The story in text:

The objective of this project is to develop circuit boards quickly and cheaply (less than $1) without the use of etching chemicles common in today's PCB fabrication processes. To achieve this, two methods are employed. The first uses a Roland MiniMill to cut copper away from a small fiberglass backed coard, leaving only the traces. The second uses a vinyl cutter to cut the circuit form, that can then be pulled away from a vinyl backing and adhered to an epoxy base. Both require about ten minutes of time, once the board is laid out and brought into a program used within the fablab project for file translation, CAM.py.

MiniMill Fab Process:

1. Layout the board you would like to design. For the exercise here, we used the Hello.nc file provided on the fablab site. The circuit is simple, containing an ATiny13 programmable chip, that will allow future testing of home made rainbow cables. Layout can happen in just about any program, including OpenOffice Draw in the simplest of cases, as it has a good subtractive shapes feature.

2. Save the file you want to use to the computer that talks to the MiniMill, and bring it into the cam.py program. You want to contour the shapes and raster the uneeded regions so that you have no extraneous copper. You will have to rename the file, and then be sure to select the .rml format before sending the file. The cam.py setup should look like:

Cam.py was written by FabLab to address formatting troubles with most CAM software and to get around the proprietary, machine specific nature of most of these programs given the diffusion pattern desired by FabLab central.

3. Before sending your file, you must prep the machine. First, pick up the copper plated sheet, and apply double sided tape to half of the back. Place the corner of the plate at 2,2 on the grid. The tape should be under the corner that is at 2,2. Using a command line, enter: move 1 1 . This will bring the tool forward over the copper piece. Next, you want to remove the bit. Use an allen key to loosen the chuck and insert your tool bit. (For this application, we used a tool with 4 flutes with carbide tip) After tightening the bit in place, use the up/down arrows on the control pad to lower the head until the tip of the bit just about rests on the plate. Carefully loosen the chuck again such that the tool slips down, resting on the surface. Tighten the chuck. You are now ready to send!

4. Sending the file is simple. After checking to see that all instructions in the cam.py window are correct, click "send to". The cutting process should take about 5 minutes for a small board. The 'HELLO' board is about one by two inches, and takes about 6 minutes.

5. Once the board is complete, clean up!!! I used the shop vac that is hanging on the wall in the lab, but any device that pulls in air and is used to pick up debris will work. Once the surface is clean, select view from the control panel, which sends the tool home and allows you to remove your board. Life it from the surface by pulling on the tape. (This is why it is important to leave extra tape sticking out from both sides) Remove the tool from the chuck and return it to its case to save the tip for another day!

6. The last step before stffing the board, is trimming. I used a scroll saw to cut away the extra material and save it for another day in the not too distant future. This step took about a minute, and was neat because the saw blade is soft to the touch until under tension.

Vinyl Cutter!

The process for the vinyl cutter is similar to that for the mill, but slightly different at all steps. Attention is awesome when it comes to detail. The purpose for these circuits is two or three fold, depending on who you are. First, because the copper and backing is flexible, and back of epoxy sticky, these circuits can go onto surfaces that have multi-dimensional curves. Second, the mass and volume of the board is smaller, which is good for weight or space sensative applications. Lastly, the vinyl cutter is about a thousand dollards cheaper, which might make better sense for some who prefer the other applications of a vinyl cutter over the mill.

1. The first step here is to make a file, if you need it. We were given the file.

2. Again, open cam.py and import the file. Here, I only asked for a contour cut and adjusted the cut force and speed to suit the weather. Rename the file and be sure to send it to the CAMM device.

3. Before sending the file, take the copper coated vinyl into the feed slot for the cutter. You will have to open the feed by flipping the lever in the back, and then align the paper between the two white stripes on the machine. Using the control interface to ensure that the machine knows that you are using a piece or a roll, and be ready to click send!

4. After sending the file, you have about 30 seconds before the Hello Circuit is complete. Once it has printed, you need to weed the unnecessary copper from the circuit using tweezers. To do this, I took some masking tape and pulled up all of the copper within the outermost cut. Once the copper is free, I applied it to the epoxy backing material supplied, and pressed down gently. (The adhesive on the back of the circuit is pressure sensative! If you press hard here, you will never get the unwanted copper up.) Post light adhesion, all unneeded copper is carefully removed and then the remaining, relevant bits firmly rubbed on. You are ready to stuff!

Stuffing the Board, Vinyl or MiniMill:

Once the board is complete, it needs componentry or it won't do much. To begin, identify what you will need. From here on in, comments are specific to the Hello (1) board. We used Eagle for schematics and board layout because it is free for smaller items in appropriate quadrants