{"$schema":"nativecad-dfm-pack/1","id":"load-driven-detailing","title":"Load-driven detailing: rotating bodies, castings and fabricated frames","sector":"load-driven-detailing","version":"2026-10-23","summary":"Cited rules for taking material out of gear/pulley/sprocket bodies, castings and fabricated frames the way engineered parts are: rim backup ratio, web, hub, lightening holes, cast wall/draft/rib/boss, rail taper and flanged holes.","aliases":["load-driven detailing","load-driven design","lightening holes","material removal","gear web","gear rim","backup ratio","cast ribs","cast wall thickness","ladder frame","chassis rail","pulley body","flanged lightening hole"],"crossSector":false,"size":"full","sources":[{"id":"agma-2001-d04","title":"ANSI/AGMA 2001-D04 Fundamental rating factors and calculation methods for involute spur and helical gear teeth (rim thickness factor K_B)","accessed":"2026-10-23"},{"id":"iso-6336-3","title":"ISO 6336-3 Calculation of load capacity of spur and helical gears, Part 3: tooth bending strength (rim factor Y_B)","accessed":"2026-10-23"},{"id":"shigley-ch14","title":"Budynas & Nisbett, Shigleys Mechanical Engineering Design, ch. 14 (AGMA bending, K_B, backup ratio m_B)","url":"https://highered.mheducation.com/sites/dl/free/9814595284/1054140/Budynas_Chapter_14.pdf","accessed":"2026-10-23"},{"id":"iastate-me325","title":"Iowa State ME 325 handout: bending stress in gears (K_B piecewise form)","url":"https://engineering.iastate.edu/~gkstarns/me325/bending_stress_gears.pdf","accessed":"2026-10-23"},{"id":"thin-rim-2024","title":"Int. J. Automotive Technology 2024: thin-rim gear bending; standard K_B not applicable below backup ratio 0.5","url":"https://link.springer.com/article/10.1007/s12239-024-00020-y","accessed":"2026-10-23"},{"id":"gearsolutions-rim","title":"Gear Solutions: rim thickness factor origin (Drago, 1982); AGMA 2001 valid for external gears only","url":"https://gearsolutions.com/?p=25857","accessed":"2026-10-23"},{"id":"iso-53","title":"ISO 53 Cylindrical gears for general and heavy engineering: standard basic rack tooth profile (ha = 1.0 m, hf = 1.25 m)","accessed":"2026-10-23"},{"id":"machinerys-handbook","title":"Machinerys Handbook (Industrial Press): gear, flywheel and key/keyseat sections","accessed":"2026-10-23"},{"id":"dudley-gear","title":"Dudley, Handbook of Practical Gear Design (CRC Press): gear blank, web and hub proportions","accessed":"2026-10-23"},{"id":"schaeffler-needle","title":"Schaeffler / INA needle roller and cage assemblies catalogue (shaft/bore raceway hardness 58-64 HRC)","accessed":"2026-10-23"},{"id":"bralla-dfm","title":"Bralla, Design for Manufacturability Handbook, 2nd ed. (McGraw-Hill), casting chapters","accessed":"2026-10-23"},{"id":"nadca-pss","title":"NADCA Product Specification Standards for Die Castings (wall, draft, rib, boss guidance)","accessed":"2026-10-23"},{"id":"asm-hbk-15","title":"ASM Handbook Vol. 15 Casting (design of castings, section modulus, gating)","accessed":"2026-10-23"},{"id":"campbell-casting","title":"Campbell, Complete Casting Handbook (Chvorinov solidification rule, hot spots)","accessed":"2026-10-23"},{"id":"engineersedge-sand","title":"Engineers Edge: design for sand casting (minimum wall, draft, section change)","url":"https://www.engineersedge.com/sand_cast.htm","accessed":"2026-10-23"},{"id":"giessereilexikon-design","title":"Giessereilexikon: favorable casting design (fillet radius a third to a quarter of wall; hot spots at re-entrant angles)","url":"https://www.giessereilexikon.com/en/foundry-lexicon/Encyclopedia/show/favorable-casting-design-4660/","accessed":"2026-10-23"},{"id":"xometry-diecast","title":"Xometry die casting design guide (rib thickness, draft, boss coring)","url":"https://xometry.com/resources/design-guides/die-casting-design-guide/","accessed":"2026-10-23"},{"id":"iso-8062-3","title":"ISO 8062-3 Geometrical product specifications: dimensional and geometrical tolerances for moulded parts and required machining allowance (RMA)","accessed":"2026-10-23"},{"id":"asm-hbk-2","title":"ASM Handbook Vol. 2 Properties and selection: nonferrous alloys (A356.0-T6, A380.0)","accessed":"2026-10-23"},{"id":"astm-a48","title":"ASTM A48/A48M Gray iron castings (Class 30: 30 ksi min tensile)","accessed":"2026-10-23"},{"id":"astm-a536","title":"ASTM A536 Ductile iron castings (65-45-12)","accessed":"2026-10-23"},{"id":"en-10025-2","title":"EN 10025-2 Hot rolled structural steel, non-alloy grades (S355 yield 355 MPa to 16 mm)","accessed":"2026-10-23"},{"id":"astm-e155","title":"ASTM E155 Reference radiographs for inspection of aluminum and magnesium castings","accessed":"2026-10-23"},{"id":"niu-airframe","title":"Niu, Airframe Stress Analysis and Sizing: lightening holes in webs, flanged