RPVC sheet machine hanger type head​

日期:2019/6/9 10:47:59 / 阅读: / 来源:本站

RPVC sheet machine hanger type head
The hanger type head is named after the shape of the nose is similar to the shape of the hanger. It is mainly composed of a guide channel, an upper mold body, a lower mold body, a resistance block and a mold layer block. It is widely used because of its obvious effect on extrusion processing of plastics. Compared with the T-type and fish-tail type heads, the hanger-type head has two advantages in extrusion molding: one is that the melt residence time is short and it is not easy to degrade, which is beneficial to various resins, especially PVC. The molding process of the heat-sensitive resin; the second is that the cavity sector area is large, and the melt is easily discharged uniformly along the width direction of the die lip, which is advantageous for improving the thickness uniformity of the wide-width plate (sheet) product and increasing the output of the machine.
In the extrusion process, the wider the extrusion plate (sheet), the greater the width of the die lip, the better the uniformity of the product. The uniformity index of the RPVC transparent plate (sheet) is practical. An important indicator. Although the lip gap has been adjusted according to the thickness of the plate (sheet) at each boot temperature, changes in melt flow rate, pressure and temperature, especially any fluctuations in the temperature of the cavity and lip region, may result in no discharge. The thickness of the plate and the plate are uneven. This is because not only the flow of the melt to the lip but also the extrusion pressure is not an absolute value, and the temperature in the lip region is not easily constant. The melt generates frictional heat in the large-area flow of the cavity, forming a temperature difference distribution between the cavity and the lip region. At the same time, the flow of the melt before it exits the lip
The two results are obtained, that is, the melt slides along the guide channel and the mold wall, and is smoothly extruded through the lip region; or because of the upper and lower mold bodies and
The raw material is decomposed and coked, and when processing PVC, it is of course the former rather than the latter. Only when the melt slides smoothly in the guide channel and the cavity, the surface quality and physical properties of the RPVC transparent plate (sheet) can be obtained. Therefore, in actual production, it is necessary to fully understand the melt flow characteristics, especially the guide channel, the cavity and the lip region located in front of the twin-screw head as a key part. The set head temperature is: 180 ° C for the upper and lower mold bodies, 155 ° C for the upper and lower mold lips, and 175 ° C for the left and right end faces of the lip. At the same time, it is necessary to frequently observe and detect the thickness value of each part of the width section of the extruded plate (sheet), and make full use of a row of 30 screws arranged on the top of the upper die lip to carry out the lip spacing of the melt resistance block. Self-rising
The down regulation is used to achieve microscopic control of the melt flow rate to meet the surface quality and thickness uniformity requirements of the RPVC transparent plate (sheet).


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