Deformation Machining - A New Hybrid Process

This paper describes a novel hybrid process, Deformation Machining, that combines two emerging manufacturing processes - machining of thin structures and single point incremental forming. This hybrid process enables the creation of structures that have geometries that would be difficult or impossible to create using any other processes. A feasibility study has been conducted exploring the toolpath planning and deformation force data was collected. Because the forming operations occur on sheet-like material made by machining rather than rolling, we have conducted experiments testing the formability of machined sheet. Preliminary results are encouraging, and point to a broad range of industrial applications for this process.     

Virtual process systems for part machining operations

This paper presents an overview of recent developments in simulating machining and grinding processes along the NC tool path in virtual environments. The evaluations of cutter–part-geometry intersection algorithms are reviewed, and are used to predict cutting forces, torque, power, and the possibility of having chatter and other machining process states along the tool path. The trajectory generation of CNC systems is included in predicting the effective feeds. The NC program is automatically optimized by respecting the physical limits of the machine tool and cutting operation. Samples of industrial turning, milling and grinding applications are presented. The paper concludes with the present and future challenges to achieving a more accurate and efficient virtual machining process simulation and optimization system.     

Advanced monitoring of machining operations

CIRP has had a long history of research and publication on the development and implementation of sensor monitoring of machining operations including tool condition monitoring, unmanned machining, process control and, more recently, advanced topics in machining monitoring, innovative signal processing, sensor fusion and related applications. This keynote follows a recent update of the literature on tool condition monitoring and documents the work of the cutting scientific technical committee in CIRP. The paper reviews the past contributions of CIRP in these areas and provides an up-to-date comprehensive survey of sensor technologies, signal processing, and decision making strategies for process monitoring. Application examples to industrial processes including reconfigurable sensor systems are reported. Future challenges and trends in sensor based machining operation monitoring are presented.     

Burrs—Analysis, control and removal

Increasing demands on function and performance call for burr-free workpiece edges after machining. Since deburring is a costly and non-value-added operation, the understanding and control of burr formation is a research topic with high relevance to industrial applications. Following a review of burr classifications along with the corresponding measurement technologies, burr formation mechanisms in machining are described. Deburring and burr control are two possible ways to deal with burrs. For both, an insight into current research results are presented. Finally, a number of case studies on burr formation, control and deburring along with their economic implications are presented.     

Titanium machining with new plasma boronized cutting tools

Titanium is a commonly used material in various critical applications such as aerospace and biomedical applications. In this article, for the first time in the literature, development and implementation of a novel plasma boronizing process on Tungsten Carbide (WC) cutting tools is introduced. Plasma boronizing on WC tools is performed with gas combination of 10% BF₃, 40% Argon and 50% H₂ at different temperatures and durations. Performance enhancements of plasma boronized WC tools on Titanium (Ti-6Al-4V) machining are investigated under various cutting conditions. It is found that new plasma boronizing of WC is a very cost effective solution for significantly increasing tool life in Titanium machining.     

油膜附水滴加工液的物理特性与加工性能

21世纪是生产工厂追求生态加工与零排放生产的时代,工业生产须对环境影响最小。就机械加工而言,切削、磨削加工过程中大量循环使用有毒有害传统加工液和大量排放加工废液的现状迫切需要改变。作为对策,多种以最小量润滑和加工废液减量为原则的新加工液形态如干加工及冷风、微量油和微量水等,近年来得到了研究、开发与实施。这些形态的加工液能改善环境、节省能源和降低成本,但冷却性能却不及传统加工液如乳化液。显然,采取结合加工对象和条件的多样化加工液对策十分必要。因此,本文应用冷风、可自然降解油剂和水经喷雾形成油膜附水滴加工液^[1-6]来替代传统加工液。通过进行物理特性试验考察其油膜形成效果,并在加工中心机床和数控平面磨床上进行大量的加工性能试验研究其加工适用性。试验结果表明：油膜附水滴加工液具有良好的润滑效果和一定的冷却效果,适用于切削、磨削加工。     

Chemical Aspects of Machining Processes

Machining processes used to create surfaces are influenced by the mechanical, thermal, and chemical loading in the contact zone. In addition, the tribo-physical and tribo-chemical interactions between the cutting tool, workpiece, metalworking fluid and surrounding medium have an influence on the properties of the resulting surface. In order to design efficient machining processes and control the chemical state of the surface produced, a basic understanding of the chemical mechanisms in the contact zone is needed. The chemical effects of metalworking fluids on the processes of machining and grinding are discussed, including the chemical interactions which occur between the various participating surfaces. The impact of the resulting chemical state of the surface produced is addressed.     

Capability Profile of Hard Cutting and Grinding Processes

This keynote paper aims at matching the supply of research results with the industrial demands in hard cutting and grinding. The capability profiles of the processes are characterised and several manufacturing solutions are discussed. The comparison of hard cutting and grinding operations is carried out with regard to certain evaluation criteria based on the functionality of the machined workpiece itself, discussed at different levels, and the process economical efficiency. The basis for a roadmap of future development of hard machining technology is provided, e. g. the main technological developments associated with multi-processing hard machining concepts are given detailed consideration.     

