{
  "schema": "cad-agent-references/1",
  "built": "2026-11-04T22:52:31-08:00",
  "revision": "3a4ec137a2a7cf52fa6072b5bc81b7e320d49701",
  "area": {
    "slug": "compliant-mechanisms",
    "title": "Compliant mechanisms",
    "domain": "mechanical",
    "scope": "One-piece parts that flex instead of sliding or screwing."
  },
  "fields": {
    "status": "`source`: read, with a dated `verified` note, and may be cited. `catalogued`: listed from a survey and not yet read; never cite one",
    "kind": "what the source is (research/references/vocab.yaml `kind`); a read source from before schema 2 has none",
    "evidence_class": "its rung on the evidence ladder, lowest first: snippet-only, read, verified-at-source, encoded, measured",
    "confidence": "#143: {level, estimate, sources}, derived from the evidence; `unknown` when the record has no evidence block",
    "licence": "{spdx, class, read, note}: `read: false` means the licence text was not read, only stated by the survey",
    "placed": "the docs/areas.yaml areas the record is listed in (`unplaced` when its areas match none)",
    "placed_note": "its row on the site, which [ref:<id>] in any page links to, is /references/<first placed area>#<id>",
    "vocab": "every coded value is explained in research/references/vocab.yaml"
  },
  "index": "https://cad-agent.valpatel.com/catalog/references/index.json",
  "count": 15,
  "coverage": [
    {
      "id": "ca-8-snap-fit-and-living-hinge-strain-limits",
      "number": "8",
      "topic": "Snap-fit and living-hinge strain limits",
      "status": "partly",
      "areas": [
        "snap-fits",
        "living-hinges"
      ],
      "where": "mechanical/compliant/snapfit.py:29-33, :328 check_cantilever, :77 MATERIALS; allowables.py:43; profile:1599 sls-living-hinge-hubs, :2119 mjf-snap-root-min-hubs",
      "defaults": "Allowable strain PC 4%, PC/ABS 2.5%, POM 6-8%, PA66 4-6%, GF PA 0.8-1.5%; printed = min(0.7 UTS/E, 0.5 elong); repeated x0.6; root R >= 0.381 mm; hinge 0.3-0.5 mm",
      "sources": "Covestro snap-fit guide Table 2/3, DuPont Module I Table 10.06, Bambu/Polymaker TDS",
      "gap": "Cantilever and annular/torsion done; no living-hinge strain/fatigue calculator (e=t*theta/2L only in research/compliant-mechanisms.md:20); Fictiv H/5-H/8 ratio absent; no PP/TPU hinge materials.",
      "draft_issue": {
        "title": "Add living-hinge strain and thickness calculator",
        "body": "Living hinges are only min-thickness rules. Add a calculator (strain e = t*theta/(2L), thickness H/5..H/8, land 1.5 mm, PP/PE/TPU limits, printed-layer direction) beside snapfit.py with the cited Protolabs/Fictiv/PlasticsToday figures.",
        "posted": false
      },
      "placed": [
        "compliant-mechanisms"
      ]
    }
  ],
  "records": [
    {"id":"protolabs-living-hinge","title":"Living Hinge Basics for Injection Molding","authors":[],"org":"Protolabs","year":null,"url":"https://www.protolabs.com/resources/blog/living-hinge-basics-for-injection-molding/","access":"free","terms":"cited and summarised, never copied","areas":["compliant-mechanisms","moulding","moulded-part-design"],"used_for":["research/compliant-mechanisms.md"],"verified":"2026-10-31: opened the page. Read the hinge guideline (0.012 in thick, about 0.060 in spacing, 0.008 in reduction on the folding side, 0.030 in radius on the tension side). Byline is \"Protolabs\".","status":"source","kind":"guide","category":"manufacturing-guides","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"processes":["injection"],"process_groups":["mould"],"evidence":{"numbers":"some","tested":"no","authority":"primary"},"confidence":{"level":"low","estimate":0.4,"sources":1},"summary":"Living hinges break the uniform-wall rule; flow restriction causes a pressure drop beyond the hinge, so gate placement matters.","imported":"4b08c4af8cfa6006","evidence_class":"read","placed":["compliant-mechanisms","mould-design"],"source_file":"research/references.yaml","extended_in":"research/references/guides-mould.yaml"},
