Milling of a printed circuit board
We are currently working on our [Bad Link] (Mendel). Sadly the control board that we ordered (Generation 6) was broken. Somehow it turned mad whenever we tried to home the printer. Thus we decided to manufacture a control board on our own. We took the layout files of [Bad Link] and used [Bad Link] to turn the layout into GCode for a 0.7mm end mill. These preperations were quite easy, but the final step turned out to be rather time-consuming.
This was our attempt with PCB milling, thus we needed to experiment a bit.
For the milling process we prepared a small water basin to keep the plate covered with liquid during the operation. Otherwise we would pollute the air with ugly small particles attacking our lungs. We simply used tape to create this more-or-less waterproof basin. The plate was screwed to the t-slot table via four holes in its corners. Overall the water basin was not very reliable and quite a good amount of water went down into the t-slot table below. The table was made of simple spruce and sucked all the water, albeit its shape was transformed significantly. Luckily the table was quite worn anyway, thus we did not feel sorry about is loss.
We used tiny drills (0.7mm), since the smallest holes in the plate were around this size. But the tiny drills broke too easily. During the milling process we lost three drills, thus we needed to expirement a lot with feedrate and spindle speed. I guess, we learnt that you should prepare a toolpath for all small features of the plate and then run the rest with a bigger tool. This would have saved us a lot of time and probably one or two drills.
But in the end we were very happy with the result: all the features of the PCB look clean and perfect. Hopefully the new board will work better than its predecessor with the Reprap machine …
Comments
would love some more details
If you have a chance I’d love to hear a more detailed coverage of this, specifically: what your pcb2gcode millproject config file included (stuff like cut-infeed values), what sort of bit you used to mill the copper, how you set up the mill to get the pcb dead flat perpendicular to the spindle, and how you aligned it for milling two sides while maintaining registration.
As this was one of our first
As this was one of our first adventures in pcb milling I don’t really think our advice is very valuable, but here are some details from the millproject file we used:
cutting the pcb was done with a 2mm flat end mill bit.
cutter-diameter=2.0
zcut=-4
cut-feed=50
cut-speed=1500
cut-infeed=1
offset=1.0
the isolation routing was done with an engraving mill bit with IIRC 60° and a 0.1mm tip.
zwork=-0.2
zsafe=3
zchange=50
mill-feed=200
mill-speed=1500
we tried milling out the holes with a 0.75mm flat end bit, which while producing the desired results also cost us 3 of those bits :) Lesson learned: Use real drill bits of the right size and live with having to change them often. In the end thats faster and cheaper than milling out the holes with small bits.
Regarding your aligning question: This particular board was one-sided only. For 2-sided boards I would probably prepare the pcb by drilling 4 symmetrical holes in each corner (e.g. 5mm distance from each adjacent side) and than screw on the pcb through these holes. Turning the pcb while maintaining registration would then be easy: screw off, rotate the board, screw on again. We use this technique for wooden objects quite successfully.
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