Розглянуто процеси екструзійного формування безперервних виробів із термопластичних матеріалів та устатковання для їх реалізації. Проаналізовано проблеми, що виникають під час екструзійного формування, і засобів їх усунення, запропоновано шляхи удосконалення існуючих формувальних пристроїв.
Meeting the needs of geometric complicated articles of plastic is impossible without optimizing design and process parameters of equipment and processes of polymers and compositions with their use. Ultimate parameters of the polymeric and composite production are takes into forming tool.
In the design of the forming equipment we must consider that its working channels can has different geometry and processed material – different hydrodynamic and thermal regimes. All of these parameters bound to change the rheological properties of the processed material.
The aim of the paper is to analyze the main factors that affect the quality of the process of polymer products extrusion forming, and means to eliminate defects in extruded products.
For high speed extrusion the conditions for achieving marginal adhesion strength can be created and defective surface arise as a result of highly turbulence. This phenomenon is predicted to achieve a theoretical or experimentally determined critical shear rate. Typically, this problem can be eliminated by reducing the rate of extrusion, increasing the temperature in the forming extrusion die channels, and by addition of external lubricants into the polymer.
For compensation of these effects a new extrusion die design was proposed, which structural elements can absorb vibrations occurring. Annular extrusion die contains a matrix that forms the outer surface of the polymer product, and mandrel, forms the inner surface of the product and which the input and output parts consists. The output parts of the matrix and mandrel are fixed in the moving part of mandrel support, and creates a channel for the melt flow with the output area, and besides the matrix and the output of the mandrel can move back and forth along the axis relative to the fixed part mandrel support with changing of the channel length for the melt flow. In matrix elastic and damping elements are placed that transmit force from it on the cover. The melt was included in the die, enters in the channel between the output mandrel part and the input part, and forms a pressure drop, which leads to the formation of an axial force that moves the matrix of the original part mandrel and moving parts of the mandrel support relatively fixed part of the mandrel support. The length of the channel increases, and the pressure in the die starts to decrease. Matrix, moving in the axial direction, passes through the efforts of the lid damper that reduces the speed of movement, and the spring that tries to take the matrix to its original position. As the process is continuous, as the matrix of the input part of the mandrel takes reciprocates, thereby absorbing pulsation.
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