    {"id":"qiu-2003-bistable-thesis","title":"An Electrothermally-Actuated Bistable MEMS Relay for Power Applications","authors":["Jin Qiu"],"org":"Massachusetts Institute of Technology (PhD thesis; supervisor Alexander H. Slocum)","year":2003,"url":"https://pergatory.mit.edu/research/jqiu/thesisscreen.pdf","access":"free","terms":"cited and summarised; never copied","areas":["compliant-mechanisms"],"used_for":["research/compliant-mechanisms.md"],"verified":"2026-10-31: opened the PDF; read the title page (author, degree, June 2003, supervisor). The equations were read by research/compliant-mechanisms.md on the same day.","status":"source","evidence_class":"read","confidence":{"level":"unknown","estimate":null,"sources":0},"placed":["compliant-mechanisms"],"source_file":"research/references.yaml"},
    {"id":"klahn-2016-am-snapfit","title":"Design Guidelines for Additive Manufactured Snap-Fit Joints","authors":["Christoph Klahn","Daniel Singer","Mirko Meboldt"],"org":"Procedia CIRP 50 (KITopen repository)","year":2016,"url":"https://publikationen.bibliothek.kit.edu/1000142464","access":"free","terms":"cited and summarised; never copied","areas":["snap-fits","fdm"],"used_for":["docs/compliant.md","research/compliant-mechanisms.md","research/fea-and-process-tools.md","research/process-profiles.md"],"verified":"2026-10-31: opened the repository record. Read the title, authors and abstract. The volume and year are as recorded in research/compliant-mechanisms.md, which read the paper on the same day. For research/process-profiles.yaml: read by research/compliant-mechanisms.md on this date (a cantilever built along Z is poor; keep the bending in the layer plane).","status":"source","evidence_class":"read","confidence":{"level":"unknown","estimate":null,"sources":0},"placed":["compliant-mechanisms","3d-printing"],"source_file":"research/references.yaml"},
    {"id":"dupont-design-module-1","title":"General Design Principles for DuPont Engineering Polymers (Design Guide - Module I)","authors":[],"org":"E. I. du Pont de Nemours and Company","year":2000,"url":"https://www.emcoplastics.com/assets/pdf/acetal/General%20Design%20Principles%20for%20Engineering%20Polymers.pdf","access":"free","terms":"cited and summarised, never copied","areas":["snap-fits","moulding","materials","ribs-and-bosses","injection-moulding"],"used_for":["src/cadagent/mechanical/compliant/snapfit.py","src/cadagent/mechanical/compliant/allowables.py","docs/compliant.md","research/compliant-mechanisms.md","research/fea-and-process-tools.md","research/process-profiles.md","research/process-profiles.yaml"],"verified":"2026-10-31: opened the 136-page PDF (a distributor's copy). Read the title page, the copyright line (2000) and Table 10.06, \"Suggested Allowable Strains (%) for Lug Type Snap-fits\". For research/process-profiles.yaml: opened the 136-page PDF (a distributor's copy, copyright 2000); read the text of chapter 3 (fillets and radii, Table 3.01 draft, bosses, blind holes, undercuts, moulded-in inserts) and the rib text in chapter 4. Figures 3.10 (boss proportions) and 4.07 (rib proportions) have no text layer, so on review PDF pages 12 and 30 were rendered and their values read from the figures.","status":"source","evidence_class":"read","confidence":{"level":"unknown","estimate":null,"sources":0},"placed":["compliant-mechanisms","housings-and-enclosures"],"source_file":"research/references.yaml"},
    {"id":"hubs-snapfit-3dp","title":"How do you design snap-fit joints for 3D printing?","authors":[],"org":"Protolabs Network (formerly Hubs)","year":null,"url":"https://www.hubs.com/knowledge-base/how-design-snap-fit-joints-3d-printing/","access":"free","terms":"cited and summarised, never copied","areas":["snap-fits","fdm","sls","mjf","sla"],"used_for":["research/compliant-mechanisms.md","research/fea-and-process-tools.md","research/process-profiles.md","research/process-profiles.yaml"],"verified":"2026-10-31: opened the page. Read the clearances (0.5 mm FDM; 0.3 mm SLS, SLA, MJF, material jetting) and the 1 mm minimum cantilever base and overhang depth. No byline. For research/process-profiles.yaml: opened the page; read the nominal clearances (FDM 0.5 mm; SLA, SLS, MJF 0.3 mm), the MJF cantilever base of at least 1 mm and the 5 mm minimum clip width.","status":"source","evidence_class":"read","confidence":{"level":"unknown","estimate":null,"sources":0},"placed":["compliant-mechanisms","3d-printing"],"source_file":"research/references.yaml"},
