extrusion die
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The article presents the original technology of the extrusion of hollow curved pipes. The curvature radius of pipe axis was obtained directly during extrusion by eccentric alignment of the annular calibration gap of the extrusion die. Theoretical relationships describing the radius of curvature of the extruded part as a function of the eccentricity e of position of the annular calibration gap in the die were developed. A die with replaceable inserts with eccentricity e equal to 1, 2, 3, 5, 7 mm was designed and fabricated. Experimental tests were carried out to extrude lead pipes with an outer diameter of 20 mm and an inner diameter of 18 mm. Measurements of the radii of the curvature of the extruded pipes were consistent with the values calculated from the developed theoretical relationships. Numerical modelling of the proposed method of extrusion in a finite element-based QForm 3D program was carried out. The finite element method (FEM) numerical calculations were carried out for lead. Numerical simulations and experimental studies have shown that, by changing the value of the eccentric gap, the radius of curvature of the extruded pipe can be controlled.

Abstract A new type of extrusion die is put forward, in which cemented carbide material is used to inlay the working part of the die, so as to improve the wear resistance of the die. The necessity of using cemented carbide in extrusion die is introduced. The selection of cemented carbide was introduced by taking the actual round tube aluminum profile as an example. The method for determining the size of cemented carbide and the mosaic method of cemented carbide were described. Based on the results of extrusion, the common extrusion die and cemented carbide extrusion die were compared. The results show that the wear resistance of the die can be greatly improved by the use of cemented carbide. Thus the life of the die is greatly improved.

Some inventions along with theoretical and experimental research made it possible to increase the output of a thermally homogeneous melt provided by the screw. However, the quality of the extruded product depends on some specific features of the extrusion die and to a large extent on the rheological behavior (viscous and elastic) of the polymer melt. The mismatch between the design of the screw-cylinder subassembly and the design of the extrusion die results in products with relatively short service life. The present paper has drawn up the working field of the extruder die and adjusted it based on the limitations imposed by the screw-cylinder subassembly, namely: - the maximum output rate that ensures the required thermal homogeneity of the melt; - the maximum output at which the heating system on the barrel (and possibly the screw) ensures the extrusion temperature; - the minimum economic output corresponding to the diameter of the screw. The working field of some extrusion dies for blown films of the following polymers have been plotted: polypropylene, low density polyethylene, high density polyethylene and ethylene vinyl acetate.

There is a growing body of laboratory and industrial evidence that the viscoelastic characteristics of molten polymers contribute to improving the efficiency of polymer extrusion molding. Understanding the behavior of molten polymers in manufacturing processes requires the qualitative and quantitative determination of flow kinematics and stress distribution. The optimization of the forming processes and the final properties of the transformed products requires the mastery of high-performance simulation models. So, it is necessary to be able to correctly describe the non-linear rheological behavior of the molten polymers by appropriate constitutive equations and a relatively easy implementation in computer codes. In this work, experimental and numerical studies are performed to investigate the rheological behavior of branched polybutadiene into a two-dimensional channel of a capillary rheometer. The stress field in the flow was analyzed with a birefringence device to identify areas of stress concentration and to show its progress in different areas of the extrusion die. Also, we obtain the stress field with numerical simulations using ANSYS Fluent 16.0 as a solver and Gambit as a mesh generator. The rheological model adopted in the numerical study is the power-law or Ostwald-de Waele model.

Aluminium extruded profiles are used for light weight structures used in architecture, transportation, aerospace, industrial sectors etc. Increasing use of profiles for applications has been driving extruiders to focus on reliable techniques to produce profile that meet consistent quality. In aluminium extrusion, profitability can be achieved by pushing maximum number of billets i.e maximum speed during production. However, in the shopfloor different aluminium alloys and geometries are limited by manufacturibility limitations which based on alloy properties and metal flow charcateritics. Hence, product quality is largely dependant on the closer control of metal flow charcateritics that can be compensated by right quality aluminium billet and die design paramaters. In this regard, numerical simulation studies have been adopted prior to production to ensure the consistent and reliable quality of profiles. In this technical communication, metal flow characteristics such as velocity, temperature and strain rate in an extrusion die were compared using numerical simulation studies for two alloys namely AA6063 and AA7075.