ZMorph Knowledge Base

How to Prepare a File for PCB Engraving

If you would like to engrave a PCB using ZMorph milling feature and you don’t know how to prepare the files, then you will learn how to do it from this tutorial.

First of all, prepare your PCB project using any software you want. You can use KiCad EDA, CadSoft EAGLE PCB, Altium Designer, etc.

The first step, that you need to do is to export .dxf file from your PCB software. DXF file would be later edited in the milling workflow of Voxelizer software. Since there are a lot of designing apps, we'll show you how to export it in Eagle and KiCad.

CadSoft EAGLE PCB:

Open up your PCB design. Switch to the board preview and open Layer settings… Click None, and choose which layers should be shown: we are interested only in Top, Pads, Vias and Dimension (this is to see the size of output printed circuit board). If you would like to export the bottom footprint, you must mirror the whole board and still set Top to visible (do mirroring operation before setting the layers visibility).

Now, click File > Export > DXF. Set the location and name of output, .dxf file. Untick “Always vector font” and “Fill Areas”, set Unit to mm, and click OK.

 

KiCad EDA:

Open up your PCB design. Click Plot button in top toolbar. In Plot window, first change the plot format to DXF. Now choose layers that should be shown on your dxf file. Make sure only F.Cu layer is chosen. Now change Drill marks from None to Actual size. Click Plot button and your file is exported. Also you can choose Output directory of the file (if left empty it will be saved in your project directory).


 

DXF file processing:

When you have a .dxf file exported from your designing software, it is necessary to prepare the milling paths. To generate a correct file, you need to follow these simple rules:

  1. Circuit paths should consist of closed outlines with no crossings.
  2. Holes should be marked with a very small circle (0.05mm diameter is enough).
  3. Set the PCB in certain place and remember the value - this will determine where to put your plate for milling.
  4. Add offset equal to half a diameter of used cutter (when using V-shaped cutter set it to around 0.2mm). Starting from Voxelizer version 1.4.16 it is possible to add offset automatically (see this tutorial for reference)

Since there are a lot of software's that can edit .dxf files, we can’t show you specifically how to do it in all of them. The gif above shows how it should work in AutoCad software and the output form of the file.


Setting Voxelizer software:

The last step of file preparation is generating a .gcode file in Voxelizer software. Open it up, go to 2d milling workflow and import the previously prepared .dxf file.

Set up the properties of the machine:

  1. Work speed - safe value for PCB milling is 2-3mm/s.
  2. Travel z - set it around 1mm more than your PCB thickness.
  3. Work z - this is the height of the first layer on which the mill will operate. Since in most cases, the thickness of the copper layer is around 0.35mm, we can’t make it in one run. It is better to repeat the same sequence four times, lowering the working height each time. Use this equation: work z = plate thickness - 0.1
  4. Start z - beginning height of milling, set the same as travel z.
  5. Repeat count - we wanted to mill in four runs, so set it to 4.
  6. Drop length - set to 0.1 mm. It is a safe value for milling copper on laminate.

When all the settings are set, you can GENERATE DRILL PATHS, save your .gcode file and start milling.

 

Machine preparation:

  1. Use the CNC PRO instead of old Dremel-based toolhead. CNC PRO toolhead has more power, therefore, mills more easily.
  2. Use V-shaped engraving mill cutters.

  3. Laminate gives high resistance while milling, so make sure your plate is attached firmly. You can also fasten it with a screw to your milling plywood table.

 

NOTES:

  • The tutorial was written using CadSoft EAGLE version 6.5.0 and KiCad EDA version xxx. The exporting procedure might vary between software versions but the basis should be the same.
  • DXF processing was made in AutoCad Mechanical 2015. The lines showing the position of PCB are offset 20mm in X and Y axis from the origin (0,0 position).
  • Milling double sided PCBs is very difficult and requires a very precise PCB mounting while one side is already milled. You must experiment on your own.
  • It is better to only mark the THD holes with the cutter and then drill them manually afterward.
  • If you would like to mill two G-codes on the same plate, don’t reset the machine. Leave it homed, so it remembers the position.
  • If the thickness of copper on the plate you are planning to mill is higher/lower than described above, use more/fewer repeats accordingly.
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