holes","accessed":"2026-10-23"},{"id":"peterson-kt","title":"Pilkey, Petersons Stress Concentration Factors (hole in plate: Kt = 3.0 infinite plate, uniaxial tension)","accessed":"2026-10-23"},{"id":"roark","title":"Young & Budynas, Roarks Formulas for Stress and Strain: beams, uniform-strength sections, shear","accessed":"2026-10-23"},{"id":"blodgett-weldments","title":"Blodgett, Design of Weldments (Lincoln Electric): distortion, HAZ, joint detailing","accessed":"2026-10-23"},{"id":"aws-d1-1","title":"AWS D1.1 Structural Welding Code - Steel (weld detailing, gusset and fatigue categories)","accessed":"2026-10-23"}],"entries":[{"id":"ldd-rim-backup-ratio","kind":"rule","tier":1,"title":"Rim backup ratio m_B = t_R / h_t","summary":"Backup ratio m_B = rim thickness under the tooth root t_R divided by whole tooth depth h_t (2.25 m for the ISO 53 rack). Compute it before drilling anything in a gear body: every rim cut is checked against it.","applies":["gear","rim"],"basis":"SRC: AGMA 2001 / Shigley ch.14 define m_B = t_R/h_t; ISO 53 gives h_t = 1.0 m + 1.25 m.","sources":["agma-2001-d04","shigley-ch14","iso-53"],"tags":["backup-ratio","rim","gear"],"value":{"value":"m_B = t_R / h_t, h_t = 2.25 m","unit":"ratio"}},{"id":"ldd-rim-factor-kb","kind":"rule","tier":1,"title":"Rim thickness factor K_B (AGMA 2001) for thin rims","summary":"K_B = 1.0 for m_B >= 1.2; K_B = 1.6 ln(2.242 / m_B) for m_B < 1.2 (1.29 at m_B 1.0, 2.40 at 0.5). Multiplies tooth bending stress. Continuous at 1.2. Covered range 0.5 <= m_B; external gears.","applies":["gear","rim","lightened gear"],"basis":"SRC: textbook piecewise form (Shigley 14); ISO 6336-3 carries an equivalent Y_B. Check constants against the purchased standard.","sources":["agma-2001-d04","iso-6336-3","shigley-ch14","iastate-me325"],"tags":["kb","rim-factor","bending"],"value":{"table":[{"m_B":1.2,"K_B":1},{"m_B":1,"K_B":1.29},{"m_B":0.8,"K_B":1.65},{"m_B":0.6,"K_B":2.11},{"m_B":0.5,"K_B":2.4}]}},{"id":"ldd-rim-min-thickness","kind":"dimension","tier":1,"title":"Rim thickness for K_B = 1.0","summary":"Keep t_R >= 1.2 h_t = 2.7 m under the root so K_B = 1.0 (m=2: 5.4 mm; m=3: 8.1 mm). Thinner is allowed only down to m_B 0.5 with the K_B penalty on the bending check.","applies":["gear","rim"],"basis":"SRC: 1.2 x 2.25 m from the m_B >= 1.2 knee of K_B.","sources":["agma-2001-d04","iso-53"],"tags":["rim","module"],"value":{"min":2.7,"typical":2.7,"unit":"ratio"}},{"id":"ldd-rim-below-half","kind":"rule","tier":2,"title":"Backup ratio below 0.5 is outside the standard","summary":"Below m_B 0.5 the AGMA/ISO rim factor is not applicable and is conservative against FEA; do not lighten there on the formula alone. Run a CalculiX tooth-root solve (cad_fea_run) and cap the cut at the FEA result.","applies":["gear","thin rim"],"basis":"SRC: 2024 thin-rim study reports the factor unusable below 0.5; AGMA/ISO fit range is 0.5 to 1.2.","sources":["thin-rim-2024","gearsolutions-rim"],"tags":["fea","thin-rim"],"value":{"min":0.5,"unit":"ratio"}},{"id":"ldd-rim-internal-gear-excluded","kind":"note","tier":3,"title":"K_B covers external gears only","summary":"AGMA 2001 K_B is stated for external gears; an internal (ring) gear with a thin rim needs its own calculation or FEA, not the external curve.","applies":["ring gear","internal gear"],"basis":"SRC: Gear Solutions note on AGMA 2001 scope.","sources":["gearsolutions-rim"],"tags":["internal-gear"]},{"id":"ldd-web-thickness","kind":"rule","tier":1,"title":"Web thickness against face width","summary":"Web thickness t_W = 0.25 to 0.40 of face width F, and not less than half the rim thickness t_R. A thin web is limited by stiffness and tooth alignment, not shear, so verify deflection with FEA before going thinner.","applies":["gear","web"],"basis":"EST: handbook proportion (Dudley) for webbed gear blanks; strength is rarely the limit, rim deflection is. Verify by cad_fea_run.","sources":["dudley-gear","machinerys-handbook"],"tags":["web","face-width"],"value":{"min":0.25,"max":0.4,"typical":0.3,"unit":"ratio"}},{"id":"ldd-web-position","kind":"rule","tier":2,"title":"Centre the web for spur and helical blanks","summary":"Put the web on the face-width centreline (offset <= 0.1 F) on spur gears; offset webs tilt the rim under load and spoil lead alignment. Helical and bevel blanks may offset to clear the mating gear.","applies":["gear","web"],"basis":"EST: standard blank practice; alignment effect is the reason (Dudley).","sources":["dudley-gear"],"tags":["web","alignment"],"value":{"max":0.1,"unit":"ratio"}},{"id":"ldd-hub-od","kind":"dimension","tier":1,"title":"Hub OD against bore","summary":"Hub OD = 1.6 to 2.0 x bore for a keyed steel hub (1.8 to 2.2 x for cast iron or aluminium). The wall left under the keyseat must still carry the