For the g-code sending software, I have had much better results when probing a heightmap grid before the engraving step. Even if it was possible to mill a perfectly flat spoilboard on the CNC, I have measured 0.5mm deviations in the blank PCBs I use. That plus the variability of the 2 layers of painters tape with superglue in between for workholding means that an engraving depth of 0.1mm is hard to achieve without some extra help.
For the g-code sending software, I have had much better results when probing a heightmap grid before the engraving step. Even if it was possible to mill a perfectly flat spoilboard on the CNC, I have measured 0.05mm deviations in the blank PCBs I use. That plus the variability of the 2 layers of painters tape with superglue in between for workholding means that an engraving depth of 0.1mm is hard to achieve without some extra help.
@ -78,3 +79,18 @@ My surface prep is to clean and rough up the copper with a scouring pad, then wi
It's hard to find reliable information from a search engine in the age of AI slop, but it seems that the ink itself could be starting to deteriorate. I double-checked with my bench agent who concurs:
It's hard to find reliable information from a search engine in the age of AI slop, but it seems that the ink itself could be starting to deteriorate. I double-checked with my bench agent who concurs:
It turns out, the UV ink works just fine, but I hadn't spread it out thin enough. I had this figured out, but since it had been awhile since I last made a board, I forgot why using a paintbrush doesn't work. Maybe with a different paint, or stronger UV light, it might not matter, but what does work is cleaning the pcb, applying some ink, then adding the sacrificial piece of transparent printer film. Then, carefully spread the ink out by applying pressure from the top of the film with a straight edge (even a credit card works for this, it just needs to have some flex). The idea is the squeeze the ink into a very thin layer, which is one more thing that takes some practice. Here are some pictures of the end result of the main board I made recently after re-learning how to apply the ink:
Second, The vibration and noise from cutting the PCB out seemed worse than I remembered, and I think that was due to a worn end mill bit. I've been re-using the same 2mm end mill bit for awhile, since it's the only one in that size I have left, and all my gcode expects it. For milling single sided boards, I found some blank [phenolic boards](https://en.wikipedia.org/wiki/FR-2) that seem to be pretty easy on tools. The double sided blank boards are [FR4](https://en.wikipedia.org/wiki/FR-4), made on a fiberglass substrate, and is apparently a much more abrasive material for the tools. I think the recommendation for using a bigger CNC machine for milling is still applicable, but I'll order some new bits, and test again before I look at upgrading. Here's a microscope image showing the difference between the old bit and a fresh one:
