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Injection and over-molding processes are commonly used in many industries for the production of plastic and composite components. The rise of the smartphone in the last two decades saw hundreds of manufacturers design protective casing for these devices.

These manufacturing processes allow for the rapid prototyping and production of phone cases in different colors and materials. It involves the injection of liquid polymers into molds that cool and “cure” into the desired shape, with minimal tolerances to ensure optimal fit and function of the case to the phone.

Injection molding and over-molding processes are affordable, reducing manufacturing costs. Manufacturers can create complex designs and shapes with precision dimensions and access to the device’s ports and buttons. The result is a model-specific form-fitting cellphone case with tight tolerances and precision fitment to the device.

These highly efficient manufacturing processes allow high-volume production of thousands of phone cases per hour to meet high market demand. With economies of scale, manufacturers can produce cases for cents per unit.

Phone cases feature designs with three types of materials, and each performs differently in injection-molding and over-molding processes. This post examines each of these materials in detail and the processes involved with creating high-quality phone cases.

Silicone phone case

Silicone phone case

TPU Phone Cases

Thermoplastic Urethane (TPU) is a common material used in phone case manufacturing. It features excellent rigidity and texture for the phone case. This hard plastic is the opposite of soft and flexible silicone phone cases.

TPU phone cases are highly durable and drop and heat-resistant, providing excellent wear and scratch resistance. TPU is water resistant and protects your phone from contaminants like oils and greases.

The most important part of the production process in TPU phone cases is the “curing” or drying of the material after completing the molding of the case. The injection molding machine removes all the moisture from the material, achieving a mold design that suits the shape of the phone case.

Manufacturers typically run a standard of less than 0.02% water content in the material. After curing, the dry TPU materials are sent to the mold for shaping into the phone case design. The injection or over-molding tooling features a set melt temperature to ensure even distribution of the material during manufacturing.

The screw injects the TPU material into the mold cavity under pressure, creating the phone case in the mold’s shape. After curing, the manufacturer ejects the case from the mold. This process is usually automated, allowing for fast production of TPU phone cases.

Injection Molding for Silicon Phone Cases

Silicone is another popular material used in phone case design and manufacturing. The durability and flexibility of silicone make it a top choice for phone cases, creating a shock-absorbing case that won’t crack when dropped.

Silicone also offers easy machining of the material for finishing the phone case to custom dimensions. The machine-capable properties of silicone mean it’s easy to shape. The lightweight, sleek look of silicone has a soft feel in the hands, and a better texture and surface grip than ABS or TPU plastics.

Silicone has water-resistant properties and is suitable for use in over-molding and injection molding processes. Compression and low-pressure injection molding are the most common production methods, especially in high-volume phone case production using this material.

Manufacturers soften silicone pellets under heat, injecting the materials into the mold under pressure. The process liquefies the plastic pellets, injecting them into the phone case mold, where they form the product’s final shape.

After curing, the finished phone case is ejected from the mold and trimmed to specifications. Trimming can involve manual or CNC processes to form the final shape of the cell phone case.

Engineering Plastics Phone Cases

Many premium cell phone cases feature design and construction with “engineering plastics.” These plastics are expensive compared to the first two options in this review. However, these materials offer several advantages for phone case design over those previously mentioned.

Engineering plastics are durable and lightweight, with excellent chemical and physical properties. Some of the common engineering plastics used in cell phone case production include polycarbonate, polypropylene, and Acrylonitrile Butadiene Styrene.

Polycarbonate is one of the stiffest and strongest plastics available in phone case design and manufacturing. It offers excellent durability and service life and retains its color with frequent exposure to the sun’s UV rays. Polycarbonate is also highly resistant to moisture and chemicals.

Acrylonitrile Butadiene Styrene (ABS) is another highly popular material used in phone case production. ABS is highly impact-resistant for excellent drop resistance. The glossy look of the case is attractive, and manufacturers can produce cases in any color requested.

Polypropylene (PP) is a semi-transparent, semi-hard plastic offering excellent resistance against UV rays and moisture. It’s another popular material used in phone case production, giving excellent results.

In Closing

Manufacturers must consider several factors when planning the production process for cell phone cases. Choosing the right polymer for the project is vital to the finished product’s appearance and performance properties.

While selecting the right polymer for the project is essential to producing the desired product with the right characteristics, tooling is another top consideration.

Injection and over-molding production processes rely on the correct tooling design to ensure a final production that meets design specifications. Mold design plays a vital role in the consistency and quality of the final phone case.

Typically, a company looking to produce a top-quality product will consult with a manufacturing firm to finalize the project before it goes into high-volume production. The manufacturer may create a prototype to settle on the final design parameters before building tooling for mass production of the phone case.

Another factor to consider when planning out your project is the mold design and production processes. Injection molding can create complex designs and features on phone cases. However, the manufacturer must use the right injection molding machine model. They must ensure monitoring of the correct injection pressure and time to get optimal production results.

By considering all these factors, manufacturers can produce high-volume production of high-quality phone cases in various materials and design styles.