Mechanical principle of extruder

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Introduction

china plastic extrusion machine extrusion molding is also known as basic model molding. It means that the powder or granular material is added from the hopper into the barrel of the extruder, and the material is conveyed and compacted forward by the friction between the inner wall of the barrel and the surface of the screw under the extrusion and pushing action of the screw rotation. The heating device and frictional preheating outside the cylinder are melted and plasticized under high temperature and high pressure conditions. Then, the continuously rotating screw of the jwell extruder pushes the molten material into the die of the die, and the molten material extruded from the die of the die is cooled and shaped into the desired plastic product.

The working principle of the extruder is: using a screw with a specific shape to rotate in the heated barrel, the plastic sent from the hopper is extruded forward, so that the plastic is uniformly plasticized (that is, melted), through the head and different shapes. The mold is used to extrude the plastic into various shapes of plastic layers required for continuity, and extrude it on the core and cable.

tpu film extrusion line

The extrusion process is divided into two stages

  • Plasticize the solid plastic, even if it becomes a viscous fluid state and pass through a special-shaped die under pressure to become a continuum with the same cross-section as the die shape.
  • Use appropriate cooling methods to make the extruded continuum lose its plasticity and become solid, that is, the desired product.

Extrusion molding production process

The extrusion molding process of jwell extruder includes: melting and plasticizing of plastic raw materials → extrusion molding → cooling and shaping → cooling → traction → cutting → inspection → packaging → storage.

Host: An extruder consists of the following three parts: extrusion system, rotation system, heating and cooling system.

Auxiliary machine: The composition of the extruder is determined according to the type of product. Generally, the auxiliary machine consists of the following parts: head, setting device, cooling system, traction device, cutting device, stacking and coiling device.

Control system: The control system of the extruder is mainly composed of electrical instruments and actuators. Its main function is to control the driving motors of the main machine and auxiliary machines, so that the speed and power of the operation are normal, and to ensure the temperature and pressure of the main machine and auxiliary machines. , flow and product quality, to achieve automatic control of the entire unit.

The molding process is mainly divided into three stages

1. Plasticization

Through the action of the barrel temperature and the screw, the material is transformed into a uniform continuous melt with a certain fluidity.

2. Molding

The uniform melt with fluidity enters the die through the perforated plate due to the rotary extrusion of the screw, and is formed into a parison with a certain shape according to the die core rod.

3. Cooling and setting

That is, under the action of extrusion pressure and traction, the parison is formed into a product with certain strength, rigidity and dimensional accuracy after vacuum cooling and shaping.

4. Granulation process

The jwell extruder granulation process is an operation process in which resin and various additives are calculated, mixed and masticated into compact spheres, cylinders and cubes that are easy to form. There are many methods of granulation, such as:

Resin+auxiliaries→weighing→mixing→extrusion→round bar→cooling→line pelletizer

Sheet Extrusion Line extrusion pelletizing operation is continuous, airtight, easy to filter out impurities, high output, low labor intensity, clean environment, low noise, but the plasticizing quality is not as easy to control as the sheet refining method.

plastic extruder detail

Extrusion Process Control

The extrusion process control of jwell extruder includes the control of molding temperature, extrusion speed, vacuum dehumidification, vacuum speed, vacuum cooling and shaping.

1. temperature control

The extrusion molding temperature is a necessary condition to promote the plasticization of the molding material and the flow of the plastic melt. It directly affects the rheological state of the material in the entire processing process, and is of great importance to the plasticization of the plastic and the yield and quality of the profiled material. meaning.

In the whole processing process, the material needs to realize the transformation from glass state to high elastic state and then to viscous flow state, and the temperature control of each section is not the same.

(1) Temperature device in barrel area

How to set the temperature of the barrel temperature, we must have an understanding of the function of our screw in the extrusion process. The barrel area can be divided into four areas: feeding area, compression area, ventilation area and metering area.

(2) Connector temperature

It is the transition section between the extruder barrel and the mold. The temperature control in this area is very important. The temperature in this area directly affects the rheological state of the material when it enters the mold and has a great influence on the uniformity of the discharge of each part of the profile.

(3) Screw temperature

Due to the small gap between the screws, the frictional heat generated between the screws is large. In order to ensure that the material does not decompose, the temperature is set lower, generally at 120-140 °C.

(4) Die temperature

The mold temperature of the jwell extruder is one of the important conditions for maintaining stable molding. In order to prevent the phenomenon of mold warpage caused by the temperature difference between the mold temperature and the melt difference, the mold temperature setting should be consistent with the melt temperature, generally 190-210 ℃ . in addition. The mold temperature is affected by the geometry of the profile. The complex shape, due to the large surface area of ​​the cavity, will hinder the flow of the material, so a higher mold temperature is sometimes required to improve the flow properties of the melt.

2. Speed ​​control

The speed control includes the control of the feed screw and extrusion screw speed and traction speed.

Applicable resins: most thermoplastics, such as PVC, PS, ABS, PC, PE, PP, PA, PMMA, PET, PBT, TPE, TPU, etc.

Application fields of jwell extruder products: plastic films, nets, products with cladding, pipes with a certain section and continuous length, plates, sheets, bars, packing tapes, monofilaments and profiles, etc., and can also be used for powder Granulation, dyeing, resin blending, etc.

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