key bearing load.","applies":["gear","timing pulley","chain sprocket","idler","flywheel"],"basis":"EST: common handbook proportion; keyseat depth from Machinerys Handbook key tables.","sources":["machinerys-handbook","dudley-gear"],"tags":["hub","bore"],"value":{"min":1.6,"max":2,"typical":1.8,"unit":"ratio"}},{"id":"ldd-hub-length","kind":"dimension","tier":2,"title":"Hub length against bore","summary":"Hub length = 1.0 to 1.5 x bore, and at least the key length; a hub shorter than 1.0 x bore rocks on the shaft and loads the key at its ends.","applies":["gear","timing pulley","chain sprocket","idler","flywheel"],"basis":"EST: handbook proportion (key length >= bore diameter for a hub that must not rock).","sources":["machinerys-handbook"],"tags":["hub","key"],"value":{"min":1,"max":1.5,"typical":1.25,"unit":"ratio"}},{"id":"ldd-web-fillet","kind":"rule","tier":2,"title":"Web-to-hub and web-to-rim fillets","summary":"Fillet the web into the hub and rim with R = 0.5 to 1.0 x web thickness; a sharp internal corner at the web root is the usual fatigue origin in a lightened body.","applies":["gear","web"],"basis":"EST: stress-concentration practice (Peterson Kt falls steeply by r/t = 0.5).","sources":["peterson-kt","dudley-gear"],"tags":["fillet","fatigue"],"value":{"min":0.5,"max":1,"unit":"ratio"}},{"id":"ldd-lighten-ligaments","kind":"rule","tier":1,"title":"Lightening-hole ligaments to rim, hub and each other","summary":"Leave a ligament >= max(t_W, 4 mm) from each hole to the rim inner face and to the hub OD, and >= max(1.5 t_W, 6 mm) between neighbouring holes. This keeps the rim at its t_R and the hub wall intact.","applies":["gear","pulley","flywheel"],"basis":"EST: ligament >= web thickness so no hole edge is thinner than the web it sits in.","sources":["dudley-gear","niu-airframe"],"tags":["ligament","lightening-hole"],"value":{"min":1,"unit":"ratio"}},{"id":"ldd-lighten-hole-count","kind":"rule","tier":2,"title":"Lightening-hole count and diameter","summary":"Use 4 to 8 equal holes on a web whose radial span (rim ID to hub OD) is >= 3 t_W; hole dia = radial span - 2 x ligament. Pick the count so the hole-to-hole ligament stays >= 1.5 t_W at the hole centre radius.","applies":["gear","pulley","idler"],"basis":"EST: derived from the ligament rule; counts of 4 to 8 are customary for webbed gears 100 to 300 mm.","sources":["dudley-gear"],"tags":["lightening-hole","count"],"value":{"min":4,"max":8,"unit":"count"}},{"id":"ldd-when-solid","kind":"rule","tier":1,"title":"When a rotating body stays solid","summary":"Keep the blank solid when (root radius - hub OD/2) < t_R + 2 x ligament + 6 mm: no hole fits that respects both ligaments. For m=2 that is roughly any gear under about 40 teeth on a 25 mm bore.","applies":["small gear","pinion"],"basis":"EST: geometric consequence of the ligament and rim rules; the 6 mm minimum drillable hole is the floor.","sources":["dudley-gear","agma-2001-d04"],"tags":["solid","pinion"],"value":{"min":6,"unit":"mm"}},{"id":"ldd-web-vs-spoke","kind":"rule","tier":2,"title":"Web or spokes by size and process","summary":"Machined or forged gears use a web with holes up to about 500 mm pitch diameter; cast blanks above that take 4 to 6 spokes of elliptical section, and welded gears use a plate web. Spokes cost a pattern, a web does not.","applies":["large gear","cast pulley","flywheel"],"basis":"EST: handbook practice for large gear and pulley blanks (Machinerys Handbook, Dudley).","sources":["machinerys-handbook","dudley-gear"],"tags":["spoke","web"],"value":{"value":500,"unit":"mm"}},{"id":"ldd-free-gear-limits","kind":"rule","tier":2,"title":"Free gears on needle cages and synchro cones","summary":"A free gear with dog ring, synchro cone and needle-cage bore stays near solid: no holes within 1 m + dog height of the dog teeth or under the cone, bore raceway hardened 58 to 64 HRC. Lighten only the plain web between them.","applies":["free gear","synchro","gearbox"],"basis":"EST: the gear bore is the needle-roller raceway (hardness per Schaeffler/INA) and the dog and cone zones carry shift loads; FEA sets the rest.","sources":["schaeffler-needle","dudley-gear"],"tags":["needle-bearing","dog-ring","synchro"]},{"id":"ldd-pulley-sprocket-body","kind":"rule","tier":2,"title":"Timing pulley and chain sprocket bodies","summary":"Treat the root circle as a gear root: rim >= 0.6 x chain pitch (sprocket) or >= 1.0 x belt tooth height + 2 mm (pulley) under the root, then web and holes by the gear rules. Idler and tensioner pulleys follow the same ligaments.","applies":["timing pulley","chain sprocket","idler","tensioner"],"basis":"EST: no published backup ratio for chain or belt drives; the gear rim rule is applied by analogy and checked by