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How to successfully produce soft PU phone cases on a mobile cover making machine？

2025/10/20 By le zhan

mobile cover making machine 5-5

According to a survey by the Mobile Phone Accessories Market Report, 65% of US consumers prefer soft PU phone cases due to their superior feel, anti-slip properties, and shock absorption, making them one of the best-selling phone case types. However, many cases suffer from uneven softness, surface bubbles, or incomplete mold filling. One Indian customer we worked with wasted 15% of their PU material on defective phone cases because their standard mobile cover making machine couldn’t handle PU’s unique viscosity. After collaborating with Topstar, we provided a mobile cover making machine specifically designed for soft PU production—the TS 130 injection molding machine. This injection molding machine perfectly meets all the requirements for PU phone case production.

Why do soft PU phone cases require a dedicated mobile cover making machine?

Soft PU phone cases cannot be produced on just any mobile cover making machines. Soft PU has unique material properties, requiring precise control:

Viscosity: PU is thicker than rigid plastics like PC or TPU, requiring higher injection speeds and pressures to fill mold details and avoid voids ideally.

Temperature Sensitivity: PU degrades above 220°C and exhibits poor fluidity below 180°C. Even a ±5°C temperature difference can destroy its softness or cause surface defects.

Cooling Requirements: Soft PU requires gradual cooling to maintain its flexibility; rapid cooling can make the phone case hard and brittle.

Furthermore, conventional mobile cover making machines often fall short in this regard: their maximum injection speed is limited to 100 mm/s, and they utilize basic heating elements. The Topstar TS 130 injection molding machine, designed specifically for soft and semi-soft materials, easily addresses these challenges.

Why do soft PU phone cases require a dedicated mobile cover making machine

Speed ​​and Pressure of the Topstar TS 130 Injection Molding Machine

High injection speeds and high pressure are essential for producing soft PU phone cases, and these mobile cover making machines excel in both areas. Here’s how its specifications translate into higher-quality PU phone cases:

Maximum Injection Speed: 145 mm/s: 45% faster than standard machines, ensuring the viscous PU flows quickly into every mold crevice. For phone cases with narrow camera rings, this speed prevents incomplete filling that could result in an unmolded ring.

Maximum Injection Pressure: 290 MPa: High-pressure, densely packs the PU into the mold, eliminating air bubbles and ensuring consistent density.

High-Quality Screw Assembly: The TS 130 utilizes a 32 mm diameter chrome-plated screw with a special thread design that evenly melts the PU and smoothly pushes it into the mold. Unlike standard screws, this design prevents material degradation.

TS130 Injection Molding Machine

Ceramic Heating Elements for Precise Temperature Control of the PU

Temperature control is critical for soft PU materials. The inlet of this phone case making machine uses ceramic heating elements to ensure the polyurethane (PU) temperature remains within the ideal range, achieving an accuracy of ±1°C. Ceramic elements heat up faster than standard steel elements, providing more precise temperature control. This means the PU temperature can be maintained between 180°C and 220°C, preserving its softness and fluidity.

The ceramic elements also offer fast adjustment sensitivity. If the inlet temperature drops by 2°C, they respond within 0.5 seconds, preventing PU cold blocks and mold filling issues. Maintenance costs are also lower, as the ceramic elements resist corrosion from PU additives and have a service life twice that of steel elements. This reduces maintenance downtime and ensures smooth production. Comparative testing with other equipment demonstrated that the TS 130 consistently maintained an inlet temperature of 200°C throughout an 8-hour PU production cycle.

Step-by-Step Guide to Producing Soft PU Phone Cases on a Mobile cover making machine

Here’s a practical, step-by-step guide on how to produce soft PU phone cases on a mobile cover making machine:

Step 1: Prepare the PU Material
Dry the PU pellets at 80°C for 4 hours. Load the dried PU pellets into the hopper of the making machine, using a material filter to remove any dust or debris.

Step 2: Install the Mold

Install the single-cavity mold on the machine’s platen, ensuring it is evenly aligned. Also, check the mold’s cooling channels to ensure they are clean and connected to the machine’s cooling system.

Step 3: Program Production Parameters

Set the injection speed to 120-145 mm/s, the injection pressure to 250-290 MPa, the feed port temperature to 190°C-210°C, and the cooling time to 15-20 seconds.

Step 4: Run a Test Batch and Make Adjustments

Produce 10-20 phone cases and inspect for defects. If air bubbles are present, increase the injection pressure by 10 MPa. If the case is too stiff, reduce the cooling water temperature by 5°C.

Step 5: Start Full Production

Once the phone cases pass quality inspection, full production can begin. Monitor the consistency of the first 100 cases and check hourly to ensure parameters remain on track.

PU Phone Case Case Study

To help phone case manufacturers better understand the actual operation of the TS 130 mobile cover making machine, we’re sharing a real-world project. The goal was to produce soft PU phone cases with precise dimensions and consistent softness. Project details and results are as follows:

Machine: Topstar TS 130 injection molding machine.
Mold: Single-cavity mold.
Material: Soft PU.
Product Specifications: Weight = 26.5 g, Dimensions = 152 mm × 76 mm × 13 mm.
Production Parameters: Injection Speed: 130 mm/s, Injection Pressure: 270 MPa, Inlet Temperature: 200°C, Cooling Time: 18 seconds.
Cycle Time: 41 seconds.
Results: 98.5% yield rate, consistent softness across all products, and dimensional accuracy within ±0.1 mm.

The brand’s production manager noted, “We used to spend two hours a day sorting out defective PU phone cases. With the TS 130, that time has been reduced to 15 minutes, allowing us to produce more cases while reducing waste.”

mobile cover making machine

The TS 130’s Definitive Advantages in PU Phone Case Production

For manufacturers looking to capitalize on the market demand for soft PU phone cases, Topstar’s TS 130 injection molding machine, with its 145 mm/s injection speed, 290 MPa pressure, and ceramic heating elements, addresses the biggest challenges in PU production. This allows you to produce soft PU phone cases that meet consumer expectations for grip, softness, and durability.

 

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