PVC Profile Processing Common Problems&Causes

The feeding fluctuates, the feeding is difficult and unstable

1. The powder is wet

2. The speed of the feeding screw is unstable, or the density of the dry turbid material fluctuates

3. The dry mix has poor fluidity

4. The temperature of the feeding port is too high

5. The dry mixture forms stagnation, bridging or wall hanging in the hopper

6. The feeding port or feeding screw is blocked

1. Dry the raw materials, do not let the dry mix get wet

2. Stable working voltage and stable hot mixing process conditions

3. Improve the dry fluidity of dry mixes

4. Reduce the temperature of the feeding section or cool the feeding port

5. Check the discharge of the hopper, or install the agitator

6. Clean the hopper or feeding screw

7. Try to make the mixing ratio of recycled material and powder material constant and uniform

The torque value of the extruder or the current of the host is unstable, and the torque increases

1. Uneven quality of dry mix

2. Low temperature and poor plasticization

3. Too much feeding amount and poor plasticization

4. There are foreign objects in the machine

1. Check raw materials and mixing process

2. Increase the heating temperature

3. Adjust the metering feeding and screw speed

4. Check and disassemble the screw and barrel

Torque value drops

1. Insufficient feeding of the barrel

2. The temperature of the feeding section is too high

3. The temperature of the compression section is too low

1. Check whether there is material in the hopper, whether there is a bridge, and the feeding condition of the metering screw

2. The feeding section is cooled by cold water

3. Increase the temperature of the compression section

There is coke between the top of the screw, the die and the filter screen

1. The temperature of the barrel or the diversion campus is relatively high

2. The resistance of the filter plate or filter screen is large

3. Poor thermal stability of dry mix

1. Lower the die temperature

2. Clean up and increase the passage section of the filter plate

3. Check the thermal stability of raw materials such as PVC and dry blends

Decomposition in the die head, there are decomposed yellow lines on the surface of the product

1. Die temperature is too high

2. Poor thermal stability of raw materials and dry blends

3. There are depressions or material accumulation on the surface of the machine head

4. The structure of the die is unreasonable

1. Lower the die temperature

2. Check the thermal stability of raw materials and the quality of the mixture

3. Check and clean the machine head

4. Try to eliminate the dead angle in the machine head and reduce the time of material stagnation here

The surface of the profile is rough, and there are nodules, clouds, and corrugations.

1. The material mixing quality is poor and uneven

2. The temperature of the machine head is low

3. Mixed resins with different colors and different relative molecular weights

4. Excessive external lubricant

5. There are precipitates on the inner wall of the die

6. Die resistance is not enough

1. Check the mixing process and improve the quality

2. Properly increase the temperature of the machine head

3. Generally do not mix different grades and types of resins

4. Reduce the amount of external lubricant

5. Clean up the die

6. Reduce the section of the filter screen and filter plate and increase the extrusion volume

The surface of the profile is yellowed

1. The temperature of the machine head, transition section and die is too high

2. Poor stability of raw materials or dry mixes

1. Appropriately reduce the temperature of the area

2. Check the thermal stability of PVC and other raw materials to improve the quality of dry mix

darkened surface

1. The temperature of the machine head, transition section and die is low

2. The color of the dry mix is not good

1. Appropriately increase the temperature of the area

2. Check the mixing process and feeding sequence

Profile edges are burrs or jagged

1. The processing temperature is low

2. The object is poor plasticization

3. The edges of the die are rough

4. The formula is unreasonable

1. Increase the temperature of the machine head or barrel

2. Increase the barrel temperature or speed

3. Adjust and polish

4. Properly adjust the amount of lubricants and processing aids and reduce the amount of fillers

Profile size does not meet specifications

1. The vacuum degree is not enough, and the gap of the shaping die is blocked

2. The vacuum degree is not enough on the water, and the vacuum degree on the surface of the profile is not enough

3. Too fast traction and insufficient extrusion

4. The center position of the shaping die and the die is not aligned

1. Improve the degree of vacuum and clean up the gap of the shaping die

2. Increase the amount of water in the vacuum and improve the vacuum degree

3. Reduce the traction speed and increase the speed

4. Adjust the setting die and the center of the die to be in a straight line

There are bubbles in the section of the profile

1. The moisture or volatile content of the material exceeds the standard

2. The temperature of the barrel is too high, resulting in decomposition gas

3. Low vacuum degree of extruder exhaust

4. The friction heat of the screw is too high

5. Poor material stability and insufficient amount of stabilizer

1. Control the moisture of raw materials such as resin, pay attention to removing it when mixing, and add a pre-dryer if necessary

