多孔金属纤维烧结板制造技术及应用研究进展

多孔金属纤维烧结板是随着新型化材料制备以及机械加工复合技术的飞速发展而出现的一类新颖的多孔金属材料。近年来由于其特殊孔隙结构的开发和多学科领域的强大应用需求,多孔金属纤维烧结板的制造技术取得快速进步,其相关应用领域正从传统的应用领域不断地向高新技术应用领域拓展。根据其制造工艺过程综述了金属纤维制造技术(熔抽法、拉拔法和切削法)和多孔金属纤维烧结板制造技术(固相烧结和液相烧结技术)的最新研究进展,并详细分析了其已有或潜在的应用领域,最后展望了多孔金属纤维烧结板的应用前景。     

An expert system for process planning of sheet metal parts produced on compound die for use in stamping industries

Process planning of sheet metal part is an important activity in the design of compound die. Traditional methods of carrying out this task are manual, tedious, time-consuming, error-prone and experience-based. This paper describes the research work involved in the development of an expert system for process planning of sheet metal parts produced on compound die. The proposed system is organized in six modules. For development of system modules, domain knowledge acquired from various sources of knowledge acquisition is refined and then framed in form of ‘IF-Then’ variety of production rules. System modules are coded in AutoLISP language and user interface is created using visual basic (VB). The system is capable to automate various activities of process planning including blank modeling, blank nesting, determining punch force required, selection of clearance between punch and die, identifying sheet metal operations, and determining proper sequence of operations for manufacturing the part. The proposed system can be implemented on a PC having VB and AutoCAD software, therefore its low cost of implementation makes it affordable even for small scale sheet metal industries.     

Integrated and concurrent approach for compound sheet metal cutting and punching

In sheet metal processing and manufacturing, there are a lot of small- and medium-sized job shops. These small- and medium-sized manufacturing companies have been facing keen competitive pressure in the market. This pressure has forced these companies to make every effort to shorten product development lead-time, improve production efficiency, approach high-quality standards, but at the same time cut down the costs. To meet the needs of these companies, this paper presents a compound cutting and punching production method supported by an integrated CAD/CAPP/CAM system in sheet metal manufacturing. Many existing commercial CAD/CAM systems are not suitable for this manufacturing method, especially under concurrent and global design and manufacturing environments. Some problems have to be solved before these CAD/CAM systems can be employed and integrated for this compound manufacturing method. This paper deals mainly with the solutions to solve some of these problems. The solutions include an integrated data integration platform based on Pro/INTRALINK and STEP, and a knowledge-based real time CAPP (RTCAPP) system for compound sheet metal cutting and punching. Within the presented CAD/CAPP/CAM system, some key modules have been developed. They are the automatic tool selection and manufacturing sequencing module, a shortest tool path optimization module, a cost estimation module and an automatic insertion of auxiliary path module based on knowledge bases. These modules will be addressed here.     

PROCEDURES FOR SOLVING SINGLE-PASS STRIP LAYOUT PROBLEMS

Strip layout is an important step in the planning of operations using blanking dies. Typically the strip layout problem has been resolved using methods which provide approximate solutions, since it is viewed as a class of general 2-D nesting problem which is NP-Hard. This implies that we need to investigate special cases of the strip layout problem that will permit polynomial running time algorithms, while having some practical application in processes of cutting shapes from sheet stock. In this paper we present an exact procedure with polynomial running time for die single-pass single-row layout problem. This problem tries to layout identical shapes on a strip that will go thorough a single row die only once, such as to maximize die number of parts to be yielded by the strip. The paper investigates this problem for two cases: the case for which die width of die strip is larger than any possible orientation of the part, and the case for which the width of die strip is restricted so mat not every orientation is feasible. We also consider the problem of cutting a sheet of metal into strips so as to maximize die sum of me parts yielded by each sheet.     

A novel approach to include sustainability concepts in classical DFMA methodology for sheet metal enclosure devices

Nowadays sustainable design is a mandatory requirement in the product development process. For this reason, design methodologies are addressed to establish a close relationship between environmental, social and economic impact indicators and product features from early design stages, especially in those features related to its manufacturing. In this paper, the design for manufacturing and assembly—DFMA methodology is adapted to sheet metal enclosure devices, integrating functional and component relationships to minimize particular sustainability indicators such as energy consumption, carbon footprint, number of parts, required amount of material, assembly time and manufacturing costs. Savings with the proposed method are achieved following specific sub-tasks oriented to define new simplified product components, considering changes in manufacturing processes and re-defining mechanical connections between parts. Traditional DFMA approaches consider manufacturing and assembly issues related to a reduction of product complexity and economic savings. The proposed method aims to examine the benefits in life cycle stages such as raw material consumption, service, maintenance, upgrading and end of life—EOL. The methodology is validated through a redesign of a sheet metal industrial clock, in which the sustainability impacts are calculated from a comparison of an existent product vs. a new product development. The implementation of the method in the case study demonstrate reductions of more than 25% in product mass, consumed energy and CO₂ footprint, and more than 50% in theoretical assembly time and product complexity. Sustainability indicators of the proposed method are selected from literature analysis and taking into account attributes of sheet metal enclosure devices.     

