Complex-shaped Parts Research Articles

Machining of complex-shaped parts with guidance curves

Nowadays, high-speed machining is usually used for production of hardened material parts with complex shapes such as dies and molds. In such parts, tool paths generated for bottom machining feature with the conventional parallel plane strategy induced many feed rate reductions, especially when boundaries of the feature have a lot of curvatures and are not parallel. Several machining experiments on hardened material lead to the conclusion that a tool path implying stable cutting conditions might guarantee a better part surface integrity. To ensure this stability, the shape machined must be decomposed when conventional strategies are not suitable. In this paper, an experimental approach based on high-speed performance simulation is conducted on a master bottom machining feature in order to highlight the influence of the curvatures towards a suitable decomposition of machining area. The decomposition is achieved through the construction of intermediate curves between the closed boundaries of the feature. These intermediate curves are used as guidance curve for the tool paths generation with an alternative machining strategy called “guidance curve strategy”. For the construction of intermediate curves, key parameters reflecting the influence of their proximity with each closed boundary and the influence of the curvatures of this latter are introduced. Based on the results, a method for defining guidance curves in four steps is proposed.

Superplastic-like forming of Ti-6Al-4V alloy

Superplastic forming of titanium alloys is used for producing structural components, since it is an effective way to manufacture complex-shaped parts in a one-step operation. An optimized sheet-forming process has been designed incorporating a non-isothermal heating system to establish a fast forming process. This work sought to expand the advantages of the technology to the forming of Ti-6Al-4V alloy at 800 °C and shorter cycle time. The minimum thicknesses area was found at the outward corners, showing a maximum percent thinning of 54 %. In addition to stress variations, the cracks resulting from hot drawing and the oxidation on the sheet surface are the other reasons leading to thickness reduction. From the oxidization behavior of Ti-6Al-4V alloy, it was revealed that the decrease in forming temperature from 900 to 800 °C significantly reduced the formation rate of oxide film on the sheet surface. The study also showed that the main microstructure evolution of Ti-6Al-4V alloy under these conditions was recrystallization.

Postprocessing of CL Data in CAD/CAM system Edgecam using the Constructor of postprocessors

Introduction into problems - the present CAD/CAM systems integrate part modelling and engineering design, proposal of technological documentation in the form of NC programs and operational management of production within a one computer system. Their utilization allows the programmer to create machining technology, to define the tool paths and to generate NC programs for very complex shape parts [7]. Final product of CAM system is CL Data files, which include all the steps of toolpaths and technological process. If we want to connect the information produced by the CAM system with the concrete CNC machine, we need to use NC postprocessor. Generator of postprocessors to help users faster creates the specific postprocessor. Universal postprocessor does not exist. Unfortunately, it is necessary to create and to program it for each machine separately. This paper presents a use of the software tool "Constructor of postprocessors", by the creation of postprocessor in CAD/CAM system Edgecam. Postprocessor was developed for turning machine EMCO Concept Turn 55 with control system SIEMENS 840D at the Department of Automation and Production Systems (DAPS) Faculty of Mechanical Engineering.

열진공성형에서 적층필름 두께변화에 대한 수치 및 실험적 해석

Vacuum-assisted thermoforming is one of the critical steps for successful application of film insert molding (FIM) to make parts of complex shape. If the thickness distribution of the formed film is non-uniform, then cracking, deformation, warpage, and wrinkling can easily occur at the injection molding stage. In this study, the simulation of thermoforming was performed to predict the film thickness distribution, and the results were compared with experiments. Uniaxial tensile tests with a constant crosshead speed for various high temperatures were conducted to investigate the stress-strain behavior. An instance of yielding occurred at the film temperature of , and the film stiffness increased with increasing crosshead speed. Two types of viscoelastic models, G`Sell model, K-BKZ model, were used to describe the measured stress-strain relationship. The predicted film thickness distributions were in good agreement with the experimental results.

