Analysis on the Forming Quality of PVC Double Wall Corrugated Pipe Produced by Plastic Extruder


Plastic extruder will inevitably have some quality problems in the production of polyvinyl chloride (PVC) double wall corrugated pipe, in addition to the problems of equipment itself, there are still very cases of quality problems. We can ignore the problems caused by equipment, because generally, the equipment manufacturers will debug the equipment for normal production free of charge. The quality problems and related analysis of six common bellows in the production process are as follows.

1The shape of the outer surface ripple of the pipe is irregular

aThe corrugated forming die of two half open die is in dislocation. The running speed of the two half die shall be adjusted again to synchronize or the two half die shall be adjusted to be correct accurately.

bThe transmission chain for two half opening dies is seriously worn, and there is accumulated error during synchronous operation, resulting in dislocation of two half opening dies after running for a period of time. The transmission chain should be repaired and replaced.

cThe working speed of extruder screw is unstable, which makes the extrusion flux of extruder inconsistent, the shape error of the pipe blank is large. The screw transmission system shall be repaired for failure.

dThe pressure of compressed air is unstable, which makes the shape of the corrugated in the blowing and expanding forming have a large shape error. The stable supply pressure should be adjusted.

eThe high temperature of molten material for forming pipe blank makes it difficult to form molten material. The melt temperature should be reduced properly.

2The surface of the pipe is dull

aThe melting temperature is low and the plasticization of raw materials is not comprehensive, so the process temperature of barrel and die should be increased appropriately.

bThe temperature of cooling water is too high, and the temperature of low cooling water should be reduced.

cThe length of the straight section of the pipe blank setting is insufficient, and the sizing pressure is small, so the structure and size of the die should be improved.

3Brittle pipe

aThe formula should be improved because the proportion of calcium carbonate is too high or the proportion of lubricant is unreasonable. Some acrylic resin processing aids are added to the raw materials to improve the gel rate of the melted materials.

bIf the moisture or impurity content in the raw material exceeds the standard, the raw material shall be dried or replaced.

cBecause of the insufficient pressure in the forming die, the forming quality of the pipe wall is poor, so the die structure should be improved.

dThe molten material temperature control of the formed pipe is unstable. The high or low molten material temperature is easy to make the pipe brittle after shaping. It should be noted that the temperature of the plasticized molten material should not be too high or too low, or the temperature difference is too large.

4Adhesion force between inner and outer walls of double wall corrugated pipe is poor

aThe temperature of the molten material in the molding mould is low, so the temperature of the forming die should be properly increased.

bThe proportion of lubricant in raw material is too large, so the lubricant addition should be reduced properly.

cThe cooling rate of pipe blank is too fast, and the two layers of material are not fused firmly. Pay attention to slow down the cooling rate of pipe blank properly.

5Longitudinal scratches on the inner wall of the pipe

aIf there are scratches or scraps on the mandrel of the inner wall surface of the formed pipe adhering to the working face, the scratches should be polished or the scraps on the working face should be removed.

bIf lubricant is stuck on the cooling set, the lubricant addition amount in the raw material formula shall be adjusted in time to remove the residual materials on the cooling set.

6There are cracks or corrugations on the inner wall of the pipe

aThe high pressure of the air used for forming the inner wall of the pipe or the insufficient pressure of the air used for forming the outer layer of the pipe will cause cracks or waves on the pipe wall. The pressure of the air for forming the pipe wall should be adjusted properly.

bThe compression ratio in the forming die is too small, resulting in the fusion strength of the fusion material at the rib of the splitter cone support being low, and cracks are easy to occur. The compression ratio of the structure in the mould to the molten material should be increased properly.

Above are some analyses on the problems of forming quality of PVC double wall corrugated pipe produced by plastic extruder. If you need some help, welcome to contact us. Ningbo Fangli Technology Co., Ltd., as a manufacturer with a complete set of extruder production line equipment for nearly 30 years, we have a lot of equipment manufacturing experience. We will provide you with professional technical guidance, and give you some help of purchasing appropriate plastic extruder equipment.

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