SOLVED how do I make a solid volume within a larger volume?

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I want to make a 'solid' box, several cms in each dimension and within that box I need to place some solid volumes to screws to be inserted.

How do I go about this please.

I'm using an O+ with Cura 3.4

[gr5 1,331]

Short answer: Using CAD software.

 

I'm not sure exactly what you are asking.  When you put "solid" in quotes the first time - that's probably for a good reason.  I think you mean "hollow"?

 

Or maybe you are saying you want some parts of the model to have light infill - say 20%.  And other parts of the box to have 100% infill?  Is that what you want?  That can be done in Cura.  Here is a video to explain the second thing.  Maybe you want a 3rd thing and just need to draw a picture of what you mean:

 

[PRB 0]

Indeed, the second is what I want. The video is most instuctive, thanks.