Blow moulding is everywhere—from plastic bottles to bespoke containers. But unless you’re in engineering or manufacturing, it can seem like a black box. This guide is designed to demystify blow moulding for product designers, startup teams, and clients exploring custom manufacturing for the first time.
What Is Blow Moulding, in Simple Terms?
Blow moulding is a manufacturing method used to create hollow plastic parts—think bottles and enclosures. The principle is simple but powerful: plastic is heated, shaped into a tube, placed inside a mould, and then expanded using air pressure until it takes on the shape of the mould cavity.
To picture it another way, imagine inflating a balloon inside a mould—except the balloon is molten plastic, and the mould is engineered to specifications.
How Does It Work?
There are several types, but the general process goes like this:
Plastic is melted into a tube shape called a parison (or preform).
The parison is placed into a metal mould.
Air is blown into the parison, inflating it like a balloon until it takes the shape of the mould.
The part is cooled, ejected, and trimmed.
Here’s a quick comparison of the three main types:
| Type | Best For | Notes |
|---|---|---|
| Extrusion Blow Moulding | Bottles, containers, tanks | Continuous and cost-effective |
| Injection Blow Moulding | Small medical or cosmetic bottles | High precision, tight tolerances |
| Stretch Blow Moulding | Carbonated drink bottles (PET) | Stronger, lightweight structures |
Why Choose Blow Moulding?
- Cost-effective for medium to high volumes
Once the tooling is created, unit costs drop. - Fast cycle times
Blow moulding machines are designed for rapid production, often delivering finished parts in seconds. - Efficient material usage
Wall thickness can be tightly controlled. - Ideal for complex, hollow shapes
The process excels at producing enclosed forms like bottles, tanks, ducts, and enclosures.
Design Considerations
If you’re designing for blow moulding, keep these in mind:
Uniform wall thickness is crucial
Avoid sharp corners—they create stress points
Incorporate draft angles to allow clean release from the mould
Plan early for tooling split lines and material flow
💡 Tip: Involve your manufacturing partner early. A 3D model is just the beginning—designing for manufacture (DFM) saves time and cost later.
What Materials Can Be Used?
Clear, food-safe, good gas barrier
Durable, used in packaging & automotive
Chemically resistant, but less commonly used
Lightweight & flexible
Real-World Applications
Blow moulding is used across industries to create strong, lightweight, and seamless plastic parts. You’ve likely handled dozens of them without realising it. Common applications include:
Consumer packaging – Bottles for water, shampoo, & cleaning products.
Medical and pharma – Sterile containers, inhaler parts, and fluid reservoirs.
Automotive – Air ducts, fuel tanks, and under-the-bonnet components.
Industrial – Custom tanks, tool housings, and safety equipment casings.
Product design – Bespoke enclosures and functional parts in small to large runs.