Polishing of Structured Molds

High precision molds for the replication of structured optical elements like Fresnel lenses or prism arrays are generated by diamond machining or precision grinding. In some cases surface quality of the replicated components is not sufficient to meet the increasing demands concerning surface roughness and form accuracy for optical applications. Subsequent polishing of the structures may therefore be necessary. Within this work structured molds were finished by a newly developed abrasive polishing process, by laser polishing, and by abrasive flow machining. This paper focuses on the material removal mechanisms and achievable surface quality in abrasive polishing. Surface quality is compared to that achieved by laser polishing and abrasive flow machining.     

Layer Generation Process on Work-piece in Electrical Discharge Machining

In recant years, surface modification of metals and machining of insulating ceramics by electrical discharge machining (EDM) have been successfully carried out. In surface modification by EDM with semi-sintered electrodes, worn substances in the gap region form the material source of the layer generated on the work-piece surface. In the machining of insulating ceramics by EDM, a crystallized carbon layer or carbide layer from the working oil covers the surface of the insulator. Increase in the thickness of the generated layer, however, tends to stop at a certain maximum value in both surface modification by EDM with semi-sintered electrodes and machining of insulating ceramics by EDM processes. In these machining operations, accretion and removal phenomena occur alternately. In this paper, the mechanisms of machining insulators and the accretion process are discussed considering the characteristics of the generated layers on the work-piece surface.     

Recent advances in modelling of metal machining processes

During the last few decades, there has been significant progress in developing industry-driven predictive models for machining operations. This paper presents the state-of-the-art in predictive performance models for machining, and identifies the strengths and weaknesses of current models. This includes a critical assessment of the relevant modelling techniques and their applicability and/or limitations for the prediction of the complex machining operations performed in industry. This paper includes contributions from academia and industry, and is expected to serve as a comprehensive report of recent progress, as well as a roadmap for future directions. Process models often target the prediction of fundamental variables such as stresses, strains, strain-rates, temperatures etc. However, to be useful to industry, these variables must be correlated to performance measures: product quality (accuracy, dimensional tolerances, finish, etc.), surface and subsurface integrity, tool-wear, chip-form/breakability, burr formation, machine stability, etc. The adoption of machining models by industry critically depends on the capability of a model to make this link and predict machining performance. Therefore, this paper would identify and discuss several key research topics closely associated with predictive model development for machining operations, primarily targeting industry applications.     

Modeling and Identification of an Industrial Robot for Machining Applications

Industrial robots represent a promising, cost-saving and flexible alternative for machining applications. Due to the kinematics of a vertical articulated robot the system behavior is quite different compared to a conventional machine tool. This article describes the modeling of the robot structure and the identification of its parameters with focus on the analysis of the system's stiffness and its behavior during the milling process. Therefore a method for the calculation of the Cartesian stiffness based on the polar stiffness and the use of the Jacobian matrix is introduced. Based on the results of the identification and the experimental validation the machining performance of the robot is evaluated and conclusions are drawn.     

Machining contour errors as ensembles of cutting, feeding and machine structure effects

CNC machining has been studied from the perspective of either cutting or feeding. However, machining quality is the outcome of both of these processes. This work investigates the contour errors of a complete CNC machine system. A system model is developed to cover all groups of functions, including trajectory planning, trajectory tracking, cutting process and machine structure. Analysis results reveal the limitations of traditional studies. The dependence of contour errors on trajectory curvature, feed-rate, cutting depth and tracking control is investigated as well. A new model of CNC machining is developed.     

Analysis–synthesis of dimensional deviation of the machining feature for discrete-part manufacturing processes

Dimensional deviation analysis has been an active and important research topic in mechanical design, manufacturing processes, and manufacturing systems. This paper proposes a comprehensive dimensional deviation evaluation framework for discrete-part manufacturing processes (DMP). A generic, explicit, and transmission model is developed to describe the dimensional deviation accumulation of machining processes by means of kinematic analysis of relationships between fixture error, datum error, machine tool geometric error, fixturing force inducing error and the dimensional quality of the product. The developed modeling technology can deal with general fixture configurations. In addition, the local contact deformations of the workpiece–fixture system are determined by solving a nonlinear programming problem of minimizing the total complementary energy of the frictional workpiece–fixture subsystem in machining system. Moreover, the deviation of an arbitrary point on machining feature can be also evaluated based on a point deviation model with prediction dimension deviation from the transmission model. The dimensional error transmission within the machining process is quantitatively described in this model. A systematic procedure to construct the model is presented and validated. This model can be also applied to process design evaluation for complicated machining processes.     

