What are the precautions for using food extruders

Food puffing machines are key equipment used for producing puffed foods such as corn cobs, rice cakes, and wheat rings. Their operation involves high temperature, high pressure, and mechanical transmission. If used improperly, it may lead to a decline in product quality, equipment damage, and even safety accidents. The following are the usage precautions for food extruders, covering the preparation before operation, monitoring during operation, safety protection and maintenance after shutdown, etc.

I. Preparations Before Operation

1. Equipment inspection

Mechanical components

Check whether the vulnerable parts such as the screw, screw sleeve and die head are worn or cracked. If so, replace them in time (if the gap between the screw and the screw sleeve exceeds 0.5mm, adjust or replace them).

Make sure the tension of the drive belt is moderate (5-10mm sunken when pressed by finger) to avoid slippage or breakage.

Check the lubricating oil level of the bearings and gearboxes. When it is lower than the mark, add food-grade lubricating oil (such as NSF H1 grade).

Electrical system

Check whether the insulation layer of the power cord and control line is damaged and whether the plug connection is firm.

Test whether safety devices such as the emergency stop button, temperature controller and pressure sensor are sensitive.

Heating system

Check whether the heating tube and thermocouple are in good condition and ensure that the temperature display is accurate (error ≤±5℃).

Preheat the equipment to the set temperature (usually 150-200℃) to prevent the material from gelatinizing due to cold start-up.

2. Material preparation

Raw material selection

Use dry and impurity-free raw materials (such as corn flour and rice flour), with a moisture content controlled at 12% to 14% (if it is too high, it will lead to insufficient puffing; if it is too low, it is prone to burning).

Avoid using raw materials that are lumpy, moldy or contain metal foreign objects to prevent the screw from being clogged or the die head from being damaged.

Formula adjustment

Adjust the dosage of the leavening agent according to the characteristics of the raw materials, usually 0.5% to 2% of the weight of the raw materials.

When producing a new formula, conduct a small-scale trial production first to confirm the puffing effect before proceeding with mass production.

Ii. Monitoring During Operation

Parameter control

Temperature

Feeding area temperature: 80-100℃ (to prevent material caking).

Compression zone temperature: 120-150℃ (promoting starch gelatinization).

Temperature in the puffing zone: 160-200℃ (to cause water to vaporize instantly and form a puffed structure).

When the temperature fluctuation exceeds ±10℃, the machine should be shut down for inspection of the heating system.

Pressure

The pressure in the puffing chamber is usually 0.8 to 1.5MPa. If the pressure is too low, it will result in insufficient puffing rate; if it is too high, it may cause the die head to burst.

Regularly clean the exhaust valve to prevent blockage and abnormal pressure.

Screw speed

Adjust the rotational speed according to the characteristics of the material (usually 100-300r/min). A speed that is too fast will cause excessive shearing of the material, while a speed that is too slow will result in insufficient puffing.

2. Observation of material status

Feeding speed

Keep the feeding uniform and avoid feed breakage or accumulation. Material shortage can cause the screw to idle and wear, while material accumulation may lead to local overheating.

When using a variable frequency feeder, set the minimum and maximum feeding limit values to prevent overloading.

Puffing effect

Observe the shape of the product at the discharge port: An ideal puffed food should have a smooth surface, uniform pores, and no burnt or unpuffed particles.

If the puffing rate of the product is insufficient, the temperature or the screw speed can be increased. If it gets burnt, the temperature or feeding speed should be reduced.

Iii. Safety Protection

1. Personal protection

Operator

Wear heat-resistant gloves (with a temperature resistance of ≥200℃), goggles and dust masks to avoid injury from high-temperature steam or splashes.

Do not wear loose clothing or jewelry to prevent entanglement in the transmission components.

Equipment protection

Make sure the protective cover and safety door are closed to prevent hands or tools from touching the high-temperature and high-speed components such as the screw and die head.

A splash guard is set up at the die head outlet to prevent high-temperature materials from splashing.

2. Emergency response

Blockage treatment

Stop the machine immediately and cut off the power supply. After the equipment cools down, disassemble the die head to clean the materials. Do not poke with hard objects at high temperatures.

Fire prevention

Keep the equipment free of flammable materials and be equipped with fire extinguishers (dry powder or carbon dioxide type).

In case of spontaneous combustion of materials, immediately turn off the heating system and use a fire extinguisher to put out the fire. Do not pour water on it.

Iv. Shutdown and Maintenance

1. Normal shutdown

Steps

Stop feeding. After no material is discharged from the discharge port, turn off the heating system.

Continue to run the screw for 5 to 10 minutes to discharge the remaining material and prevent it from hardening and clogging after cooling.

Turn off the power and clean the equipment after it has cooled down.

Cleaning

Use a soft-bristled brush to clean the inner walls of the screw and screw sleeve. Avoid using steel wool balls to scrape.

After disassembling the die head, soak it in neutral detergent, wipe it with a soft cloth and then let it dry.

2. Long-term shutdown maintenance

Rust prevention treatment

After cleaning, apply food-grade anti-rust oil (such as mineral oil), with a focus on protecting the metal parts like the screw and die head.

Disassemble vulnerable parts (such as sealing rings) and store them separately to avoid deformation under pressure.

Environmental requirements

Store in a dry and well-ventilated indoor area, with the temperature controlled between 5 and 35℃ and the humidity no more than 70%.

Power on and run for 10 minutes every month to prevent components from getting stuck or damp.