Milling operations in continuous flow production lines

Within the Collaborative Research Center CRC 666 at the TU Darmstadt bifurcated structures in integral style are produced out of steel sheet band. In this context, the cutting technology is used to prepare the semi‐finished product for subsequent forming and machining operations as well as to even manufacturing induced shape and dimensional inaccuracies. In contrast to conventional cutting processes, the workpiece is constantly moved because of the continuous flow production. Thus, high dynamics of the machining process are required. To meet this demand, special built machine tools and the high speed cutting (HSC) technology are applied. This article shows the achieved results in sheet metal and edge milling.     

An approach in modeling the temperature effect in thermo-stamping of woven composites

Made with high-strength continuous fibers, textile composites are of increasing interest in automotive and aerospace industries due to their high-strength/weight performance as compared to sheet metals. Nevertheless, significant reduction in manufacturing cost is required to use textile composites for mass production applications. Highly efficient thermo-stamping operations possess the potential to substantially reduce fabrication time and cost compared to the much slower autoclave forming process. In this paper, thermo-forming of woven fabric-reinforced thermo-plastic composites is simulated using a non-orthogonal material model. The temperature effect is taken into account by modifying the equivalent material properties for the composite sheet based on the contact status between the tooling and the blank. The approach is exemplified on the hemispherical thermo-stamping of a plain weave composite sheet.     

Optimization of the LCD optical film cutting problem

The manufacturing of liquid crystal display (LCD) plays an important role in electronics manufacturing industries, such as televisions, smart phones, pads, laptops, monitors and electronic appliances. Due to the fact that the cost of LCD’s film materials may reach 60–70% of the production cost, appropriate cutting schemes can lead to better raw material utilisation and thus enhance manufacturers’ profitability. Accordingly, the determination of the optimal production plan for cutting different-sized LCD optimal films with the designed cutting angles to fulfil the customers’ orders is a critical issue for the LCD industry. In the past, few studies integrated the different cutting allocation strategies into a synthetic decision. This study proposes a mathematical programming model for the two-stage cutting problem for LCD optical films to determine the optimal cutting allocation strategy with consideration of the costs of raw materials, processing and disposal during the manufacturing process. For large-scale problems in which the runtime for obtaining the optimal solution may grow exponentially as the problem size increases, a heuristic algorithm is also provided to obtain the approximate solution within a reasonable time. Finally, the results of the practical case shows that, compared with the existing fixed-angle cutting method, the proposed approach reduces the total cost by 6.2% due to the better material utilisation. In addition, the processing cost is also reduced due to a decrease in the required materials.     

Process planning for small batch manufacturing of sheet metal parts

The paper describes process planning for order-based small batch sheet metal part manufacturing. In this domain, general purpose CNC machinery and standard tools are being used. An example of a process planning system is given and some areas of special interest are discussed in more detail. Process planning for sheet bending and tolerance reasoning are important and intricate tasks within process planning, whereas abstractions in design and nesting are important due to their relations with other manufacturing functions. In general, manufacturing functions tend to become increasingly intertwined and traditional boundaries become blurred. Sheet metal industries, customers and suppliers alike, can benefit from this.     

Modelling component cost in compression moulding of thermoplastic composite and sandwich components

Thermoplastic composite and sandwich materials offer a potential of reducing component weight and improving recyclability while at the same time enhancing process economy through reduced manufacturing cycle time. The economical aspects of compression moulding of three different thermoplastic composite and sandwich material systems are modelled herein and are compared to compression moulding of a thermoset sheet moulding compound and stamping of sheet metal. A program has been developed which predicts component cost for different component sizes and complexities. It is found that raw material cost strongly dominates component cost for compression moulding of composite components, while in sheet metal stamping component cost is dominated by equipment costs.The model shows that thermoplastic composites are cost competitive for small to medium sized components and short production series of large components. The sandwich concepts offers a potential of further reducing component cost compared to composites, thus making the concept interesting for larger components, but still for short to intermediate production series, which is illustrated by calculating component cost for compression moulding of a sandwich tailgate.     

