A Machining Allowance is necessary if the optimization optimisation result is manufactured with the Additive Manufacturing processes . After printing the part all where functional surfaces (Non-Design Spaces) are post processed and therefore enough material needs to be available. So the optimization actually needs to produce . With MSC Apex Generative Design Machining Allowances can applied on surfaces where a specified amount of additional material will be included to later be removed in a precision machining process like milling.
The optimisation produces different outputs for different requirements of the model - once a norm print geometry and once a printing nominal geometry.The optimization is carried out and calculated without taking the Machining Allowance into consideration. It is added after the calculation process is done but before any smoothing algorithm has run over the geometry to guarantee a design without any transition problems between these different geometries.
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The Machining Allowance need needs to be added to all functional surfaces. The picture below shows an example of the GD-Bracket.
GD Bracket Model Browser with MA
So the Machining Allowance should be applied in combination with the Non-Design Spaces. Touching faces should always be selected in one Machining Allowance because only then the Machining Allowance is one connected volume instead of just several offsets of the faces. The picture below shows the difference of the selections:One MA vs. several for connecting faces
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The optimisation is carried out and calculated without taking the Machining Allowance into consideration. It is added after the calculation process is done but before any smoothing algorithm has run over the geometry to guarantee a design without any transition problems between these different geometries.