Differences

This shows you the differences between two versions of the page.

--- pcbetching [2022-02-01 17:17] – jtdburton
+++ pcbetching [2022-02-12 17:54] – jtdburton
@@ Line 22: / Line 22: @@
 There are a few approaches to this process. These instructions will assume you're using KiCad and FlatCam (both open source) for PCB design and file manipulation.
-Make sure to design your board with nice thick traces - start with at least 0.8mm and then try going smaller once you've got the hang of the masking and etching process. Try to fit everything onto a single-sided board if possible, as this means you can use the laser cutter for machining which is currently much simpler than the CNC (see notes under "Cutting" below).
+Make sure to design your board with nice thick traces - start with at least 0.8mm and then try going smaller once you've got the hang of the masking and etching process. If you can fit everything onto a single-sided board, you might be able to use the laser cutter for cutting and drilling; if not, you'll need to use the CNC (both options are detailed below).
 The first thing to create is your trace file. In KiCad, go to File - Plot. Set "Plot format" to "SVG". Select your copper layers ("F.Cu", "B.Cu", or both). Tick "Plot Edge.Cuts on all layers" (this is to help you align the mask to your cut board), make sure "Drill marks" is set to "None", and click Plot.
 Open your plot file in your vector editing programme of choice and invert the colours (assuming you're using negative photoresist film - see notes under "Exposure" below). In Illustrator, the easiest way to do this is to create a white filled rectangle slightly larger than your board, put it behind your traces, and then select all and click "Edit" - "Edit Colours" - "Invert Colours".
+===== Cutting (CNC)  =====
+The CNC is a bit tougher to get going on than the laser, but it opens up a lot more options, most notably two-sided boards.
+Start by going back to KiCad's Plot dialogue. Make sure "Edge.Cuts" is the only layer selected. Select the Gerber plot format and click Plot.
+Now click "Generate Drill Files...". Select "Excellon" as your file format here, and tick "PTH and NPTH in single file". Make sure the "Absolute" and "Millimetres" options are selected and click "Generate Drill File".
+Open up FlatCam and use File - Open Gerber to load your edge cuts and File - Open Excellon to load your drill plot.
+It's a good idea to go into the "Options" tab at the left here and make sure "mm" is selected as FlatCam defaults to inches.
+Double-click the drill plot in the file list. You can skip over all the CNC settings here, just enter your tool size under "Mill Holes" (a 0.7mm bit is usually good) and click "Generate Geometry".
+Now go back to the "Project" tab and double-click the new drl_mill layer.
+Enter your CNC settings here. Typical values will be around -1.6mm cut Z (this is the thickness of your board), 1mm travel Z, 200mm/min feed rate, and 10,000 RPM spindle speed. Click "Generate".
+Back in the "Project" tab again, you'll have a new .drl_mill_cnc layer. Double-click this, and enter "M30" in the "Append to G-Code" box (this is an "end of program" signal, and LinuxCNC won't process a file without it). Click "Export G-Code". Grab the SD card from the CNC laptop and save your gcode file on there with the file extension .ngc.
+The procedure for the edge cuts is similar. Double-click the .gbr layer in the Project tab, enter your tool size under "Board cutout". The Margin setting is best left at 0. The Gap size setting can be used to add a few points around the  edge of the board where it's not fully cut out from your stock, so it stays anchored in the CNC router. 4mm tabs are a good size. Once all these are set, hit "Generate Geometry". Then go back to the Project tab, double-click the new .gbr_cutout layer, enter your CNC job parameters again, and click "Generate". Back to the Project tab one more time to open up the .gbr_cutout_cnc layer and export the g-code.
+Tip: at each stage of the FlatCam process you can save your settings for next time by going to Options - Transfer options - Object to Application.
+From here, pop the SD card in the CNC laptop, load it into LinuxCNC, and proceed with the usual CNC process.
 ===== Cutting (Laser Cutter) =====
-The simplest way to cut your board is with one of the laser cutters. This is subject to two major restrictions: use FR1 or FR2 boards ONLY (FR4 vapourises into some VERY nasty stuff), and use only single-sided boards (you can't laser through copper). Instructions for cutting a board with the CNC router will be added here eventually, but the file prep steps are similar so you may be able to figure it out for yourself.
+Another way to cut your board, which you may find simpler, is with one of the laser cutters. This is subject to two major restrictions: use FR1 or FR2 boards ONLY (FR4 vapourises into some VERY nasty stuff), and use only single-sided boards (you can't laser through copper). Instructions for cutting a board with the CNC router will be added here eventually, but the file prep steps are similar so you may be able to figure it out for yourself.
 Start by going back to KiCad's Plot dialogue. Make sure "Edge.Cuts" is the only layer selected. Select the Gerber plot format and click Plot.
@@ Line 40: / Line 66: @@
 You should be able to improt this SVG directly into LaserCut 5.3, but it may take some cleanup in Inkscape/Illustrator first.
-Place your workpiece in the laser cutter copper side DOWN. Cut settings may need some experimenting to get right. The aim is to cut all the way through the substrate without hitting the copper hard enough to cause lots of sparks. My best results have come from using the big laser with speed 25, power 60, corner power 50 on 1.5mm board.
+Place your workpiece in the laser cutter copper side DOWN. Cut settings may need some experimenting to get right. The aim is to cut all the way through the substrate without hitting the copper hard enough to cause lots of sparks. My best results have come from using the big laser with speed 25, power 60, corner power 50 on 1.5mm board. However, some boards are much tougher than others so your mileage can and will vary - try cutting out a small circle as a test for new stock.
-Run the cuts. Give it a couple of minutes before you open the lid, vapourised FR1/2 isn't as bad as FR4 but it's still unpleasant.
+If you're sure you've got usable laser settings, download and run your cuts. Give it a couple of minutes before you open the lid, vapourised FR1/2 isn't as bad as FR4 but it's still unpleasant.
 {{::20220114_183346.jpg?400|}}
-Take the workpiece out and pop your board out of it. What you're doing here is snapping the copper layer along the lines you've cut in the substrate, it'll be tough but doable. You may need to flex the board a bit. You can leave the through-holes for now, although you may find it useful to drill out a couple to help you align the trace design in the exposure step.
+Take the workpiece out and pop your board out of it. You'll need to snap the copper layer along the lines you've cut in the substrate, which should be tough but doable. You may need to flex the board a bit, or even use scissors or a guillotine on the edge lines. You can leave the through-holes for now, although you may find it useful to drill out a couple to help you align the trace design in the exposure step.
 {{:20220115_113716.jpg?400|}}