    {"id":"basf-snapfit-prospector","title":"Improving Snapfit Design (Part 3)","authors":["Chul Lee"],"org":"BASF, published on UL Prospector Knowledge Center","year":null,"url":"https://ulprospector.ul.com/1248/snapfit-3/","access":"free","terms":"cited and summarised, never copied","areas":["snap-fits","moulding"],"used_for":["research/compliant-mechanisms.md"],"verified":"2026-10-31: opened the page. Read the byline (Chul Lee, Applications Technology Leader, BASF) and the pointer to Figures IV-4 and IV-5 (worked examples for an Ultradur PBT and an Ultraform POM grade). The BASF Snap-Fit Design Manual tables themselves were not read.","status":"source","evidence_class":"read","confidence":{"level":"unknown","estimate":null,"sources":0},"placed":["compliant-mechanisms"],"source_file":"research/references.yaml"},
    {"id":"covestro-snapfit","title":"Snap-Fit Joints for Plastics - A Design Guide","authors":[],"org":"Covestro LLC (formerly Bayer MaterialScience LLC)","year":null,"url":"https://cdn.sparkfun.com/assets/home_page_posts/1/4/1/0/Plastic_Snap_fit_design.pdf","access":"free","terms":"cited and summarised, never copied; the PDF is not redistributed","areas":["snap-fits","moulding","materials"],"aliases":["covestro","covestro-friction"],"used_for":["src/cadagent/mechanical/compliant/snapfit.py","tests/mechanical/test_snapfit.py","docs/compliant.md","research/compliant-mechanisms.md","src/cadagent/formulas/_registry.py","src/cadagent/formulas/beams.py","src/cadagent/formulas/torsion.py","src/cadagent/mechanical/printed_joints.py"],"verified":"2026-10-31: opened the Bayer-branded 26-page copy at this URL (pdftotext). Read the contents page, the root-radius rule (not less than 0.015 in), Table 2 heading and the 60 % frequent-use note, the 70 % of yield strain rule for amorphous resins, and Examples I and II. No year or authors are printed. The Covestro-branded edition cited in snapfit.py was not opened in this pass.","status":"source","evidence_class":"read","confidence":{"level":"unknown","estimate":null,"sources":0},"placed":["compliant-mechanisms"],"source_file":"research/references.yaml"},
    {"id":"basf-snap-fit-design-guide-scribd-copy","kind":"guide","category":"manufacturing-guides","title":"BASF Snap-Fit Design Guide (Scribd copy)","authors":[],"org":"BASF","year":null,"url":"https://www.scribd.com/document/781414276/BASF-Snap-Fit-Design-Guide","access":"free","terms":"cited and summarised, never copied","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"areas":["snap-fits"],"processes":["snap-fit"],"process_groups":["mould"],"evidence":{"class":"snippet-only","numbers":"claimed","tested":"no","authority":"primary"},"confidence":{"level":"low","estimate":0.4,"sources":1},"summary":"BASF manual: classical beam theory, improved cantilever with magnification factor, U- and L-shaped snaps; allowable-strain tables for eight materials. Note: Scribd upload, not BASF-hosted; Ultramid values not shown.","used_for":[],"imported":"8369af034f02466c","status":"catalogued","evidence_class":"snippet-only","placed":["compliant-mechanisms"],"source_file":"research/references/guides-mould.yaml"},