FEA.","sources":["dudley-gear","machinerys-handbook"],"tags":["pulley","sprocket","idler"],"value":{"min":0.6,"unit":"ratio"}},{"id":"ldd-flywheel-damper-inertia","kind":"rule","tier":2,"title":"Flywheels and dampers: put mass at the rim","summary":"Ring inertia I = 0.5 m (r_o^2 + r_i^2); a thin web carries the rim, so remove web and hub mass first. Cast-iron rim speed is held near 30 m/s; check burst margin by FEA, not by this figure.","applies":["flywheel","crank damper"],"basis":"EST: inertia is textbook dynamics; the 30 m/s rim-speed order is a handbook rule of thumb (Machinerys Handbook flywheel section).","sources":["machinerys-handbook"],"tags":["inertia","rim-speed"],"value":{"typical":30000,"unit":"mm/s"}},{"id":"ldd-cast-wall-sand-al","kind":"dimension","tier":1,"title":"Sand-cast aluminium nominal wall","summary":"Nominal wall 4 to 8 mm by size (minimum 2.5 mm, 0.10 in, for small areas); keep every wall within +-25 percent of nominal so solidification stays directional.","applies":["sand casting","aluminium casting","gearbox case"],"basis":"SRC: 0.10 in minimum for aluminium sand castings (Engineers Edge); size bands EST from Bralla.","sources":["engineersedge-sand","bralla-dfm"],"tags":["wall","sand"],"value":{"min":4,"max":8,"typical":5,"unit":"mm"}},{"id":"ldd-cast-wall-iron","kind":"dimension","tier":2,"title":"Grey and ductile iron nominal wall","summary":"Grey iron nominal wall 5 to 12 mm (minimum about 3 mm small parts); ductile iron needs about 1 mm more than grey at the same size. Larger castings take the upper end.","applies":["grey iron","ductile iron","engine block"],"basis":"EST: Bralla/ASM Handbook 15 section-size practice; grey flows into thinner sections than ductile.","sources":["bralla-dfm","asm-hbk-15"],"tags":["wall","iron"],"value":{"min":5,"max":12,"unit":"mm"}},{"id":"ldd-cast-wall-hpdc-al","kind":"dimension","tier":2,"title":"High-pressure die-cast aluminium wall","summary":"Nominal wall 2.0 to 3.5 mm (minimum about 1.2 mm on small areas); thicker walls trap gas porosity and sink. Beyond 4 mm choose permanent mould or sand.","applies":["die casting","timing case","cam cover"],"basis":"EST: NADCA guidance bands (verify against the current PSS table for the alloy and projected area).","sources":["nadca-pss","xometry-diecast"],"tags":["wall","hpdc"],"value":{"min":2,"max":3.5,"typical":2.5,"unit":"mm"},"see":["automotive/diecast-draft-angle"]},{"id":"ldd-cast-wall-pm-al","kind":"dimension","tier":2,"title":"Permanent-mould aluminium wall","summary":"Nominal wall 3 to 6 mm (minimum about 2.5 mm); gravity-fed permanent mould sits between die casting and sand in wall and in surface finish.","applies":["permanent mould casting"],"basis":"EST: Bralla process comparison.","sources":["bralla-dfm"],"tags":["wall","permanent-mould"],"value":{"min":3,"max":6,"unit":"mm"}},{"id":"ldd-cast-draft","kind":"dimension","tier":1,"title":"Draft by casting process","summary":"Draft per side: sand 1 to 3 deg (2 standard, 1 minimum); permanent mould 2 to 3 deg; HPDC 1 deg outside, 1.5 to 3 deg inside and on deep cores. Add draft to every face parallel to the pull, ribs and bosses included.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"SRC: sand figures from Engineers Edge; die-cast figures from the Xometry/NADCA guide; PM EST.","sources":["engineersedge-sand","xometry-diecast","nadca-pss"],"tags":["draft"],"value":{"table":[{"process":"sand","min_deg":1,"typical_deg":2,"max_deg":3},{"process":"permanent mould","min_deg":2,"max_deg":3},{"process":"HPDC outside","min_deg":1},{"process":"HPDC inside","min_deg":1.5,"max_deg":3}]},"see":["automotive/diecast-draft-angle","consumer/draft-angle-minimum"]},{"id":"ldd-cast-rib-thickness","kind":"rule","tier":1,"title":"Rib thickness against wall","summary":"Rib root thickness 0.6 to 0.8 x wall in sand and iron, 0.4 to 0.6 x wall in die-cast aluminium; a rib as thick as the wall makes a hot spot and a sink at the root.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"SRC: 40 to 60 percent (die casting, Xometry); sand/iron band EST from the same hot-spot logic (Campbell).","sources":["xometry-diecast","campbell-casting","bralla-dfm"],"tags":["rib"],"value":{"min":0.4,"max":0.8,"unit":"ratio"},"see":["automotive/diecast-rib-thickness-ratio"]},{"id":"ldd-cast-rib-height","kind":"rule","tier":2,"title":"Rib height","summary":"Rib height <= 5 x rib thickness (3 to 5 x wall) for a one-piece casting; taller ribs need draft >= 1 deg both sides and a fading height at the free end so the die releases.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"EST: handbook practice; limit is core strength and ejection.","sources":["bralla-dfm","nadca-pss"],"tags":["rib","height"],"value":{"max":5,"unit":"ratio"}},{"id":"ldd-cast-rib-spacing","kind":"rule","tier":2,"title":"Rib spacing","summary":"Space ribs >= 2 to 3 x wall apart (centre-to-centre >= 3 x wall); closer ribs make a thin die-steel finger between them and a hot mass of metal under it.