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08/08/2025

Thin-Wall Thermoplastic Injection Moulding: The Key to Lighter, More Sustainable Packaging

In a market that increasingly demands sustainability, production speed, and efficient design, thin-wall injection moulding is emerging as a key technology for transforming the packaging sector. But what exactly does this process involve? What materials and technologies make it possible?

What Is Thin-Wall Injection Moulding?

A moulded part is considered “thin-wall” when the product thickness is less than 0.5 mm and the length-to-thickness (L/t) ratio exceeds 200:1. This type of moulding is characterized by:

Ultra-fast cycles (1.8–3 s)
Very high injection rates
Process pressures above 2000 bar
Multi-cavity moulds with highly efficient cooling/heating

Reducing wall thickness by just 0.1 mm can increase the required pressure by more than 10%, which demands not only high-flow materials but also perfectly synchronized machinery and moulds.

Current Technologies in Thin-Wall Moulding

Today, various types of equipment are used in thin-wall thermoplastic injection moulding to achieve very thin part thicknesses with plastic materials that offer enough flowability to fill the parts before the material cools prematurely.

The main technologies include:

High-Speed Injection (Accumulators)

Ideal for PP food packaging. These systems reach speeds of 1200 mm/s with L/t ratios above 400. Accumulators and auxiliary equipment supply hydraulic pistons with enough energy to achieve these high injection speeds.

Injection-Compression (Coin Mould)

Perfect for caps and disc-shaped parts. This technology reduces injection pressure by up to 50%, avoids warping, and improves surface finish by applying even compression pressure across the mould surface.

HEAT & COOL

Used for high-end aesthetic technical parts. It dynamically controls mould temperature to produce thin walls with excellent surface quality. Plastic is filled and packed at high mould temperatures for better flow and then rapidly cooled to boost productivity.

Micro-Injection

Designed for small, high-precision parts with wall thicknesses under 0.3 mm. This technique injects materials via high-speed pistons and uses specialized moulds to prevent instant cooling. In many cases, the aspect ratio does not meet traditional thin-wall definitions.

Recommended Materials for Thin-Wall Applications

Adapting to thin-wall packaging technology involves more than equipment or processing methods—the material also plays a critical role in achieving such thin part dimensions.

The polymer’s nature and flowability directly influence achievable thickness and aspect ratios. Lower viscosity materials not only allow for thinner walls with longer injection paths but also suffer less shear stress in the mould cavity.

Thus, understanding the material’s properties, the application, and the part design is essential to optimize flowability and performance. Specific additive solutions tailored to certain polymer matrices are crucial to achieving the required characteristics for thin-wall applications.

For example, PET is widely used in the packaging sector, both in its virgin and, more commonly, recycled (rPET) formats. It is increasingly being applied in small containers, cups, jars, sometimes with in-mould labelling (IML) for dairy, yogurt, and other food packaging.

However, PET’s high intrinsic viscosity presents a challenge for thin-wall injection. Therefore, both the process and material must be adapted to improve flowability, allowing proper mould filling before the material cools and compromises the process.