    {"id":"basf-snapfit-online-tool-and-blog","kind":"guide","category":"manufacturing-guides","title":"BASF Snapfit online tool and blog","authors":[],"org":"BASF","year":null,"url":"https://ultrasimweb.basf.com/snapfit/blog/introduction/","access":"free","terms":"cited and summarised, never copied","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"areas":["snap-fits"],"processes":["snap-fit"],"process_groups":["mould"],"evidence":{"class":"snippet-only","numbers":"some","tested":"no","authority":"primary"},"confidence":{"level":"low","estimate":0.4,"sources":1},"summary":"BASF Snapfit app compares operating strain with allowable strain and returns a suitability verdict; worked examples use PBT and POM. Note: Only an intro blog title seen; details from related result summaries.","used_for":[],"imported":"bc8e8743185f2482","status":"catalogued","evidence_class":"snippet-only","placed":["compliant-mechanisms"],"source_file":"research/references/guides-mould.yaml"},
    {"id":"plasticstoday-by-design-polypropylene-part-design-part-2","kind":"guide","category":"manufacturing-guides","title":"By Design: Polypropylene part design, Part 2 - Living hinges","authors":[],"org":"PlasticsToday","year":null,"url":"https://www.plasticstoday.com/materials/design-polypropylene-part-design-part-2-living-hinges","access":"free","terms":"cited and summarised, never copied","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"areas":["moulded-part-design","snap-fits"],"processes":["injection","snap-fit"],"process_groups":["mould"],"evidence":{"class":"snippet-only","numbers":"claimed","tested":"no","authority":"reference"},"confidence":{"level":"low","estimate":0.4,"sources":1},"claims":[{"text":"Hinge land about 0.060 in (1.5 mm), thickness 0.008-0.015 in (0.2-0.4 mm)","status":"corroborated","evidence":"MIT hinge guide: 0.008-0.010 in, max about 0.015 in; Protolabs 0.012 in with 0.060 in spacing. Eng. Machine Design says 0.01-0.02 in."}],"summary":"PP living hinge land length and web thickness values. Note: Attribution of the quoted rule to this page is likely but not certain.","used_for":[],"imported":"38fad6d758593bcb","status":"catalogued","evidence_class":"snippet-only","placed":["mould-design","compliant-mechanisms"],"source_file":"research/references/guides-mould.yaml"},
    {"id":"fictiv-design-guide-for-living-hinges-fictiv","kind":"guide","category":"manufacturing-guides","title":"Design Guide for Living Hinges (Fictiv)","authors":[],"org":"Fictiv","year":null,"url":"https://www.fictiv.com/?p=1242","access":"free","terms":"cited and summarised, never copied","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"areas":["moulded-part-design","snap-fits"],"processes":["injection","snap-fit"],"process_groups":["mould"],"evidence":{"class":"snippet-only","numbers":"claimed","tested":"no","authority":"primary"},"confidence":{"level":"low","estimate":0.4,"sources":1},"claims":[{"text":"Hinge thickness T = H/5 to H/8, H being adjoining wall thickness","status":"unconfirmed","evidence":"Search for H/5 to H/8 found no source stating that ratio; others give absolute 0.2-0.5 mm (0.007-0.015 in)."}],"summary":"Living hinge sizing relative to adjoining wall; may need molding in open position. Note: Page title was only a read-time label; attribution from URL.","used_for":[],"imported":"71df523890da0074","status":"catalogued","evidence_class":"snippet-only","placed":["mould-design","compliant-mechanisms"],"source_file":"research/references/guides-mould.yaml"},
    {"id":"fictiv-how-to-design-snap-fit-components","kind":"guide","category":"manufacturing-guides","title":"Fictiv: How to Design Snap-Fit Components","authors":[],"org":"Fictiv","year":null,"url":"https://www.fictiv.com/articles/how-to-design-snap-fit-components","access":"free","terms":"cited and summarised, never copied","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"areas":["snap-fits","moulded-part-design"],"processes":["snap-fit","injection"],"process_groups":["mould"],"evidence":{"class":"snippet-only","numbers":"unknown","tested":"no","authority":"primary"},"confidence":{"level":"low","estimate":0.4,"sources":1},"summary":"12-minute Fictiv article on snap-fit component design; only title and read time shown. Note: Title only; content unseen.","used_for":[],"imported":"9ac41c6122e7d4d4","status":"catalogued","evidence_class":"snippet-only","placed":["compliant-mechanisms","mould-design"],"source_file":"research/references/guides-mould.yaml"},
