Abnormal phenomena, causes and solutions in the process of soft PVC pipe forming
The soft PVC pipe is made of PVC resin and the pipe made of plastic with plasticizer content of more than 20 parts (generally 40~60 parts) is called soft PVC pipe. The commonly used soft PVC pipe has an inner diameter of 1~40mm.
Soft PVC pipe production process
The production process of soft PVC pipe is divided into four parts: pre-treatment of raw materials, kneading, granulation and extrusion of pipes:
1. Pretreatment of raw materials The PVC resin, plasticizer, stabilizer, lubricant, filler, pigment, etc. used are sieved and ground.
2. Kneading The processed raw materials are kneaded by an inefficient kneading machine for a long period of time, so that the various ingredients are uniformly dispersed, and the swelling and absorption effect is good.
3. Granulation The kneading material can be granulated by two methods of extrusion or calendering.
4. Extrusion pipe extrusion extruder is divided into flat extrusion method [see Figure (a)] and flat extrusion method [see Figure (b)] to extrude the pipe.
Soft PVC pipe extrusion device
Abnormal phenomena, causes and solutions in the process of soft PVC pipe forming:
First, the soft PVC pipe surface is dull
Cause: Poor plasticization, low temperature of the head
Solution: increase body temperature and increase head temperature
Second, the surface of the soft PVC pipe hose has particles
Cause: improper sieving of the resin or fisheye of the resin itself
Solution: Carefully screen the resin or replace the resin
Third, the soft PVC pipe wall is not round
Cause: Extrusion temperature is too high, cooling conditions are not suitable
Solution: Reduce processing temperature, adjust water volume and cooling tank length
4. The surface of soft PVC pipe has cloud, plaque and rough surface.
Cause: The temperature of the head is too high, the die stick is decomposed, and the temperature is too high when driving.
Solution: Reduce the temperature of the machine head, clean the die, adjust the driving temperature, and apply a layer of lubricant to the nose before driving.
Five, soft PVC pipe material pipe blistering
Cause: The host temperature is too high, and the semi-finished product contains moisture.
Solution: reduce temperature, semi-finished product drying
Sixth, soft PVC pipe wall has material marks
Cause: There are impurities in the machine head, die, and there are scars at the exit of the mandrel.
Solution: clean the machine head, polish the die and core mold
Seven, soft PVC pipe has weld lines
Cause: The structure of the core mold shunt is unreasonable, the temperature of the head is too low, the compression ratio of the head is small, the length of the set is too short, and the temperature is too high.
Solution: Improve the structure of the runner, improve the temperature of the head, and improve the design parameters of the head
Eight, soft PVC pipe material is too soft, pipe drooping
The discharge is too soft and the pipe is drooping
Cause: Temperature control is too high
Solution: Reduce the temperature
Nine, soft PVC pipe material thickness is uneven
Cause: The gap between the barrel and the screw is large, the extrusion pulse phenomenon occurs, the compression ratio of the head is too small, the feeding is uneven, and the traction speed is abnormal.
Solution: The main machine should be repaired, the design of the machine head should be improved, the feeding system should be repaired, the traction speed should be corrected, and the traction roller should be adjusted.
Ten, coke or decomposed yellow line appears on the wall of soft PVC pipe
Cause: The machine head has a dead angle, the material is partially decomposed, the main material is partially decomposed, the temperature of the main machine or the head is too high, and the material stability is poor.
Solution: demolish the mold or improve the design of the machine head, clean the main machine, adjust the temperature, check the heating ring, improve the formula design, improve the material stability
11. Soft PVC pipe has pitting or impurities on the surface of the pipe.
Cause: There is decomposition stock in the machine head
Solution: Increase the speed, use the material to bring out impurities or decomposition materials, if it is invalid, clean the die
Twelve, soft PVC pipe diameter size specifications do not match
Cause: Large diameter: the die temperature is too low, the draw ratio is small, and the pipe diameter is small: the die temperature is too high, and the draw ratio is large.
Solution: adjust the die temperature, adjust the draw ratio, adjust the die temperature, adjust the draw ratio
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