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"EST: die-steel finger strength rule used by die casters (NADCA).","sources":["nadca-pss"],"tags":["rib","spacing"],"value":{"min":2,"max":3,"unit":"ratio"}},{"id":"ldd-cast-boss-od","kind":"dimension","tier":1,"title":"Boss OD at a bolt","summary":"Boss OD = 2.0 to 2.5 x thread diameter (M10: 20 to 25 mm); core out the middle so the boss wall equals the nominal wall, and give the tapped hole at least 1 x d of thread engagement in aluminium.","applies":["bolt boss","bolted flange"],"basis":"EST: handbook proportion; coring to keep a uniform wall is the die-cast practice (Xometry guide).","sources":["xometry-diecast","bralla-dfm"],"tags":["boss","bolt"],"value":{"min":2,"max":2.5,"typical":2.2,"unit":"ratio"}},{"id":"ldd-cast-boss-transition","kind":"rule","tier":2,"title":"Boss-to-wall transition","summary":"Join a boss to the wall with 2 or 3 ribs (0.6 x wall thick) and a root fillet R = 0.25 to 0.33 x wall; an isolated boss on a plain wall is a hot spot and a shrink cavity.","applies":["bolt boss"],"basis":"SRC: fillet a quarter to a third of wall (Giessereilexikon); rib-to-boss practice from the die-casting guide.","sources":["giessereilexikon-design","xometry-diecast"],"tags":["boss","hot-spot"],"value":{"min":0.25,"max":0.33,"unit":"ratio"}},{"id":"ldd-cast-fillet-radius","kind":"rule","tier":1,"title":"Inside fillet radius at every junction","summary":"Inside fillet R = 0.25 to 0.33 x wall (a quarter to a third); the outside radius = inside R + wall so the section stays constant round the corner. Too large a fillet makes a hot spot of its own.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"SRC: Giessereilexikon (quarter to a third of wall); outside = inside + wall is the constant-section rule (Bralla).","sources":["giessereilexikon-design","bralla-dfm"],"tags":["fillet","corner"],"value":{"min":0.25,"max":0.33,"unit":"ratio"}},{"id":"ldd-cast-section-transition","kind":"rule","tier":2,"title":"Section-change limit","summary":"Keep adjoining sections within 2:1 thickness and blend them with a taper no steeper than 1:4; a step from 8 mm to 3 mm freezes the thin side first and starves the thick side.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"SRC: 2:1 and 1:4 from the Engineers Edge sand-casting guide.","sources":["engineersedge-sand"],"tags":["transition","taper"],"value":{"max":2,"unit":"ratio"}},{"id":"ldd-cast-hotspot-junction","kind":"rule","tier":1,"title":"Hot spots at junctions","summary":"Solidification time scales with (volume / cooling area)^2 (Chvorinov). Keep the largest circle inscribed at an L, T or X junction <= 1.25 x wall, and stagger ribs so no four-way crossing remains.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"SRC: Chvorinov rule (Campbell); the 1.25 x inscribed-circle limit is EST design practice.","sources":["campbell-casting","asm-hbk-15"],"tags":["hot-spot","junction","chvorinov"],"value":{"max":1.25,"unit":"ratio"}},{"id":"ldd-cast-machined-pads","kind":"rule","tier":2,"title":"Machined pads only where a face mates","summary":"Raise a pad 2 to 3 mm (sand) or 0.5 to 1 mm (die-cast) above the cast face and machine only that: mating faces, bearing bores and bolt seats. Leave everything else as cast.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"EST: machining allowance category per ISO 8062-3 RMA; the bands here are typical for small to medium parts.","sources":["iso-8062-3","bralla-dfm"],"tags":["pad","machining-allowance"],"value":{"min":2,"max":3,"unit":"mm"}},{"id":"ldd-cast-pad-on-section","kind":"rule","tier":2,"title":"Pads on thick sections, clear of the parting line","summary":"Place pads over a rib or boss (not on a bare wall) so the cut does not thin the wall below 0.75 x nominal, and keep them >= 5 mm clear of the parting line and the draft break.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"EST: a pad cut into a bare wall removes the allowance from the wall itself.","sources":["bralla-dfm"],"tags":["pad","parting-line"],"value":{"min":5,"unit":"mm"}},{"id":"ldd-rail-taper-moment","kind":"rule","tier":1,"title":"Rail depth follows the bending moment","summary":"For constant stress at fixed width, section modulus follows M(x): depth h ~ sqrt(M). Cantilever end load (M ~ x) gives a parabolic taper, uniform load (M ~ x^2) a straight linear taper. Depth tracks the moment, not the length.