Common FAQs About Twin Screw Extruder Barrel And Screw

How to Clean The Extruder Screw?

The extruder screw cleaning material adopts high-efficiency surface-active technology, which can effectively improve the cleaning ability. In the extrusion process of the twin screw extruder, only a small amount of cleaning material is needed for cleaning the screw carbon deposit and stubborn color adhesion. The cleaning process is highly efficient, does not damage the twin-screw machine, and emits no irritating, toxic smell.

Cleaning extruder screw process:

1. Manually add the washing machine material from the discharge port until the extruded strip has the same color and luster as the washing machine material pellets, and then stop feeding, empty the material, and stop rotating the twin-screw extruder screw.

2. Open the die head of the screw extruder and start cleaning the screw.

3. Rotate the screw and take out the orifice plate, discharge the residual washing material in the barrel, and then clean the orifice plate.

4. Pull out the screw and observe whether it is cleaned. The residue needs to be removed manually. After cleaning, install the screw back to its original position, add new material to flush the remaining washing material in the barrel, and stop the screw rotation.

5. Install the XPS or PET twin-screw extruder orifice plate and die head, and the machine will start a test run after cleaning.

Heating And Cooling of Extruder Screw Barrel

How to heat the extruder screw and barrel

The heating of the machine adopts the method of resistance heating, and the thermocouple is used to realize the segmented temperature control and side detection. Resistance heating uses resistance to generate heat to heat the barrel, and then transfer the heat to the plastic in the barrel. Resistance heating mainly includes strip heaters, cast aluminum heaters, ceramic heaters, etc. These heaters have the advantages of small size, convenient manufacturing, and maintenance.

Heating power of extruder screw barrel

When determining the heating power of the twin screw extruder machine barrel, in addition to meeting the heat required for plasticization, it is also necessary to meet the productivity requirements of the injection molding machine to ensure that the barrel has a sufficiently fast heating rate. The heating time for small extruders is generally not more than 1 hour, and the heating time for medium and large machines is about 2 hours.

Cooling of extruder screw barrel

Under normal circumstances, the barrel does not equip with a cooling control system, and natural cooling can meet the process requirements. However, if the temperature of the feed port is too high, a "bridging" phenomenon will occur at the feed port, making feeding difficult or even impossible.

To prevent the heat of the screw extruder machine barrel from being transferred to the transmission components, a cooling jacket (slot) should be set at the feeding port of the barrel, and the amount of cooling water adjusted according to the process requirements. Besides, when processing heat-sensitive plastics at higher speeds, the machine must be cooled and temperature-controlled to prevent the heat-sensitive plastics from being decomposed by heat.

What Is The Effect of Excessive Clearance Between The Screw And Barrel?

1. If the matching gap between the ETPU extruder screw and the barrel is too large, the flow of the extruded melt is unstable during extrusion production, and the product surface is prone to horizontal wrinkles.

2. If the gap is too large, the extrusion melt pressure will be unstable, which makes the cross-sectional geometric shape and size error of the product change greatly.

3. If the gap is too large, the melt will flow back when it moves forward in the barrel during extrusion, so that the melt will stay in the barrel for too long and cause the surface to become discolored or have focal spots.

4. If the gap between the screw and the barrel is too large, it makes the output of extruded products unstable or decreased.

How to Maintain The Extruder Barrel And Screw When They Are Not Used for A Long Time?

In the plastics industry, although the extruder barrel and screw is only an accessory, it has always occupied an important position. If you leave the barrel and screw for a long time, their service life will be affected, and the operating efficiency of the extruder will be affected later. Therefore, if you do not use the extruder barrel and extruder screw for a long period, you need to do its maintenance work.

1. Extruder barrel screw and die

Before being out of service for a long time, the staff needs to open the mold first and keep a certain distance. The hinge of the mold clamping machine should be kept in a semi-extended state and not stressed.

2. The barrel 

Before stopping use, you need to clean up the remaining material in the double screw extruder barrel. After cleaning, you need to loosen the screw to ensure that the screw head will not be burned when it is used again.

3. Electrical protection

Before being out of service for a long time, you need to turn off the power switch of the extruder equipment and pay attention to the protection of the power cord to avoid being bitten by rats. The electric box needs to be waterproof and fireproof.

Why Is There Noise During The Operation of The Extruder Barrel And Screw?

During the extrusion process, the screw of the twin extruder will make a sound when it rubs against the inner wall of the barrel. The reasons for this friction phenomenon are nothing more than the following four reasons:

1. The assembly gap between the extruder screw and its supporting drive shaft is too large, and the two shaft centers are not concentric when rotating, and the error is too large.

2. The screw of the extruder is bent and deformed, and the straightness of the shaft centerline is out of tolerance.

3. The end face of the extruder barrel and the base of the connecting flange has a large vertical error with the centerline of the barrel.

4. The extruder screw is assembled in the extruder barrel, and the error of the concentricity of the two parts is large.

How to Choose A High-quality Flat Twin-screw Barrel?

The parallel twin-screw barrel has the advantages of reasonable screw structure design, good plasticizing effect, high output, and stable extrusion. The spiral surface of the parallel twin-screw barrel is usually spray-welded with double alloy, which can effectively extend the service life of the screw barrel. The parallel twin-screw barrel has large load-bearing torque and low energy consumption. It can effectively avoid defects such as black and yellow lines in the plate and sheet extrusion process.

The method of choosing a high-quality flat twin-screw barrel:

1. Look at the raw materials for screw and barrel production. The high-quality double screw barrel is derived from high-quality raw materials, which can provide continuous, stable, and high-yield, with a strong anti-damage level.

2. Look at the surface treatment of the screw and barrel. The surface of a good screw barrel is usually spray-welded nickel-based alloy powder or tungsten carbide alloy powder, which can greatly improve the wear resistance of the screw and prolong the service life.

3. Look at the production process. A good pair of parallel twin-screw barrels must go through multiple heat treatment processes, such as quenching and tempering, tempering, qualitative, nitriding, etc., to meet various technical requirements. 

4. Look at the R&D capabilities of the manufacturer. Parallel twin-screw barrel manufacturers with research and development capabilities can introduce advanced screw structure research and study at home and abroad. Corresponding improvements can be made to the original structure according to the specific requirements of customers to achieve low energy consumption and achieve high quality and high yield.

Feininger is the first professional manufacturer of XPS Extrusion Line and XPS Foam Board in China. At the same time we are the unique enterprise specializing in XPS Foam as well as developing, manufacturing and selling of XPS extrusion line. We also manufacturing ETPU extrusion line, PET production line, EPS production line, recycling and pelletizing machine, etc. Contact us for more details.