Design lab
Interface, chute, cleaning and materials
The metering concept is only half the machine. These four labs cover the parts around it: how the bottle is held and sealed, how a pill gets to the tray without harm, how the machine is kept clean between products, and what it is made of. Two labs use the physics engine; two are first-principles models with their assumptions written out.
The concept statement asks for an adjustable holder, interchangeable adapters and a compliant silicone gripper or seal. A seal must squeeze hard enough to hold vacuum and the bottle's weight, but not so hard that it crushes a thin plastic neck, and real necks vary by ±0.3–0.5 mm and are never quite round. This lab runs a Monte-Carlo over those tolerances for three interface designs.
Set up the neck
After metering a pill has to reach the tray. Free fall gives it speed; a ramp turns the fall into a slide; the tray must hold it there until the patient takes it. Every run below is the real engine: 30 pills per configuration, random orientation and mass, impact speed judged against each pill's drop rating (damage starts near 60 % of the rated speed).
Try a configuration
ready
Tablets shed dust. If the next product is a different drug, what remains on the metering surfaces can cross-contaminate. The optional cleaning step is a filtered, low-pressure air purge. Whether a jet can lift a particle depends on wall shear against adhesion, so it works on coarse chips and fails on fine dust. This is a first-principles model (assumptions listed below), not a particle-resolved simulation.
Purge settings
Assumptions
- Jet speed u = √(2ΔP/ρ); wall-jet speed 25 % of the nozzle speed at the surface; skin friction Cf = 0.006, so wall shear τ = ½·Cf·ρ·(0.25u)².
- Drag on a sphere resting on the wall in shear: F = 32.0·τ·r² (Goldman–Cox–Brenner / O'Neill). Adhesion: JKR pull-off F = 1.5π·W·r × roughness factor f, work of adhesion W = 0.05 J/m².
- A particle lifts when drag ≥ adhesion; adhesion is log-normal (σln = 0.8) between contacts. Pulsed flow is 2× more effective per pulse than steady flow; vibration adds 30 %.
- Dust sizes are log-normal (geometric σ = 1.7) and mass-weighted (∝ d³). Each pulse acts on what the previous left.
- Redeposition of removed dust elsewhere in the machine is 35 % without extraction, 0 % with it. Carry-over = residual × 4 % pick-up per dose on a 0.5 g dose.
The concept statement lists stainless steel, polymers and elastomers. Tick what a part needs and the table ranks materials for it. Values are typical handbook ranges for the material families (not a specific supplier grade); confirm any choice against the supplier's data sheet and the applicable USP / FDA requirements.