Reverse engineering

Reverse engineering runs the design process backwards: instead of drawing and then making, it starts from an existing part to arrive at a CAD model and manufacturing drawing. It is common for spare parts of old machines, imported components with no supplier, and inherited designs without documentation.

How it works

The process combines measurement (calipers, micrometers, measuring arm or 3D scanning), interpretation and modeling. Interpretation is the engineering part: a used part is worn and deformed, so you must decide which nominal size and tolerance make sense, whether a hole is a metric or inch thread, and which fit the assembly needs. The result is a parametric STEP and a drawing that allows remaking the part, not a copy of its defects.

Practical example

A gear on a 1987 machine broke and the builder no longer exists. The part was scanned and measured, module and tooth count were identified, the material was analyzed and the drawing came out with fit tolerances. The new gear was machined and the machine was running again within a week.

Common mistakes

• Copying the worn part’s size as if it were nominal.
• Ignoring the mating part, which defines the required fit.
• Delivering only a scanned mesh, which is useless for machining.