What to pay attention to when changing the mold of Dalian blown film unit

1、 Preparation work before mold replacement

Equipment shutdown inspection

Ensure that the unit is completely shut down, turn off the main power, and hang a "No Operation" warning sign

Confirm that the extruder temperature has dropped to the safe range (usually below 100 ℃)

Check if the pressure in the mold head area has been completely released

Preparation of tools and materials

Prepare specialized lifting equipment (such as electric hoists, hydraulic trucks, etc.)

Check if the specialized tools for the mold head (torque wrench, heating rod, etc.) are complete

Prepare cleaning supplies (copper shovel, asbestos cloth, specialized cleaning agents, etc.)

Prepare installation accessories for the new mold (sealing rings, bolts, etc.)

Personnel safety protection

Operators must wear a full set of protective equipment (heat-resistant gloves, protective face shields, heat-resistant clothing, etc.)

Confirm that the lighting in the work area is sufficient and the ground is free of oil and water stains

Arrange at least two people to work together and clarify the division of labor

2、 Mold disassembly process

Heating system processing

Disconnect the power supply of the die head heater and mark the wiring position

Slowly cool down to below 80 ℃ before starting disassembly

Retain precision components such as thermocouples to prevent damage

Bolt disassembly sequence

Use diagonal sequence to gradually loosen bolts

Use a specialized wrench to avoid slipping teeth

Record the length and specifications of bolts in each part

Precautions for mold head lifting

Confirm that the rated load of the lifting equipment is greater than the weight of the mold

Use specialized lifting equipment and prohibit the direct contact of steel wire ropes with molds

Maintain horizontal lifting to avoid collision with surrounding equipment

3、 New mold installation specifications

Mold inspection and pretreatment

After the arrival of the new mold, the dimensions of the excellent rows will be verified

Clean the mold cavity and flow channel, remove rust proof oil

Check the flatness of the sealing surface (using red lead powder for inspection)

Installation and positioning requirements

Use positioning pins to ensure accurate alignment

Tighten bolts evenly in stages (50% torque first, then 80%)

Operate according to the torque value table provided by the manufacturer

Temperature system recovery

Install the heating strip correctly and maintain even spacing

The installation position of the thermocouple meets the process requirements

Check the insulation resistance of each heating zone

4、 Key points of debugging after mold change

Temperature rise program control

Segmented heating (50 ℃ every 30 minutes)

Keep warm for more than 2 hours after reaching the set temperature

Verify the actual temperature using an infrared thermometer

Sealing test

Check all connections under low voltage conditions

Use specialized leak detectors to detect minor leaks

Only after confirming that there is no melt leakage can the pressure be increased

Process parameter adjustment

The initial extrusion speed is controlled at 30% of the rated value

Observe the uniformity of mold lip discharge

Gradually adjust parameters such as wind ring and traction

5、 Common problem handling

Difficulty in mold installation

Check if the positioning pin is aligned

Confirm that the mold body is not deformed (using a ruler for inspection)

Do not forcefully strike to avoid damaging the mating surface

Abnormal temperature rise

Heating zone not heating up: check the fuse and relay

Large temperature fluctuations: Verify thermocouple wiring

Local overheating: adjust the position of the heating belt

Uneven discharge

Clean the lip of the mold (using copper tools)

Check if there is any blockage in the mold cavity flow channel

Adjust the lip gap of the mold (requires professional personnel to do so)

6、 Safety precautions

high-temperature protection

The surface temperature of the mold head can reach over 200 ℃

Double layer protection is necessary when in contact with the melt

Prepare emergency cooling equipment

Mechanical injury prevention

Do not manually enter the mold lip to adjust the gap

Evacuate personnel from hazardous areas during lifting operations

Use specialized tools instead of temporary substitutes

Electrical safety

Do not operate electrical components with wet hands

Regularly check the insulation condition of the circuit

The grounding system must be in good condition

7、 Maintenance suggestions

Mold storage specifications

Vertically placed on a dedicated rack

Apply anti rust oil to the mold cavity

Protecting precision mating surfaces

Regular inspection items

Check the pre tightening force of bolts every month

Quarterly testing of lip flatness

Annual professional manufacturer maintenance

Service life management

Record the hours of mold usage

Regular replacement of key components

Establish mold archives

By strictly following the above mold replacement operation procedures, the efficiency of mold replacement can be improved (ideally controlled within 4 hours), waste generation can be reduced (mold replacement waste can be controlled within 50kg), and the service life of the mold can be extended (usually up to 3-5 years). After each mold change, a complete mold change record form should be filled out, including information on the operator, time, abnormal situations, etc., to provide a basis for subsequent maintenance.