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Design guides & articles
Practical know-how on gears, pulleys, bearings and designing for 3D printing — formulas, size tables, tolerance advice — linked to the generators.
- 2026-10-06Gear module explained: choosing a module for 3D printing and DIYModule m is the basic size unit of a metric gear. Learn how it relates to pitch diameter, circular pitch and tooth depth, where each module fits, and what to choose for 3D-printed gears.Read article
- 2026-10-06The complete guide to 3D-printed gears: materials, tolerances and processesHow to print gears that work: PLA, PETG, nylon, resin and SLS / MJF compared for wear and strength, plus backlash, bore compensation, orientation and finishing tips.Read article
- 2026-10-063D-printed hole tolerances: why holes shrink and how much clearance to addWhy FDM, SLA and SLS holes come out undersized, recommended compensation per process, press / slide / loose fit clearances and tips for captive nuts, bearings and pins.Read article
- 2026-10-06Rack and pinion: a design guide to turning rotation into linear motionHow to pair a rack and pinion: matching module, mounting distance, travel per revolution, stepper resolution and printing long racks in segments.Read article
- 2026-10-06GT2 timing pulley guide: tooth count, belt width, flanges and centre distanceHow to compute GT2 (2GT) pulley pitch and outside diameters, choose tooth count, belt width and flanges, and size the centre distance and steps/mm.Read article
- 2026-10-06How to read bearing numbers: 6204, 608 and deep-groove ball bearing sizesThe deep-groove ball bearing numbering system — type, size series and bore code — with a size table for 608, 6000, 6200 and 6300 series and shaft / housing fit advice.Read article
- 2026-10-07Metric screw size chart M2–M12: pitch, tap drill, head dimensions and property classes 8.8 / 12.9Look up M3, M4, M5 and M6 screw sizes: ISO 261 coarse and fine pitches, tap drill and clearance holes, ISO 4762 socket head, ISO 7380 button head and ISO 4017 hex head dimensions, spanner sizes, and what property classes 8.8, 10.9 and 12.9 mean — with tightening torque estimates.Read article
- 2026-10-07How to calculate gear ratio: single-stage, compound and planetary gear ratio formulas (with torque and speed)Gear ratio = driven teeth ÷ driver teeth. Learn how single and compound gear trains set output speed and torque, typical efficiencies of each drive, and where the planetary ratio 1 + Zr/Zs and its assembly conditions come from — with a worked design example.Read article
- 2026-10-07Helical vs spur vs herringbone gears: contact ratio, axial thrust and module conversion comparedWhy are helical gears quieter than spur gears? Compare spur, helical and herringbone gears by contact (overlap) ratio, axial thrust Fa = Ft·tanβ, bearing needs and manufacturing cost, with a normal-to-transverse module conversion table and 3D-printing advice.Read article
- 2026-10-07Worm gear design: lead angle, self-locking, ratio and efficiencyWorm drive ratio = wheel teeth ÷ worm starts. A guide to lead angle γ = atan(z₁/q), the self-locking condition tan γ < μ, an efficiency table, centre distance and forces, plus material, lubrication and 3D-printing advice for worms and worm wheels.Read article
- 2026-10-07Roller chain and sprocket guide: chain size chart, tooth count, link count and centre distancePitch and dimensions of No.25, 35, 40, 50, 60 and 80 roller chain (ANSI / JIS / ISO 606), why sprockets should have 17 teeth or more, how chordal action causes speed variation, why link counts should be even, and advice on chain speed, lubrication, tensioning and 3D-printed sprockets.Read article
- 2026-10-07ISO fit tolerance basics: choosing H7/g6, H7/h6, H7/k6 or H7/p6 — with IT grade tableRead Ø25 H7/g6 on a drawing: ISO 286 tolerance zone letters and IT grades, an IT5–IT14 tolerance table, clearances and interferences for common hole-basis fits, how to judge clearance, transition and interference fits, bearing fits, and what 3D printing versus CNC machining can hold.Read article
- 2026-10-07Choosing 2020, 3030 or 4040 aluminium extrusion: slot width, T-nuts, corner brackets and stiffnessSlot widths, matching T-nuts and centre-bore tap sizes, mass and second moment of area for 2020, 3030 and 4040 T-slot extrusions; stiffness compared with deflection formulas; corner brackets versus end tapping; cut-length tolerances, frame length maths and typical applications.Read article
- 2026-10-07How to calculate stepper motor steps/mm: belts, leadscrews, microstepping and Marlin / Klipper setupThe steps/mm formula with worked values — GT2 20-tooth pulley = 40 mm/rev = 80 steps/mm, T8 leadscrew = 400 steps/mm — plus lead versus pitch, the torque cost of microstepping, resolution versus accuracy, Marlin M92, Klipper rotation_distance and GRBL $100 settings, and extruder E-steps calibration.Read article
- 2026-10-07Design for 3D printing: minimum wall thickness, 45° overhangs, supports, hole tolerances and FDM vs SLA vs SLS vs MJFHow to design parts that actually print: minimum wall, hole, feature and text sizes for FDM, SLA, SLS and MJF, the 45° overhang rule, supports and bridging, hole and pin compensation with fit clearances, and how print orientation sets strength.Read article
- 2026-10-07How to fasten 3D-printed parts: self-tapping screws vs heat-set inserts vs captive nuts vs through-bolts (M2–M5 hole sizes)What hole size for screws in 3D prints? Compare self-tapping screws, heat-set inserts, captive hex nuts and through-bolts for strength, torque and reusability, with M2–M5 self-tap holes, heat-set insert holes (vendor reference values), nut pocket sizes, and tightening torque versus washer bearing pressure.Read article
- 2026-10-07Belt vs lead screw vs ball screw vs rack and pinion: how to choose a linear drive (accuracy, speed, backlash, steps/mm)GT2 belts, T8 lead screws, ball screws and rack and pinion compared: travel-per-revolution formulas, accuracy, backlash, speed, travel and cost tables, worked steps/mm and thrust examples, plus lead screw efficiency, self-locking and critical speed.Read article
- 2026-10-07Bevel gear design guide: pitch cone angle, cone distance, face width and straight vs spiral bevel gearsHow to design bevel gears: pitch cone angle δ = atan(z1/z2) and the general shaft-angle formula, cone distance R, face width ≤ R/3, outside diameter and virtual teeth with a size table for common ratios, plus straight, Zerol, spiral and hypoid gears compared, miter gears, mounting, force calculation and 3D printing tips.Read article
- 2026-10-07Compression spring design: spring rate formula, spring index, free length and solid height (with worked example)How to design a compression spring: spring rate k = G·d⁴ / (8·D³·n), a spring index C = D/d of 4–12, the Wahl stress factor, free length and solid height for the four end types, shear modulus G of music wire (SWP) and SUS304 stainless, plus a complete example from load requirement to wire, coils and pitch.Read article
- 2026-10-07Planetary gearbox design: tooth count rules, gear ratio calculation and 3D printing tips (with valid tooth combinations)How to design a planetary gearbox: where the ratio 1 + Zr/Zs comes from, the coaxial condition Zr = Zs + 2Zp, the assembly condition (Zs + Zr)/N = integer and the adjacency condition, a table of valid tooth combinations for ratios 3–10, profile shift for non-standard tooth counts, and module, backlash and layout tips for 3D-printed planetary gearboxes.Read article