How Plastic Cosmetic Bottles Are Manufactured

A cosmetic bottle is produced by one of two routes, and the route explains most of what you can and cannot specify.

Injection blow moulding

Used for PET and PP bottles, typically 15–300 ml.

1. A molten parison is injection moulded onto a core pin, forming a precise preform with a finished neck
2. The preform moves to a blow station and is stretched and blown to the final shape
3. The part is ejected with a fully formed neck finish (±0.2 mm typical)

Strengths: clarity, tight neck tolerance, consistent wall distribution. Limits: higher tooling cost, less efficient at large volumes.

Extrusion blow moulding

Used for HDPE, PP and PCR blends, typically 250–1,000 ml.

1. A tube of molten plastic (parison) is extruded downward
2. The mould closes around it and air inflates it against the cavity wall
3. The part is trimmed; the neck is formed by the mould and a calibration tool

Strengths: cost-efficient at volume, excellent for opaque formats and recycled content. Limits: wider wall tolerance (±0.5 mm), less clarity.

Multi-layer constructions

Multi-layer extrusion blow moulding stacks polymers: an outer layer for appearance, a core layer that can carry PCR content or a barrier resin, and an inner layer for contact safety. This allows recycled content or barrier performance without changing what the customer sees.

Tooling and cavity planning

Annual volume per size	Suggested cavities	Rationale
Under 50,000 pcs	1–2	Lowest tooling cost
50,000–200,000 pcs	2–4	Balances tool cost and cycle efficiency
200,000–1,000,000 pcs	4–8	Moulding efficiency dominates
Above 1,000,000 pcs	8+ or hot runner	Cycle time becomes decisive

More cavities reduce cycle cost per part but raise tool cost, so the crossover depends on your volume. See custom mould development.

From moulding to shipment

1. Resin intake: grade, lot, MFI and colour verification
2. Moulding: parameter sheet per mould, weight and dimension checks
3. Decoration: printing, hot stamping, coating with adhesion testing
4. Assembly: closures fitted and torqued, or packed separately
5. Inspection: AQL final inspection with dimension, leak and appearance checks
6. Packing: quantity verification, carton marking, drop and stacking checks

What this means when buying

• Ask for the parameter sheet for your mould; it is what holds quality stable across repeat orders
• Confirm wall thickness and part weight in grams, not visually
• Expect ±0.2 mm neck tolerance on injection blow moulded PET and ±0.5 mm wall on extruded HDPE
• Test the assembled bottle and closure with your formula before mass production