1、 The material selection for the barrel screw is 38CrMoAlA, and the structural characteristics of several types of barrel screws are introduced as follows:

1. Differences in conventional, low fill, and high fill structures

(1) Geometric shape and pairing relationship of screw ribs and grooves

Low CaCO3 content: larger between screw edges

High CaCO3 content: The gap between screw edges should be small, with the aim of improving shear force and increasing plasticization

(2) The role of each regional segment. The screw is generally divided into: feeding section, compression section, retaining section, mixing section, exhaust section, and metering section.

Feed section: Generally, the screw edge gap in the conveying section is large, resulting in fast conveying. Conversely, it is small. It is also related to the formula and CaCO3 composition.

Compression, blocking, and mixing: The main impact is on the plasticization ability. If there is no blocking before compression, plasticization can be increased. If there is a blocking, it is not suitable for high calcium. Mixing and compression are set together, generally only suitable for low calcium.

Exhaust section: The plasticizing ability of the material can be observed from the vacuum port, including granular, powder, and ribbon shapes.

Measurement section: If the screw clearance is large, the extrusion speed is fast, otherwise, it is small.

2. Introduction to the structural characteristics of low and high fillers: The feeding section, compression, and mixing of the low filler screw are connected together. During machining, the lead of the rear section of the feeding section becomes smaller and becomes a compression section. Then, a groove is made on the compression section, and 2 circles of material blocking are added to increase plasticization. The gap between the exhaust section and the metering section is slightly larger compared to the screw edge; The high packing screw structure consists of a feeding section, a blocking section, a compression section, a blocking section, a mixing section, an exhaust section, and a metering section. The screw edge gap between the feeding section and the metering section is relatively small.

3. Introduction to the Constant Temperature Control Structure of Screw and Barrel

Internal circulation: automatic circulation of distilled water

External circulation: The screw temperature control can be set to control the material temperature. It can protect the screw during startup and production processes, ensuring stable production. If not used, the product needs to change color in terms of the processing technology of the profile.

Barrel temperature control: There are two types: air cooling and oil cooling. Relatively speaking, the accuracy of oil cooling temperature control is greater than that of air cooling temperature control. However, the oil circuit is prone to blockage during use, and the failure rate is higher than that of air cooling.

2、 The Influence of Screw Structure on Pipe Products

1. Requirements for screw structure of PVC pipe products with fillers below 30, 80, and 120 parts:

120 parts or more of CaCO3: The gap between the measuring sections should be small. If the gap between the measuring sections is large, the compression is insufficient. Mixing increases the number of grooves, which determines the plasticizing effect. High calcium screws are used; Under 80 portions, high calcium screws are used, but the gap between the feeding and metering segments is reduced; Less than 30 parts: the feeding mixing section and compression section are connected together, and the measuring section has a relatively large clearance between the screws.

2. The structural changes of low and high filling screw have an impact on processing technology and mechanical properties of products

Different formulas require different screws, such as the amount of CaCO3 and lubricant. If there are many lubricants, the plasticization effect is not good and the flow performance is significantly improved.

3. The impact of high filler production formula on the lifespan of machine barrels, screws, materials, heat treatment, etc

The high filler production formula has a significant impact on the wear of the machine barrel and screw, with a short service life. Generally, wear begins in 5-6 months when the content of 100 CaCO3 is above, and in about a year when the content of 80 CaCO3 is below. Quality problems such as blue lines and black lines appear, and the wear of the machine barrel mostly occurs above the vacuum port and metering section. The screw, except for the feeding section, has varying degrees of wear. The measuring section of the machine barrel and screw is made of alloy, and the wear condition is relatively better than that of ordinary structures, but the service life will not exceed two years.