B1500HS材料热成形后冷冲切试验

目的研究热冲压零件冷冲切刀块易磨损寿命低的问题。方法设计开发一套多功能冷冲切试验模具,对热成形后B1500HS材料进行连续冲切试验,并对3组模具间隙、4种典型模具钢材质对应的冲切试样进行断面质量检测及统计,以此分析热冲压高强钢冷冲切合理模具间隙和典型冷冲切模具钢的冷冲切特性。结果 8%~10%料厚模具间隙在冲切初期毛刺较小,且在连续冲切过程中毛刺高度比较稳定,为合理的模具间隙范围;4种典型模具钢中,ASP60冲头耐磨性性能最优,SKD11冲头耐磨损性最差,SKH-9和CALDIE介于两则之间。结论热冲压钢的冷冲切稳定性及刀块寿命相对常规高强钢还存在较大差距,针对其冲切特性有必要开发更高寿命、高性价比的模具钢及热处理方法,以提高刀块寿命和生产效率,降低零件制造成本。     

Prediction of non-uniform thinning in superplastically formed spherical domes

Abstract

Superplastic forming is an attractive manufacturing process, which allows the production of complex sheet metal components. The gas pressure bulging of metal sheets has become an important forming method. As the bulging process progresses, significant thinning in the sheet material becomes obvious. A prior knowledge about non-uniform thinning in the product after forming helps the designer in the selection of initial blank thickness. This paper suggests a simple procedure to obtain the variation in thickness of a gas pressure formed spherical dome at any instant of time during the bulging process. This simple procedure is validated by comparing predicted and measured thicknesses of a formed titanium hemispherical dome.     

An experimental investigation of forming load and side-wall thickness obtained by a new deep drawing die

Deep drawing is an important process used for producing cups from sheet metal in large quantities. The deep drawing process is affected by many variables such as blank shape, punch and die radii, material’s formability characteristics, and many more. In order to obtain optimal process parameters with regard to part geometry, the blank and die geometry are particularly important factors. In this study, we investigated the effects of blank holder and die shapes, using six different blank holder and die shapes. We measured the distribution of blank holder force (BHF), the forming load at different drawing depths as well as thickness reduction of cup wall thickness for each set of die and punch geometries. The experimental study shows that the angle of blank and die surface influence the forming load and blank holder force distribution. Deep drawing dies with matrix and blank holder angle designed in this study provided deep drawing ratios that are about 25 % larger than those that usually can be obtained by a conventional die.     

Failure analysis of an EDM machined mold-printing die used for the production of truck spare parts

A company produces truck wheel covers as spare parts for the local market. The production of these parts is based on a progressive die performing consecutive forming and selective cutting stages throughout the initial circular steel sheet. The failure occurred to the final stage of manufacturing, as the die marks, by mold-printing, the assembly configuration of the wheel cover onto the wheel rim. The paper presents a thorough failure analysis of the broken tool. The investigation includes preliminary examination, hardness measurements and chemical analysis. In depth microscopic examination was carried out using stereoscope and optical and electron microscopy. The failure mechanism was investigated from macroscopic and microscopic perspective and conclusions regarding the crack initiation and propagation were conducted and analyzed. The causes that led to the total fracture were discussed. The design of the tool and improper surface roughness are considered to be the main causes of the failure. Some complementary recommendations were proposed so to enhance the production rate of the specific tool.     

Improving geometrical accuracy for flanging by incremental sheet metal forming

Incremental Sheet Forming (ISF) is a manufacturing technology for individualized and small batch production. Among the opportunities this technology provides there is the possibility of a short ramp-up time and to cover the whole production chain of sheet metal parts by using a single reconfigurable machine set-up. Since recent developments proved that manufacturing of industrial parts is feasible, finishing operations such as flanging and trimming gain importance, which are an integral part of manufacturing process chains of many sheet metal parts. This paper analyses the technological capabilities of performing flanging operations by ISF. Due to the localized forming zone and the absence of surrounding clamping devices, ISF exhibits a different material flow than conventional flanging processes. In this paper, the influence of the tool path characteristics, the flange length as well as the flange radius is analysed in order to establish a process window and to compare it to the process limits of conventional flanging operations. Since geometrical deviations occur when flanging operations are performed by ISF, a new adaptive blank holder is developed, which acts in the vicinity of the forming tool and reduces unwanted deformation outside the primary forming zone. The experimental results show the benefits of the adaptive blank holder with respect to geometric accuracy. The established process window and the adaptive blank holder hence contribute to the applicability of incremental flanging operations, such that ISF can be used for all forming and flanging operations along the process chain.     

