Assemblies and standard parts

An assembly is more than a collection of parts in the right place. It should explain which component establishes the product, how the remaining components are located, and which motion or adjustment is meant to remain.

Choose the component that anchors the product

Insert the main frame, housing, or another stable component first and fix it when that matches the intended assembly reference. Add functional groups as subassemblies instead of placing every fastener and bracket at the top level. A clear structure makes selection, review, and later replacement easier.

Do not fix every component just to remove visible movement. Fixed placement hides whether the engineering relationships are actually defined.

Add mates from function outward

Use mate relationships to describe the contact and alignment that exist in the real product. The published assembly tools include coincident, parallel, perpendicular, coaxial, distance, angle, tangent, and fastened relationships. Select references that represent the interface—not an incidental edge created by a decorative detail.

After each small set of mates, move or rotate the component and check its remaining degrees of freedom. A shaft may need to stay coaxial while remaining free to rotate; a cover may need its orientation and seating face controlled but still require a separate fastener pattern. Fully constrained is not automatically correct.

Diagnose conflicts instead of stacking mates

When a mate reports an error, inspect the existing relationships before adding a replacement. Two faces cannot be both coincident and perpendicular, and an indirect chain of mates can create the same kind of contradiction across several components.

Delete a relationship that no longer matches the design, suppress it temporarily if you need to inspect the remaining motion, or edit the selected objects, direction, distance, or angle. The aim is the smallest set of relationships that describes the mechanism.

Treat standard parts as engineering choices

Reuse standard components rather than rebuilding common hardware, but verify their size, specification, clearance, and interface before release. A familiar-looking bolt, bearing, or fitting is not interchangeable simply because it occupies the same space.

Finish by checking the assembly from the viewpoints that matter: motion, service access, interference, tool clearance, and product structure. Then change one controlling part dimension and confirm that the assembly relationships still behave as intended.