Using CopperCAM to engrave PCBs

CopperCAM is the software used to engrave PCBs.

Designing your board

How to design PCBs is beyond the scope of this page, but some tips are offered for designing for the engraving process.

If you are new to PCB design and looking for somewhere to start, CadSoft Eagle is a good package to learn on. It has a restricted but still-useful freeware version, and many tutorials on how to use it can be found online. At OxHack, we have developed a '.cam' output description file for Eagle, simplifying the process of outputting to CopperCAM.

In any package, it is important to be aware of the limitations of the CNC mill when designing your board.

• The engraving bit can reliably machine a groove down to around 0.3mm [???] in width.
• The smallest drill bit we have available is 0.8mm
• Holes 1mm and above can be machined with the 1mm slot drill
• The more different tools your board requires, the longer it will take to machine
• Engraved boards will have no solder resist layer, and so are harder to solder neatly. Be aware that solder can flow easily across the copper surfaces, and consider this while designing.

Exporting files

CopperCAM imports Gerber and Excellon files, which are an industry standard for PCB manufacture. These files can be exported by many common PCB design packages. If you develop a reliable workflow for exporting CopperCAM-compatible files from a specific PCB design package, please document it in this wiki.

CadSoft Eagle

Gerber and Excellon files are output from Eagle using its CAM processor tool. ('File -> CAM processor...') Eagle uses '.cam' files to describe output settings specific to certain manufacturing processes or PCB houses. A '.cam' file for the MDX-40 mill can be downloaded [here]. Open it in the CAM Processor using 'File -> Open -> Job...'. Each tab in the CAM processor now represents an output file. Click 'Process Job' to create the output files. [where will they go?]

CopperCAM basics

CopperCAM has been pre-programmed with the tools available at OxHack. It analyses the PCB files you import, and makes decisions about which tool to use for which operation.

It represents PCBs in 6 layers:

• Layers 1-4: copper tracks
• Layer 5: drilling
• Layer 6: contour (PCB outline; useful for non-rectangular boards)

Most functions are available by clicking buttons on the CopperCAM toolbar. Hovering over buttons gives you move options.

The following steps assume the source files have been output data from Eagle, using the '.cam' file provided above. They should however be adaptable to other packages' outputs.

Importing your PCB design

Start a new PCB job using 'File -> Open -> New circuit' Find the files output from Eagle and select bottom layer. A request to use RS274-X format may pop up; this can be ignored. A pad selector appears. It gives the opportunity to resize pads if you're concerned they may not machine correctly. It can be dismissed by clicking 'ok'. You can always resize pads later. The software should automatically recognise the outline of the PCB, which is included in the bottom layer file; click 'Yes' if it's correct. Click 'File -> Open -> Additional layer...' and select the top layer from your output files. Click 'File -> Open -> Drills' and select the drill file.

All the elements of your board design should now have imported correctly, and will be on the following CopperCAM layers:

• 1: Bottom layer
• 2: Top layer (note top and bottom layers will be reversed if you open them in opposite order)
• 5: Holes
• 6: Board outline

Click 'Calculate contours' button on toolbar, and choose the contour parameters. Successive contours = 1, and extra contours around pads = 0 are good basic settings to start with.

Checking CopperCAM's output

CopperCAM has been set up with the tools available for PCB machining. It attempts to figure out the best tools to use to machine your board, but sometimes some human input is needed.

Click the 'Drill list' to see how CopperCAM intends to create the holes in your board. You may find holes (for example those smaller than 0.8mm) where the correct drill size is not available, so a larger one has been used. If a hole is resized and it looks like the pad underneath it is now too small, it is possible to adjust the pad size to compensate, without going back to the PCB design. Click the 'Pads' button and find the incorrectly sized pad(s) in the list under 'Number'. You can adjust the sizes from here.

Adding tabs

Tabs allow the mill to cut most of the perimeter of the board, whilst leaving small breakable tabs preventing it from coming loose. Hovering over the 'Card contour' button will show the 'Cut tabs' button. Click this and enter the required size of the tabs, then click on the board's perimeter to show where you want the tabs to be located.

Outputting to the mill

When you're satisfied with the setup, it is advisable to save your work as a .PCB file. This file is independent of your gerber files, and contains all the information needed to machine your board.

Now, click the 'Calculate contours' button to create the toolpaths for machining the board.

Fixing problems

If you find a machining operation incorrectly leaves tracks on your board connected, you can use the 'Add separator segments' function to fix this. Click the button, then the two features you want to separate, and it will add a cut between them. You can also add cuts manually with 'Add contour segments'.

Milling your board

Setting up the mill

The best bed for engraving PCBs is currently the white sacrificial bed. Boards can be stuck down to it with double sided tape, and any through-holes can be drilled through the board, into the bed, without concerns. Only use the tape stored by the mill, because it's known to peel off easily and not leave any gungy residue.

File:PCB_engraving_sample.jpg

Milling

When you're happy with the way your board is to be machined, click the 'Mill' button.

The 'Final output' window will open. This shows a 'Sequence' of operations to send to the mill. It is important to send only one operation at a time, because the output does not pause for a tool change between operations. So make sure 'Section #1' is the only line ticked. 'Flip X' for all layers machined from the underside of the board. Be aware that if you're using the white cross as your origin, flipping output also flips the origin to the other side of the board.

An example of cutting a single sided board might consist of the following steps:

Select the layer you want to machine, and make sure the mill has the correct tool fitted, and that its Z datum is set to the top surface of the PCB.

For some reason CopperCAM doesn't end each job properly, so when it's finished, you have to []

Materials

Avoid glass-fibre (FR4) boards, as they blunt the mill tools rapidly. Paper-resin type (FR2) boards are the best to use with the mill. There is a stock of this material in by the CNC machine.

Settings

Machine layers separately; there's no pause to change tools otherwise. Take care the 0.8mm drill isn't used as a slot drill UCS origin is bottom left of board, Z=0 is surface.

Parameters used: V engraver: 0.2mm depth, 10mm/s feed Holes: 2mm depth