Understanding the role of the Assembly module

When you create a part, it exists in its own coordinate system, independent of other parts in the model. In contrast, you use the Assembly module to create instances of your parts and to position the instances relative to each other in a global coordinate system, thus creating the assembly. You position part instances by sequentially applying position constraints that align selected faces, edges, or vertices or by applying simple translations and rotations.

You can also create instances of other models in your main model, allowing you to add complete subassemblies in addition to individual parts. Model instances are created in the exact same way as part instances and can be positioned and manipulated in a similar fashion.

An instance maintains its association with the original part or model. If the geometry of a part or model changes, Abaqus/CAE automatically updates all instances of the part or model to reflect these changes. You cannot edit the geometry of an instance directly.

Your main model can contain many parts and model subassemblies, and a part or model can be instanced many times in the main model assembly; however, a model contains only one top-level assembly. Loads, boundary conditions, predefined fields, and meshes are all applied to the complete assembly. Even if your model consists of only a single part, you must still create an assembly that consists of just a single instance of that part.

A part instance can be thought of as a representation of the original part. You can create either independent or dependent part instances. An independent instance is effectively a copy of the part. A dependent instance is only a pointer to the part, partition, or virtual topology; and as a result, you cannot mesh a dependent instance. However, you can mesh the original part from which the instance was derived, in which case Abaqus/CAE applies the same mesh to each dependent instance of the part.

A model instance is always dependent, not independent.