Assembly modeling relationships: In 3D parametric assemblies, does the last part added to the assembly automatically become the “parent” of previously placed components?

Introduction / Context:
Modern CAD systems use constraint-based assembly modeling. Understanding how “parent” and “child” relationships are formed prevents fragile models and broken references. This item targets the misconception that add order determines parental control in an assembly.

Given Data / Assumptions:

• A parametric 3D CAD environment is used (constraint-based).
• Components are positioned by mates/constraints or grounded references.
• Top-down strategies may include skeleton or master sketches.

Concept / Approach:
Parent/child dependencies stem from references. If component B is constrained to faces, planes, or datums of component A, then A is a logical parent for those referenced features. The time when a component was added does not automatically create such a relationship. Many workflows ground the first-placed base component; others use a skeleton part to drive positions. In both cases, constraints—not chronology—govern dependency.

Step-by-Step Solution:

Verification / Alternative check:
Reorder the feature tree or insert a part late in the process without creating any constraints to existing parts. No parent/child relation forms until you reference geometry or parameters, proving that order of insertion alone is irrelevant.

Why Other Options Are Wrong:

• The last-added component is not automatically the parent (option B).
• File age (option C), mass (option D), or alphabetical name (option E) have no bearing on dependencies.

Common Pitfalls:
Over-referencing many parts to a single face; creating circular references; assuming grounding equals parenthood; ignoring robust strategies like skeleton-driven top-down design.

Final Answer:
Incorrect: parent/child is defined by constraints, not add order