2. Reduce the temperature of the material in the barrel

3. Clean the pipeline, open the vacuum exhaust, and increase the vacuum degree as appropriate

4. Cool the screw and adjust the screw temperature

5. Check the resin stability and adjust the amount of stabilizer if necessary

Profile bending or warping

1. The center lines of the machine head, shaping, traction and other devices are not on the same straight line

2. The mold assembly is not level

3. The temperature of the machine head is uneven, and the discharge is uneven

4. The extrusion speed is too fast and the cooling is insufficient

5. Insufficient cooling of molding die and water tank

1. Adjust the production line to a straight line

2. After the mold is installed, calibrate it with a level ruler

3. Adjust the heating temperature and reduce the heating temperature on the side where the discharge speed is fast

4. Reduce extrusion speed and improve cooling conditions

5. Reduce the water temperature, increase the amount of cold water, or increase the length of the cooling water tank

Deformation or fracture of the inner reinforcement of the profile

1. Inappropriate traction speed

2. The temperature of the die is not suitable

1. When the inner rib shrinks or becomes thinner, reduce the traction speed; the inner rib is bent or corrugated to increase the traction speed

2. When the inner rib shrinks or becomes thinner, increase the die temperature; the inner rib is bent or corrugated to reduce the die temperature

The inner wall of the profile is rough

1. The screw speed is too fast

2. The barrel temperature is low

3. The material has high moisture and volatile content

4. If it occurs during driving, the temperature of the mold core may be low

1. Reduce the screw speed

2. Properly increase the barrel temperature

3. Clean the pipeline and improve the exhaust vacuum

4. Appropriately increase the temperature of the core or body

High longitudinal or transverse shrinkage of profiles

1. The temperature of the machine head is too high

2. The traction speed is too fast and does not match the extrusion speed

3. Insufficient cooling of the shaping die

1. Reduce the temperature of the machine head

2. Reduce the traction speed

3. Ensure the cooling water temperature and water pressure, improve the cooling efficiency, and lengthen the length of the cooling molding die if necessary

Profile slows down or stalls in the mold

1. Insufficient amount of lubricant

2. Not enough traction

3. Insufficient cooling

4. There is a deviation between the center of the stereotyped die and the die

1. Adjust the amount of lubricant

2. Increase the track pressure

3. Increase the amount of cooling water and reduce the temperature of the cooling water

4. Adjust the center position of the shaping die and the die into a straight line

Large shrinkage at profile reinforcement

1. The traction speed is too fast

2. The extrusion speed is too fast and the cooling of the inner ribs is insufficient

3. Die rib groove is stretched

4. Improper vacuum operation

1. Reduce the traction speed

2. Reduce the extrusion speed

3. Improve the fluidity of materials

4. Before the profile enters the shaping die, prick several small holes with copper needles on its surface to make the profile open and strengthen vacuum adsorption

Product traction fracture

1. The traction speed is too fast

2. The resistance in the setting mold is too large

1. Reduce the traction speed

2. Reduce friction, appropriately reduce the degree of vacuum, and try to use dry and wet mixing and shaping devices

Poor physical and mechanical properties of profiles

1. Poor quality of dry mix and uneven kneading

2. Improper extrusion process conditions

3. Improper control of die head and setting die

4. The resistance of the filter plate and the filter screen is small, and the back pressure is small

1. Check the formula and strictly control the mixing process

2. Adjust the metering feeding speed and the extruder screw speed to match

3. The heating temperature in the barrel should not be too high

4. Ensure that the material is well plasticized and uniform and stable

5. The traction speed and extrusion speed should be matched

6. The screw speed should not be too low, generally it should be 50~75%

7. The extruder must open the vacuum exhaust device and ensure a certain degree of vacuum

8. The stereotyped model should not be cooled quickly, but slow cooling is appropriate

9. The water temperature and water pressure of the circulating cooling water should meet the standard requirements

10. There is suitable pressure in the machine head

11. Increase the resistance of the filter plate and filter screen to increase the back pressure

The profile has obvious seam lines

1. The temperature of the machine head is low

2. Poor material temperature plasticization

3. Flow stress is not eliminated

4. The die design is unreasonable

5. The structure of the die is unreasonable

1. Increase the temperature of the machine head

2. Check the mixing and extrusion process parameters to improve the plasticization state of the material

3. Increase the length of the forming section

4. Increase the pressure in the front section of the die, or increase the length of the die setting section

5. Increase the material flow at the entrance of the die