In ShowCut, my void layer doesn't cut the stock layer completely

Technote 239
Date: June 2009
Product: All Milling and Turning Applications
Version: 16+

The ShowCut Void Layer doesn't appear at all, or appears to partially cut the stock layer. Much like what is pictured below.

Void layer doesn't completely cut the stock

Version 16 introduces a Void Layer entry in ShowCut to define areas to remove from the Stock or Fixture Layers. The Void Layers are defined just like the Stock/Fixture Layers, but instead of creating a shaded solid from them, they instead remove any shaded stock within their bounds.

The issue is that if the stock or fixture top/bottoms are exactly the same as the void top/bottoms, a zero thickness 'film' is left. Adjusting the Void Z Level and Prof Top by any distance that ensures a clear intersection between the Stock/Fixture and Void volumes will eliminate this film. To attempt to have the software 'decide' which is the correct direction to change the definitions would be impossible since there is no association between the them.

Here is how this model defines the stock and void layers.

Stock and void layers

In this example the blue stock is at profile top of 1 inch. The red void is also at profile top of 1 inch. This creates a 'film' that intermittently covers the pocket.

Put the void layer in the active group and Property Change the Prof Top as shown below.

Property Change panel

This will make the void height slightly higher than the stock top, thus eliminating the film that covers the pocket.

Proper stock and void defined

If this were a through hole, where the void and stock were the same level and thickness, the same idea would apply. In the example below, the stock is the same (level zero, profile top = one). The Void layer should lower the level and raise the Prof Top. Here, it is at Level -.001 and a Prof Top of 1.001.

Proper stock and void defined for a through hole