Study on the usability and robustness of polymer and wood materials for tooling in sheet metal forming

The traditional market of sheet metal parts is based in high production volumes normally greater than 10.000 parts by using high-speed presses and highly automated operations, being the tooling usually made from steel or cast iron, which ensures the needed robustness for such production volumes. Current trends in stamping industries can be characterized by the increasing demand for individualization of products which leads to a growing development towards an increasing number of product variants, lower production volumes and shorter innovation cycles. These trends have triggered research in the development of faster and cost-effective tool manufacturing techniques suitable for low production volumes, since high investments in steel tools can only be compensated by huge volume series of one and the same part during long life cycles. A promising approach for production of small series of complex sheet metal parts is the use of non-conventional tooling materials such as polymers, wood and low melting point metals. The usage of these alternative materials in tooling is still looked with some suspicion, due to the lack of know-how on its processing and also on its wear durability, influenced by the required product geometry, blank material and expected production volume.

In this paper a study on the use of non conventional materials for tooling, to be used for producing a complex sheet metal part, is performed. The evolution of tool wear, roughness and geometrical changes in punch and die radius were measured and its influence in the stamped part geometry evaluated, for an imposed production volume target of 500 parts. Also a comparative study of the tooling costs is presented in order to assess the aptitude and economical feasibility of the use of these tooling materials for low production series.     

Workpiece and Tool Handling in Metal Cutting Machines

Recently many researchers have focused substantial efforts on understanding the cutting process in mechanics, capability and design. Advances in machine performance with research towards high performance cutting (HPC) and high speed cutting (HSC) have led to improved tool properties and application of advanced materials. Because of that, primary processing time has been successfully reduced, which leads to the need for re-focusing on reduction of secondary processing time. Minimizing the time for workpiece and tool changing, re-positioning, workpiece handling, and tool handling systems shift attention towards improvement of these systems which are currently installed in various metal cutting machine tools. This paper presents an approach for the assessment of the technological effectiveness of workpiece and tool handling systems for metal cutting machine tools, gives an overview of the state of the art of these systems, surveys recent developments and elaborates requirements for future systems.     

Dry turning of sintered molybdenum

Molybdenum is a refractory metal which is recommended for advanced engineering applications requiring high mechanical strength and corrosion resistance at extremely high temperatures. However, Molybdenum-based alloys are generally difficult to machine, due to their superior physical and mechanical properties, usually requiring effective refrigeration. In this work, the feasibility of dry machining of sintered Molybdenum using commercial tools in finish longitudinal turning was investigated. A list of suitable tools was selected and cutting tests were performed in order to evaluate their performance and assess the machinability of sintered Molybdenum. Specifically, chip formation and chip control, surface roughness and cutting forces were considered. It turned out that most of the tools were inadequate for this application, therefore tool life tests were carried out on the remaining tools. Nevertheless, the analysis of experimental data confirmed that good surface quality and satisfactory tool life can be achieved in dry conditions at relatively high cutting speeds by using commercial tools.     

Sensor signals for tool-wear monitoring in metal cutting operations—a review of methods

The state of a cutting tool is an important factor in any metal cutting process as additional costs in terms of scrapped components, machine tool breakage and unscheduled downtime result from worn tool usage. Several methods to develop monitoring devices for observing the wear levels on the cutting tool on-line while engaged in cutting have been attempted. This paper presents a review of some of the methods that have been employed in tool condition monitoring. Particular attention is paid to the manner in which sensor signals from the cutting process have been harnessed and used in the development of tool condition monitoring systems (TCMSs).     

Analysis of friction between stainless steel sheets and machine hammer peened structured tool surfaces: experimental and numerical investigation of the lubricated interaction gap

Forming of stainless steel with stringent requirements on surface integrity is currently realized using protective foils as a separating agent between tools and workpiece. The protective foils are applied with special machines and need to be removed after the forming process or at the end customer. This approach has pronounced economic and ecological disadvantages. Alternative tribological systems for a foil free forming are insufficiently researched and not yet reliably applicable in a production process. Recent developments in the field of machine hammer peening motivate the investigation of surface modifications for foil free sheet metal forming. The research question of this paper is: under which tribological boundary conditions do structured tool surfaces provide a total separation of tools and workpiece? The performed research work is based on experimental analyses investigating the friction behavior of surface structured tools. Numerical simulations of normal and sliding contact using finite element method enable the investigation of the lubricated interaction gap in order to identify significant tribological process parameters.     

