Different Types Of Machine Tools Research Articles

Study on material removal mechanism and control strategy of multi-axis fast ED-milling

Diffuser-shaped film cooling holes, which have been used extensively in advanced aero-engines, are usually machined by electrical discharge machining (EDM) by means of drilling and die-sinking approaches in a sequence. However, this sequential machining on different types of machine tools suffers from low machining efficiency and accuracy severely. To cope with this problem, a multi-axis fast ED-milling method that uses tubular electrodes and high-pressure inner flush is proposed for various diffuser machining, such that the fabrication of diffusers can be realized on a single machine tool, is developed in this paper. However, the material removal mechanism and proper control strategies in this machining method are yet not fully investigated. To address this issue, with a dedicated observation platform, single-pulse discharge experiments were firstly carried out to achieve a better understanding of the gap discharge phenomena. The observation results imply that a high-pressure inner flushing can significantly promote the expelling of molten material from a molten pool as well as the evacuation of debris from a discharge gap. After that, characteristics of this machining method such as the electrode wear behavior and the gap discharge state variations were analyzed. Based on the analytical results, a dedicated electrode wear compensation strategy was proposed. Machining tests indicate that the new method guarantees rather higher machining efficiency and comparable surface quality in contrast with layer-by-layer fast ED-milling.

Design of a machine tool control system for function reconfiguration and reuse in network environment

Abstract Computer numerical control (CNC) systems are becoming multi-functional as the requirements for manufacturing quality, efficiency and product diversity are becoming more rigorous. The reconfigurability and scalability property of CNC are important for reducing manufacturing costs and functional redundancy and shortening manufacturing time. However, in current CNC systems, functions are closely coupled in a real-time operation environment. This has been a main obstacle for implementing a scalable and reconfigurable CNC system. This paper proposes a new type of CNC system named invisible numerical control (INC) system to simplify CNC architecture and improve CNC architecture reconfigurability and function reusability. INC system consists of three sub-systems, namely project center, motor controller and mobile terminal. The functions of the sub-systems are machine control instructions generation, execution of machine control instructions and process control respectively. The sub-systems are organized in loosely coupled manner. This is enabled by current computer/information resources and technologies such as high speed data transmission, large capacity and high speed storage, standard communication protocols and compiled operation of machining programs. By configuring different functions in project center, it can generates uniform machine control instructions for multiple and different types of machine tools. Therefore, reconfigurability and function reusability are achieved. This paper illustrates the functions, architecture and information model of INC and builds an INC prototype. Case studies show that by using current off-the-shelf hardware, INC can be implemented to undertake different manufacturing tasks.

Novel approach for machine tool maintenance modelling and optimization using fleet system architecture

Abstract In this paper, a novel approach is developed for machine tool maintenance modelling considering fleet system architecture. The fleet system architecture consisting of different types of machine tools from various OEMs operated at different users, but supported by a single repair depot is considered. The prime objective of this paper is to jointly optimize the decisions of Level of Repair (LOR) i.e. repair/move/discard, and Preventive Maintenance (PM) schedules considering user’s cost structure and shop floor policy parameters. It is observed that integrated PM and LOR approach gives better Life Cycle Cost (LCC) performance compared to isolated approaches. Also, the importance of user’s cost structure and shop floor operations policy parameters in LOR and PM planning is evident from the results. The proposed approach is very useful for the machine tool manufacturers (i.e. OEM) who want to engage into long term maintenance contract with their customers. Integrating LOR and PM is a complex problem. The complexity further increases due to consideration of time dependent failure rate of the machine components, imperfect maintenance which brings partial restoration to the components/systems, and stochastic natures of model parameters. Consequently, a simulation based genetic algorithm approach is used to solve the problem.

Experimental study on energy consumption of computer numerical control machine tools

Machining processes are responsible for substantial environmental impacts due to their great energy consumption. Accurately characterizing the energy consumption of machining processes is a starting point to increase manufacturing energy efficiency and reduce their associated environmental impacts. The energy calculation of machining processes depends on the availability of energy supply data of machine tools. However, the energy supply can vary greatly among different types of machine tools so that it is difficult to obtain the energy data theoretically. The aim of this research was to investigate the energy characteristics and obtain the power models of computer numerical control (CNC) machine tools through an experimental study. Four CNC lathes, two CNC milling machines and one machining center were selected for experiments. Power consumption of non-cutting motions and material removal was measured and compared for the selected machine tools. Here, non-cutting motions include standby, cutting fluid spraying, spindle rotation and feeding operations of machine tools. Material removal includes turning and milling. Results show that the power consumption of non-cutting motions and milling is dependent on machine tools while the power consumption of turning is almost independent from the machine tools. The results imply that the energy saving potential of machining processes is tremendous.

