Thin Wall Injection Molding

We specialize in advanced thin wall molding solutions that deliver superior strength while significantly reducing part weight and material usage. Our state-of-the-art equipment and proprietary processes achieve exceptional dimensional accuracy with wall thickness as thin as 0.5mm, accelerating cycle times for high-volume production.

From intricate consumer electronics to durable food containers, we help you achieve lighter, stronger, and more cost-effective products.

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What is thin wall injection molding?
What is the principle of thin-wall injection molding?
Thin-wall injection molding selecting raw materials guide
Thin-wall injection mold manufacturing guide
Why use thin-wall injection molding？
What are the applications of thin-wall injection molding？

What is thin wall injection molding?

Thin-wall injection molding is a specialized injection molding process used to manufacture parts with thin walls.

This technology is often referred to as thin-wall plastic injection molding, and it can be defined in three ways:

The molded product has a wall thickness of less than 1 mm, with a projected area of the plastic part exceeding 50 cm².
The wall thickness of the molded product is below 1 mm (or 1.5 mm), or the ratio of thickness (t) to diameter (d) of disc-shaped plastic parts is under 0.05. This is considered thin-wall injection molding.
The flow length (L) from the mold’s main channel to the furthest point of the finished product, divided by the wall thickness (t) of the product, is referred to as the flow length/wall thickness ratio. When this ratio exceeds 150 (L/t > 150), the process is categorized as thin-wall injection molding. If the thickness is not uniform, the ratio can be calculated in sections.

plastic food container made by thin-wall injection molding

flow length wall thickness ratio in thin-wall injection molding process

For example:

For a disposable lunch box made from PP (with a viscosity factor of 1), the flow length is 135 mm and the wall thickness is 0.45 mm. The flow length/wall thickness ratio is 300 (135/0.45), which is greater than 150, qualifying it as thin-wall injection molding.
For a mobile phone battery shell made from PC (with a viscosity factor of 2), the flow length is 38 mm and the wall thickness is 0.25 mm. The flow length/wall thickness ratio is 152 (38/0.25), and when multiplied by the viscosity factor (2), the ratio becomes 304, which is also greater than 150, thus also classified as thin-wall injection molding.

What is the principle of thin-wall injection molding?

The cold mold cavity wall causes the molten metal to solidify upon contact, forming a solidified layer that reduces the thickness of the flow channel. This effect is more pronounced when the wall thickness is thinner.

The key principles of thin-wall injection molding include the following aspects:

1

Fast injection speed:

Thin-wall injection molding requires injecting hot molten plastic material into the mold in a very short time, and usually requires the use of a high-pressure injection machine and a high-speed injection cavity to achieve a fast injection speed.

2

Rapid cooling and solidification:

In order to ensure the uniformity of wall thickness and dimensional stability of thin-wall injection molded products, rapid cooling and solidification are required after injection. Usually, cooling systems and rapid mold opening systems are used to achieve rapid cooling and solidification.

3

Suitable injection molding materials:

Thin-wall injection molding requires the selection of plastic materials with good fluidity and fast solidification properties to ensure that the material can achieve the desired effect during rapid injection and rapid cooling.

For a 1mm wall thickness, a 0.2mm solidified layer forms, leaving a 0.6mm thick remaining flow channel. For a 0.5mm wall thickness, the solidified layer is also 0.2mm, leaving just 0.1mm for the flow channel. If the solidified layer becomes too thick and obstructs the flow channel, the mold may not fill completely.

As a result, thin-wall injection molding requires the injection of hot-melt plastic material into the mold within a very short time. This ensures rapid cooling and solidification, enabling the production of thin-walled plastic products.

Injection Flow Process

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Guide to Selecting Raw Materials for Thin-Wall Injection Molding

When selecting materials for thin-wall injection molding, key principles to consider include excellent fluidity, high impact resistance, superior thermal stability, low orientation, and excellent dimensional stability.

Commonly used materials for thin-wall injection molding include polypropylene (PP), polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), PC/ABS blends, and PA6, among others.

High Thermal Stability:

Thin-walled injection molded parts are often used in environments with elevated temperatures, so the materials must exhibit excellent thermal stability. This ensures that the material retains its physical and chemical properties under heat, preventing deformation or aging.

Low Directionality:

To maintain consistent product performance in all directions, thin-walled injection molded parts require materials with low directivity. This reduces the risk of uneven performance caused by directional differences, ensuring uniform quality throughout the part.

Excellent Dimensional Stability:

The raw materials used in thin-wall injection molding should offer excellent dimensional stability. This ensures that the molded parts experience minimal dimensional changes during both processing and usage, meeting the required precision standards.

