Operations - Insulation Milling

Insulation milling operation moves the milling tool along the outline of the traces thus isolating them from surrounding copper. It’s the first of the two copper milling operations. It involves the steps described below.

Placing PCB laminate on the machine bed

As instructed, put PCB laminate and spacer on the machine bed. You can use Manual control popup to move the machine’s head out of the way.

Inserting cutting tool

Here you need to select the tool that you will be using for this operation. If you have more than one milling tool in your disposal, you can list all of them in the settings. This way you’ll have fast access to your favorite milling parameters for each of the tools.

Establishing Z axis offset

Z axis offset is a position of Z axis of the machine, when cutting tool just touches the surface of PCB.

Insulation milling operation is very sensitive to tool engagement depth: too high means the traces aren’t separated from the surrounding copper, too low can mill away a trace at all (given conic shape of commonly used tools) and puts unnecessary stress on a fragile tool. This is why it’s important to specify Z axis offset (which effectively determines the depth) as precise as possible.

cirQWizard offers you the following way of determining the offset:

  • select small sacrificial place on the laminate (it needs to be 3mm long and can be in the corner or along the edge of the board – so that you don’t waste laminate space)
  • make a test cut at an offset which is certainly above the surface of PCB
  • lower the offset by a little but until the tool makes a satisfactory cut

This way it is possible to precisely determine Z axis offset taking all uncertainties off the result.

If, by whatever means, you already know the offset and don’t need to go through the described procedure, you can select *I know it, I’ll tell you" option and enter the offset in the corresponding text field.

If you want to use described procedure, select I want to try option. Then enter coordinates of sacrificial place on the laminate. If you want to check where it is, push Go button – this will move the machine head to the coordinates you entered (you can also press Enter in coordinates text fields).

Initial Z offset value is populated from settings.

Pressing Test button will move the machine head to the location specified in Scrap place location pane, turn the machine spindle on, lower the head according to the Z offset specified, move the head in the selected direction, return the head to the original position and turn the spindle off. Lower and test button does the same, decreasing the Z offset value by 0.02mm beforehand.

Thus, the usual way to find Z offset is to select I want to try option and press Lower and test button until the tool makes a satisfactory cut.

Generating toolpaths

The program now has enough information to generate the tool paths for insulation milling of your PCB. Depending on your PCB design dimensions and complexity this might take a while.

Milling

Now you need to review the tool paths generated. To zoom in or out you can use one of the following ways:

  • click on the corresponding icons in the upper left corner of PCB design pane
  • hold Ctrl (or Cmd on Mac OS X) button and use the scroll wheel of your mouse
  • press Ctrl+= (or Cmd+=) to zoom in, or Ctrl+- (Cmd+-) to zoom out

If you spot a trace, which does not have a tool path generated around it, this means the clearance between this trace and neighbouring traces is too small for the tool diameter specified. Depending on your PCB layout and the tools that you have at your disposal, you might want to change Tool diameter parameter value in Settings popover and regenerate tool paths (to regenerate tool paths, press Enter in Tool diameter field).

You can also select, which tool paths are going to be milled (this is useful if you didn’t like the result in some places and want to have another go there). Tool paths can be selected with mouse. Selected tool paths can be enabled and disabled with toolbar buttons or with keyboard shortcuts: Ctrl+E (or Cmd-E on Mac OS X) to enable, and Ctrl+D (or Cmd+D) to disable. Shortcut Ctrl+A (Cmd+A) selects all tool paths.

For your convenience offsets that were entered on previous steps can be checked (and should it be necessary edited) in Offsets popover. The same way all of the relevant settings can be accessed and changed in Settings popover.

If you wish to have a look at G-Code that will be send to the machine, you can press a button with wrench icon in the toolbar.

When you are happy with all of the settings, press Run button. cirQWizard will send generated G-Code to the machine.