Why do some parts disappear and others dont when i weld shapes?

[Rick (Technical Evangelist)]

Have a look at this to understand the different Boolean operation and when to use each:

Tip ‘O the Day - Booleans Features

Here is another in a series of useful Tips, Tricks and How-to videos. This video demonstrates the Boolean operations in LightBurn, with a detailed look at how Union and Weld differ, and demos the use of Subtract and Intersect features. LightBurn Demo - Booleans - YouTube Connecting a name to an ornament using Union (not Weld) - YouTube