CAD assembly-strategy and -hierarchy

pib is, in it’s entirety, a quite complex system. The pib-CAD (Onshape) is supposed to hold all relevant construction-information, which includes the 3d-printable “skeleton” as well as the metal-parts (bearings, screws, rods,…) as the electronics. Being a (the? ) central source of information and still being easy to navigate with also a reasonable performance is difficult to achieve. This is what this assembly-strategy and hierarchy adresses, keeping our CAD navigateable, easy to learn and also fast.

Using sub-assemblies in a hierarchy

Onshape allows to build assemlies based on lower-level sub-assemblies. The advantage gained here is, that the changes of parts lead to recalculations of the affected sub-assemblies only, which is fast. The resusage of these sub-assemblies in higher-level-ones is a leightweight calculation, so that a strategy involving nested assemblies leads to significant performance-gains. The next chapters describe the strategy behind our assembly-hierarchy, so that new pib-developers can easily understand it and deveopment is done consistently.

Bottom level of assemblies

The lowest level of assemblies uses the individual parts and creates a logical, re-usable basic components. Examples for this level are fingers, the neck, etc…

Intermediate levels of assemblies

These basic components are building-blocks of the next assembly-level and lead to entities like a hand, an arm or the head. In order to combine the sub-assemblies correctly, the neccessary connecting-elements are added also (screws, nuts,…).

Question: should it be valid to add mechanical parts also on this level or should they all come from the sub-assemblies?

The full pib assembly

The highest level contains the full pib. This assembly is the central entry-point for navigating pib and thus its performance and logical structure is of great importance.