Carvera PCB tutorial
This tutorial will guide you through PCB milling using the Carvera machine, which is an impressive low-cost milling machine with automatic tool changing. In the context of PCB milling, this means that the machine can cut the traces with a fine tool, then swap it for a larger one to cut the board's edge, all automatically.
1. Securing the copper clad
The easiest way to secure the copper clad to the machine is to use clamps. When using clamps, be mindful of two things:
- The machine has no knowledge of where the clamps are, and will happily mill into it if you tell it to. That would damage the tool, and possibly the machine itself.
- You need a sacrifical layer under the clad you're planning to cut, or your program will reach the machine's bed when cutting the edge of your board.
Next, secure this stack using the clamps. Make sure the lower left corner of your copper clads is pushed against the L bracket present on the machine's bed, with no gap. Use the side of the clamp with a lip, and check that the lip has good engagement with the top of the clad.
Use the bracket's two screws to secure the lower-left corner. Make sure they're effectively compressing the top of the clad stack:
Finish off with two more clamps in the back of the machine:
Congratulations! You now won't have to touch the machine until the end of the process. We basically just have to load the file and hit "play".
2. Preparing the file with mods
For the purpose of PCB milling, we'll assume the machine has the following tools loaded:
- Tool n°3: 1/32" (0.8mm) flat end mill
- Tool n°5: 1/64" (0.4mm) flat end mill
To produce the g-code to mill your PCB, first open mods in a web browser. Right-click, then go to programs->open program, and find the "Carvera mill 2D PCB" program under "machines":
The program looks very daunting, but your input is only needed on the left side:
To continue, you'll need a png image of your board's traces, and another png image of your board's edge. You can obtain those files in many ways, for example by converting your gerber files to images using gerber2img.
Load the two images by clicking "select png file" in the respective nodes, on the left of the program. Double check the DPI value of those images, as it can sometimes fail to be automatically detected, in which case you can change it manually.
Next, check the "Tabs" node. Make sure a thin line is connecting the side of the image to your board. If needed, adjust the length of the tabs. If your board has a special shape, you might need to add them manually using some image editing software; just make sure they reach the every last pixels on the left and right sides of the image.
To obtain your g-code file, simply click on "Calculate" on the central node, marked by a note. The program will become slow or freeze for a few seconds. At the end, you will get a preview and time estimate in the lower right side of the program. The g-code file will autmatically be downloaded to your hard disk. If in doubt, check your Downloads folder, or the browser's download history.
3. Loading the file into CarveraController
Launch CarveraController, and make sure the machine is connected through USB:
Next, load the file by clicking the icon in the lower-left corner. The Carvera needs the file to be loaded into its internal memory, so you'll need to upload the file first, by clicking on "upload":
Navigate to the file produced by mods, and click on "Upload". Don't click on "Open", as that won't upload the file to the machine.
Next, click on "Close" to go back to the machine's locally stored files. Select the one you just uploaded, and click on "Select".
The toolpath is displayed:
Make sure it looks correct, then click on the gear icon in the lower left corner. A new dialog box opens, letting you configure your program before launching it:
First, you'll need to set the lower left corner of your program. If your PCB clad has already been used before (as should be the case most of the time), you'll need to measure the X and Y offsets needed to not run into it. Using calipers and a ruler, measure the X and Y distances from the L bracket at which you'd like to mill your board. Make sure to leave some margin, and check that your board will fit in the spot you've picked.
Click on "Config" under "Set Work Origin". Configure the following:
- Tick Anchor1 as the reference
- X Offset: the X offset you measured (in mm)
- Y Offset: the Y offset you measured (in mm)
Click on "Ok" to confirm. Next, let's configure auto-leveling with the probe. Tick both "Scan Margin" and "Auto Leveling", and click on "Config" under Auto Leveling.
