Joints & assemblies

Mechanism fundamentals

4 articles

Why a printed mechanism behaves nothing like a machined one: the clearances, layer orientation and embedded hardware every moving part is built on.

• Tolerances for moving parts
• Layer orientation for motion
• Embedded hardware: magnets, bearings, and inserts
• Interference without cracking

Joining parts for good

5 articles

Fixed joints for two parts that must never come apart: press fits, snap-fits, printed joinery, threaded inserts and rivets.

• Press-fits that hold
• Snap-fits that won't release
• Printed joinery: dovetails and joints
• Threads, inserts, and nuts
• Rivets, barbs, and staking

Removable but stable joints

11 articles

Hold firm and don’t rattle, yet come apart by hand again and again.

• Reversible snap-fit: the click that assembles and releases
• Conical twist lock: locking by cone friction
• Bayonet mount: insert and quarter-turn to lock
• Dzus quarter-turn fastener: the cam that draws two panels together
• Over-center draw latch: cross the dead point and tension
• Magnetic closure: effortless, self-aligning joining
• Ball and spring detent: a positional click in a notch
• Keyhole hook and slot: insert and slide to lock
• Demountable tab and slot: boxes and panels that assemble by hand
• Captive thumb screw: the screw that won't fall out
• Ball-lock pin: radial retention released by a button

State and click

6 articles

Latch on press, or two stable states with no energy.

• Over-center toggle: a bistable that stays where you leave it
• Snap dome and Belleville washer: elastic with a tactile snap
• Ball detent and indexed knob: clicking into position
• Magnetic detent: states defined by magnets
• Push-push: press to latch, press to release (heart cam)
• Compliant bistables: buckled beam, flexible four-bar, and negative stiffness

Buttons and controls

6 articles

The feel and behaviour of a physical control.

• Momentary cantilever-beam button
• Snap-dome button with tactile click
• Trigger: a lever with return
• Detented slide and wheel: positions that stay put
• Push-push latching button with a heart cam
• Beyond the button: membrane, lever, joystick, wheel, and handle

Springs and flexures

8 articles

Storing energy or returning a part.

• Helical compression spring: the classic printed coil
• Leaf and cantilever springs: the most reliable FDM spring
• Serpentine flexure: stiffness tuned by segment count
• Accordion and bellows: large axial travel
• Belleville disc spring: high force in short travel
• Elastic band channel: a real spring, embedded
• Coil spring variants: extension, torsion, garter, and wave
• Advanced springs: clock spiral, constant force, TPU, and lattice

Structures and metamaterials

6 articles

Fold, expand, grip, or give “impossible” properties.

• Print-in-place flexi chain
• Chainmail and scale armor: rigid-flexible fabric
• Kerf bending: cut patterns that bend the rigid
• Living-hinge folding box: print flat, fold to shape
• Fin-Ray gripper that wraps around the object
• Metamaterials: auxetics, origami, gyroid, and tensegrity