An Investigation On The Polymer Precision Extrusion And Uniformity Of Wall Thickness

Improving extrusion precision is an important tendency for the development of modern extrusion processing technology. Precision extrusion can prominently improve the products' precision and quality , satisfy the processing request for many high-tech products, and widen the application fields of extrusion. On the other hand, by improving the wall thickness uniformity of the products, it can distinctly reduce the resin waste and the production cost. What's more, precision for extrusion is easy to realize the products' automatic assembly and streamline production, and is propitious to enhance the automatization level for production. In a word, precision extrusion can bring a lot of economic and social benefits.Extrusion is mainly used for continuously producing products with same section sizes and shapes. So, in order to ensure the products' high precision and high quality, it is important to guarantee the extrusion output stability in the first step, then, on the basis of it, to control the circumferential size distribution of the products, so as to improve the wall thickness uniformity and guarantee the essential size tolerance.On the basis of some studies carried out by the formers, this paper summed up some factors affecting the output stability such as pressure fluctuation, temperature fluctuation, flow rate fluctuation, the instability of solid conveying, the breaking up of solid beds, the loss-weight metering feed controlling and the screw parameters. And the corresponding controlling measures and settling methods are also advanced. For the problem of the products' section size distribution uniformity, in this paper, the advanced automatic controlling technology for the wall thickness was introduced, and the impacts of the circumferential temperature distribution of the die on the products' wall thickness was researched. The conclusion was obtained that the magnitude of the impacts of die temperaturedistribution on the uniformity of wall thickness are related to the activation energy of the material, the non-Newtonian index of the melt, the basic temperature of the melt and the temperature fluctuation. For the phenomenon of the extrusion swelling after the polymer melt left the die, in this paper, the impacts of the extrusion swelling fluctuation on the products' size precision were researched, which may offer some references for further investigation on the precision form and size setting of extrudate.