Parametric Sketching, Constraints & Mass Properties

Why Design Intent Matters in 3D CAD

A well-constrained SolidWorks sketch captures design intent so that when a bore diameter or mounting pitch changes, the 3D solid updates cleanly without broken geometry.

Example Hollow Cylinder Cross-Sectional Area For a hollow shaft with outer diameter $D_o$ and inner bore $D_i$, the cross-sectional area is $A = \frac{\pi}{4}(D_o^2 - D_i^2)$.

Step-by-Step Worked Example

Calculate the cross-sectional area and mass of a 6061-T6 Aluminum hollow shaft in Python:

import math

d_outer_m = 0.060
d_inner_m = 0.030
length_m = 0.250
density_kg_m3 = 2700.0  # Aluminum 6061-T6

area_m2 = (math.pi / 4.0) * (d_outer_m**2 - d_inner_m**2)
volume_m3 = area_m2 * length_m
mass_kg = volume_m3 * density_kg_m3
print(f"Area: {area_m2*1e4:.2f} cm^2 | Mass: {mass_kg:.3f} kg")

Real-World Engineering Application

Always fully define sketches with geometric relations (concentric, symmetric, tangent) before applying dimensional驅 parameters.