Study on Preparation Process of Magnetic Abrasive Particles

Abstract: With the industrial development and improvement of mechanical product quality, the demand of part surface quality and accuracy gets more and more high. As some parts of complex shape, can’t be machined by the traditional processing technology, therefore, the magnetic abrasive technique was proposed. The magnetic abrasive particles play an important role in the magnetic abrasive finishing, it use strong magnetic iron particles and abrasive particles mixed together (called magnetic abrasive). The prepared method of magnetic abrasive one of is sintering method, the aim is to change the internal structure of abrasive particles, make the abrasive particles is distributed on the surface of magnetic iron particles, get a kind of magnetic abrasive, which can be magnetized in a magnetic field and improve processing efficiency and surface quality in magnetic abrasive finishing. In this paper, sintering method is used to make iron particles, abrasive particles mixed with some binder, after suppression, drying, sintering, cooling, break up and sieving, analysis surface morphology and composition of the magnetic abrasive particles by scanning electron microscopy, discusses the effect of the abrasive particles size ratio, sintering time, sintering temperature for the finishing performs, the preparation process of the magnetic abrasive has been optimized, work out the standard of preparation of the magnetic abrasive process

Laser-arc hybrid welding of wrought to selective laser molten stainless steel

Selective laser melting (SLM) is a successful tool-free powder additive technology. The success of this manufacturing process results from the possibility to create complex shape parts, with intrinsic engineered features and good mechanical properties. Joining SLM steel to similar or dissimilar steel can overcome some limitations of the product design like small dimension, undercut profile, and residual stress concentration. In this way, the range of applications of the SLM process can be broadened. In this paper, the hybrid laser welding of selective laser molten stainless steel was investigated. A high-power fiber laser was coupled to an electric arc and austenitic stainless steel wrought and SLM parts were welded together. The power and speed parameters were investigated. The joints were analyzed in terms of weld bead profile, microstructure, microhardness, and tensile test. The efficiency of the welding process was evaluated through the line energy input versus the weld molten area.

Powder injection moulding: processing of small parts of complex shape

Powder Injection Moulding (PIM), Metal Injection Moulding (MIM) when is limited to metals, is a fabrication route of parts with the final shape desired. This process combines the high capability of polymer injection moulding to produce complex shapes with the advantages of a powder route to process metallic, ceramic or composites materials. The process has some limitations that comes from different technological steps involved in the production of the part (feedstock production, injection, debinding and sintering). All of these different steps can be industrially controlled, being the PIM process a real alternative to produce complex parts in a high rate production method that can compete with many other processing methods to produce materials. In this work, we will go through the different steps of this manufacturing process, making special emphasis on the solutions provided by the powder technology group of the University Carlos III of Madrid (UC3M).

Draft dynamic student learning in design and manufacturing of complex shape parts

The contribution deals with the dynamic teaching of students through blended learning and teaching online distance teaching which can be considered nowadays to be a very effective and dynamic education of students. Content of the article is focused on the sphere of programming with CNC machines and use Cax systems for the production of a particular shape complex parts - shearing knife. The article presented also proposed effective teaching resources. The motivation for solution of this project is that dynamic education leads students to gaining experience and skills, individual identification of the issue, creativity, suggestion of problem solving variations. The achieved way of education and its confirmed and verified positive results can be applied for various target groups of students and their fields of study

Research Status and Developing of Metal Injection Molding

Metal injection molding(MIM) is a high efficient and near net shape manufacturing technology, which is appropriate for parts of small size and complex shape. MIM provides a viable method to fabricate metal and metal matrix composites with discontinuous reinforcements, and micro metal injection molding (μMIM) is applied to manufacturing products at micro scale. The status of the research and development of MIM and μMIM are reviewed. Processes including mixing, injection molding and subsequent debinding and sintering are summarized. And technical characteristic, injection processing and application of μMIM are introduced. The disadvantages in mixing, injection molding and debinding processes limit MIM to fabricating components with small size, low precision and mechanical properties, and it is necessary to prevent the powder from reuniting and avoid any oxidation and impurity during μMIM process. Further investigations in these areas will give rise to being explored of full potential of MIM technology.

Mini-Thixoforming of a Steel Produced by Powder Metallurgy

Semi-solid processing is complicated by various inherent technical problems. However, once these problems are solved, thixoforming allows intricately shaped components to be manufactured very effectively – often with microstructures that cannot be produced by any other techniques. The recently introduced mini-thixoforming method is an example of such a novel technique for semi-solid processing of steel. The wall thicknesses of resulting parts are about 1 mm. Microstructures of semi-solid-processed steels typically consist of a high proportion of globular particles of metastable austenite embedded in a carbide network, the latter being much harder and more brittle. This paper illustrates that mini-thixoforming allows inverting that microstructural configuration. As an experimental material, powder steel with increased content of vanadium and chromium was used. The post-thixoforming microstructure consisted of a dispersion of carbides and high-vanadium and high-chromium eutectic in an austenitic matrix. Applying optimised processing parameters, complex-shaped parts could be produced. According to the high hardness of resulting microstructural components, the new materials are likely to exhibit extraordinary strength and wear resistance.

Optimization of the cycle time in resin transfer molding process by numerical simulation

Resin transfer molding is a popular manufacturing process for composite materials because of its ability to manufacture complex-shaped parts with high efficiency and low pollution. Despite the intense interest in the modeling and simulation of this process, minimization of mold filling time without losing the part quality remains an important issue in the resin transfer molding process. Various methods in the literature are suggested to achieve this. However, inappropriate injection methods lead to numerous air entrapments, and fiber mat deformation. In this study, we are interested in developing and improving new methods to optimize the cycle time. The effects of several parameters on the filling process are deeply investigated. A computer code based on the control volume finite element method is developed to study the mold filling process in all cases. The validity of the computer code used is checked by analytical results and close agreement is found.

Powder metallurgy industry and managerial economics micro/nanosized refractory powder injection molding machine

A design of an injection molding machine for the fabrication of complex-shaped parts from mixtures of thermoplastics and micro- and nanosized powders is presented. This machine provides uniform temperature distribution in the barrel and formation of parts with required qualitative characteristics. The machine was used to produce a pilot batch of paint spray nozzles from micro-and nanosized powders.

고정밀 신관 부품의 MIM 공정에 관한 연구

During the past two decades, Metal Injection Molding(MIM) has become a very competitive technology to fabricate small, precise and complex-shaped parts in large quantities. In this research, the applicability of MIM technology in the mass-production of the high precision fuze parts to save manufacturing cost was investigated. The water-atomized 17-4PH stainless steel powder, one of the best corrosion-resistant high strength materials, was injection-molded into real-shape fuze part and flat tensile specimens. The injection-molded parts were thermally debound in hydrogen gas flow without solvent extraction. Sintering of the debound parts was carried out in vacuum at temperatures ranging from <TEX>$1150^{\circ}C$</TEX> to <TEX>$1370^{\circ}C$</TEX>. The sintering behavior, mechanical properties, dimensional precision, corrosion resistance of the MIMed 17-4PH stainless parts were investigated. It was found that almost all the properties of the MIMed parts were comparable to those of the mechanically machined parts. Also, actual military field tests using both MIMed and mechanically machined fuze parts were performed as well and were found to be very successful.

A first approach to characterize the surface integrity generated by ball-end finishing milling

A simplified procedure is proposed to predict the surface integrity of complex-shape parts generated by ball-end finishing milling. Along a complex cutting path, the tool inclination may vary within a large range. A geometrical study is performed to predict the effect of the tool inclination (lead angle) on the micro-geometry of the machined surface and on the effective cutting speed. This geometrical study brings out a range of values of the lead angle for which the machined surface is damaged by cutting pull-outs. This geometrical study also brings out a range of values of the lead angle for which the effective cutting speed is null. This case corresponds to extreme values of the cutting forces and to high compressive residual stresses. These predictions are verified for a selection of tool inclinations and other cutting parameters such as cutting speed, feed per tooth and cusp height. These machining tests are performed on a high-strength bainitic steel. The experimental campaign includes milling tests with cutting forces measurements, 2-D optical micro-geometry measurements and X-ray diffraction measurements.

Topological model for machining of parts with complex shapes

Complex shapes are widely used to design products in several industries such as aeronautics, automotive and domestic appliances. Several variations of their curvatures and orientations generate difficulties during their manufacturing or the machining of dies used in moulding, injection and forging. Analysis of several parts highlights two levels of difficulties between three types of shapes: prismatic parts with simple geometrical shapes, aeronautic structure parts composed of several shallow pockets and forging dies composed of several deep cavities which often contain protrusions. This paper mainly concerns High Speed Machining (HSM) of these dies which represent the highest complexity level because of the shapes’ geometry and their topology. Five axes HSM is generally required for such complex shaped parts but 3 axes machining can be sufficient for dies. Evolutions in HSM CAM software and machine tools lead to an important increase in time for machining preparation. Analysis stages of the CAD model particularly induce this time increase which is required for a wise choice of cutting tools and machining strategies. Assistance modules for prismatic parts machining features identification in CAD models are widely implemented in CAM software. In spite of the last CAM evolutions, these kinds of CAM modules are undeveloped for aeronautical structure parts and forging dies. Development of new CAM modules for the extraction of relevant machining areas as well as the definition of the topological relations between these areas must make it possible for the machining assistant to reduce the machining preparation time. In this paper, a model developed for the description of complex shape parts topology is presented. It is based on machining areas extracted for the construction of geometrical features starting from CAD models of the parts. As topology is described in order to assist machining assistant during machining process generation, the difficulties associated with tasks he carried out are analyzed at first. The topological model presented after is based on the basic geometrical features extracted. Topological relations which represent the framework of the model are defined between the basic geometrical features which are gathered afterwards in macro-features. Approach used for the identification of these macro-features is also presented in this paper. Detailed application on the construction of the topological model of forging dies is presented in the last part of the paper.

Electrochemical Machining Technology and its Latest Applications

Electrochemical machining （ECM）is a kind of special processing technology which is applied widely, it is particularly suitable for difficult to machine materials, Complex shape or thin-walled parts. The principle of ECM, machining process, the electrode reaction, electrolytic processing speed are analyzed; The electrolytic processing technology and its applications are researched in detail; Research and develop directions of ECM equipment are given; The develop tendency of ECM technology is prospected finally.

Surface Integrity of Titanium Alloy Ti-6Al-4V in Ball end Milling

Abstract With the evolution of machine tools and the emergence of new cutting tools such as cermet, CBN; and in framework of the production of parts with complex geometry, the manufacturers were able to realize more and more parts of complex shape. The multi-axis machining is the main technique for achieving the free form; in fact the multi-axis milling with ball end tools attracts the interest of the aerospace industry and the mussel industry which continues to seek ways to improve the surface quality of finished parts. The titanium alloy is widely used in aerospace industry is the subject of this study in fact, the integrity of the surfaces of parts produced by multi-axis milling is an issue more relevant than ever for the aerospace industry. This paper aims to study the influence of the tool position and the parameters cutting precisely the speed feed V f , the engagement of the tool on the roughness 3 D, micro-hardness and microstructure alteration created in sub-surface during the milling of concave surface of titanium alloy type Ti-6Al-4 V.

Studying the influence of initial powder characteristics on the properties of final parts manufactured by the selective laser melting technology

Selective laser melting (SLM) is an additive manufacturing process that enables direct manufacturing of 3D complex shape parts and internal architecture from powder materials. The SLM technology is characterised by high temperature gradients and solidification rates that have a significant effect on the microstructures and properties of final parts. The present paper aims at understanding the influence of the initial properties of various martensitic stainless steel powders on the final microstructures and mechanical properties of parts manufactured using the same optimised SLM process parameter settings. The results obtained show that for applied optimum process parameters, the thermal effects are the same for all martensitic powders used. Besides, the final microstructures and properties are different. The results clearly show the effect of the initial complex chemical composition of the martensitic precipitation hardening powder on the microstructures of final parts, and consequently, on their properties.

Build orientation analysis for minimum cost determination in FDM

The main idea behind this paper is to highlight efforts made to improve the application potential of the fused deposition modelling (FDM) process by producing the rapid prototyping parts at minimum cost. Build orientation analysis for prismatic, curved boundary, and complex-shaped parts is carried out. The mathematical model is formulated to estimate the total cost of part preparation in FDM. Optimal part build orientation and the values of parameters resulting in the minimum total cost of parts preparation are identified. The parts produced by the FDM rapid prototyping process are considered for build orientation analysis. The concept can be extended for parts produced with any layered manufacturing process. This is the first attempt to deal with diversified types of part geometries and formulate a universal cost model applicable for all types of parts to determine minimum cost in FDM.

Evolution of Precipitate Microstructure During Creep of an AA7449 T7651 Aluminum Alloy

Creep forming is a process where plastic deformation is applied at the material’s aging temperature. It enables to obtain parts of complex shape with reduced internal stresses and finds applications, for instance, in the aerospace industry. In this article, we report in-situ small-angle X-ray scattering measurements during creep experiments carried out on an AA7449 Al-Zn-Mg-Cu alloy in the T7651 temper. In the range of temperatures of 413 K to 453 K (140 °C to 180 °C), we show that the initial microstructure is not stable with respect to the applied stress/strain. Accelerated precipitation coarsening is shown to occur, clearly related to the plastic deformation. This strain-induced microstructure evolution is shown to happen even at temperatures well below the aging temperature that has led to the initial temper.