Papers by Keyword: Extrusion Die

Abstract: This paper is devoted to the study of the technological process for the production of tape from polyethylene and wood-polymer composite by extrusion. At the first stage, the wood-polymer composite granulate was obtained on a co-rotating twin-screw extruder. The tape was made on a Rheomex 19/25 PolyLab OS single-screw extruder with a barrel length L/D = 25. The processing temperature of the wood-polymer composite was in the range of 145 ... 160°C. The tensile strength and elasticity modulus in tension, water absorption per day and density were investigated for the developed wood-polymer composite and polyethylene. It has been found out that for the developed wood-polymer composite, the strength and elastic modulus along the stretch direction increase by 11% and 6%, respectively. Orientation stretching has a significant effect on the physical and mechanical properties of wood-polymer composites.

Abstract: Mechanical properties of extruded aluminum are known to significantly depend on the process parameters such as temperature, numbers of extrusion pass and extrusion load among others. This implies that these properties can be influenced by tuning the process parameters. Herein, the effects of these parameters on the tensile strength and hardness of aluminum 6063 series were investigated by using equal channel angular extrusion (ECAE). Experiments were designed using Design Expert software. Analysis of variance (ANOVA) was then used to investigate the main and interactions effects of the process parameters. An empirical mathematical model was generated that shows the relationship between the input and output variables using response surface methodology. Temperature was found to be the most significant factor while extrusion load was the least factor that influenced the hardness and tensile strength which were the output factors. There was a significant increase in tensile strength and hardness after extrusion at different mix of factors. The optimum input variable was discovered at 1020.58 kN, 489.67°C and 3 numbers of extrusion passes.

Abstract: Polymer extrusion is one of the most widely utilized manufacturing processes across many industries including automotive, architecture, aerospace etc. However, in order to maintain normal operations, polymer extrusion dies are conventionally designed with large dimensions and thick walls which results in the overweight of them. In this paper, a shape optimization method is proposed to reduce the weight of polymer extrusion dies without sacrificing the required performances of extrudate. Firstly, Finite element simulation of the extrusion process is conducted using the commercial software HyperXtrude to study both the essential flow characteristics of polymer melts and the deformation and stress distribution of extrusion die. Secondly, shape optimization is conducted to find the minimum weight of extrusion die while satisfying the required properties and productivity of polymer product. The extrusion die is then redesigned according to the result of shape optimization and compared with the original one. A Medium-sized polymer profile extrusion die is selected as case study, the result of which shows that the weight of the extrusion die is reduced by 31.6%,though the maximal deformation and stress of the die are increased by 1.7% and 16.1% respectively. The proposed approach is demonstrated to be effective for the lightweight design of polymer extrusion die.

Abstract: As traditional screw extrusion die tolerance analysis has characteristics like manual calculation, experience dependence so far, this paper aims at applying CAT (Computer Aided Tolerancing) into extrusion field with the assistance of tolerance modeling and self-generation algorithm of retrieval dimension chain to analyze tolerance and reassign tolerance based on the technology used for aircraft assembly referring to chemical characteristics of the manufacturing process. Practice on production line testified the rationality of improved tolerance design.

Abstract: It is one of the keys that determining reasonable damping block geometry in the process of designing the extrusion dies. In this paper, the finite element software POLYFLOW was used to simulate the flow process of tread rubber in the head channel. In addition, the orthogonal experiment method was adopted for the optimum design of the damping block in the head channel. After optimum design, the flow velocity of rubber melt becomes more uniform in the full width at the head outlet. Consequently, the warping deformation of the rubber, which flow through the head channel, is also significantly reduced.