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"SRC: beam of uniform strength (Roark; Shigley ch.3), h = sqrt(6 M / (b sigma)).","sources":["roark"],"tags":["taper","moment","rail"],"value":{"value":"h(x) = sqrt(6 M(x) / (b sigma_allow))","unit":"ratio"}},{"id":"ldd-rail-taper-limit","kind":"rule","tier":2,"title":"Where the taper stops","summary":"Stop tapering where shear governs: web depth >= 1.5 V / (t tau_allow), and keep the half-angle <= 15 deg for cut-and-weld rails so web buckling and weld detailing stay simple. Taper from the support toward the free end only.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"EST: shear check from beam theory (Roark, tau = 1.5 V / A); 15 deg is a fabrication practice limit.","sources":["roark","blodgett-weldments"],"tags":["taper","shear"],"value":{"max":15,"unit":"deg"}},{"id":"ldd-hole-dia-vs-web","kind":"rule","tier":1,"title":"Lightening-hole diameter against web depth","summary":"Unflanged hole diameter <= 0.5 to 0.6 x web depth at that station; flanged hole up to 0.8 x web depth. The hole sits on the neutral axis, in low-shear mid-span, never within one web depth of a support or load point.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"EST: airframe practice (Niu, lightening holes in webs); limits come from shear buckling of the strip left above and below.","sources":["niu-airframe","roark"],"tags":["lightening-hole","web"],"value":{"min":0.5,"max":0.8,"unit":"ratio"}},{"id":"ldd-hole-edge-distance","kind":"rule","tier":2,"title":"Edge distance and hole-to-hole spacing","summary":"Hole edge to web edge >= 0.2 x web depth and >= 2 x plate thickness; hole-to-hole ligament >= 1.0 x hole diameter. Smaller ligaments buckle in shear before the web yields.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"EST: conservative airframe-style limits (Niu); settle thin cases with an FEA buckling run.","sources":["niu-airframe"],"tags":["ligament","edge-distance"],"value":{"min":0.2,"unit":"ratio"}},{"id":"ldd-hole-flange","kind":"feature","tier":2,"title":"Flanged lightening holes","summary":"A flanged (drawn) hole turns up a lip of height >= 3 x plate thickness and radius >= 1 x thickness; the lip restores the buckling stiffness the hole removed, which is why flanged holes may reach 0.8 x web depth.","applies":["sheet web","plate rail"],"basis":"EST: aircraft-structure practice (Niu); lip geometry from a press-forming limit of about 3 t.","sources":["niu-airframe"],"tags":["flange","lightening-hole"],"value":{"min":3,"unit":"ratio"}},{"id":"ldd-hole-kt","kind":"rule","tier":1,"title":"Stress concentration of a hole","summary":"A circular hole in a wide plate under tension has Kt = 3.0 (4.0 in pure shear): the edge sees three times nominal stress. Put holes where nominal stress is under a third of allowable, near the neutral axis, with slot corners at R >= 1 x plate thickness.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"SRC: Peterson Kt for a circular hole, infinite plate (3.0); slot corner radius EST.","sources":["peterson-kt"],"tags":["kt","hole","stress-concentration"],"value":{"value":3,"unit":"ratio"}},{"id":"ldd-gusset-crossmember","kind":"rule","tier":1,"title":"Gussets at crossmember joints","summary":"Gusset thickness >= 0.8 x joined member wall, leg length >= 1.5 x member depth, 45 deg bias, with a corner scallop R >= 20 mm so welds never cross. Use where a crossmember meets a rail.","applies":["crossmember joint","ladder frame"],"basis":"EST: weldment practice (Blodgett, AWS D1.1 detailing); verify the joint by FEA at the load case.","sources":["blodgett-weldments","aws-d1-1"],"tags":["gusset","joint"],"value":{"min":1.5,"unit":"ratio"}},{"id":"ldd-fish-plate","kind":"rule","tier":2,"title":"Fish plates across a joint","summary":"Fish plate length >= 2 x member depth each side of the joint, thickness >= member wall, welded all round with a 25 mm return; tapered ends reduce the stiffness step.","applies":["crossmember joint"],"basis":"EST: weldment practice (Blodgett); end taper spreads the load.","sources":["blodgett-weldments"],"tags":["fish-plate","joint"],"value":{"min":2,"unit":"ratio"}},{"id":"ldd-hole-to-weld","kind":"rule","tier":1,"title":"Hole-to-weld distance","summary":"Keep a hole edge >= 2 x plate thickness (and >= 6 mm) from a weld toe: the heat-affected zone, distortion and the weld-toe stress riser should not overlap a hole edge.