What should be paid attention to in temperature control of ABA blown film machine

1、 The importance of temperature control in ABA blown film machine

As a key equipment for plastic film production, the temperature control of ABA blown film machine directly affects product quality and production efficiency. The thin film of ABA structure (A-B-A three-layer structure) requires that each layer material can bond well in the molten state while maintaining their respective performance characteristics. Excessive temperature can lead to material degradation, bubble formation, and a decrease in film strength; If the temperature is too low, it will cause poor plasticization, increased melt viscosity, and increased extrusion pressure, affecting the uniformity and surface quality of the film.

Accurate temperature control can ensure:

The material is fully plasticized but not excessively degraded

Good interface bonding between each layer of materials

Uniform and consistent thickness of the film

Smooth and flawless surface

Stable production efficiency

2、 Key points for temperature setting in each heating zone

1. Temperature control in the feeding section

The temperature in the feeding section should be relatively low, usually set at 70-80% of the material's melting point. Excessive temperature can lead to premature melting of materials, forming a "molten pool" during the screw propulsion process, affecting the efficiency of solid transportation, and even causing the phenomenon of "bridging". For ABA structures, special attention should be paid to the different melting point characteristics of materials in the A and B layers.

2. Compression section temperature setting

The temperature of the compression section should gradually increase to gradually melt the material. At this stage, the temperature gradient should be gentle to avoid sudden temperature changes that may cause melt fracture. For co extrusion systems, the compression section temperature of each layer of material needs to be set separately according to its melting characteristics.

3. Temperature control in the measuring section

The temperature in the measuring section is more critical, and it should be ensured that the material is completely plasticized and the viscosity is moderate. Usually set near the upper limit of the recommended processing temperature range for materials, but it is necessary to consider:

Differences in thermal stability of different materials

The influence of screw speed on shear heat

The pressure rise effect caused by the filter screen

4. Mold head temperature adjustment

The mold temperature directly affects the surface quality and thickness uniformity of the film. Usually 5-10 ℃ lower than the melt temperature to appropriately increase the melt strength:

Flat mold head: The temperature distribution should be uniform, and the temperature on both sides can be 2-3 ℃ higher than the middle to compensate for heat loss

Rotating die head: Temperature control needs to be more precise to avoid film oscillation caused by uneven temperature

3、 Temperature treatment for special circumstances

1. Temperature adjustment during material replacement

When switching between different materials, the temperature curve must be adjusted accordingly:

Switching from high melting point materials to low melting point materials: first cool down to an intermediate temperature, clean, and then lower to the target temperature

Transition from low melting point materials to high melting point materials: segmented heating to avoid local overheating

2. Response to changes in environmental temperature

Attention should be paid to seasonal changes:

Summer high temperature: The set temperature can be appropriately lowered by 2-3 ℃, considering the efficiency of the cooling system

Winter low temperature: it is necessary to extend the preheating time and insulate the equipment if necessary

3. Handling of abnormal situations

When there is a large temperature fluctuation: check the thermocouple, heating coil, and temperature control module

Local overheating: Check if the heating coil is in good contact and if the heat dissipation is normal

The temperature cannot reach the set value: confirm whether the heating power is sufficient and whether the insulation measures are complete

4、 Coordination between temperature and other process parameters

Temperature control is not isolated and needs to be coordinated with other process parameters:

1. Relationship with screw speed

An increase in rotational speed will increase shear heat, and the heating temperature should be appropriately reduced. Generally, for every 10 rpm increase, the temperature can be lowered by 1-2 ℃.

2. Relationship with back pressure

An increase in back pressure will cause the temperature of the melt to rise, and the temperature setting needs to be adjusted accordingly to maintain stable melt viscosity.

3. Coordination with cooling system

The setting of air ring cooling, internal cooling and other systems should be matched with the extrusion temperature to ensure good cooling of the film without generating internal stress.

5、 Key maintenance points for temperature control system

Regularly calibrate temperature sensors: Verify with a standard temperature source at least once every quarter, and replace them promptly if the error exceeds ± 1 ℃

Check the heating element: measure the resistance of the heating coil every month, and replace it if the deviation exceeds 10%

Clean the installation holes of thermocouples: avoid the influence of oxide scale or carbon deposition on temperature measurement accuracy

Check the wiring terminals: prevent looseness and increase in contact resistance

Update aging control system: Temperature control modules that have been in use for over 5 years should be considered for upgrading

6、 Temperature control characteristics of different materials

1. LDPE (Low Density Polyethylene)

Processing temperature range: 160-210 ℃

Attention: The thermal stability is good, but it is prone to oxidation at high temperatures

2. LLDPE (Linear Low Density Polyethylene)

Processing temperature: 180-230 ℃

Characteristics: Low melt strength, requiring precise control of die temperature

3. HDPE (High Density Polyethylene)

Processing temperature: 180-250 ℃

Attention: High melting point, cooling rate affects crystallinity

4. PP (polypropylene)

Processing temperature: 200-250 ℃

Characteristics: Melt flowability is temperature sensitive

5. PA (Nylon)

Processing temperature: 240-280 ℃

Key point: Strictly prevent moisture and oxidation

7、 Energy saving and temperature control

Adopting zone temperature control to reduce unnecessary heating

Using new insulation materials to reduce heat loss

Consider utilizing waste heat in a heat recovery system

Optimize temperature curve to reduce energy consumption

8、 Safety precautions

High temperature surfaces require protection and warning measures

Contact is only allowed when the temperature drops below 80 ℃ during shutdown

Prevent melt leakage from causing burns

Regularly check the overheat protection device

9、 Record and analyze

Establish a complete temperature recording system:

Record the actual temperature at each point every 2 hours

Record temperature anomalies and their handling measures

Analyze the correlation between temperature fluctuations and product quality

Establish a temperature parameter database for future reference

Through the comprehensive temperature control measures mentioned above, the ABA blown film machine can ensure stable and efficient production of high-quality thin film products. In practical operation, it is necessary to make fine adjustments based on equipment characteristics and product requirements, accumulate experience data, and form a more suitable temperature control scheme.