Application of information fusion to volumetric error modeling of CNC machine tools

In order to solve the problem of low measurement efficiency of volumetric errors and predict the volumetric errors of CNC machine tools online, a new volumetric error modeling method based on information fusion technology is proposed in this paper, which was used for the volumetric error prediction of a two turntable five-axis machine tool. In order to fulfill the volumetric error modeling, the displacement variables, temperature variables, and cutting force variables were determined firstly, then the determined variables and the volumetric errors were measured and analyzed, and a volumetric error model was presented based on the determined variables. In order to optimize the parameters of the presented model, grey correlation analysis method is used for the second time prediction of the volumetric errors. Finally, the performance of the model was tested by an experiment. The result shows that the approximation ability of the model is very well, and the residual error is smaller than 2 μm. Comparing with conditional modeling methods, this method can be used in different types of machine tools with different operating conditions by regulating the weight matrix, and the robustness of the fusion model is improved.

Adaptive setup planning of prismatic parts for machine tools with varying configurations

Setup planning for machining a part is to determine the number and sequence of setups (including machining features grouping in setups) and the part orientation of each setup. Tool accessibility plays a key role in this process. An adaptive setup planning approach for various multi-axis machine tools is proposed in this paper focusing on kinematic analysis of tool accessibility and optimal setup plan selection. In our approach, feasible Tool Access Directions (TADs) of machining features are denoted by partially sequenced unit vectors; The Tool Orientation Spaces (TOS) of different multi-axis machine tools are generated according to their configurations through a kinematic model, and represented on a unit spherical surface. Starting from a 3-axis-based machining feature grouping, all possible setup plans of a given part for different types of machine tools (3-axis, 3-axis with an indexing table, 4-axis, and 5-axis machines) can be achieved effectively by tool accessibility examination. The optimal setup plans are selected from obtained candidates by evaluating both their locating and grouping factors. A so-generated setup plan can provide not only the best coverage of machining features and the primary locating directions but the optimal orientations of the work-piece for each setup. Only prismatic parts are considered in this proof-of-concept study, and the algorithms introduced in this paper are implemented in MATLAB. A case study is conducted to validate the algorithms.

Development and Application of a Direct Drive Motor for Performance Enhancement of Versatile Machine Tool Systems

For highly productive machining operations, multi-axis versatile machine tools are drawing more attention in today's market. In order to maintain the stability and the motion accuracy over a long operation time, it is important for such a versatile machine tool to avoid complicated mechanisms, such as an indirect drive, from the viewpoint of machine design. This paper presents a design methodology for the specification of a direct drive (DD) motor to enhance the overall performance of versatile machine tools. Practical application examples to different types of machine tools are also presented.

Some Empirical Evidence on Machine Tool Deterioration and its Use in Projecting Machine Tool Requirements

This paper presents the results of research efforts to estimate the rate at which machine tools deteriorate. A relationship between machine tool deterioration based on component wearout “failures,” and the resulting decline in the productivity of the machine is defined and used as an aid in planning machine tool overhauls and replacements. Deterioration rates for 35 different types of machine tools are estimated via regression analysis using data obtained from a survey on the collective experiences and policies of U.S. industries on over 15,000 machine tools. The results show that different types of machine tools deteriorate at significantly different rates. This information is then embodied in a computerized planning model which incorporates product line sales forecasts, current machine utilization patterns, and machine productivity related to deterioration factors. The planning model can assist manufacturing managers by identifying machine tools which are good candidates for further detailed cost-benefit analysis concerning replacement or overhaul.

A Multiprocessor Control System as a Universal Modular System for the Design of Machine Tool Controllers

The increasing number of special functions required by machine tools for economic operating calls for a modular system with standardized interfaces. Such a system has been developed as part of the German Second Data Processing Research Program. Alongside the special functions all components habe the same hardware and software interfaces. These building blocks permit an adaptation to specific applications by means of appropriate software modification.This paper will discuss the principle of these controllers and describe the important characteristics of the hardware and software interfaces. The first pilot applications and the use of the control system in connection with different types of machine tools, as well as in related applications, will also be described.