Dry Machining and Minimum Quantity Lubrication

Modern machining processes face continuous cost pressures and high quality expectations. To remain competitive a company must continually identify cost reduction opportunities in production, exploit economic opportunities, and continuously improve production processes. A key technology that represents cost saving opportunities related to cooling lubrication, and simultaneously improves the overall performance of cutting operations, is dry machining. The elimination of, or significant reduction in, cooling lubricants affects all components of a production system. A detailed analysis and adaptation of cutting parameters, cutting tools, machine tools and the production environment is mandatory to ensure an efficient process and successfully enable dry machining.     

飞机铝合金薄壁件的加工质量研究

在薄壁件切削加工过程中的加工变形和良品率低等问题成为了影响零件的加工精度和生产率的主要因素。因此,研究薄壁件加工中变形误差较大和良品率低等问题在理论研究和实际应用中都具有重大意义。对于铝合金薄壁件主要采用实验研究和限元分析相结合的方法,分析数控加工中薄壁件加工质量的主要影响因素,并论述了加工过程中,从加工工艺方案、装夹方案、刀具的选择和走刀路线等方面控制薄壁件的变形、加强加工过程中其刚度的具体改进措施,以提高薄壁件加工效率和质量。     

A modelling framework for comparing the environmental and economic performance of WAAM-based integrated manufacturing and machining

Additive Manufacturing has proved to be suitable for supporting or even replacing traditional manufacturing approaches in some industrial contexts. Among the various processes that can be used to produce metal parts, Wire Arc Additive Manufacturing (WAAM) is known to be an economically convenient, welding-based direct energy deposition technique for large parts with reduced complexity. The present paper proposes a structured modelling framework to assess whether WAAM could successfully substitute machining processes. The costs, manufacturing times, energy demand and carbon footprint are considered. A case study is presented to clarify and demonstrate the applicability of the proposed methodology.     

Compensation for machining defects due to spindle dilatation

Defects are a common occurrence in industry when it comes to prolonged machining tasks (machining moulds, series of work-pieces, etc.). The relatively long machining time is generally what gives significant value added to the work-piece. We therefore need to avoid having to produce test work-pieces as much as possible [NC Machines, Hermès Paris (1997)]. This article considers dispersions introduced by dilatation of the spindle during machining on NC machine tools. Such dispersions are obviously prejudicial to obtaining accurate dimensions along the Z-axis of the machine. Firstly, we introduce the context of the study and the problem we had to confront. Secondly, the experimental study enabled us to highlight those parameters having an influence and quantify defects. By expressing dilatation and relaxation in the form of an equation, we were then able to calculate defects at a given instant. This enabled us to generate an algorithm for processing of the N.C. program so we could correct errors by compensating for defects during machining. We completed the study by machining a series of work-pieces using the programme integrating compensation for dilatation so as to validate the approach.     

Machining of Composite Materials

Machining of composite materials is difficult to carry out due to the anisotropic and non-homogeneous structure of composites and to the high abrasiveness of their reinforcing constituents. This typically results in damage being introduced into the workpiece and in very rapid wear development in the cutting tool. Conventional machining processes such as turning, drilling or milling can be applied to composite materials, provided proper tool design and operating conditions are adopted. An overview of the various issues involved in the conventional machining of the main types of composite materials is presented in this paper.     

Magnetic field assisted abrasive based micro-/nano-finishing

Micro-/nano-machining (abbreviated as MNM) processes are classified mainly in two classes: traditional and advanced. Majority of the traditional MNM processes are embedded abrasive or fixed geometry cutting tool type processes. Conversely, majority of the advanced MNM processes are loose flowing abrasive based processes in which abrasive orientation and its geometry at the time of interaction with the workpiece is not fixed. There are some MNM processes which do not come under the abrasive based MNM category, for example, laser beam machining, electron beam machining, ion beam machining, and proton beam machining. This paper gives a comprehensive overview of various flowing abrasive based MNM processes only. It also proposes a generalized mechanism of material removal for these processes. The MNM processes discussed in this paper include: Abrasive Flow Finishing (AFF), Magnetic Abrasive Finishing (MAF), Magnetorheological Finishing, Magnetorheological Abrasive Flow Finishing, Elastic Emission Machining (EEM) and Magnetic Float Polishing. EEM results in surface finish of the order of sub-nanometer level by using the nanometer size abrasive particles with the precisely controlled forces. Except two (AFF and EEM), all other processes mentioned above use a medium whose properties can be controlled externally with the help of magnetic field. This permits to control the forces acting on an abrasive particle hence the amount of material removed is also controlled. This class of processes is capable to produce surface roughness value of 8 nm or lower. Using better force control and still finer abrasive particles, some of these processes may result in the sub-nanometer surface roughness value on the finished part. Understanding the mechanism of material removal and rotation of the abrasives in these processes will help in rationalization of some of the experimental observations which otherwise seem to be contradicting with the established theories. It also explains why a magnet used in MAF should have a slot in it even though the area under the slot has “non-machining” zone. It elaborates based on the experimental observations why to use pulse D.C. power supply in MAF in place of smooth D.C. power supply.