数控机床在线检测系统的定位误差补偿实验研究

为了提高数控机床在线检测精度,研究机床各个轴的定位误差对数控机床在线检测精度的影响。针对数控机床误差补偿进行实验研究,采用激光干涉仪在数控机床上测量出各个轴的定位误差,将各个轴的定位误差依次进行补偿;并以Visual C++6. 0为工具,编写了三次样条曲线的算法程序,将测量的数据点拟合成一条曲线,达到可以预测机床任意点误差的效果;进行标准块检测实验。结果表明:在数控机床在线检测系统中实施误差补偿,效果较为明显,利用补偿软件可以实现对数控机床任意点进行补偿。     

Applications of Cr-Based Metal Nitride Hard Coatings Using Multi-Magnetron Sputtering Sources and Elemental Metal Targets

METAL NITRIDE or carbide coatings on cutting toolsare effective ways of improving tool performance.Thedriving force for high productivity and precision inmetal machining has led to the requirement of acontinual improvement of conventional hard coatings.It is necessary that those attractive properties of hardcoatings could be simultaneously retained.Highhardness resists abrasive wear.High chemical orthermal stability reduces dissolution wear andmaintains physical properties at a high tempe…     

改善机床灰铸铁铸件性能的措施

总结了目前我国高精度机床灰铸铁铸件生产中存在的问题,叙述了制造业发展对机床灰铸铁铸件的质量要求,介绍了影响机床灰铸铁铸件性能的因素,提出了实现高碳当量高强度机床灰铸铁铸件生产的有效途径.     

Rapid tooling analysis of Stereolithography injection mould tooling

Increasing competition in global markets is exerting intense pressure on companies to trim their product cycles continuously. As delivery times and costs of tools are on a downward trend, the modern tool manufacturer is under pressure to produce tools quickly, accurately and at a lower cost. Reducing the time to produce prototypes is a key to speed up the development of new products. Rapid tooling (RT) with particular regard to injection mould fabrication using rapid prototyping (RP) technology of Stereolithography (SL) may lead to savings in cost and time. In this paper, SL is used to directly build rapid injection mould tools for short run production. SL tools have been evaluated to analyse the maximum number of successful injections and quality of performance. SL epoxy tools were able to resist the injection pressure and temperature and 500 injections were achieved. The tool failure mechanisms during injection are investigated and tool failure either occurs due to excessive flexural stresses, or because of excessive shear stresses.     

Improvement of Drill Performance in Metal Cutting Using MoST Solid Lubricant Coatings

METAL CUTTING or MACHINING plays a crucialrole in most manufacturing industries.New alloys andengineered materials that have to be machined are hard,tough,and abrasive and can also cause chemical wearof cutting tool materials.Depositing hard coatings on cutting tools is animportant development,which has enhanced cuttingtool performance as a result of providing higher wearresistance,lower friction,lower cutting forces,bettersurface finish of the workpieces,and longer tool life,which ena…     

Material adapted tool design in cold forging exemplified by powder metallurgical tool steels and industrial ceramics

The advantages of today’s cold forging technology, such as excellent mechanical properties of the workpiece and minimum waste of material together with energy saving via near net shaping increase its competitiveness against other production methods. However, as a result of extremely high loading of the tools when compared with warm and hot forging, tool life is distinctly more confined resulting in increased production costs. Due to separately or concurrently emerging damaging mechanisms of fatigue and wear at different sections of a cold forging die, process specific tool material selection and design of cold forging dies play a decisive role in near-net-shape forging of various parts. Two case studies utilizing powder metallurgical tool steel and ceramic as tool materials are presented in this paper. Successful adaptation of these materials with the help of FE simulations led to increased tool life and workpiece quality.     

Simulation of parallel kinematic machine tools with minimal effort

New innovative machine tool concepts like parallel kinematics require the development process to be continuously supported by simulation. Otherwise it will be impossible to exploit their full potential due to the complexity of the kinematic and dynamic behavior. Nevertheless, machine tool manufacturers often refrain from employing simulation tools because of the high effort and expenses expected for the introduction of this technology. It is against this backdrop that the paper presents a method to support the development process of parallel kinematic machine tools with a minimum of effort. An analysis of the development process identifies the machine characteristics that have to be determined for each stage. A simulation method is developed based on these results and on the requirements for a seamless integration of the simulation techniques into the different stages of the process. It is implemented and tested by the example of a parallel kinematic machine tool that has already been successfully introduced in industry.     

A direct comparison of the machining performance of a variax 5 axis parallel kinetic machining centre with conventional 3 and 5 axis machine tools

The current trend within the Tool and Die manufacturing sector is to machine components directly from hardened material using high speed 5-axis machining. This has been driven by the increasing requirements for cost competitiveness and lead-time reduction. Significant research effort has been applied to the optimisation of the process with factors such as tooling and machining strategies being considerably improved. However, the underlying structures of the machine tools used have remained unchanged and still consist of a serial kinematic chain. One of the standard justifications for the development of machines designed around parallel kinematic chains is that they should exhibit inherently greater stiffness, have higher axis accelerations and be capable of generating significantly higher cutting forces than conventional serial machines. This suggests that they should be ideally suited to the direct manufacture of tools and dies from hardened material.The comparison of different machine tool types is a complex and difficult process, particularly when their structures are fundamentally different. This paper describes an approach used to compare the performance of three very different types of machines. The technique uses two parameters; surface finish and geometric accuracy to assess the relative performance of different machine tools when cutting hardened material. The method is used to compare a serial kinematic 5-axis machining centre, a serial kinematic 3-axis machining centre and a parallel kinematic 6-axis machining centre.The results of the comparison are presented in this paper and show that all the machine tools performed to an equal standard for materials with a hardness of 54HRc but for very hard materials, 62HRc, the parallel kinematic machine out performed the serial machine tools.     

