When the tool touches the board, the input pin is pulled low and the Machine Control Software records the tool height for that specific XY position.Ĭontinue reading “Mill Warped PCB Blanks On An Uneven Bed” → Posted in cnc hacks Tagged autoleveling, autoleveller, PCB mill, PCB milling Milling Curved Objects With A G-Code Ripper The tool spindle is grounded with a clip lead. An input pin on the parallel port is pulled high with a resistor and connected electrically to the PCB board. This is easy to do if communicating to the CNC Machine via a computers parallel port. There is one catch: the Machine Control Software has to be set up to accept a probe. The result is a clean and usable PCB on the first try. Then, when running the program, it adjusts the height of the tool bit on the fly so that the actual depth of cut is consistent over the entire board, regardless of how flat or not it is. When the modified g-code file is run on the CNC Machine, it first probes the surface of the PCB in a grid pattern and maps the flatness variation of the PCB’s surface. He created a software program called AutoLeveller that takes a g-code file and adds a probing section to the beginning before the milling operation. PCB fabrication enthusiast had this exact problem, and in true hacker fashion, decided to do something about it. Even if the bed is flat, the PCB may be warped or bent. If the bed is not flat, the PCB won’t be. There are two main contributors to the flatness problem the PCB board and/or the machine’s bed. If you have a hard time picturing what 0.010 inches is, think the thickness of two pieces of paper, it’s not a lot. Since an ideal depth of cut is about 0.010 inches, even a very small amount of waviness or out of flatness can cause a serious problem in the milling process. The side where the traces are missing from is lower than the other so the tool bit is not able to reach that part of the board. This happened because the circuit board was not flat. The traces on the left side of the board appears to have just faded away. Shallow cuts can result in another problem, inconsistent cut depth over the surface of the board. Cutting too deep can weaken the board, break a bit, or in an extreme case, cut through the entire board. When milling a board the ideal situation is to mill just deep enough to get through the copper but not cut too deep into the fiberglass backer board. The copper on a PCB blank can be anywhere from about 0.001 to 0.006 inches thick. Sure, just export your Eagle design to CNC-Machine-understandable g-code and fire up your mill…. There is a downside though, it’s a little tough. Milling a PCB at home is a great way to save some time and money if you are making one-off circuit boards.
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