What characteristics of screw?
Plasticizing screw in accordance with the geometric shape to distinguish three sections:
1, the feed zone (feed zone) of this section of the screw groove of the fixed screw 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.) crystal: about 48 ~ 58% L ... ... (PA, POM, PE, PP, CA, etc.) of Singapore: about 45 ~ 55% L
2, the compression zone (compression zone) of this section for the 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.) crystal: about 22 ~ 32% L ... ... (PA, POM, PE, PP, CA, etc.) of Singapore : about 28 ~ 40% L PVC: 100% L
3, measurement area (metering zone) of this section of the spiral groove for the screw fixed Goushen, its main function mixing, melt conveying, metering, but also must provide sufficient pressure to maintain uniform temperature and melt stability of the molten plastic of traffic.
General length: non-crystalline: about 15 ~ 58% L ... ... (AS, ABS, PS, etc.) crystal: about 48 ~ 58% L ... ... (PA, POM, PE, PP, CA, etc.) of Singapore : about 45 ~ 55% L While plasticizing screw to follow function, or geometric shape to distinguish, but the actual process of plastics, each section features overlap, it is difficult to distinguish between intervals.
The study plasticizing screw, nothing more than thought:
First, enhance shear mixing (dispersive mixing) effect.
Second, the modified uniform mixing (dispersive mixing).
Third, improve the plasticizing capacity (plasticating capacity).
Fourth, to improve melt temperature uniformity. When the feed section of teeth deeper depth greater throughput, but the larger screw torque required; teeth deep feed section is too shallow, not enough throughput, compression ratio of less than. When the metering section teeth deep is too deep, the compression ratio of less than the required force feeding large; shallow that are susceptible to fire and burned. General dental depth of 0.03 to 0.07 times the screw diameter. Therefore, a plasticizing screw conveyor, melting, mixing, compression and metering functions, the quality of the plastics play an important role.
Plasticizing screw material profile
1, ACM2 (West Germany material, commonly known as black and white cross): ACM2 aluminum-molybdenum-nickel-molybdenum alloy steel, quenched and tempered up to HB280 ~ 320, after processing nitrogen 72hr up to HV> 800 hardness, has excellent wear resistance, However, hard chrome plating of the results are poor, for the general control group of plastic material and melting plastic screw plasticizing cylinder use.
2, MAC24 (Mitsubishi Materials, quenched and tempered steel nitride): aluminum-free ingredients, so less white layer after nitriding, nitriding hardness of about HV800 ~ HV950, chromium plated acid corrosion of good effect.
3, two alloys: the manufacture of PTA teeth into the top spray mode and HP / HVOF spraying two, to be selected according to different plastic properties. Hardening the surface hardness of HRC74, with good wear characteristics of superhard alloy, the film density as high as 98 to 99.8%, while the surface adhesion strength 10000psi more. Can be said is that plasticizing screw injection molding machine in the heart of the component responsible for the delivery of plastic raw materials, melting, mixing, metering and so on, so plasticizing screw is closely related with the quality of molded products.