Causes and Solutions of Abnormal Phenomenon of PVC Extrusion Plastic Profile

April 13, 2018

 

 

As one of the most professional PVC Extrusion manufacturers in China, today we are going to introduce the causes and solutions of abnormal phenomenon of PVC Extrusion plastic profile:

 

 

First, the fluctuation of feedstock of the PVC Extrusion Plastic Profile

 

1. Possible reasons:

 

1) poor fluidity of raw materials;

 

2) the material is easy to form hollow wall hanging in the center of the hopper, and the material of the bridge frame is stagnant;

 

3) the feeding temperature is too high ;

 

4) too high humidity at the bottom of hopper.

 

2. Solutions:

 

1) dry mixture of PVC powder with suitable fluidity;

 

2) install stirring feeder to prevent bridge building, check frequently and deal with it in time;

 

3) cooling through cooling water in feed section or lowering the temperature of feeding section;

 

4) remove the wet material from the hopper to keep the hopper dry.

 

 

 

Second, Section bending of the PVC Extrusion Plastic Profile

 

1. Possible reasons:

 

1) the whole production line is not straight;

 

2) improper cooling method;

 

3) abnormal vacuum cooling channel;

 

4) the head; the flow channel and clearance are unreasonable, the wall thickness is wide;

 

5) the extrusion speed is too fast;

 

6) the upper and lower tracks of the tractor are out of sync;

 

7) irregular assembly of dies;

 

8) the resistance of each forming surface of the shaping die is not balanced.

 

2. Solutions:

 

1) adjust the production line to keep it in a straight line;

 

2) strengthening the partial cooling of the wall thickness and lowering the water temperature;

 

3) check the vacuum cooling system to normal;

 

4) correcting the flow channel and wall thickness to uniform discharge;

 

5) reducing extrusion speed;

 

6) checking and adjusting the synchronous running of the upper and lower track of the tractor;

 

7) after the mold is installed, the center of the mould is corrected with water;

 

8) cleaning model or professional maintenance.

 

 

 

Third, local contractions of the PVC Extrusion Plastic Profile

 

1. Possible reasons:

 

1) the resin movement in the mouth die is slow and the groove is stretched;

 

2) improper vacuum operation or unsuitable vacuum control;

 

3) the cooling water temperature is too high;

 

4) Local cooling is too fast.

 

2. Solutions:

 

1) cleaning die correction model to reduce the traction speed or rib flow speed within the die;

 

2) adjust the vacuum degree, or use the chuck tool to poke a small hole in the material before entering the mould, so that the profile is open and the vacuum adsorption is strengthened;

 

3) lowering water temperature and improving cooling efficiency;

 

4) turn off small local cooling water.

 

 

 

Fourth, the profile after the shrinkage rate is large

 

1. Possible reasons:

 

1) high traction speed;

 

2) the cooling of the mould is not enough;

 

3) too high head temperature;

 

2. Solutions:

 

1) adjusting traction speed;

 

2) improving cooling efficiency;

 

3) reduce the temperature of the machine head;

 

 

Fifth, the size of the product, when the thickness of large and small

 

1. Possible reasons:

 

1) fluctuation of feed;

 

2) abnormal heating of electrothermal coil;

 

3) unstable traction surface, sliding of traction motor or fluctuation of speed;

 

4) uneven mixing;

 

5) change of die clearance;

 

6 ) There is material stagnation in the die head .

 

2. Solutions:

 

1) use dry PVC powder with proper fluidity;

 

2) overhaul the electric heating ring;

 

3) checking the tractor belt, whether the transmission is not sliding, whether the products on the track are sliding and whether the clamping is appropriate;

 

( 4 ) Check whether the mixture is uniform ;

 

5) check the test clearance of maintenance die;

 

6) reload inspection after cleaning.

 

 

 

Sixth, the end of the product is cracked or serrated

 

1. Possible reasons:

 

1) poor plasticization of formula;

 

2) low temperature of die;

 

3) the local temperature of die is low.

 

2. Solutions:

 

1) check and adjust the formula;

 

2) increasing die temperature;

 

3) avoid small stimulation.

 

 

 

Seventh, the appearance of weld marks

 

1. Possible reasons:

 

1 ) the structural design of the die is not good ;

 

2) material selection and molding conditions are inconsistent.

 

2. Solutions:

 

1) uniform material flow in the die;

 

2) increasing the head pressure of the front end;

 

3) increasing the length of the end of the die;

 

4) setting the material pool behind the die core support;

 

5) increase resin runner at resin entrance;

 

6) reducing the external lubricity of mixture;

 

7) adopting materials with low melt viscosity;

 

8) increasing fuselage temperature and lowering die temperature;

 

9) reducing extrusion speed.

 

 

 

Eighth, Blobs or bulges on the surface or inner wall of the profile

 

1. Possible reasons:

 

1) the raw materials are mixed with impurities;

 

2) the content of water or volatile in raw materials is high;

 

3) the stacking time of powder is too long;

 

4) low temperature of fuselage and high temperature of head;

 

5) poor thermal stability of materials;

 

6) the extrusion speed is too high.

 

2. Solutions:

 

1) examining the sources of impurities in order to remove them;

2) drying raw materials to reduce moisture content

 

 

Other knowledge about PVC Extrusion, please visit www.lcpvc.com to learn more.

 

 

 

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