Now you are free to make adjustments to the traces. Like add texts that you want milled on to the board. If you have a milling bit that can cut 0.2mm neatly, a 2mm tall letters in bold are neatly visible on the board. Anything smaller than that and the 0.2mm bit wont fit in to the lines to cut them. Adjust the size accordingly for the bit you have for making the traces. The tricky thing is to remember where the isolation is while adjusting the traces. The reason why I like to do the texts here in gimp instead of in eagle. Is that in eagle the texts are cut out, the texts made in gimp are cut in. In other words, the texts made in eagle make the milling bit go around them, cutting more than necessary making the text hard to read. The texts made in gimp are cut in, the milling bit travels inside the letters, not outside of them. making them much more visible and very nice looking.

Anoter thing worth the effort while working on the traces, is to fill up the holes. if you compare my exported file for raspi shield, to its traces file you can see its holes are filled in. The purpose of this is, that if you dont fill the holes the hole will get cut when doing the traces. While the strain of the milling bit is not the reason why, the reason is the hole itself. Normally the holes are cut with the milling bit you use the cut the board off, it is a big bit and it might cut more than the hole is supposed to be in the eagle desing. So now, if you clear the hole of copper while making traces, the pads around the holes might get ripped off because there just isnt enough that holds them to the circuitboard. But if you fill the holes in before runnign traces, the pads have better chance of surviving.

Once you are done with the traces file, like adding all the texts and graphics you like, just save the file as png, it helps to name it after the original file but with -traces in the name. Then just close it off. So now we need to make the file for cutting the board off. In this case it is simple we just delete the traces off the picture and save it, as -borders

Now we have two files ready for cutting, one to make the neat traces and the other to cut the board off. If you have to be picky about the hole size, and have a smaller, preferrably 0.5mm milling bit, you can make a second file similar to traces, but with bucket pour or white making sure only the innards of the holes are visible. For example the holes file of my raspi shield, the holes for the 2x20 pin connector are too small and needed the 0.5mm bit to make properly. As such they needed their own file, but the 2,7mm mounting holes were big enough to be neatly cut with the normal milling bit.

Now we use the Fab Modules to make the files for roland mill. since the images we made are in the PNG format, we click the input format tab and choose to open a .png file. While there are a good deal of more options for the fab modules output format, we pick from that tabs list the Roland mill (.rml). Now we need to choose the process, and since we are running the traces first we choose PCB traces. For normal cutting the default settings are good enough, but since I have the 0.2mm bit I can be more demanding and had adjusted my design rules file accordingly. with the 0.4mm next to none of my lines get cut out, but when I go down to 0.2mm you can see all the lines of the board being properly cut.

The machine this makes the files for is the Roland Mill SRM-20, so you need to pick that from the output list. The speed is ok at 4mm/s so you dont need to touch it but the origo needs some tweaking. The default value for the X0,Y0, and Z0, is 10 this means that the work starts 10mm from the point you defined as the machine origo. This means that unless you insert a zero here, the mill will move in a completely wrong place, and your job fails. the Z jog is good at 2 millimeters, as it is how much the mill lifts the head up before moving to the next place. It is not necessary to change the home values for the axis, what it does is that when the job is done, it moves the bed forward to 152,4mm and milling head moves all the way to the left, to x0. Also the head gets lifted to 60,5mm so it is out of the way. In essence it moves the completed board right to the front where it easy to remove, with the head out of the way.

Now we do the borders file, as the PCB outline (1/32), if you are making all these files at the same while, the origo settings for the machine persist, In general since the usual bit for the outline is around a 1mm thick, you dont need to change any of the default values. Unlike with the traces where we want to go just deep enough to clear off the copper layer, with the outline we make multiple passes along the edge. Our cut depth is usually at 0.6mm, meaning an average board needs three passes to cut through it, each of the passes going 0.6mm deep at maximum. The usual thickness for the stock, or the PCB board you have placed in the machine, is 1,7mm, so there is no real need to change this value unless you have measured to see that your stock material is of different thickness. The tool diameter is used to tell the machine how thick of a milling it has, and it is possible to chea the machine by saying it is thinner or thicker than it really is. the only difference when making the smaller holes is that altough you run it as an outline, you drop the cut depth to 0.25mm and tool diameter to 0.5mm this gives you a file that cuts the holes properly

Then you just run the jobs on the roland mill, while the longest run of the traces is going on, you can go and pick the components you need for your board. If you have a PCB usb connector, like the programming sticks usually have, you will want to look into making a simple bottom cover for your board, the commercial USB sticks usually are 2,1mm thick, youll want to design a bottom for your connector that adds enough thickness to match that then attach it with some doublesided tape. It makes life easier.

First you need to put your PCB material into the roland mill, you will find out that there are good and bad double sided tapes as you try to find one that suits you the most. Then you put in the milling bit for the traces, in this case I am using my 0.2mm bit, that apparently was originally meant for wax runs but seems to do circuit boards just as well.

Then with the roland interface you move the milling bit to the location you want to be the bottom left corner or XYorigo for your job.

Once the bit is where you want it, you simply bring it down, almost close enough to touch the plate, then you open the screw holding the bit in place and let the bit drop the last little bit to the plate. This realiably gives you the origo for Z, then you go into the roland interface, and on the darker side, set the origins for bot Xand Y and then the Z. This is done separately so that when you change your mill bit, the Z will change because you never really can put two bits at the same exact height. but you want to maintain the origo of the X and Y so that the new bit will cut the right places. If you dont check your Z origo before starting a job you can break your bit if it dives too deep.

Now you can click CUT on the roland interface, and open your prepared roland mill file. Once you hit the OUTPUT button, the job begins, so you will want to be sure you have set the origo in the roland interface, or that you have the right bit in the mill for that run.

Once your run is done, I have found it to be efficient to use soaped steelwool, the kind usually meant for pots and pans, to clear the board of the protective layer and give it a really beautiful shine.