How to clean the clogged mold head of Dalian blown film unit

1、 Cause Analysis of Die Head Jam

The blockage of the mold head of the Dalian blown film unit is one of the common faults in the production process of plastic film. Understanding the cause of blockage can help prevent and deal with it in a targeted manner:

Raw material impurities: Hard impurities such as metal shavings and sand are mixed into plastic particles, which get stuck in the narrow slit of the mold head under high temperature and pressure.

Carbonization deposition: Plastic stays at high temperatures for a long time, causing local overheating and carbonization, forming black hard blocks.

Additive precipitation: Lubricants, stabilizers, and other additives crystallize at specific temperatures.

Improper temperature control: The temperature in the heating zone is uneven or fluctuates too much, causing inconsistent melting states of the plastic.

Shutdown residue: The mold head was not thoroughly cleaned after production, and the residual plastic cooled and hardened.

Mechanical damage: Scratches on the inner wall of the mold head produce burrs, which become the starting point for impurity accumulation.

2、 Preparation work before cleaning

Adequate preparation is required to safely and effectively clean the mold head:

Shutdown cooling: Stop production first, turn off the heating system, and let the mold head temperature drop to 80-100 ℃ (different plastic materials have different temperature requirements).

Power off tagging: Cut off the power supply of the equipment and hang a "Do Not Operate" warning sign to prevent accidental startup.

Tool preparation:

Copper scraper, aluminum scraper (with lower hardness than mold steel to avoid scratches)

Brass brush, nylon brush

Special mold cleaning paste

High pressure air gun

Non woven fabric, release agent

High temperature resistant gloves, protective goggles

Technical information: Prepare the die structure drawings and understand the internal flow channel design.

3、 External cleaning steps of die head

Surface softening: Apply specialized cleaning paste evenly to the lip outlet of the mold and let it sit for 15-20 minutes to soften the residue.

Mechanical cleaning:

Gently scrape the softened plastic along the mold lip direction (not horizontally) with a copper scraper

Stubborn residues can be brushed with a brass brush and cleaning agent

Gap treatment: For mold lip gaps of 0.1-0.5mm, carefully clean with a specially made thin copper sheet

Final cleaning: Use non-woven fabric dipped in alcohol or specialized cleaning agent to wipe until bright and residue free

4、 Method for deep cleaning inside the mold head

For situations where severe blockage requires disassembly and cleaning:

Dismantling of mold head:

Loosen the connecting bolts in order and record the disassembly position

Use a specialized lifting device to smoothly remove the upper mold body

Pay attention to protecting the mirror fitting surface of the mold head

Channel cleaning:

Soak areas with severe carbonization using specialized chemical cleaning agents

The inner wall of the flow channel is cleaned with a rotating nylon brush and compressed air

Stubborn sedimentation can be gently shaken off with wooden tools (direct tapping with metal tools is prohibited)

Ultrasonic cleaning (if conditions permit):

Place the mold head components into the ultrasonic cleaning tank

Use plastic specific cleaning solution and control the temperature between 60-80 ℃

Cleaning time 30-60 minutes

Inspection and repair:

Check for damage to the lip of the mold with a magnifying glass

Measure whether the dimensions of key parts are within the tolerance range

Scratches found require professional polishing treatment

5、 Assembly and debugging after cleaning

Assembly preparation:

Clean all contact surfaces with alcohol

Apply high-temperature anti rust grease evenly

Replace all seals and damaged bolts

Precision assembly:

Use a torque wrench to gradually tighten the bolts in diagonal order

The final torque value must comply with the requirements of the equipment manual

Check the uniformity of the lip gap (measured with a feeler gauge)

Heating up debugging:

Step by step heating to operating temperature (usually takes 2-3 hours)

Initial extrusion using cleaning material transition

Adjust the die head bolts to make the film thickness uniform

6、 Measures to prevent mold blockage

Raw material control:

Use high-quality filters (recommended 80-120 mesh)

Screening of raw materials to remove impurities

Keep the raw materials dry (humidity<0.02%)

Process optimization:

Set a reasonable temperature curve (to avoid local overheating)

Regularly replace the filter (every 8-12 hours)

Empty the mold head with cleaning material before the end of production

Equipment maintenance:

Check the working status of the mold head heater every month

Quarterly professional polishing die flow channel

Establish a record of mold cleaning and maintenance

Operating standards:

Avoid sudden shutdown

Do not apply pressure until the temperature meets the standard

Regularly check the pre tightening force of the mold head bolts

7、 Safety precautions

High temperature protection: Even if the mold head remains at high temperature after shutdown, insulated gloves must be worn

Harmful gases: When cleaning carbonized plastics, irritating gases are generated, and ventilation should be maintained

Mechanical injury: Use appropriate lifting equipment when disassembling heavy components, and do not operate with bare hands

Electrical safety: Confirm complete power outage before cleaning, especially for the heating system

Chemical use: Use cleaning agents according to MSDS requirements and avoid contact with skin

Through the cleaning methods and preventive measures of the above system, the problem of clogging of the blown film unit mold head can be effectively solved, production efficiency can be improved, and equipment service life can be extended. After each cleaning, the specific situation should be recorded to accumulate experience data and provide reference for subsequent maintenance.