Engineering plastics are widely used in industrial parts and various shell manufacturing due to their excellent characteristics - high strength, heat resistance, impact resistance, and anti-aging. However, cracking of plastic products is also a headache. The causes of cracking involve molds, molding processes, plastic materials, environmental stresses, etc. Today,
html will discuss the causes and solutions for cracking of plastic products in 0 days;1. Brief analysis and improvement suggestions for cracking causes
Different cracking causes will lead to different types of cracking. According to the cracking situation encountered during the actual development process, there are usually four situations for cracking of plastic products:
1. Release cracking, the plastic products will crack directly when they are taken out of the mold. The causes and consequences of this cracking are easier to estimate;
2. reliability test cracking, such as drop test , environmental test, distortion test local cracking or cracking occurs;
3. Assembly cracking, the product cracks during assembly;
4. Application cracking, the product cracks after being left for a period of time or during use. This cracking is often difficult to predict and the consequences may be devastating.
The above cracking situations have internal and external factors, and the same causes are also the same reasons; in response to the above problems, we comprehensively analyze the main factors affecting product cracking from the following aspects;
2. The impact of product design
1. The product wall thickness is too large, and the local shrinkage is severe;
2. During the design, the local bone position of the product is too thin and cannot withstand a large impact force;
3. The design strength of the whole machine is too weak, and the reinforcement ribs are too few;
4. There are too many sharp corners inside the product, and the glue is not smooth during injection molding. It is best to use rounded corners to transition to reduce the cracking risk of when stress concentration in ;
3. The impact of mold design
1. The glue inlet
2. The design distribution of gate is unreasonable, which is easy to form welding wires, and the product strength is the weakest near the welding wire;
3. The cooling system design is unreasonable, and local overcooling or overheating produces stress shrinkage;
4. The demolding slope is not
5. Poor mold cavity design (internal stress concentration occurs)
6. Insufficient exhaust
7. Product ejection is unbalanced, and it is easy to cause cracking when ejected;
8. The mold surface is too rough
4. The influence of injection molding process
1. Too much material metering
2. The resin temperature is too low
3. The mold temperature is too low
4. The injection pressure is too high and too small will affect the product Strength, too high pressure will cause the product structure close to the gate to become brittle due to the large stress, too low pressure will cause the strength of the joint wire at the end of the product to become weaker, and the product is also prone to cracking. It is recommended to adjust it based on the mold flow analysis of data;
5. The injection pressure is too large
6. The injection time is too long
7. The ejection speed is too fast or too slow
5. The influence of plastic raw materials
1. The material contains volatiles
2. Mix and matches of different materials.
3. The material has not been dried
4. Incorporate water nozzle material too much
5. The surface process during surface treatment has a corrosive effect on the product, and cracks will occur over time;
There are many factors that affect cracking of injection molded products, and comprehensive analysis and consideration must be made. Many factors restrict each other. Product design should be reviewed in advance with mold design, make reasonable choices, solve problems, and improve quality;
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