Condition-based preventive maintenance of main spindles

Machine tools need to be highly reliable with minimal down time. Unintended failure incurs high costs due to repairs and production losses. Maintenance is a major cost factor and is still handled reactively to a great extent. Maintenance plans by manufacturers that recommend preventive maintenance based on operating hours are often not consistently implemented. Ideally condition-dependent preventive maintenance of the most critical and cost-intensive assemblies of a machine tool would be performed. This would enable a shift of planned maintenance times to non-productive periods and would also enable procuring any spare parts at the right time. Eventually, this would lead to cost savings. This article describes the design of a condition monitoring system for machine tools and shows examples of main spindle monitoring.     

Turning and Drilling of NiTi Shape Memory Alloys

Shape memory alloys based on NiTi have a high potential for a large variety of applications. This functional material is very difficult to machine because of its high ductility, its different shape memory properties in dependence on temperature and the strong work hardening when this material is deformed. This paper presents the process design for producing a pipe coupling from NiTiNb. The design is based on experiments regarding turning and drilling of the intermetallic compound NiTi. The influence of the cutting tool material on the machining process was evaluated. As a result of the experiments, the metal removal rate was increased significantly and the tool life could be extended while at the same time ensuring a high work piece quality.     

基于载荷损耗系数的数控机床效率和能量利用率的研究

针对数控机床能量效率低下,机床效率和能量利用率在线获取困难的问题,为提高其加工过程中的能效,提出一种基于载荷损耗系数的能耗数学模型而建立的机床效率和能量利用率的计算方法。采用控制变量的思想,测试机床在不同材料、不同工艺参数下的输入和空载功率,计算出机床的切削功率、效率和能量利用率。通过响应曲面的方法分析切削负载率、实载率和机床效率、能量利用率的关系。结果表明:同种材料的机床效率和能量利用率随着切削负载率和实载率的增大而增大;而对于异种材料,其随着有用切削功率所占比例的增大而增大。为提高机床加工过程的能效,分析了提高机床效率和能量利用率的途径。     

高精度复杂型线刀具制造工艺与装备研究

以高精度复杂型线刀具制造工艺与装备为研究对象，以菌形叶片叶根型线加工专用刀具为切入点，通过分析叶根型线的特点及加工工艺的优劣，确认以单边两次成型加工作为刀具加工工艺方案；并在此基础上确定刀具的轮廓度精度、前后刀面表面粗糙度等各项参数及精度要求。通过分析专用刀具的加工要求，确定专用磨床的整体布局及结构方案，并对机床的关键部件磨削装置的结构做了具体设计与阐述。分析磨削点在B轴回转轴线延伸线上的结构优点可知，B轴回转的角度误差未使磨削点位置发生偏差，可有效提升刀具的加工精度。为验证设计的合理性，通过制造与装配机床，利用雷尼绍XK10激光校准仪检测可知，几何精度均达到设计要求。最后，采用设计的刀具加工工艺方案及专用磨床对某菌形型线刀具进行加工，Zoller检测仪检测结果表明：刀具轮廓公差为工作面±0.005 mm,其余面±0.015 mm。     

Conception of tooling adapted to thixoforging of high solid fraction hot-crack-sensitive aluminium alloys

Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<?_s<1), which involves the processing of alloys in the semi-solid state. Tooling has to be adapted to this particular process to benefit shear thinning and thixotropic behaviour of such semi-solid material. Tooling parameters, such as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and tool. These thermal exchanges influence the high-cracking tendency and the rheology of the semi-solid material during forming, which affects parts properties and therefore their quality. Extrusion tests show how thermal exchanges influence quality of thixoforged parts made of 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal protector. Thus an optimum in terms of thermal exchanges has to be found between surface quality and mechanical properties of the part. A direct application is the evaluation of surface quality of thixoforged thin wall parts made of 7075 aluminium alloy.     

电化学方法制备金刚石工具的胎体材料性能研究

金刚石工具因其超强的加工能力，在石材、地质、陶瓷、机械、电子领域被广泛应用，研究电镀用胎体材料性能对提高金刚石工具的使用寿命和加工效率具有重要意义。本文从胎体材料合金化、复合化和细晶化3个方面对近20年来有关电镀金刚石工具胎体性能改进方面的报道进行了综述，提出了目前胎体材料性能改进方面存在的问题，并对其今后研究的重点提出了展望和建议。