Study guide — what to focus on

This module is curated — the teaching is a top free course (linked in the card above); our job is to point you at the right things, make you prove it in Forge, and certify you.

The plan

1. Watch the course (the card above). You don't need every lecture — aim to understand the DFM and tolerance ideas below, then use the study notes here to pick up the GD&T vocabulary the course touches only lightly.
2. Focus on these — they're what the check tests and what you'll use for real:
   • Uniform wall thickness — why uneven walls sink and warp, and why you core out thick sections instead of leaving them solid.
   • Draft — the slight taper (≈1–2° per side) that lets a moulded part eject cleanly; a pure moulding concern.
   • Print vs mould DFM — the rules differ. On an FDM print, overhangs past ~45° from vertical need support; on a mould, you worry about draft, sink and ribs. Same part, two DFM checklists.
   • Ribs & bosses — a rib ≈40–60% of the wall stiffens without telegraphing a sink mark to the show face; bosses want a fillet and a gusset, not bulk.
   • Tolerances & stack-up — every dimension carries variation, and along a chain it accumulates. Two parts that each pass inspection can still refuse to fit if nobody budgeted the stack.
   • Fits — a clearance fit (hole larger than shaft) slides and assembles freely; an interference/press fit (shaft larger) is forced in and held by friction. Choosing the right one is a design decision, not an accident.
   • GD&T — a datum is the agreed reference to measure from; flatness is a form control on one surface (no datum); position locates a feature (like a hole) relative to datums. This is the language that makes "it must fit" unambiguous on a drawing.
3. Prove it in Forge (next section) — design a manufacturable enclosure and reason about wall thickness, draft and fit.
4. Take the K-Check to earn your certificate.

Why this connects to building real products

This is the half of design that decides whether a part survives contact with a factory or a printer. In Forge, when you go from Prototype (the 3D part designer) toward Build, every one of these rules becomes a real constraint: the wall has to be thick enough to print and mould, the lid has to clear the base by a real tolerance, the boss has to actually accept a screw. Knowing DFM, tolerances and GD&T lets you read why a design is shaped the way it is — and produce parts that fit the first time instead of the third.

Time to apply it. The course taught you design for manufacture; now make a part that has to survive being made.

Send the prompt below in the Forge 3D part designer and watch how it resolves a real enclosure — walls thick enough to print and mould, draft on the vertical faces, and a lid that clears the base by an actual tolerance rather than a wish.

As you read the result, connect it back to the course: where would a sink mark show up, which faces need draft, and what fit did it choose between the mating parts? That reasoning — DFM and tolerance thinking applied to a part you can hold — is the whole point.