5. Electronics Production
Goals for the week:
Group Assignment
Learning How To Mill
For our group assignment, we split into two groups to learn about the two different mills we have in our lab; the Roland SRM-20, and the Sainsmart Genmitsu 3018. Following the instructions posted in the Wheaton Fab Lab resources page, we got to work following the steps to mill out an example board that would demonstrate the capabilities of each mill.
The next step was to take these images to the mods website, which is a tool Fab Academy uses for generating toolpaths for PCB milling. The instructions told us to right-click anywhere, open server program, and select the png toolpath generator that matched our machine. We also had to make some changes to the program itself, such as changing the spin up time from 1000 seconds to 1 second (that would sure save some time), though I will link all programs I edited so no one else has to go through that. You can load a locally-saved program by selecting 'open local program'; make sure your program matches your file type !
Mods Programs
Important Info Regarding Mods
  • Once you load a file into the mods program, make sure that the traces of your board are white, as the mill will cut the areas that are black; thankfully, you can invert the images you upload in the mods interface
  • Mods will almost always add 10 mm to every axis for the origin position of the Roland mill, this will not only make the mill cut air, but offset where the mill starts cutting. To fix it, go to the module labelled Roland SRM-20 milling machine, and set the 'origin' values of each axis to zero.
  • Before you calculate any toolpath, make sure that the correct tool setting is selected on the module labelled set PCB defaults.
Once the toolpaths were created, we opened up a milling program for the Sainsmart called Candle, the Roland has it's own custom milling interface that sadly doesn't show the cool rendering of the milling process that Candle does. On the computer set up in our lab, our Candle program was in German for some reason, but we still figured it out reasonably well.
This is what Candle displayed once the toolpath for the traces was loaded. To begin milling, we just had to click 'send'; but first, we had to prepare our material
After using some double-sided tape to secure the material to the milling bed, and inserting the correct end mill for the traces, it was time to calibrate the z-position. This is necessary after every tool change because the mill does not know how far the end of the tool is from the material. For the Sainsmart, we place this probe under the head and connect the alligator clip to the end mill. When the mill touched the probe, it will complete a circuit that activates a sensor in the mill; and since the mill program knows how tall the probe is, it will calibrate itself to the correct height.
After another tool change, calibration, and milling, this is the finished product. The milling plate or the material must not have been perfectly level as there is some copper that wasn't removed around some traces, likely due to the tape being uneven and bunched up under the material. Nevertheless, this still gives us a good idea as to what width traces are best for future boards.
Design Files: lineTest toolpaths
Board Purpose & Design
One Board to 'Rule' Them All...
The first board we need to make is one that can be used to program any future boards ourselves so we don't have to rely on the FTDI (a type of USB-to-Serial converter format) programming cables kept in the lab.
Our resident physics master Professor Goodman created this page to provide us with some basic instruction on how to use the milling machines we have here at Wheaton lab, and this page for the board design.
NOTE: As of June 6th, this design has been revised since this week was first attempted as the initial board design wasn't completed to working condition by anyone in the lab. The revised version of the instructions can be found here.
Milling
Soldering