Forming sheet metals by means of multi-point deep drawing method

Multi-point deep drawing (MPDD) is an advanced manufacturing technology for 3D sheet metal parts and it can form a variety of part shapes without the need for solid dies. In this study, a test set has been prepared for multi-point deep drawing process utilizing the multi-point forming technology. Drawability attributes of gradually rectangular shaped container have been observed using a sheet, which has the quality of Erdemir 7114 and is suitable for deep drawing process, and also using multi-pointed punch with a given tool geometry and a draw velocity. The blank shape to be drawn without wrinkling and tearing has been determined. Wrinkles and dimples are the major forming defects in the MPDD process. In conventional deep drawing, the method to form sheet metal with a blank holder is an effective way to suppress wrinkling; and the same is true in MPDD. The process of multi-point forming technology decreases production cost of die, provides flexible usage, and it is convenient to achieve the most even deformation distribution.     

Automated manufacturability evaluation system for sheet metal components in mass production

Automated manufacturability evaluation of a given design is a key requirement in realizing complete integration of design and process planning. It would still be better to control the designing process itself with manufacturability information. The purpose of such an evaluation is to assist designers in their effort to come up with manufacturable parts economizing in terms of cost and time, without compromising on quality and functional requirements. The present work deals with one such system developed for manufacturability evaluation of sheet metal components. Unlike most of the work done in the sheet metal area in the past, which concentrates on specific domain or phase of manufacturability evaluation, the present work is more comprehensive combining characteristics of all the existing methods and phases of manufacturability evaluation. The prime components of the present system are design evaluation and process plan generation. Design evaluator and process planner use different types of data and knowledge to identify design and process planning violations which are overcome by suggesting design changes. A process planner also uses manufacturing resource and process information to arrive at manufacturable parts by generating feasible process plans. Results of manufacturability evaluation are presented for typical sheet metal parts to be produced by bending and shearing (blanking and piercing) processes.     

Optimisation of process parameters in flanging operation in order to minimise stresses and Lemaitre’s damage

The objective of this work is modelling and optimisation of sheet bending process by means of numerical simulation. One of the problems to be solved in the sheet metal forming processes of thin sheets is the taking into account of the effects of technological process parameters so that the part takes the desired mechanical characteristics. Accordingly, it has been a crucial research subject for designing bending tools guaranteeing an optimal performance of products in terms of mechanical properties and good rigidity. In this paper, we propose a numerical procedure allowing the definition of the optimal values of process parameters in flanging operation, which minimises the residual stresses and the material damage at the end of the bending phase. The concept of continuum damage mechanics fully coupled with elasto-plasticity has been retained to describe the progressive damage accumulation into the sheet metal. According to parametric investigation on the maximum stress and calculated damage values, it has been found that the punch-die clearance and the die radius have significant effects on mechanical behaviour of parts. An application of design of experiments was developed as a preliminary step for the optimisation of the process parameters by using response surface methodology. This model allows the identification of the influential parameters of an optimisation problem and the reduction of the number of evaluations of the objective function.     

柴油机喷射系统泵体精密挤压工艺

目的为了提高燃油喷射系统泵体的综合性能和制造效率,采用精密挤压来实现变量泵泵体的高效绿色制造。方法通过工艺设计,初步确定了锻件形状、分模形式和模具结构,采用有限元法对泵体精密挤压工艺进行仿真分析,研究了挤压成形时金属在型腔的流动规律,模具结构对挤压时的影响,以及锻件边角的充型情况。结果通过模拟仿真,对设计的挤压工艺进行了理论验证,坯料流动主要以充填法兰和外侧飞边的方向为主,外六角根部、法兰底部均充填完全,最终多余的金属流向模具间隙,没有出现紊流和涡流的现象。结论通过最终的工艺试制试验,验证了设计的工艺方案,精密挤压的变量泵泵体充型饱满,法兰顶部及根部六角形均充型完全,经机加工后成品尺寸稳定,满足产品的技术要求。     

Modelling and simulation of adhesive curing processes in bonded piezo metal composites

This work deals with the modelling and simulation of curing phenomena in adhesively bonded piezo metal composites (PMC) which consist of an adhesive layer, an integrated piezoelectric module and two surrounding metal sheet layers. In a first step, a finite strain modelling framework for the representation of polymer curing phenomena is proposed. Based on this formulation, a concretised model is deduced and applied to one specific epoxy based adhesive. Here, appropriate material functions are provided and the thermodynamic consistency is proved. Regarding the finite element implementation, a numerical scheme for time integration and a new approach for maintaining a constant initial volume at arbitrary initial conditions are provided. Finally, finite element simulations of a newly proposed manufacturing process for the production of bonded PMC structures are conducted. Thereby, a representative deep drawing process is analysed with respect to the impact of the adhesive layer on the embedded piezoelectric module.