Does weighting parts by mass change which shop process, and which machine, matters?

What it found

Follow-up to simdesign-processcover: coverage of a sampled bracket family by FDM, CNC, laser and casting, with each part weighted by arm volume (a same-material mass proxy) instead of counted equally. With a tip load, FDM alone covers 0.30 of parts by count and 0.58 by mass, casting 0.22 and 0.46, laser 0.18 either way, and the laser-versus-CNC order flips. At budgets 600–800 on one seed, exhaustive search picks the laser cutter by count but the casting setup by mass; for the large-part family at 800 it picks the CNC router by count and casting by mass. Stylised: assumed rules and prices, one density, single-seed machine choice. Simulated only.

A figure from its own output

Paper, code and results

• README and method
• Experiments and results
• Code
• Tests

More in Simulation-first design

• Do the mass-weighting machine-choice flips of simdesign-coverweight survive across seeds?Do the mass-weighting machine-choice flips of simdesign-coverweight survive across seeds? Over 20 seeds, log flips from the laser cutter (count) to the casting setup (mass) in 20/20 at budgets 600–800, large only at 800, small never; the 1100–1400 flips are near-ties (≤0.26 points). Stylised, assumed rules and prices, simulated only.
• How wide are the budget bands where mass weighting changes the machine choice when prices are uncertain?How wide are the budget bands where mass weighting changes the machine choice when prices are uncertain? With ±20% independent price noise the log flip band widens from budgets 600–800 to 500–1000 but softens at its edges (about one half), and large's single nominal flip at 800 shows up in only 44% of price draws. Stylised, assumed rules and prices, simulated only.
• Which share of a bracket family can each shop process make, and which machine should a shop add next?Share of a sampled bracket family each shop process can make under the simdesign-dfm rules: geometry alone adds nothing beyond FDM (negative), with a tip-load requirement the processes separate (FDM alone 30%, +casting +laser 41%) and the best next machine depends on budget and part size, where greedy sometimes loses 1–2 points to exhaustive search (stylised, assumed rules).
• Does a mesh-aware stress margin change what manufacturing rules cost a sized bracket?Re-runs simdesign-dfm with a stress knock-down and a finer search mesh, checking designs at h = 0.7 mm: the price ordering (casting ~1.4, CNC ~1.23, FDM 1.0) survives the mesh, the laser-cutting price does not (1.01–1.22, noisy), and a 1.3 margin leaves designs at 0.88–1.02 of the limit (stylised, assumed rule values).
• Does a patch-averaged stress converge under mesh refinement where the peak element stress does not?Compares peak and patch-averaged von Mises stress under mesh refinement on the L-bracket: the peak rises 18–41% from h = 2.5 to 0.55 mm while a 3 mm patch average moves 1–6%, but it reads only 0.45–0.69 of the peak so needs its own limit (stylised, assumed values).
• Does a patch-averaged stress change what manufacturing rules cost a sized bracket?Repeats the process-rule bracket search with a 3 mm patch-averaged stress instead of the peak: the ordering of mass prices (casting > CNC > laser ≈ FDM) holds, the laser price spread across seeds shrinks from 0.16 to under 0.005, and designs overshoot their limit by 2–12% on a fine mesh against 19–34% for the peak (stylised, assumed values, uncalibrated limit).

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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.