How to avoid problems such as bubbles, cracks or deformation in Plastic Pipes?

In the production process of plastic pipes, bubbles, cracks and deformation are common quality problems. These problems not only affect the appearance of the product, but may also lead to performance degradation or even failure. In order to avoid these problems, it is necessary to start from multiple aspects such as raw material selection, production process control and post-processing. The following are specific solutions and optimization measures:

1. Raw material selection and pretreatment
(1) High-quality raw materials
High-purity resin: Select high-quality plastic raw materials with few impurities and uniform molecular weight distribution (such as PVC, PE, PPR or HDPE) to reduce bubbles or cracks caused by raw material problems.
Drying treatment: For plastics with strong hygroscopicity (such as nylon or PC), they need to be fully dried before processing to avoid water evaporation at high temperature to form bubbles.
(2) Additive optimization
Stabilizer: Add thermal stabilizer or antioxidant to prevent material degradation during high-temperature processing.
Lubricant: Use an appropriate amount of internal and external lubricants to improve material fluidity and reduce friction and heat accumulation during processing.
Impact modifier: For brittle materials (such as PVC), impact modifiers can be added to improve toughness and reduce the risk of cracks.
2. Extrusion molding process optimization
(1) Temperature control
Heating section optimization: The temperature of the heating section of the extruder should be gradually increased to ensure that the plastic melt is evenly plasticized and avoid local overheating or incomplete melting.
Cooling rate control: Rapid cooling after extrusion (such as water cooling or air cooling), but it is necessary to avoid excessive cooling that causes internal stress concentration and cracks.

(2) Screw design
Screw structure optimization: Use a screw design suitable for the characteristics of the plastic (such as a barrier screw or a hybrid screw) to ensure that the melt is evenly mixed and reduce bubble residue.
Back pressure adjustment: Properly increasing the screw back pressure helps to remove gas from the melt.
(3) Mold design
Flow channel optimization: The mold flow channel should be smooth and have no dead corners to avoid melt retention or uneven flow.
Exhaust design: Set exhaust holes or exhaust grooves in the mold to exhaust the gas in the melt in time to prevent bubble formation.
3. Injection molding process optimization
(1) Injection parameter control
Injection speed: Appropriately reduce the injection speed to avoid high-speed mold filling, which may cause air to be drawn in and form bubbles.
Dwelling time and pressure: Extend the holding time and appropriately increase the holding pressure to ensure that the melt fully fills the mold and compensates for shrinkage.
Melt temperature: Set the appropriate melt temperature according to the material properties to avoid decomposition due to excessively high temperature or insufficient fluidity due to excessively low temperature.
(2) Mold temperature control
Uniform heating: Ensure that the temperature of each part of the mold is uniform to avoid deformation or cracking of the product due to excessive local temperature difference.
Cooling system optimization: Design an efficient cooling system to ensure uniform cooling of the product and reduce internal stress.
4. Wrapping molding process optimization
For large-diameter pipes (such as HDPE wrapping pipes), the following points should be noted:
Tension control: Ensure that the tension of the strip is uniform during the winding process to avoid deformation or cracking due to uneven tension.
Welding quality: Use high-quality hot-melt welding technology to ensure weld strength and sealing.
Cooling time: Ensure sufficient cooling time to avoid deformation caused by premature demoulding.
5. Post-processing and testing
(1) Stress relief
Annealing: Anneal the finished pipe to release internal stress and reduce the risk of cracks and deformation.
Slow cooling: Avoid sudden cooling during the cooling process and adopt a gradual cooling method.
(2) Quality inspection
Bubble detection: Use ultrasonic detection or X-ray detection technology to detect internal bubbles or defects.
Dimension detection: Use laser scanning or caliper measurement to ensure that the wall thickness uniformity and external dimensions meet the standards.
Mechanical property testing: Perform tensile, bending and impact tests to evaluate the toughness and crack resistance of the material.

Through scientific design and strict process control, the quality of plastic pipes can be significantly improved to meet the market's demand for high performance and high reliability.