First, the material selection of the barrel screw is 38 […]
First, the material selection of the barrel screw is 38CrMoAlA. The screw structure characteristics of several types of barrels are as follows:
1. Conventional, low filler, high filler structure difference
(1) Phillips, groove geometry and matching relationship
Less CaCO3 content: larger between the spiral edge and the spiral edge
More CaCO3 content: the gap between the spiral edge and the screw edge is smaller, the purpose is to increase the shear force and increase the plasticization.
(2) The role of each regional segment. The screw is generally divided into: a feed section, a compression section, a block section, a mixing section, an exhaust section, and a metering section.
Feeding section: Generally, the conveying edge has a large gap and the conveying speed is fast, and vice versa. It is also related to the formulation and CaCO3 component.
Compression, material blocking, mixing: The main influence is the plasticizing ability. If there is no material before compression, plasticization can be increased. If a material is provided, it is not suitable for high calcium, mixing and compression. Set together, generally only suitable for low calcium.
Exhaust section: The plasticizing ability of the material can be observed from the vacuum port, which is granular, powdery, and strip-shaped.
Metering section: the gap of the screw edge is large, the extrusion is fast, and vice versa.
2. Low-filler and high-filler structure features: Low-fill screw feeding section, compression and mixing are combined. When the car is processed, the last section of the feed section becomes smaller and becomes the compression section. The tank is filled with 2 turns of material to increase the plasticization. The rear exhaust section and the metering section are larger than the screw gap; the high-filled screw structure consists of the feed section, the material, the compression, the material, the mixing, and the exhaust. The section, the metering section, the gap between the feeding section and the metering section are small.
3. Introduction of screw and barrel thermostatic control structure
Internal circulation: automatic circulation of distilled water
External circulation: screw temperature control can be set, the material temperature can be controlled, the screw can be protected during the startup process and during the production process, and the production can be stabilized. If not used, the product should be discolored for the processing of the profile.
Barrel temperature control: There are two kinds of air cooling and oil cooling. Relatively speaking, the oil cooling temperature control accuracy is greater than the air cooling temperature control accuracy, but the oil circuit is easy to block during use, and the failure rate is higher than air cooling.
Second, the impact of screw structure on pipe products
1,30 parts or less, 80 parts or less, 120 parts or less of filler PVC pipe product formula for screw structure requirements:
120 parts of CaCO3 or more: the metering section gap is small. If the metering section gap is large, the compression is not enough, the mixing increases the number of slots, the number of slots determines the plasticizing effect, and the high calcium screw is used; 80 parts or less, using high calcium screw, However, the gap between the feed and the metering section is reduced; 30 parts or less: the feed mixing section and the compression section are connected together, and the other is the same, the metering section has a relatively large gap.
2, low filler, high filler screw structure changes, the impact on the processing technology, mechanical properties of the product
Different formulations require different screws, the amount of CaCO3, the amount of lubricant, if there are many lubricants, the plasticizing effect is not good, and the flow performance is obviously improved.
3, high filler production formula on the life of the barrel, screw, materials, heat treatment, etc.
The high-filling production formula has a great influence on the wear of the barrel and the screw, and the service life is not long. Generally, the wear starts in 5-6 months after more than 100 CaCO3, and below 80 CaCO3, the use time is about one year, and wear begins. There are quality problems such as blue lines and black lines. Most of the barrel wear occurs above the vacuum port and the metering section. The screw has different degrees of wear except the feed section. The cylinder and screw metering section are made of alloy, and the wear condition is relatively better than the ordinary structure, but the use time will not exceed two years.