What are the functions of an engineering plastic extrusion production line?

Engineering plastic extrusion production line is the core equipment for polymer material processing. It is mainly used to process engineering plastic particles into continuous profiles or products of specific shapes through heating, plasticizing, extrusion molding and other processes. Its functions cover the entire process from raw material processing to finished product production, and its application fields are wide.

1. Functions of engineering plastic extrusion production line
(1). Plasticizing and homogenizing raw materials
Melting plasticization: Shear heat and external heating are generated by screw rotation to melt solid plastic particles into a uniform viscous flow state (such as nylon PA66 melting temperature 260~290℃).
Mixing homogenization: Fillers such as glass fiber and flame retardant can be added to the compression section and mixing section of the screw (such as barrier screw) to ensure uniform dispersion of the material (mixing uniformity reaches more than 95%). 

(2). Continuous molding processing
Profile extrusion: production of pipes (such as PPR water pipes), special-shaped profiles (PVC profiles for doors and windows), plates (PC sun panels), etc., with an extrusion speed of 5~20 m/min.
Film/sheet production: with T-die or film blowing head, manufacturing packaging film (BOPP film thickness 10~50μm), medical sheets, etc.

(3). Functional modification
Online modification: adding functional additives such as carbon fiber (to improve strength) and anti-UV masterbatch (outdoor weather resistance) through the side feeder to achieve material performance customization.
Coextrusion technology: multi-layer coextrusion die head can produce ABA structural plates.

2. Typical Applications
Automotive Industry: Fuel pipes (PA12 extrusion), interior trim (PP+EPDM sealing strips), lightweight structural components (carbon fiber-reinforced PEEK guide rails).
Electronic and Electrical Products: Production line trunking (flame-retardant PVC), cable sheathing (halogen-free flame-retardant TPU), mobile phone cases (PC/ABS co-extrusion).
Construction and Building Materials: Door and Window Profiles (PVC-U), Drain Pipes (HDPE double-wall corrugated pipes), Sound Insulation Panels (PET foam core).
Medical Packaging: Medical Catheters (TPE extrusion), Sterile Packaging Film (HDPE/PP co-extrusion), IV Bottles (COP transparent tube blanks).

3. Common faults of engineering plastic extrusion production lines
(1) Failure of core components of extruders
1). Screw/barrel wear
Fault phenomenon: Extrusion output decreases (e.g. PA66 output drops from 100kg/h to 70kg/h), melt temperature fluctuation increases (±5°C or more).
Cause: Long-term friction of high-filling materials (e.g. 40% glass fiber), processing of corrosive materials (e.g. flame retardant decomposition products).
Solution: Use bimetallic screw/barrel (surface hardness HRC60+), regularly check the screw gap (>0.3mm needs to be repaired).
2). Heating ring failure
Fault phenomenon: Abnormal display of temperature control zone (temperature in a certain section is continuously lower than the set value), extrusion fluctuations lead to uneven product wall thickness.
Cause: Heating wire burns out (voltage is unstable or overloaded), thermocouple contact is poor.
Solution: Use ceramic heating ring (temperature resistance 450°C), and calibrate the thermocouple before starting the machine every day (error >±2°C needs to be replaced).

(2) Molding system failure
1) Accumulation of precipitates on the die head Fault phenomenon: Stripes or crystal points appear on the surface of the product, and the die head pressure continues to increase (such as from 15MPa to 22MPa). Cause: Poor thermal stability of the material (such as PVC decomposition), die head coating peeling (hard chrome layer thickness <0.05mm). Solution: Clean the die lip with a copper shovel every 8 hours (to avoid scratching the flow channel), and replace the titanium nitride (TiN) coated die head (life is increased by 3 times).
2) Poor adsorption of the vacuum shaping box Fault phenomenon: The profile warps and deforms (such as the diagonal error of the PVC window frame >2mm/m), and cooling water penetrates into the shaping mold. Cause: Insufficient vacuum pump power (<15kPa negative pressure), aging of the sealing strip (silicone strip has been used for more than 6 months). Solution: Upgrade the Roots vacuum pump (ultimate vacuum reaches -95kPa) and use fluororubber sealing strips (temperature resistance 200℃).

(3) Auxiliary system failure
1). Traction slip Fault phenomenon: Product size fluctuation (such as pipe outer diameter tolerance > ±0.5mm), traction machine alarm (encoder count abnormality). Cause: Insufficient belt tension (deflection > 10mm), product surface too slippery (such as TPE containing silicone oil). Solution: Use polyurethane synchronous belt (friction coefficient μ ≥ 0.8), add embossing roller (surface knurling depth 0.2mm).
2). Cutting system error Fault phenomenon: Cutting burrs (PC board cutting surface Ra > 3.2μm), fixed length cutting deviation (± 2mm deviation). Cause: Saw blade blunting (continuous cutting > 5000 times without grinding), servo response delay (position loop gain setting too low). Solution: Use diamond-coated saw blade (life span of more than 100,000 times), optimize PID parameters (increase gain by 20%~30%).