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"EST: Blodgett detailing guidance on HAZ and distortion; AWS D1.1 for fatigue categories.","sources":["blodgett-weldments","aws-d1-1"],"tags":["weld","hole","haz"],"value":{"min":6,"unit":"mm"}},{"id":"ldd-verify-after-removal","kind":"rule","tier":1,"title":"Re-verify after every cut","summary":"After lightening, rerun the stress solve at design load: peak von Mises incl. Kt <= yield / 1.5 (EST) and report mass removed. Reject a cut that drops the safety factor under target; stop when mass stops falling.","applies":["all load-driven parts"],"basis":"EST: 1.5 on yield is a common static factor for non-critical structure; the project sets its own target.","sources":["roark","peterson-kt"],"tags":["fea","verify","safety-factor"],"value":{"min":1.5,"unit":"ratio"}},{"id":"ldd-mat-gear-steel","kind":"material","tier":2,"title":"Case-hardened gear steel","summary":"8620 carburised: case 58 to 62 HRC, core about 30 to 40 HRC; 4140 through-hardened 28 to 36 HRC for large lightly loaded gears. Lightening holes sit in the soft core, so hole edges stay unhardened.","applies":["gear"],"basis":"EST: typical hardness bands (Shigley ch.14 tables for AGMA grades).","sources":["shigley-ch14"],"tags":["8620","4140","hardness"]},{"id":"ldd-mat-al-castings","kind":"material","tier":2,"title":"Cast aluminium alloys","summary":"A356.0-T6 sand/PM: tensile about 230 MPa, yield about 165 MPa. A380 HPDC: tensile about 320 MPa, yield about 160 MPa. Design to yield; use the lower tensile for fatigue-limited bolted joints.","applies":["aluminium casting"],"basis":"SRC: ASM Handbook Vol. 2 alloy datasheets (typical, not minimum).","sources":["asm-hbk-2"],"tags":["A356","A380"],"value":{"table":[{"alloy":"A356-T6","yield_MPa":165,"uts_MPa":230},{"alloy":"A380","yield_MPa":160,"uts_MPa":320}]}},{"id":"ldd-mat-cast-iron","kind":"material","tier":2,"title":"Cast iron grades","summary":"Grey iron Class 30 (ASTM A48): tensile 207 MPa min, no yield point. Ductile 65-45-12 (ASTM A536): tensile 448 MPa, yield 310 MPa, 12 percent elongation. Ductile for bearing caps and cranks, grey for damping and blocks.","applies":["grey iron","ductile iron"],"basis":"SRC: ASTM A48 and A536 grade designations (30 ksi, 65-45-12).","sources":["astm-a48","astm-a536"],"tags":["grey","ductile"],"value":{"table":[{"grade":"A48 Class 30","uts_MPa":207},{"grade":"A536 65-45-12","yield_MPa":310,"uts_MPa":448}]}},{"id":"ldd-mat-frame-steel","kind":"material","tier":2,"title":"Frame plate steels","summary":"S355 (EN 10025-2) yield 355 MPa to 16 mm, A36 yield 250 MPa. Higher-yield plate lets the rail taper deeper and holes grow, but stiffness (E = 210 GPa) does not change, so deflection can govern first.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"SRC: EN 10025-2 grade table; ASTM A36 yield 36 ksi.","sources":["en-10025-2","roark"],"tags":["S355","A36"],"value":{"table":[{"grade":"S355","yield_MPa":355},{"grade":"A36","yield_MPa":250}]}},{"id":"ldd-test-gear-lightened-fea","kind":"test","tier":2,"title":"Lightened gear body FEA check","summary":"Solve the gear at 1.5 x rated torque: tooth-root stress (with K_B), web shear and hub-key bearing stress must each sit below yield / 1.25 (EST); rim deflection under tooth load <= 0.02 mm per mm of face width.","applies":["gear","lightened body"],"basis":"EST: acceptance numbers set by this pack; K_B per AGMA 2001. Use cad_fea_run.","sources":["agma-2001-d04","shigley-ch14"],"tags":["fea","gear"],"value":{"value":1.5,"unit":"ratio"}},{"id":"ldd-test-cast-radiograph","kind":"test","tier":2,"title":"Hot-spot radiograph of a cast part","summary":"Radiograph the heaviest junctions (inscribed circle > 1.25 x wall) against ASTM E155 reference radiographs; shrinkage porosity at a rib or boss root above the agreed grade is a design fault, not only a process one.","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"SRC: ASTM E155 reference radiographs for aluminium and magnesium castings.","sources":["astm-e155"],"tags":["radiograph","porosity"],"value":{"value":1.25,"unit":"ratio"}},{"id":"ldd-test-frame-fea","kind":"test","tier":2,"title":"Frame lightening-hole FEA check","summary":"Shell-model solve at the torsion and bump load cases: peak stress at a lightening-hole edge incl. Kt 3.0 <= yield / 1.5; web shear buckling factor >= 1.0 at the hole station.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"EST: acceptance numbers from the Kt and safety-factor entries; buckling factor from a linear buckling solve.","sources":["peterson-kt","roark"],"tags":["fea","frame"],"value":{"value":1.5,"unit":"ratio"}},{"id":"ldd-test-rotor-overspeed","kind":"test","tier":3,"title":"Overspeed spin of a lightened rotor","summary":"Spin rotating bodies to 120 percent of the operating maximum for 30 s with no permanent growth (bore change < 0.01 mm); a hub or web with a hole near the hub OD is the first to yield.","applies":["gear","timing pulley","chain sprocket","idler","flywheel"],"basis":"EST: 120 percent is a common spin-test practice for rotating machinery; the project may set a higher figure.","sources":["machinerys-handbook"],"tags":["overspeed","burst"],"value":{"value":120,"unit":"%"}},{"id":"ldd-std-agma-2001","kind":"standard","tier":3,"title":"ANSI/AGMA 2001-D04 and ISO 6336-3","summary":"AGMA 2001 gives K_B (m_B < 1.2, applicable to m_B >= 0.5, external gears); ISO 6336-3 carries