Plasticizing screw according to the geometrical shape distinguish three sections:
1, the feed zone (feed zone) This section is fixed SCREW ditch is deep, its function is responsible for preheating and plastic solids conveying and compacting. Must ensure that the plastic in the feed end of the block starts to melt (that is to warm up to the melting point). This segment length is divided into crystalline (POM, PA?? Etc.)> non-crystalline (PS, PU, ABS, etc.)> heat-sensitive (PVC, etc.). General: non-crystalline: about 48 ~ 58% L ...... (AS, ABS, PS, etc.) crystalline: about 48 ~ 58% L ...... (PA, POM, PE, PP, CA, etc.) Singapore resistance: about 45 ~ 55% L
2, the compression zone (compression zone) This section is tapered screw and tooth deep ditch, and its function as plastic raw material melting, mixing, shear compression and exhaust pressure. This section will be completely dissolved in the plastic, the volume will be reduced, so the design of compression (compression ratio) is important. Average length: Non-crystalline: about 25 ~ 35% L ...... (AS, ABS, PS, etc.) crystallinity: about 22 ~ 32% L ...... (PA, POM, PE, PP, CA, etc.) of Singapore : about 28 ~ 40% L PVC: 100% L
3, the metering zone (metering zone) This section is fixed Goushen SCREW ditch, its main function mixing, melt conveying, metering, but also must provide sufficient pressure to maintain a uniform temperature and melt stability of the molten plastic traffic.
Average length: Non-crystalline: about 15 ~ 58% L ...... (AS, ABS, PS, etc.) crystallinity: about 48 ~ 58% L ...... (PA, POM, PE, PP, CA, etc.) of Singapore : about 45 ~ 55% L While plasticizing screw according to distinguish features or geometric shape, but the actual plasticizing process, each section functions overlap, it is difficult to distinguish between.
The study plasticizing screw, is nothing more than think:
First, enhance shear mixing (dispersive mixing) effect.
Second, the modified uniform mixing (dispersive mixing).
Third, improve the plasticizing capacity (plasticating capacity).
Fourth, improve the melt temperature uniformity. When the feed section deeper thread depth greater throughput, but the larger screw torque required; feed section teeth deep shallow, throughput is not enough, the compression ratio is insufficient. When teeth deep deep metering section, the compression ratio is less than the required force feeding large; shallow easily when burned and charred. General tooth depth of about 0.03 to 0.07 times the screw diameter. Therefore plasticizing screw has a transmission, melting, mixing, compression and metering functions in plasticizing quality plays a very important role.
Plasticizing screw Material Profile
1, ACM2 (West German material, commonly known as black and white cross): ACM2 as aluminum, molybdenum-nickel-molybdenum alloy steel, quenched and tempered up to HB280 ~ 320, after processing nitride 72hr up HV> 800 hardness, with good abrasion resistance, However, the results are poor hard chrome plating, as a general group of plasticizing barrel screw and molten plastic tube used.
2, MAC24 (Mitsubishi material, quenched and tempered nitrided steel): aluminum-free ingredients, so fewer white layer after nitriding, nitriding hardness of about HV800 ~ HV950, acid etching of the hard chrome plating effect.
3, two alloys: its manufacturing is divided into PTA crests spray and HP / HVOF spraying two kinds, to be chosen according to different plastic characteristics. Hardening the surface hardness of HRC74, with excellent wear characteristics of cemented carbide, and its film density as high as 98 to 99.8%, while the surface of the adhesion strength of 10000psi more. Can know plasticizing screw injection molding machine can be described as the heart of components responsible for the delivery of plastic raw materials, melting, mixing, metering and so on, so the plasticizing screw is closely related with the quality of molded products. ,
Article Source China Machinery Network: www.fktcc.com