Prototype Loop

Run prototypes as tight, evidence-based cycles: define a clear requirement, print the smallest test that answers one question, measure with a pass/fail threshold, then change one variable and repeat. This cuts wasted long prints and makes improvements repeatable instead of guesswork.

TL;DR

For every iteration, print the smallest “test piece” that answers one question (fit, strength, surface, etc.), measure it against a pass/fail number, then change only one variable for the next print.

Prototype LoopTopic-specific diagram for the concept, checks, and tradeoffs in this lesson.PrintMeasureChange one thingRepeat
A quick visual map of the main decisions behind the prototype loop.

What the Prototype Loop Is (and why it works)

A prototype loop is a short, purposeful cycle: make a change, print a minimal test, evaluate it with a specific metric, then revise. The goal is learning fast and keeping cause-and-effect clear, not getting a “perfect” print on every try. Small tests reduce time, filament, and the temptation to chase random slicer tweaks.

Prototype Loop Steps

  1. Define the requirement: what the part must do, where it will be used, and what counts as failure.
  2. Choose one question for this round (example: “Does this snap-fit survive 20 uses?” or “What clearance slides smoothly?”).
  3. Design the smallest test that answers that question (coupon, partial print, one critical feature).
  4. Print using known-good baseline settings so the test isolates the thing you changed.
  5. Measure against a pass/fail threshold (a number, not a vibe).
  6. Change one variable, document it, and repeat until you hit the requirement or learn the limit.

Fast Tests That Save Long Prints

  • Fit check: print only the mating features (a corner, a clip, a hole boss), not the whole body.
  • Overhang/bridging: isolate just the risky overhang section at the same angle as the final part.
  • Strength: print a short beam or a sample with the same wall count and infill scheme as the real part.
  • Surface/visibility: print a small patch oriented exactly like the final show surface.
  • Assembly: print one real component plus a simplified dummy of the mating part (enough to check interference and tool access).

What to Measure (Examples)

  • Dimensions: measure critical features with calipers (hole/boss diameters, slot widths, snap thickness), not just overall size.
  • Clearance: record the minimum gap that slides without force and without rattle, and note material pair if relevant.
  • Warping/flatness: measure edge lift or rocking on a flat reference surface; note bed adhesion method used.
  • Strength: record load at first crack or permanent bend using the same test setup each time.
  • Print reliability: did first layer succeed, were there jams, did the print finish unattended, and did supports remove cleanly?

Iteration Notes to Record (so results are repeatable)

  • Model version/filename and exactly what feature changed
  • Material type and any moisture notes (fresh/dry vs. suspect filament)
  • Nozzle size, layer height, wall count, infill, temperatures, cooling
  • Orientation and whether supports/brim/raft were used
  • What you measured and the numeric result (include units)
  • Decision: keep, revert, or next test and why