the equivalent rim factor Y_B. Cite the clause in the purchased edition; this pack quotes the textbook form.","applies":["gear"],"basis":"SRC: both standards; textbook form per Shigley ch.14.","sources":["agma-2001-d04","iso-6336-3"],"tags":["standard","agma","iso"],"value":{"value":1.2,"unit":"ratio"}},{"id":"ldd-std-iso-8062-3","kind":"standard","tier":3,"title":"ISO 8062-3 machining allowance","summary":"ISO 8062-3 sets required machining allowance (RMA) grades A to K by casting process and largest dimension; the pad height rule uses its sand and die-cast order of magnitude (2 to 3 mm, 0.5 to 1 mm).","applies":["sand casting","permanent mould casting","die casting","grey iron","ductile iron"],"basis":"SRC: ISO 8062-3.","sources":["iso-8062-3"],"tags":["standard","rma"],"value":{"min":0.5,"max":3,"unit":"mm"}},{"id":"ldd-recipe-lightened-gear-body","kind":"recipe","tier":2,"title":"Recipe: lightened gear body (m 3, 60 teeth)","summary":"Revolved hub, web and rim for a module-3, 60-tooth blank, then six dia 36 lightening holes at radius 52.5 through the 7.5 mm web; every dimension follows the rim, web, hub and ligament rules.","applies":["gear","lightened body"],"basis":"EST: Worked example of rim-min-thickness, web-thickness, hub-od, lighten-ligaments and lighten-hole-count.","sources":["iso-53","agma-2001-d04"],"tags":["recipe","gear","lightening"],"recipe":{"prompt":"Model a module-3, 60-tooth gear body with hub, web and six lightening holes, 30 mm bore, 30 mm face","steps":[{"tool":"cad_revolve_profile","args":{"profile":[[15,0],[27,0],[27,16.25],[78.15,16.25],[78.15,5],[86.25,5],[86.25,35],[78.15,35],[78.15,23.75],[27,23.75],[27,40],[15,40]]},"note":"m=3, N=60 gear body about Z: 30 mm bore, hub OD 54 (1.8 x bore), web 7.5 mm (0.25 F) centred on a 30 mm face, rim 8.1 mm (2.7 m) under the root circle R 86.25 (teeth omitted)"},{"tool":"cad_cylinder","args":{"r":18,"h":20,"origin":[52.5,0,10]},"note":"lightening-hole tool 1 of 6: dia 36 at radius 52.5, ligament 7.5 mm to hub and rim"},{"tool":"cad_boolean_subtract","args":{"of":"$0","tool":"$1"},"note":"cut the hole through the web"},{"tool":"cad_cylinder","args":{"r":18,"h":20,"origin":[26.25,45.4663,10]},"note":"lightening-hole tool 2 of 6: dia 36 at radius 52.5, ligament 7.5 mm to hub and rim"},{"tool":"cad_boolean_subtract","args":{"of":"$2","tool":"$3"},"note":"cut the hole through the web"},{"tool":"cad_cylinder","args":{"r":18,"h":20,"origin":[-26.25,45.4663,10]},"note":"lightening-hole tool 3 of 6: dia 36 at radius 52.5, ligament 7.5 mm to hub and rim"},{"tool":"cad_boolean_subtract","args":{"of":"$4","tool":"$5"},"note":"cut the hole through the web"},{"tool":"cad_cylinder","args":{"r":18,"h":20,"origin":[-52.5,0,10]},"note":"lightening-hole tool 4 of 6: dia 36 at radius 52.5, ligament 7.5 mm to hub and rim"},{"tool":"cad_boolean_subtract","args":{"of":"$6","tool":"$7"},"note":"cut the hole through the web"},{"tool":"cad_cylinder","args":{"r":18,"h":20,"origin":[-26.25,-45.4663,10]},"note":"lightening-hole tool 5 of 6: dia 36 at radius 52.5, ligament 7.5 mm to hub and rim"},{"tool":"cad_boolean_subtract","args":{"of":"$8","tool":"$9"},"note":"cut the hole through the web"},{"tool":"cad_cylinder","args":{"r":18,"h":20,"origin":[26.25,-45.4663,10]},"note":"lightening-hole tool 6 of 6: dia 36 at radius 52.5, ligament 7.5 mm to hub and rim"},{"tool":"cad_boolean_subtract","args":{"of":"$10","tool":"$11"},"note":"cut the hole through the web"}],"expect":{"volume":269760.29,"faceCount":24,"watertight":true,"note":"measured 2026-10-23: tools/run_dfm_recipe.js --expect"}}},{"id":"ldd-recipe-tapered-rail-web","kind":"recipe","tier":2,"title":"Recipe: tapered rail web with lightening holes","summary":"A 600 mm rail web, 4 mm plate, tapering from 120 mm deep at the root to 60 mm at the tip, with three round lightening holes on the neutral axis at 0.48, 0.44 and 0.40 of the local depth.","applies":["ladder frame","chassis rail","fabricated frame","plate"],"basis":"EST: Worked example of rail-taper-moment, hole-dia-vs-web and hole-edge-distance (UDL: linear taper).","sources":["roark","niu-airframe"],"tags":["recipe","rail","taper","lightening"],"recipe":{"prompt":"Model a 600 mm tapered chassis rail web, 120 mm deep at the root to 60 mm at the tip, 4 mm plate, with three lightening holes on the neutral axis","steps":[{"tool":"cad_extrude_profile","args":{"depth":4,"outer":[[0,-60],[600,-30],[600,30],[0,60]],"holes":[{"circle":{"cx":150,"cy":0,"r":25}},{"circle":{"cx":300,"cy":0,"r":20}},{"circle":{"cx":450,"cy":0,"r":15}}]},"note":"taper outline plus holes dia 50, 40, 30 at x = 150, 300, 450 (local depth 105, 90, 75)"}],"expect":{"volume":200292.04,"faceCount":12,"watertight":true,"note":"measured 2026-10-23: tools/run_dfm_recipe.js --expect"}}}]}