Common Problems and Solutions in TPU Injection Molding

TPU injection molding is a highly efficient and precise manufacturing process. TPU granules are heated to a molten state, injected into a mold cavity, and then cooled and solidified to obtain a product that meets design requirements. Common problems and solutions in TPU injection molding include:

1. Product Depressions:

Causes: Insufficient mold feed, high melt temperature, short injection time, low injection pressure, insufficient mold closing pressure, improper mold temperature, asymmetrical gate, poor venting in the depressed areas, insufficient mold cooling time, worn screw check ring, uneven product thickness, etc.

Solutions: Increase feed rate, decrease melt temperature, increase injection time, increase injection pressure, appropriately increase mold closing pressure, adjust to an appropriate temperature, adjust mold inlet size or position, add vents to the depressed areas, extend cooling time, replace screw check ring, increase injection pressure, etc.

2. Air bubbles in the finished product:

Causes: Moist raw material, insufficient injection, excessively fast injection speed, excessively high raw material temperature, low back pressure, excessively thick finished product cross-section or ribs, insufficiently small runner and overflow, uneven mold temperature, excessively fast screw retraction speed, etc.

Solutions: Thoroughly dry the raw material; check temperature, injection pressure, and injection time; reduce injection speed; reduce melt temperature; increase back pressure; change finished product design or overflow location; enlarge the runner and inlet; adjust mold temperature to uniformity; reduce screw retraction speed, etc.

3. Product Cracks:

Causes: Difficult demolding, overfilling, low mold temperature, defects in product structure, etc.

Solutions: Ensure sufficient draft angle in the mold forming space; appropriate ejector pin size, position, and type; reduce injection pressure to prevent overfilling; increase mold temperature; modify product or mold design, etc.

4. Product Warpage/Deformation:

Causes: Insufficient cooling and setting time, excessively high mold temperature, uneven cooling, and asymmetrical runner system, etc.

Solutions: Optimize mold design to avoid excessive thickness differences in the same plastic part, excessive sharp angles, and insufficient buffer zones; set an appropriate number of ejector pins and design a reasonable mold cavity cooling runner, etc.

5. Product Sticking to the Mold (Difficult Demolding):

Causes: Excessive injection or holding pressure, unreasonable mold design, etc.

Solutions: Reduce injection or holding pressure; optimize mold design to ensure sufficient draft angle and appropriate ejection method, etc.

Qingdao Xueyu Molding Products Co., Ltd. is mainly engaged in the design and manufacturing of injection molds, injection molding and secondary processing (spraying, pad printing, ultrasonic welding, stamping), etc. For more information about TPU injection molding, please contact us.

Website: www.xyzmould.com

Address: No.18 Henan Head Road, Henan Head Community, Jihongtan Street, Qingdao Industrial Park, Shandong Province, China

Email: wangmiaotian8@163.com