    {"id":"machine-design-fundamentals-of-annular-snap-fit-joints","kind":"guide","category":"manufacturing-guides","title":"Fundamentals of Annular Snap-Fit Joints (Machine Design)","authors":[],"org":"Machine Design","year":null,"url":"https://www.machinedesign.com/fastening-joining/article/21834620/fundamentals-of-annular-snap-fit-joints","access":"free","terms":"cited and summarised, never copied","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"areas":["snap-fits"],"processes":["snap-fit"],"process_groups":["mould"],"evidence":{"class":"snippet-only","numbers":"claimed","tested":"no","authority":"reference"},"confidence":{"level":"low","estimate":0.4,"sources":1},"claims":[{"text":"Permissible strain about 50% of strain at break for reinforced plastics; up to 70% of yield for PC/ABS","status":"unconfirmed","evidence":"Machine Design is the only source of 50% strain-at-break; Skill-Lync gives a different quantity (1-2% absolute for reinforced). Not independently confirmed."}],"summary":"Annular snap-fit first-order calculation; permissible strain tied to proportional limit; amorphous resins tolerate higher share of yield for brief snaps. Note: Figures from search summary, not seen verbatim.","used_for":[],"imported":"5df60a7f3037d795","status":"catalogued","evidence_class":"snippet-only","placed":["compliant-mechanisms"],"source_file":"research/references/guides-mould.yaml"},
    {"id":"plasticstoday-injection-molding-design-fundamentals-snap","kind":"guide","category":"manufacturing-guides","title":"Injection molding design fundamentals: Snap-fits for plastic parts (PlasticsToday)","authors":[],"org":"PlasticsToday","year":null,"url":"https://www.plasticstoday.com/injection-molding/injection-molding-design-fundamentals-snap-fits-for-plastic-parts","access":"free","terms":"cited and summarised, never copied","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"areas":["snap-fits","moulded-part-design"],"processes":["snap-fit","injection"],"process_groups":["mould"],"evidence":{"class":"snippet-only","numbers":"some","tested":"no","authority":"reference"},"confidence":{"level":"low","estimate":0.4,"sources":1},"summary":"Snap-fit fundamentals: strain must stay below the linear-range allowable at working temperature; annular joints usually need FEA. Note: Temperature dependence noted; no percentage given.","used_for":[],"imported":"56deb1bc4870488a","status":"catalogued","evidence_class":"snippet-only","placed":["compliant-mechanisms","mould-design"],"source_file":"research/references/guides-mould.yaml"},
    {"id":"bayer-materialscience-snap-fit-joints-for-plastics-a-design","kind":"guide","category":"manufacturing-guides","title":"Snap-fit joints for plastics: A design guide (Bayer MaterialScience; Covestro successor), mirror","authors":[],"org":"Bayer MaterialScience (now Covestro), MIT-hosted copy","year":null,"url":"https://fab.cba.mit.edu/classes/S62.12/people/vernelle.noel/Plastic_Snap_fit_design.pdf","access":"free","terms":"cited and summarised, never copied","licence":{"spdx":null,"class":"proprietary","read":false,"note":"A publisher's page; its terms were not read. Cited, never copied."},"reuse":{"text":"cite-only","geometry":"none"},"areas":["snap-fits"],"processes":["snap-fit"],"process_groups":["mould"],"evidence":{"class":"snippet-only","numbers":"claimed","tested":"no","authority":"primary"},"confidence":{"level":"low","estimate":0.4,"sources":1},"claims":[{"text":"Cantilever strain e = 3Yh / 2L^2; constant-section arm shows 46% higher strain than optimal taper","status":"corroborated","evidence":"Skill-Lync snap-fit blog gives the same e=3Yh/2L^2 formula. The 46% taper figure was not found elsewhere. Formula only."}],"summary":"Classic cantilever, torsion and annular snap-fit guide; beam strain formula and optimal tapered arm comparison. Note: Third-party mirror; authorship per Wikipedia reference, not verified.","used_for":[],"imported":"7e539e08efd41e44","status":"catalogued","evidence_class":"snippet-only","placed":["compliant-mechanisms"],"source_file":"research/references/guides-mould.yaml"}
  ]
}