Capstok — learn by doing

Why this matters

Beginners often print whatever Thingiverse shows them and miss the categories of things 3D printing is uniquely good at — and the categories where it's the wrong choice. Setting the right expectations up front lets you point your skill development at applications that will actually pay off.

Demo

Categories where FDM 3D printing wins and where it loses.

Try it yourself

List 5 things in your home you wish you could buy but can't find. Cross out the ones that would be unsafe to 3D print (load-bearing, food-contact, fire-prone). The rest are your project queue.
Find one thing on Thingiverse, Printables, or MakerWorld that you'd actually print today. Note: what filament does it need? How long would it take?
Write down 3 things FDM is bad for that you've previously tried (or seen) and explain why each failed.

Prompt your AI

Use these three in order. Each builds on the one before.

1. Basics & terminology

In one paragraph, explain what FDM is uniquely good at.

2. Why it works (the mechanism)

Walk me through choosing between FDM, machining, and injection molding for a 50-unit batch of brackets.

3. Advanced — application & what's next

Design a personal 'print queue' for the next 30 days: 5 useful prints in 5 categories. Justify each.

References

FDM IS EXCELLENT FOR:
  - Functional prototypes (test fits and ergonomics before committing to a process)
  - Custom enclosures (your specific board, your specific cable routing)
  - Repair parts (replace a broken knob, hook, clip in the home)
  - Jigs and fixtures (alignment guides for woodworking, soldering, etc.)
  - Educational models (anatomical, mechanical, mathematical)
  - Brackets, mounts, holders for sub-50N loads
  - One-offs where injection molding would cost too much
  - Geometries where machining is hard (internal channels, complex curves)

FDM IS DECENT FOR:
  - Aesthetic / display objects (with finishing work)
  - Articulated toys / posable figures (print-in-place)
  - Cosplay / props (with painting)
  - Custom-fit grips, handles, ergonomic adapters
  - Low-volume production (10-100 parts) if part cost is fine

FDM IS BAD FOR:
  - High-strength structural parts (use machined Al, steel, or composites)
  - High-precision parts (≤0.1mm tolerance — machining is better)
  - Anything load-bearing in safety-critical applications (helmets, mounts for hot things)
  - Smooth, glassy surfaces (use SLA or post-processing heavily)
  - Watertight pressure vessels (multiple wall passes can fail; SLA is usually better)
  - Parts exposed to UV outdoors (only ASA tolerates this; PLA degrades fast)
  - Parts in contact with food (most filaments are NOT food-safe; layer lines harbor bacteria)
  - High-temp environments (>60°C for PLA; PETG goes to ~80°C; ABS ~95°C; PC ~110°C)

DECISION FRAMEWORK:
  Need 1-50 copies? FDM
  Need 50-500? FDM still wins on $, but SLS or low-volume injection might be faster
  Need 500+? Outsource to injection molding or SLS

  Need looks great untreated? SLA, not FDM
  Need to drop on concrete? Machined metal, not FDM
  Need parts under 10mm with fine detail? SLA, not FDM

What You Can Actually Make