Apply primitives and Boolean operations to design functional digital objects — with design intent, constraints, and specifications.
Learn — read and understand
From sketch to digital: the translation workflow
Before opening CAD software, every professional designer completes a dimensioned sketch — a hand drawing showing the object with approximate measurements written on each part. This sketch becomes the specification that guides CAD modeling. Professional workflow: Sketch first (paper) → Dimension second (paper) → Model third (CAD) → Print fourth. Never start in CAD.
Design constraints: what limits your design
Every real design has constraints — limitations you must design within. Size constraints: 'must fit in a pencil case.' Strength constraints: 'must hold 500g without breaking.' Print constraints: 'no overhangs greater than 45°, minimum wall thickness 2mm.' Identifying constraints before modeling prevents wasted time building models that cannot be printed or used.
The hollow box method
The most common beginner error: modeling a solid box that prints in 8 hours using 200g of filament. Most containers are HOLLOW. The hollow box method: Outer box (80×80×90mm) minus smaller inner box (74×74×90mm) = 3mm walls on all sides. A 3mm-wall hollow holder uses 90% less material than a solid block.
The 3 critical 3D print constraints
(1) Minimum wall thickness: 2mm for PLA (thinner = too fragile or fails to print). (2) Maximum overhang angle: 45° without supports. (3) Minimum hole diameter: 2mm. Also: always add 0.5mm clearance to holes that accept real objects — printed holes are slightly smaller than modeled due to material shrinkage.
Explore — key design decisions for any object
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Form factor
Overall shape and size. Must fit the use context. Measure the real space before designing — never guess dimensions.
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Wall thickness
Minimum 2mm for prints. 3mm recommended for functional objects. Measure with Ruler tool after modeling to verify.
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Functional holes and slots
Size holes to the objects they must accept. Pencil = 7mm hole. Add 0.5mm clearance: model hole as 7.5mm.
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Print orientation
Design so the object prints standing on its strongest face. Avoid large overhangs — keep angles under 45° to avoid support structures.
Activity — match each constraint to the correct design decision it requires
Drag or tap a label, then drop/tap on a zone
Use hollow box method
Add 0.5mm clearance
Keep walls ≥ 2mm
Avoid overhangs > 45°
Must print light and fast
Pencil must fit in hole
Must not break easily
Must print without supports
Quiz — Designer Stage, Level 4
1What is the recommended minimum wall thickness for a PLA-printed functional object?
2Why do you add 0.5mm clearance to a hole designed to accept a 7mm pencil?
3The 'hollow box method' creates a container by…
4An overhang greater than 45° in your model will require…
5Why must you sketch and dimension an object on paper BEFORE modeling it in CAD?