A separate tool for each part
- Each tool is tuned for its own part and resin
- Output of each part can follow its own demand
- More tools to build, maintain, and track
Molded part guide: inhaler components
Injection Molded Inhaler Components
An inhaler is a small assembly in which a few molded features set how the dose leaves the device. The spray orifice in a metered dose actuator is a tiny hole formed by a steel pin, and a dose counter is a chain of small gears and ratchets that must advance once per dose. Both depend on steel that stays exact over many shots.
Where the dose is shaped
A few small features decide how the device performs
Metered dose actuators, dry powder inhaler bodies, mouthpieces, dust caps, and dose counters.
In a metered dose inhaler the canister valve stem sits in a socket in the actuator. When the canister is pressed, the dose passes through a short channel and a sump and leaves through the spray orifice. The orifice diameter and the length of its land shape the spray plume and the particle size. A small change in that hole changes the spray, which makes it the most carefully controlled feature on the part.
The orifice is formed by a core pin that reaches across the cavity and seats against the opposite steel. If the pin does not seat cleanly, a thin film of flash forms across the hole. If the pin wears or chips, the hole grows or changes shape. Pins are supported at both ends where possible, inspected on a schedule, and orifices are measured on every cavity rather than a sample.
The stem socket is a friction fit that holds the canister and seals the valve stem. It needs a consistent bore and a clean edge, because a socket that is loose leaks dose and one that is tight makes the canister hard to seat. Actuators are commonly polypropylene, which is tough and molds these fine features well.
Dry powder inhalers add a different problem. Fine powder clings to plastic surfaces through static charge, which can hold part of a dose inside the device. Surface finish, the shape of the powder path, and resin grades with lower charge buildup all reduce it, and the choice is tested with the actual formulation.
Parts
Inhaler parts and their critical features
Most of the precision sits in a handful of small features.
| Part | Critical feature | Molding focus |
|---|---|---|
| Actuator nozzle | Spray orifice size and land length | Core pin seating, wear checks, and flash control |
| Stem socket | Friction fit on the valve stem | Consistent bore and a clean entry edge |
| Mouthpiece and body | Fit of the cap and the canister | Even walls and controlled warp on a thin shell |
| Dose counter gears and ratchets | One count per dose, every time | Tooth form, pawl stiffness, and flash free edges |
| Dust cap | Stays on in a pocket, comes off by hand | Snap bead and resin chosen for repeat use |
Dose counters
Small gears that must never skip or double count
A counter turns each actuation into one step on a display wheel.
- A pawl drives a ratchet one tooth per press, and a second pawl stops it slipping back
- Acetal is common for the small gears because it is stiff, low friction, and holds tooth form
- Flash on a tooth tip or a pawl edge can cause a skip, so these edges are kept sharp in the steel
- The count depends on a stack of small tolerances across several parts, so they are reviewed as one assembly
Tooling
Many single-part tools, or family molds for the small parts
An inhaler can have many small parts. How they are grouped in tools affects matching and output.
Family molds for similar small parts
- Parts that go together are molded together, in matched sets
- Works when the parts share a resin and are similar in size
- Critical parts like the actuator usually keep their own tool
Drawing
What to send with inhaler components
The assembly matters more than any single part.
Full assembly CAD, with every molded part and the canister or powder reservoir
Orifice diameter and land length, with how they are measured
Stem socket dimensions and the valve stem drawing
Dose counter layout and the number of doses it must count
Resin for each part, and any charge or surface requirement for powder paths
Colors and markings, including any dose or product identification
Keep reading
Related guides
Other drug delivery parts, and the small mechanisms inside them.
Syringe components
Barrels, plungers, and luer tips.
Syringe componentsIV components
Luer connectors, stopcocks, and clamps.
IV componentsGears
Resin, gating, and tooth form.
GearsLatches
Snaps and catches that hold a cap or cover.
LatchesAcetal (POM)
The usual resin for small gears.
Acetal (POM)Polypropylene
The common actuator resin.
PolypropyleneFlash
Thin films that block a small hole.
FlashFamily injection molding
Molding matched sets of small parts.
Family injection moldingMolded parts hub
Every part-type guide, grouped by family.
Molded parts hubFAQ
Questions about molded inhaler components
Spray results drift over a production run. What in the tool could cause it?
Wear or damage on the orifice core pin, or flash building at the pin seat. Both change the hole a little at a time. Measuring orifices on every cavity at intervals shows the trend before it matters.
Why does the dose counter occasionally skip?
Look at flash on tooth tips and pawl edges, pawl stiffness, and the tolerance stack across the counter parts. A counter is reviewed as an assembly, not part by part.
Can molding reduce powder sticking in a dry powder device?
Partly. A smoother powder path and a resin grade with lower charge buildup help. The effect is confirmed by testing with the actual powder.
Can the parts be supplied assembled?
Assembly is a secondary operation that can be quoted with the molded parts. Share the assembly sequence and any checks each step needs.
Next step
Quote the inhaler parts as an assembly
Upload the full assembly. DFM feedback covers orifice pins, the stem socket, counter gears, tolerance stack, and how parts are grouped in tools.