TENGDA Is a Professional Plastic Extruder Machine Manufacturers in China.
Lab Scale TPE Thermoplastic Elastomers

How many types of screws are there for twin-screw plastic extruders? How to repair the screw after it is worn out?

by:TENGDA     2022-12-21
With the continuous development of the economy, the development of the industrial machinery industry is getting better and better. At the same time, the high efficiency and high performance of the twin-screw extruder has become the first choice of major plastic machinery companies. The twin-screw extruder is famous for its many The special structure of the circular plate type has won unanimous praise for its remarkable characteristics such as the distribution of dead time and the uniformity of materials. Compared with the ordinary machinery in the past, it has a larger room for improvement, so it has been widely used. So, how many types of screws are there for twin-screw plastic extruders? How to repair the screw after it is worn out? Come and find out with TENGDA Plastic Extruder Machine Manufacturers.

Twin-screw plastic extruder screw classification

The screw of the twin-screw plastic extruder can be divided into two types: integral type and combined type from the structural form.

Integral twin-screw

1. Colombo type: This is a twin-screw extruder that rotates in the same direction. Its screw is composed of three sections of single-head threads, and each section has different pitches, root diameters, and outer diameters. Its outer diameter becomes smaller step by step from the feeding section to the die, while the root diameter gradually becomes larger. This twin-screw obtains the compression ratio by changing the pitch and the inner and outer diameters of the thread.

2. Pasquetti type: This is a twin-screw that rotates in different directions, and it is also composed of three sections of thread. There is a certain gap between the inner and outer diameters of the two screws; the total length of the inner and outer diameters remains unchanged, and the compression ratio is obtained by gradually reducing the pitch. There is a non-thread area between each thread section, and the material is further mixed when passing through this area.

3. Mapre type: This is also a twin-screw that rotates in different directions, and the thread shape is rectangular. The diameter of the screw remains constant over the entire length, but the flight width gradually increases from the feed end to the die end to obtain the compression ratio.

4. Conical twin-screw: It consists of three sections of thread, and the compression ratio is obtained by the taper of the screw.

combined twin-screw

It is composed of screw elements with different numbers and different functions, which are installed on the guide key or hexagonal mandrel according to certain requirements and sequences. According to the materials to be processed and different process requirements, different quantities and types of screw elements and their optimal combinations can be selected for extrusion molding.

There are various screw elements, mainly including conveying elements, shearing elements, mixing elements, compression elements, kneading elements, etc.

1. Conveying elements: Most of them are screw type, the main function is to convey materials and mix materials.

2. Shearing element: It is composed of a shearing disc or a shearing thread, and its function is to shear the material.

3. Mixing element: It is composed of two sets of toothed discs, one set of discs of one screw is inserted between two sets of discs of the other screw; it mainly plays the role of mixing. The number and shape of the teeth depend on the mixing requirements.

4. Kneading element: It is composed of different numbers of kneading discs, each disc has a different width, and the discs are placed at different staggered angles; the cross-section of all kneading discs is the same. A wedge flow is created between the kneading disks, which causes a strong circulation of the melt, and when the melt flows from one disk to another, strong lateral mixing and shearing are generated. If several kneading disks on one screw are staggered in one direction, the material can not only flow downstream, but also flow upstream to achieve longitudinal mixing.

How to repair the screw of twin-screw plastic extruder after wear

The reason for the wear of the screw of the twin-screw plastic extruder is mainly that the outer diameter of the screw is reduced due to the friction of the rotation in the barrel, or the screw is twisted due to insufficient plasticization of the material or inclusion of metal foreign matter.

1. The screw can be repaired by hard chromium plating on the surface. Chromium is also a wear-resistant and corrosion-resistant metal. The disadvantage is that the hard chromium layer is easy to fall off.

2. The screw that is considered to be twisted should be manufactured according to the actual inner diameter of the barrel and the outer diameter deviation of the new screw given the normal clearance with the barrel.

3. The worn screw is treated on the surface of the thread, then thermally sprayed with wear-resistant alloy, and then ground to size. This method can be processed and repaired in a professional spraying factory, and the advantage is that the cost is low.

4. According to the degree of screw wear, surfacing wear-resistant alloy on the threaded part of the worn screw, surfacing 1~2mm thick, and then grinding the screw to the required size. Because the wear-resistant alloy is composed of materials such as C, Cr, Vi, Co, W, and B, the screw repaired by this method has the advantage of increasing the wear resistance and corrosion resistance of the screw, but its disadvantage is that the professional surfacing factory The cost of this kind of processing is very high, so the screws except for special requirements are generally rarely used.

The above is the screw classification of twin-screw plastic extruders sorted out by TENGDA Plastic Extruder Machine Manufacturers and how to repair the screw of twin-screw plastic extruder after wear. Of course, the specific repair of the screw after wear of the extruder needs to consider the actual situation. The situation, one is economical, the second is to consider the secondary service life of the repaired screw, and the third is to consider the impact on extrusion quality.
Nanjing Tengda Machinery Co., Ltd. supports their market leadership with savvy marketing skills to create an prime brand.
The 21st century is sure to bring more innovation, new services and newer technology, thus new products and services to sell. Nanjing Tengda Machinery Co., Ltd. will continue to shape and lead the markets in which it chooses to compete.
Nanjing Tengda Machinery Co., Ltd. provides a way for you to understand your customers, to learn what makes them unique and what motivates their behavior. We can then leverage that wealth of information to personalize our interactions and demonstrate that Application is valuable to our customers.
These plastic extruder machine manufacturers Application have made the life easier. The best feature of the is its extruder machine manufacturers.
Unlike the plastic extruder machine manufacturers, the is more flexibly used in accasions where extruder machine manufacturers .
Custom message
Chat Online
Chat Online
Leave Your Message inputting...
Dear Sir or Madam, I will reply you as soon as possible. If you are urgent to ask, please contact 008619962017883. Hello, What can I help you?
Sign in with: