Shape Manufacturing Research Articles

Crack‐Free Welding of a Co‐Base Superalloy with High γ' Precipitate Fraction

Laser cladding of superalloys provides an attractive and cost‐efficient technique for near‐net shape manufacturing, remanufacturing, or individualized repair of components. While the weldability of γ' hardened Ni‐base superalloys is limited, Co‐base superalloys should have a lower susceptibility for cracking during welding due to a lower γ' solvus temperature and less segregation than Ni‐base superalloys. The weldability of the Co‐base superalloy CoWAlloy2Mod and the resulting mechanical properties at 950 °C are investigated. In the as‐welded condition of CoWAlloy2Mod, a fine dendritic microstructure without forming cracks and limited porosity is found. After a three‐step heat treatment, recrystallized, equiaxed grains and a high γ' volume fraction are obtained leading to a very good strength. CoWAlloy2Mod shows a significantly higher strength and creep strength than the conventional weld filler Co‐alloy PWA795.

Evaluation of residual stresses in additively produced thermoelastic cylinder. Part I. Thermal fields

The study is aimed at mathematical modeling of non-stationary temperature and stress-strain fields in growing thermoelastic cylinder, which growth is due to the layer-by-layer sintering over its lateral surface. This modeling makes it possible to estimate the reciprocal impact of non-stationary temperature fields, stress-strain state and the scenario of the additive process even in manufacturing of more complicated shapes. The problem is considered in the framework of the theory of thermal stresses with non-linear radiative boundary condition. A distinctive feature of modeling is that the material composition of the body changes over time. Therefore, the mathematical model is represented by the recurrent sequence of initial boundary value problems, formulated for each step of the additive process in different domains with respect to the increments of thermal and stress fields. The domains constitute nested sequence of regions and, together with the sequence of the moments of layer sintering, define the scenario of additive process. Initial values for a step are taken to be equal to the corresponding values at the final moment of previous step. The solution for each step is represented in the form of decomposition over eigenfunctions of differential operator, generated by boundary value problem on this step. Computational modeling of various sintering modes has been carried out. A classification of thermomechanical additive processes, based on the relationship between the characteristic time of the process and the time of thermal relaxation of the attached layer is given. Special attention is paid to non-uniform volume heating, which can be obtained by skin effect during high-frequency induction. Computational simulations based on obtained analytical solution show that auxiliary inductive heating makes it possible to substantially reduce the non-uniformity of the temperature field and thus to reduce the temperature stresses caused by it.

Tool geometry analysis for plunge milling of lead-free CuZn-alloys

Plunge milling is a critical process step in mass manufacturing of rectangular shapes in electrical connector components. These shapes are manufactured by drilling a pilot hole and subsequent plunge milling with a radial offset (pitch) one or more times. The plunged cavity serves as guidance for the final broaching cut. In light of new legislative initiatives, the electronics industry is forced to use lead-free Cu-Zn-Alloys for mass manufacturing of these connectors. The plunging tool is deflected due to the higher cutting forces experienced in machining of lead-free CuZn-alloys in comparison to alloys with lead. This results in an offset of the milled cavity and negatively impacts tool guidance in the subsequent broaching process. Therefore, the geometric tolerances cannot be met. In this paper, the effect of tool geometry and cutting parameters on the workpiece geometry in plunge milling is investigated. The effect of the microstructure of the work-piece materials CuZn37, CuZn42 and CuZn21Si3P on the tool deflection and cutting force components is examined. The tools used vary regarding the design of the corner in terms of the corner chamfer and the inner shaft thickness. Friction between chips in the tools inner flutes and the cavity walls reduced workpiece accuracy. Improvements were achieved by reducing the width of the cutting corner chamfers, using large inner flutes and applying low cutting parameters.

高能激光单晶硅反射镜纳米精度控形控性制造技术

高能激光单晶硅反射镜纳米精度控形控性制造技术

Analysis of the tool nose radius influence in the machining of a green ceramic material

Advanced ceramics are applied to several technological applications, and they have special properties. However, the advanced ceramics have poor machinability at the sintered condition, the tool suffers a high tool wear rate, which leads to material removal constraints, and they are usually machined by grinding. Further, the green state machining of advanced ceramics has been investigated as a method for the manufacturing of complex shapes, which provides an alternative for fast manufacturing of near net shape ceramic parts. Some studies have been analyzed the characteristics of green ceramics machining. Although, there are no studies that evaluated the tool nose radius effects at the machining forces and surface roughness during the turning of green ceramic parts. Besides, cylindrical compacted samples were pressed isostatically at 200 MPa, and then the workpieces are turned at constant cutting conditions using three different tool nose radius (0.05, 0.1, and 0.2 mm). The workpieces were analyzed (forces, surface roughness, and SEM images) at the green state first, sintered, and then analyzed again. The results show that the tool nose radius influences the forces, mainly the feed (Ff) and passive (Fp) forces, and there is an increase in the forces between the first and the last pass because of the tool wear. Furthermore, the workpiece offers more resistance to the axial movement than to the others, and as long as the tool wear become larger, the contact area and forces increase. In this sense, the smallest contact area leads to higher pressure and more severe wear conditions, which accelerates the tool wear. Therefore, the abrasion is the predominant wear mechanism, which was characterized by parallel grooves, orthogonal to the cutting edge. Moreover, the 0.05-mm nose radius introduced severe damages on the compact surface, which favors the pulling out of the green compact agglomerates. The increase of tool nose radius can reduce the compact surface roughness (Ra) after machining, although the best condition for tool wear was 0.1 mm. Finally, the surface finishing of the green workpiece has a direct influence on the sample after sintering, and the green state damages are conducted to the final workpiece compact.

Analysis of the Problem of Granulated Material Movement in the Production Process

Plastics are the world's most widely used materials, largely due to their wide-spectrum use and relatively cheap manufacturing of complex shapes. Due to its properties, the use of plastics is possible in all manufacturing sectors. Important aspect of plastic moulding is that the heat passed to granulate is sufficient to properly heat up the plastic mixture. Another important factor is that the plastic mixture is blended as evenly as possible. Heterogeneities could lead to the formation of non-conformances with incorrect colour shades, unevenness of the mass or others. One of the factors that greatly affects the homogeneity of the mixture is the surface treatment of the guides that are designed to transport the granulate and it is important to take care of those lines.

Wear analysis of Sintered Al-B4C Composite

Abstract Manufacturing of complex shapes and porous components in the traditional methods are very difficult. Powder metallurgy is metal forming process by which complex shapes can be formed easily without any material loss. To achieve high wear resistance with high thermal conductivity metal matrix composites are used. In this research work, the composition of boron carbide is variedby 5%, 10%, 15%, and 20%. The blended mixture is compressed and sintered to the standard specimen size required. The specimen is tested for wear rate by using pin on disk wear testing machine and same is analysed with analysis software.

Automated 3D assembly of periodic alumina‐epoxy composite structures

AbstractModular composites with a 3D periodic structure, consisting of a major brittle inorganic phase (building blocks) and a minor viscoelastic organic matrix, offer great potentials for improved fracture toughness and failure probability in polymer‐ceramic composites. Alumina building blocks with dimensions of 1500 μm were assembled by a novel placing system equipped with an automatic optical inspection (AOI) system. The AOI system coupled with shape recognition enables simultaneous dimensional characterization, tolerance sorting, and flexible placing of different shaped building blocks. 3D periodic structures with cubic, monoclinic, and triclinic unit cells were fabricated by high accuracy placing of cubic building blocks enabling near‐net shape manufacturing. The placing precision of the assembled structures was determined by μCT to have a maximum deviation of ±78 μm. The structures were afterward infiltrated with a soft epoxy resin to fabricate epoxy‐alumina composites. The brick‐and‐mortar like building block arrangements of the monoclinic and triclinic structures exhibited improved bending strength, fracture toughness, and failure probability compared to monolithic epoxy, due to crack deflection and pull‐out toughening mechanisms. A maximum bending strength of 35.1 ± 7.5 MPa, a work‐of‐fracture of 814.7 ± 255.1 J/m² and a calculated fracture toughness of 4.8 ± 0.8 MPa for the triclinic structures was achieved.

ОПЫТ ПРИМЕНЕНИЯ ПОЛИМЕРНЫХ ПЛЕНОЧНЫХ МАТЕРИАЛОВ В КОНСТРУКЦИИ КРИОНЕННОГО РАЗГОННОГО БЛОКА «12 КРБ»

The results of design, fabrication, experimental testing and introduction of technological processes of manufacture of pipelines complex shapes from polymeric film materials, which was used when creating a cryogenic upper stage “12КРБ» is presented.

Experimental studies on manufacturing of the complex shapes made from copper

The paper presents the manufacturing process of a complex copper electrode. To process complex copper shapes is difficult because the material is soft and very sticky. The paper presents the steps for processing this copper electrode at a high dimensional accuracy and a good surface quality. For this process a special tooling solution is needed, optimal process parameters, smart CAD/CAM software and precise CNC equipment.

Choosing a Manufacturing Systems Model Type

Purpose: This paper considers a novel solution to one of the key problems in modern mechanical engineering – the modeling of modern manufacturing systems in the field of mechanical engineering. Design/methodology/approach: This article considers the choice of the model type of manufacturing systems. It is shown that from systemology’s perspective, all existing models are divided into imitating (replicating) and optimizing models, while the problem of designing manufacturing systems belongs to the class of semi-structured problems. Therefore, at the macro-designing stage it is expedient to use optimizing models, rather than the imitating ones. Findings and originality/value: This paper gives a broad definition of the technological process as a set of actions for constructing a product, designing the technological process for a sequence of shaping products and manufacturing. It defines production flexibility and the adaptation of the manufacturing system to changes in conditions. Originality/value: These solutions can be used in such fields of science and technology as automation in manufacturing, computer aided design (CAD) and modeling (CAM), computer aided engineering analysis, flexible manufacturing systems, flexible automation and production engineering.

Gate Location and its Impact to Flowing Characteristics of Plastic Moldings

Paper deals with simulation analysis of thermoplastic flowing in plastics product. As there is a demand in plastic products, plastic industries are growing in a fastest rate. Hence plastic injection molding process begins in manufacturing of complex shapes, in this process optimum gate location is one of the important criteria in mold design. Knowledge of ideal flow properties of thermoplastic materials give us a very good starting position for design of thermoplastics products which will be made by injection molding. By simulation software Plastic Advisor was compared injection parameters for the mold with varying gate locations. Simulated thermoplastic product is made from polycarbonate and is using for the drum washing machine as console window.

Experimental Study on the Incremental Forming of Coated Aluminum Alloy Sheets

Superficial coatings are widely used in industrial applications in order to improve the superficial properties of metallic components. In particular, in the aeronautic field, all the components are coated in order to prevent both corrosion and wear. In this field, heat treatable aluminum alloys, in age hardened condition, are used; consequently, superficial coatings must be carried out through “cold” processes, i.e. coating processes in which the component to be coated remains at low temperatures, below 100°C. Cold gas dynamic spray technique (CGDS) is a process of deposition that consists in the realization of surface coatings with high-velocity metal particles sprayed on the substrate at temperature significantly lower than the melting one of the substrate itself and at relatively low temperatures if compared to other spray techniques. When processing conditions are optimized, the process can produce near fully dense coatings. This technique could be particularly useful in the coating of rolled sheets, needing of successive cold plastic deformations. One of the cold plastic processes is incremental forming, a high flexible process for rapid manufacturing of complex sheet metal part shapes; it presents the potential to be easy to automate and particularly attractive for small batches and customized parts. In this process, a simple tool describes a path that allows to locally deform the sheet clamped along its periphery. The aim of this paper is to study the evolution and behaviour of aluminum coating deposed by CGDS on AA 2024-T3 sheets carried out by an incremental forming process. This evaluation is carried out by characterizing the cold sprayed coating after the forming process for different wall angles of simples geometries.

Research on the Influence of Die Shape in Complex Extrusion of Multi Billets

Multi-billet extrusion has been developed for a novel process in manufacturing of shapes with complex cross-section, for example a side-door impact beam for automobile. And furthermore, very wide shapes for roofs of railroad vehicles may be able to be manufactured. In this paper, fundamental experiment carried out by using modeling material and knowledge about bonding of some separated parts was obtained. It is clear that a unification angle is important for bonding intensity. The unification angle was adjusted by flow guides. It is success to manufacture a round pipe with inner liv.

A new CNC turning canned cycle for revolved parts with free-form profile

This paper presents an algorithm for improving the interpolation accuracy in turning operations. The parts considered are formed by revolving a free-form profile which is implemented in terms of Bezier formulation around a center linear axis. The demand for the manufacturing of such geometric shapes is frequently met in parts produced by casting and forging methods. The method employs a computer numerical control (CNC) turning machine and is based on the locus tracing concept. The algorithm described utilizes a real-time CNC interpolator providing the highest possible accuracy of which the turning machine is capable. The whole machining task can be programmed as a canned cycle, essentially extending the feature generating capabilities of the existing G70/G73 CNC turning fixed cycles.

Cold end forming of thin-walled PVC tubes using a die

The aim of this paper is to evaluate the applicability of tube end-forming processes, currently applied in metals, to polyvinyl chloride (PVC). The presentation is focused on four different processes (expansion, reduction, internal and external inversion) and its contents are expected to provide new fundamental level of knowledge and understanding about the mechanics of deformation and the expected modes of deformation of PVC tubes. The formability limits are defined in terms of the major operating variables with the purpose of predicting the behaviour of PVC tubes across a wide range of working conditions. The experimental findings are interpreted in the light of an innovative extension of the finite element flow formulation that is capable of modelling cold plastic deformation of pressure-sensitive materials under a non-associated flow rule. Special emphasis is placed on the analysis of load-displacement, local buckling, ductile damage and crazing. The overall results confirm that end-forming of thin-walled PVC tubes at room temperature have potential for the manufacture of custom and specific shapes.

Strain hardening behavior during manufacturing of tube shapes by hydroforming

Safe and robust process design relies on knowledge of the evolution of the mechanical properties in a tube during hydroforming. The manufacturing of tubular shapes generally consists of three main stages: bending, preforming, and expansion. The latter is usually called hydroforming. As a result of these three steps, the final product’s strain hardening history is nonlinear. In the present study, the strain hardening behavior during hydroforming was experimentally investigated. The variation of local flow stress and/or local hardness was used as an index of the strain hardening during the various steps and the local flow stress and/or local hardness were used with respective correlations to determine the effective strain. The strain hardening behavior during hydroforming after preforming has been successfully analyzed by using the relationships between hardness, flow stress, and effective strain for variable pre-strains prior to hydroforming. The comparison of predicted hardness with measured hardness confirms that the methodology used in this study is feasible, and that the strain hardening behavior can be quantitatively estimated with good accuracy.

Packaging using hot-embossing with a polymeric intermediate mould

Hot embossing allows the high precision replication of features from a mould insert into thermoplastic materials. The technique has been developed mainly for microsystem applications, in particular, the manufacture of micro-optical and micro-fluidic components and systems. It can also be applied to packaging applications. We developed a specific process based on a two-step replication process utilizing hot embossing and a rigid polymeric intermediate mould, which allows the manufacture of complex three-dimensional shapes to realize a functional optical package for optical microsystems.

A lower upper-bound solution for shear spinning of cones

The shear spinning process, where the plastic deformation zone is localized in a very small portion of the work piece, is introduced for the manufacturing of large conical shapes. This process seemingly shows a promise for increasingly broader application to the production of axially symmetric parts. This study is to gain a better understanding of the process of shear spinning and to propose a lower upper-bound solution for shear spinning cones. Velocity fields and strain rates are derived from considering the adequate deformation mode and the contact factor is introduced to obtain the lower upper-bound power. The theoretical values are compared with the experimental results of various materials. Al-1100-0, Al-1100-H14, and Al-6061-0. A comparison shows that theoretical prediction is reasonably in good agreement with experimental results.

CNC Robotic Manufacturing of Large Shapes for Fiberglass and Composite Production Tooling

A computer numeric controlled (CNC) robotic machining capability has demonstrated the capacity to manufacture large, unique shapes which are utilized for fabrication of industrial molds and tooling for fiberglass and composite parts. Single parts as large as 25 m × 4.6 m × 2.9 m (82 ft × 15 ft × 9.5 ft) can be machined from low-density materials by two 7-axis CNC robots operating from parallel tracks. Large parts can be assembled by joining several pieces. This capability demonstrated that rapid prototyping is possible via both limited production and full production tooling/molds being machined from surface and/or solid computer models. The paper also includes an overview discussion of prototype production methods that have evolved in the boating and yacht building industries in recent years. Factors influencing decisions for the equipment and materials selected are discussed. The process is discussed from design to manu-facture of a plug suitable for fabricating a production mold.