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What is the injection screw presses? What characteristics of screw?
Plastic product applications and our lives, injection molding and extrusion processing is currently the most economical and energy efficient processing methods. Which plasticizing screw of the most important key components for each of their different physical properties of plastic, making the plasticizing screw design also will be different. For the plasticizing screw design in the past are the high cost of using rules of thumb are not necessarily solve the problem, so the plasticizing screw in the design of some of the details is worthy of us to explore and analyze.
Plasticizing screw in accordance with its function can be divided into four areas:
1, the solid conveying zone (solid conveying zone)
This section linked with the feed funnel, plastic solid particles are tightly compressed to form a solid bed (solid bed), by the effects of melt shearing cylinder role, in addition to the plastic temperature gradually increased, while the plastic forward delivery.
2, the melt zone delay (delay of melting)
This section of the end for the solid conveying zone to melt pool (melt pool) before the formation of the region, its main features in the solid bed and melt rubber tube formed by the melt surface composed of thin-film layer, film layer melt by melting plastic tube viscous force (drag force) the cumulative forward screw spiral groove, formed by the end of this area a lot of pressure is enough to make solid-bed deformation, and the gradual accumulation of the first screw spiral groove formed melt pool.
3, the solid melting zone (melting zone)
This section of the end zone for the delay to melt completely melted plastic only, this area can be divided into two parts to the discussion, one for plastics (pastication), and plastics mainly from the effect of melting plastic tube shear effect, another is the melt delivery (melt conveying), the melt delivery to the melt pool.
4, melt conveying zone (melt conveying zone)
When completely melted all the plastic that entered this section, and ends at the end of the plasticizing screw, to maintain uniform temperature and melt stability of the flow of molten plastic.
Plasticizing screw in accordance with the geometric shape to distinguish three sections:
This section of the screw groove of the screw is fixed Goushen, its function is responsible for the warm-up and plastic solids conveying and push. Must ensure that the plastic at the end of the feed section began to melt (that is to be heated to melting point).
The length of this section is divided into crystalline (POM, PA??, Etc.)> Non-crystalline (PS, PU, ​​ABS, etc.)> heat-sensitive (PVC, etc.).
Generally:
Non-crystalline: about 48 ~ 58% L ... ... (AS, ABS, PS, etc.)
Crystalline: about 48 ~ 58% L ... ... (PA, POM, PE, PP, CA, etc.)
Singapore sex: about 45 ~ 55% L
2, measurement area (metering zone)
This section of the screw spiral groove fixed Goushen, its main function mixing, melt conveying, metering, but also must provide sufficient pressure to maintain uniform temperature and melt stability of the flow of molten plastic.
General length:
Non-crystalline: about 15 ~ 58% L ... ... (AS, ABS, PS, etc.)
Crystalline: about 48 ~ 58% L ... ... (PA, POM, PE, PP, CA, etc.)
Singapore sex: about 45 ~ 55% L
3, the compression zone (compression zone)
This section of tapered screw screw teeth deep ditch, its function as the molten plastic raw materials, mixing, compression and shear pressure exhaust. Plastic in this section will be completely dissolved, the volume will be reduced, so the design of compression (compression ratio) is very important.
General length:
Non-crystalline: about 25 ~ 35% L ... ... (AS, ABS, PS, etc.)
Crystalline: about 22 ~ 32% L ... ... (PA, POM, PE, PP, CA, etc.)
Singapore sex: about 28 ~ 40% L
PVC: 100% L