CAD & Mechanical Design Practice
Related: cad-cam · machine-design
Cheat sheet
Formulas
GD&T: feature control frame — characteristic | tolerance | datums
MMC/LMC modifiers affect bonus tolerance & gauge design
DFMA: reduce part count, standardize, design for access/fastening
Tolerance stack worst-case Σti vs RSS √(Σti²)
DFMA: Design for Manufacture & Assembly — reduce parts / simplify ops
GD&T: feature control frames — position, flatness, profile, …
Sheet metal: k-factor ≈ 0.3–0.5 typical starting guess
Definitions
- Datum reference frame
- Origin for measurements from A/B/C
- Material condition modifiers
- MMC/LMC/RFS — functional gauging
- Design for assembly
- Part count, orientation, self-locating features
- Poka-yoke in design
- Geometry that only assembles correctly
- Design intent
- Model updates predictably when dimensions change
- Datums
- Reference features for measurement and GD&T
Topic-wise short notes
DFMA & GD&T
- Position vs concentricity vs runout — pick correct control.
- Flatness/straightness/circularity form controls.
- Assembly sequence drives accessible fasteners & tool clearance.
CAD tool craft
- Templates, standards layers, title blocks.
- Export & revision discipline for suppliers.
Exam traps & quick notes
- Tools: SolidWorks, Creo, Solid Edge.
- Cross-link academic CAD/CAM & machine design courses.
- Portfolio: pad design, mounts, wind-tunnel flats.
- Specify datums from how the part sits in the machine/assembly.
- Don’t over-tolerances — cost rises nonlinearly.
- Communicate critical-to-quality features explicitly.
Comprehensive notes
DFMA & GD&T
Assembly-minded part count; geometric tolerances for function, not cosmetics.
External: GD&T basics (ASME Y14.5 intro) ↗ DFM guidelines overview ↗
CAD tool craft
Configs for families; drawings with balloons/BOM; export STEP for vendors.
External: SolidWorks tutorials ↗