Manufacturing & engineering
Interference detection
Definition
Interference detection is a CAD analysis that finds where selected nominal solid volumes overlap. It can locate a clash at a chosen assembly position, but a clean result does not prove adequate clearance, collision-free motion, or tolerance-safe fit.
Also known as: interference analysis, assembly interference check
Updated
What the calculation tests#
Onshape Help describes selecting two or more parts or bodies and displaying their interfering mass. Autodesk Fusion Help likewise uses selected solid bodies or components and can include coincident faces.
The result applies to the nominal geometry and assembly position included in that calculation. A different configuration, suppressed component, simplified representation, or mechanism position can produce a different result.
Intentional and misleading results#
Some overlaps represent design intent, including press fits, seals, modeled threads, and preload. Others come from representation choices. SOLIDWORKS Design Help 2026 can separate fastener and matching cosmetic-thread results, and it warns that coincident or extremely close curved geometry can produce false positives when facets collide.
An ignored result therefore needs a recorded reason. Hiding or dismissing it does not determine whether the overlap is acceptable.
What interference detection cannot prove#
A clean static result only establishes that the included nominal solids do not overlap at the tested position. It does not establish a required minimum clearance, tolerance-safe fit, collision-free motion, deformation under load, thermal growth, cable routing, or manufacturability.
Use clearance analysis for required gaps, collision or dynamic-clearance checks for motion, and tolerance analysis for dimensional variation.
Sources
Related terms
Assembly
An assembly is a CAD model made of multiple parts or subassemblies positioned relative to each other with mates or joints. Assemblies are where fit, clearance, interference, and motion get checked.
Clearance
Clearance is the positive space between components, often measured in CAD as their minimum nominal separation. Required clearance must account for function and manufacturing variation; the absence of geometric interference does not by itself provide enough clearance.
Tolerance
A tolerance is the allowed variation from a nominal dimension, such as 10.00 ± 0.05 mm. Tolerances drive fit, cost, and inspection, and they have to be specified deliberately because a CAD model on its own stores only nominal sizes.
Degrees of freedom
Degrees of freedom are the independent ways a CAD component can translate or rotate. Assembly mates remove or control those motions; leaving unnecessary freedom makes position ambiguous and can add solver work.