Faults Easily Occurred in the Production Line and Solutions


Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.


Here, we prepared some failures of pipe production line with solutions as follows for your reference:


1. The outer surface of plastic pipe is rough

Adjust the process temperature:

· Reduce the cooling water temperature, and the appropriate cooling water temperature of pipe is 20 ~ 25 ;

· Check the waterway for blockage or insufficient water pressure;

· Check whether the barrel, head and other heating rings are damaged;

· Adjust the inlet flow of sizing sleeve;

· Consult the raw material supplier and the raw material parameters of this batch;

· Check the mold core temperature. If it is higher than the die section temperature, reduce the core temperature;

· Clean the mold;


2. Groove marks appear on the outer surface of plastic pipes

· Adjust the outlet pressure of the sizing sleeve, and the water output shall be balanced;

· Adjust the nozzle angle in the vacuum setting tank to make the pipe cool evenly;

· Check whether there are sundries, burrs, etc. in the die, sizing sleeve, cutting machine and other devices;


3. Groove marks on the inner surface

· Check if the inner tube is filled with water. If it is filled with water, pinch the tube embryo of the rigid outlet die to close its inner cavity;

· Reduce the internal temperature of the die;

· Clean and polish the mold;


4. Shaking ring inside the pipeline

· Adjust the water outlet of sizing sleeve to make the water outlet uniform;

· Adjust the vacuum degree of the second chamber so that the vacuum degree of the rear chamber is slightly higher than that of the front chamber;

·  Check whether the vacuum sealing gasket is too tight;

· Check whether the tractor shakes;

· Check whether the discharge of the main machine is uniform;


5. No vacuum

· Check whether the water inlet of the vacuum pump is blocked. If it is blocked, dredge it with a needle;

· Check whether the vacuum pump works normally;

·  Check whether there is air leakage in the vacuum pipeline;

· Check whether the small hole in the middle of the core die compression screw is blocked. If it is blocked, dredge it with fine iron wire;


6. Out of tolerance of pipe outer circle size

· The size of the outer circle can be changed by adjusting the vacuum degree;

·  Adjusting the traction speed can change the size of the outer circle;

· Correct the inner hole size of sizing sleeve;


7. Pipe roundness out of tolerance

· Adjust the nozzle angle of vacuum setting machine and spray tank to make the pipe cool evenly;

· Check the vacuum setting machine, the water level height in the spray tank and the pressure of the water pressure gauge to make the spray volume large and powerful;

· Check the water temperature of vacuum setting machine and spray tank. If it is > 35 , it is necessary to configure chilled water system or add spray cooling tank;

· Check the waterway and clean the filter;

· Adjust the process;

· Check and correct the roundness of the inner hole of the sizing sleeve;

· Adjust the pipe guide clamping device to correct the ovality of the pipe;


8. Uneven pipe wall thickness

· Adjust the wall thickness on the die;

· Adjust the nozzle angle of the vacuum setting machine and the spray box to make the pipe cool evenly;

· Adjust the water outlet of sizing sleeve to make the water outlet uniform;

· Disassemble the mold, check whether the screws inside the mold are loose and retighten;


9. The plasticizing temperature is too high

· Adjust the process;

· Adjust the heating temperature of the mold core and ventilate and cool the inside of the mold


10. Inaccurate cutting length

·  Check whether the length wheel is compressed;

·  Check whether the length wheel swings, and tighten the fixing bolts of the length wheel frame; Check whether the travel switch of the cutting machine is damaged;

· Check whether the rotary encoder is damaged;

· Whether the rotary encoder wiring is desoldered (whether the aviation plug base is in good contact);

· Each single machine shell (PE terminal) shall be reliably grounded by connecting the grounding wire to one main grounding point, and the grounding point shall have a grounding pile meeting the electrical grounding requirements. It is not allowed to connect the single machine shell (PE terminal) in series, otherwise interference pulse will be introduced, resulting in inaccurate cutting length;


11.  Co-extrusion identification strip

1) Diffusion of coextrusion identification strip: generally, it is caused by improper selection of coextrusion materials used by users. PE and other special materials shall be used, and the temperature of extrusion section can be reduced if necessary;

2) Co extrusion identification strip cannot be squeezed out: if there is no co extrusion identification strip 2 hours after startup, it is generally caused by the backward screw of the co extruder; Remove the screw and retighten the screw;

3) The coextrusion identification strip is too thin or too wide: it is generally caused by the mismatch between the extrusion volume of the coextrusion machine and the traction speed of the pipe. Adjust the frequency converter of the coextrusion machine or change the traction speed to make the two speeds match; The second reason is that the cooling water jacket in the blanking section of the coextrusion machine is not connected with cooling water;

4) The identification strip of the coextrusion machine is sometimes absent: generally, due to the uneven coextrusion and blanking at the blanking port of the coextrusion machine, the water supply of the cooling water jacket at the blanking port shall be checked and the appropriate coextrusion particle size shall be selected (particle size is generally required < Φ3 × 3mm).


If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.


  • QR