films a second look, although I still think the pacing is all wrong I do like the imagery and design in the films.

I chose this prop in particular, for a few reasons. 

I liked the ancient compass design, it was a bit out of my comfort zone, I prefer to work on smooth square things. 

Also, it was obscure and to my knowledge the only others in existence are the screen used versions and a very small run of replicas made by the original artist*.

What follows are the original posts I made on The RPF

Originally Posted 14-Feb-2012

From Phelyx's* description I had a good amount to go on.

But just for myself I decided the main box was made of wood, with gilded details and exterior, and the centre dial was a solid cast piece of gold.

The top detailing looked like vines and thorns, so it had an old magic/nature type influence. The heavy amounts of verdigris looking rust/mould implied to me that maybe it had been lost at sea or the bottom of a lake and then recovered.

But the vine details still shone bright like Red had given it a quick polish with his sleeve.

Anyway, with all that at the back of my head I began on the lid piece.

Pretty simple it's just knocked up out of grey cardboard.

Although I did make a quick computer drawing to figure out what went where, this was all drawn up and constructed by hand.

I'm just giving it a quick spot fill.

Next I added a bit of detailing with a scalpel and compass cutter. Most of this detail gets covered up with the vines and texture, but you can still see traces of it in the finished piece, so in it goes.

You can also see the base plate that will hold the upper dial (hence the bearing set in it). A lot of work went into constructing and centering the bit that holds the bearing, but the rest gets covered up so I didn't do anything special to it.

Next I added on the edge detail using epoxy putty. Great stuff, but I've never used it for sculpting before, it's actually really nice to work with, not as much control as I usually like, but this whole piece is supposed to have a hand crafted feel to it. You only get 4 hours working time, max, but that's more than enough for most details :s .

I also drew out the lines for the vine details, tomorrow I'll post how they came out.

Next Time: Detailing the Lid

* The original creator known as Phelyx on The RPF posted some pictures from the handful of replicas he made as well as some of the screen used item, which were my basis of reference for this piece. He also contacted me about my replica saying he thought it was good and he was glad someone had taken an interest, always a bonus.