Abstract: According to the similar characteristics of structure, geometry and constraints conditions in the same type of extrusion process, the intelligent design system of a square tube aluminum profile extrusion forming process was established in this paper based on the VB programming language, with using parametric programming language APDL provides by ANSYS software. The parameterized optimization design plan of pre-treatment and post-processing of ANSYS analysis during a square tube aluminum extrusion forming process was achieved, and the program of a three-dimensional model of the extrusion die under Visual Lisp environment was also programmed. The human-computer interaction intelligent design system which combined with pre-processing of semi-finished product, finite element analysis of extrusion die strength, extrusion die temperature field analysis, structural optimization of the die was realized. The research results show that the system can provide program decision-making, structural design, performance analysis and graphics treatment for the actual extrusion productions of square tube aluminum extrusion process, which reduced the design time of the technical staff, and saved design cost.

Abstract: The design of extrusion die has been investigated by autofrettage technique considering the characteristics of the extrusion die. Ideal elastoplastic autofrettage model was established and the stress formulae of three loading procedures were derived and the theoretical calculation method of the maximum autofrettage pressure and working load was put forward. The simulations of stress distribution and the inwall displacement of the autofrettaged extrusion die were performed using MARC finite element software, and the results coincided well with the theoretical derivations. It was observed that the autofrettaged extrusion die can raise the elastic loading capacity under the inner displacement limit , without the appearance of reverse yielding and reyielding under the working load. The results show that the autofrettage technique is appropriate for the design of extrusion die.

Abstract: Nitriding is one of the most efficient methods used to enhance the service life of aluminum extrusion dies. In this paper, a new nitriding process has been introduced that is characterized by that 4Cr5MoSiV1 steel, a typical material used for extrusion dies, was nitrided by using two-stage nitriding process. The microstructures of nitrided layer have been analyzed by means of optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and microhardness (MH). The results show that pre-heat treatment on the 4Cr5MoSiV1 steel extrusion die can be carried out under the condition of quenching at 1040 °C, double tempering at 600 °C and 560 °C for 2 hours each. Operating parameters of two-stage nitriding are set as follow: stage one, 520 °C for 6 hours, the flow rate of NH₃ of 0.6 m³/h; nitriding pressure of 453 Pa and stage two, 580 °C for 8 hours, the flow rate of NH₃ of 0.35 m³/h; nitriding pressure of 453 Pa.

Abstract: Tools are exposed to severe working conditions during the hot extrusion process. In particular, dies and mandrels can be subjected to an excessive amount of deformation as a result of the developed high cyclic loads and temperatures. In this scenario, a physical experiment reproducing the thermo-mechanical conditions of a mandrel in a porthole die was performed with the Gleeble machine on the AISI H11 tool steel with the aim to investigate the mechanisms that influence the die deformation. The design of experiment consisted of 4 levels of temperature, 3 levels of stress and 3 types of load, i.e. pure creep, pure fatigue and creep-fatigue. In all the testing conditions, a comparable pattern of the mandrel displacement-time curve was found reproducing the 3 stages of softening typical of the strain evolution in a standard creep test but with a marked primary phase. Thus, with the aim to identify an easy-applicable equation to estimate the die deformation, the time hardening creep law was chosen. Coefficients of the time-hardening law were optimized, for each testing condition, on the basis of experimental data starting from values for similar alloys taken from the literature. Results in terms of mandrel displacement were then compared to experimental data for the creep-fatigue condition at different stress and temperature levels. The values found were validated against additional experimental data performed with different specimen geometries. A good average agreement was found between experimental and numerical results. The developed procedure was then applied to an industrial die.

Abstract: In the die manufacturing process of ceramic extrusion die, the residual stress was produced resulted from the thermal expansion coefficient mismatch between ceramic die and die core of graphite. As a result, the longitudinal cracks were formed in the ceramic extrusion die. The thermal residual stress formed in the cooling process was analyzed by finite element simulation method. The result indicated that the thermal expansion coefficient was the primary factor which could affect the tensile stress of ceramic extrusion die. Then, the thermal expansion coefficient, elastic modulus and poisson's ratio of ceramic extrusion die material were selected as design variables, and the largest tensile stress that less than allowable stress of ceramic die material was determined as the objective function, the material component were optimized according to the finite element simulation. The longitudinal cracks were eventually avoided.