Flowability:

Good flowability is essential in thin-wall injection molding to ensure that the molten material can fill the thin walls of the mold. Materials with high flowability ensure that thin-walled parts are completely filled during the injection process, preventing voids or incomplete filling. For example, PP plastics with a high melt index, such as Basell’s Moplen RP1086, are favored. PS/ABS blends are also commonly used for their combination of toughness and flowability, making them ideal for thin-wall applications.

High Impact Resistance:

Thin-walled plastic parts often need to withstand higher impact forces, so choosing materials with high impact resistance is crucial. This ensures that the parts can resist external impacts without breaking or getting damaged during regular use. As wall thickness decreases in thin-wall injection molding, materials with better physical properties are needed to maintain the strength and durability of the product.

Guide to Manufacturing Thin-Wall Injection Molds

When manufacturing thin-wall injection molds, the following factors must be considered:

Mold Steel Material Selection

For the production of thin-wall injection molds, it is crucial to select materials that offer high strength, rigidity, wear resistance, and corrosion resistance. Commonly used materials include high-quality alloy steel and stainless steel, which are durable enough to withstand the demands of thin-wall molding.

Mold Structural Design

The structural design of thin-wall injection molds needs to be efficient and well-thought-out. Like the template of the injection molding machine, the mold template should be thick enough to minimize deformation during the injection process. High-speed injection molding also requires effective venting, so ensuring sufficient exhaust grooves, using breathable mold steel, and incorporating vacuum systems are essential methods to prevent molding defects.

Mold Processing Technology

The processing technology for thin-wall injection molds must be precise to ensure the dimensional accuracy and surface quality of each component. Achieving high processing accuracy is critical to maintain uniform wall thickness around the circumference or four walls of the mold.

Mold Assembly and Debugging

Mold assembly and debugging are key steps in the production of thin-wall injection molds, with higher requirements for multi-cavity molds. These molds are equipped with ejection and blowing devices to facilitate the rapid removal of the finished product after demolding, as well as to quickly close the mold for the next cycle.

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injection mold of thin-wall plastic parts

What’s the reason of choosing thin-wall injection molding？

The cost of plastics typically represents a significant portion of the finished product cost, often ranging from 50% to 80%. By reducing wall thickness, this proportion can be lowered. As consumer electronic devices like mobile phones, digital cameras, and handheld computers continue to become smaller and lighter, the design of plastic parts is increasingly shifting towards thinner walls.

① Weight Reduction:

Thin-wall injection molding enables the production of lightweight parts with reduced material usage, making it ideal for industries like aerospace, automotive, and medical, where weight is a critical factor.

② Cost Savings:

By minimizing material usage, thin-wall injection molding helps lower production costs, particularly for high-volume production runs.

③ Increased Production Speed:

Thin-wall injection machines are capable of producing parts faster than traditional molding machines, making them highly efficient for large-scale manufacturing.

④ Improved Part Consistency:

Thin-wall injection molding ensures uniform part quality, minimizing shrinkage and ensuring consistency, which is crucial for applications requiring precise, reliable components.

What are the applications of thin-wall injection molding？

Thin-wall injection molding technology is widely used in various industries. Some common applications include:

① Food Packaging: Thin-wall injection molding is extensively used in food packaging, allowing the production of containers with excellent sealing and preservation properties, such as plastic bowls and boxes. The technology’s fast production speed and high efficiency make it suitable for large-scale production, meeting the food packaging industry’s demand for both production efficiency and high-quality products.

② Electronic Product Housing: Thin-wall injection molding is commonly used in the production of electronic product housings, including mobile phone cases, TV enclosures, and other electronic devices. This technology enables the creation of thin yet durable housings, offering high precision and dimensional stability that meet the aesthetic and accuracy requirements for electronic products.

③ Auto Parts: Thin-wall injection molding is widely applied in automotive parts manufacturing, producing lightweight yet strong components such as interior parts and automotive lighting. The technology’s fast cooling and curing process, along with its high efficiency, enhance production speed and help reduce manufacturing costs for auto parts.

④ Medical Devices: Thin-wall injection molding is crucial in the production of medical devices, offering the ability to manufacture products like syringes and infusion sets with excellent biocompatibility and ease of cleaning. The precision and dimensional stability of thin-wall injection molding ensure that medical devices meet the high standards for both appearance and accuracy required in healthcare.

Thin-wall injection molding is an essential technology for producing high-performance thin-walled plastic products. By utilizing rapid injection speeds and quick cooling and solidification, it enables the production of durable and precise parts. This technology is widely used across industries such as food packaging, electronics, automotive, and medical devices. As technology continues to advance, thin-wall injection molding will expand into even more fields, further driving innovation and efficiency across various sectors.

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