Five factors affecting the replacement frequency of screw elements and barrel

The barrel is one of the two major working parts of the twin-screw extruder, and the other is the screw. Only when the barrel and the screw form a pair of friction groups, can plastics, auxiliary materials and additives be fully mixed. How to effectively reduce the replacement frequency of the twin-screw extruder barrel and screw components? Solving this problem can help modification enterprises improve production efficiency, and at the same time reduce enterprise operation and maintenance costs.

Five factors affecting the service life of the barrel and screw elements:

01 Ordinary wear

When plastic base particles, auxiliary materials and additives enter the cylinder to be mixed and kneaded, there will inevitably be friction, which will cause the cylinder and threaded components to wear. In particular, fillers such as calcium carbonate and fiberglass, which tend to be much more abrasive to metal than molten plastic.

02 Corrosion wear

Auxiliary materials and additives may be corrosive and directly corrode the inner wall of the cylinder, resulting in a reduction in the life of the cylinder.

03 High-strength wear (heavy wear area)

In the extruder, there are usually 4 major wear zones: the feeding zone, the adding glass fiber reinforcement or filler zone, the middle zone, and the head zone.

In the feeding zone, the mechanical wear is relatively severe. At this time, the auxiliary materials have not been melted, and they are basically in a solid state. The inner wall of the cylinder is directly rubbed with the solid, which makes the inner wall very worn. This is the first heavy wear area.

In the area where glass fiber reinforcement or filler is added, the glass fiber is a filament, and the sharp corner of the splay hole will be restrained at the fiber inlet, where the cylinder will have a deep groove;

In addition, the glass fiber is sheared at high speed, correspondingly producing more shredded fibers. The shredded fibers contain sharp ends, which greatly increases the wear force and wears the inner wall of the cylinder.

In the middle area, the top of the twin screw is under pressure, so that the screw in the middle area is in a bent state during high-speed operation, and the deflection (bending amount) is the largest, the sweeping is very powerful, and the barrel wear is obvious.

In the club head area, the screw in the top area is in a cantilever state, which is affected by gravity and sags downward. After the material enters, the top of the screw will be lifted up, and the outer diameter of the screw will rub against the inner wall of the cylinder, causing wear.

04 Working conditions (temperature and pressure effects)

The working environment of the extruder is very harsh, and the melting temperature of plastic is generally high, such as: the melting temperature of polycarbonate reaches about 240 ℃, nylon reaches about 280 ℃, and PPS reaches about 290 ℃. In the case of high temperature, the physical properties of the metal are degraded, resulting in a reduction in the life of the cylinder.

05 Moisture, air, oxygen and other gas components in the cylinder

When the cylinder is mixed with oxygen and water vapor, the cylinder wears more severely.

It is difficult to change the working temperature, pressure, moisture and air in the cylinder. At present, the cylinder can only be made of more wear-resistant and corrosion-resistant materials to prolong the life of the extruder cylinder and threaded components.

At present, the materials for making cylinders and threaded components on the market mainly include carbon steel, stainless steel, alloy steel and powder steel. Compared with other steels, powder steel adopts powder metallurgy technology to make powder metallurgy raw materials into powder, and then according to a fixed ratio, it is a kind of steel produced under harsh conditions.

Compared with ordinary cast and forged steel, the segregation of nickel, chromium and molybdenum elements in powder steel is small, the grain size is small, and the sulfide inclusions are small and evenly distributed.

Therefore, the mechanical properties are improved, it is more wear-resistant and corrosion-resistant, and the cylinder and threaded components made of powder steel can prolong its service life.

Haisi Extrusion is professional manufacturer of twin screw extruder machine, we have our own finishing workshop.

Any interest in screw and barrel for twin screw extruder, please feel free to contact us!