NC Machine Research Articles

Cutting Tool Condition Recognition in NC Machining Process of Structural Parts Based on Machining Features

Cutting tools are direct performers in material cutting processes of NC machining, while the degree of cutter attrition and breakage directly influences the quality of production. Meanwhile tool condition recognition is a key technique in automatic and unmanned machining process. Aimed at this problem, the recognition of tool-condition based on machining feature in real-time is stated. Machining features are used to build relationships between geometry, processing technology and monitoring signals in order to provide the basis for cutting tool condition identification. A feature database is established with experimental results and a cutting tool condition recognition system is established based on this database. Experimental results suggested that the proposed method solves the problem of tool condition monitoring, especially for production with multi varieties and small-batches.

复合镗铣加工中心双刀库可视化设计界面

复合式镗铣加工中心是一种功能较为齐全的数控加工机床，其加工效率为普通机床的5~10倍，现在已经普遍应用于各机械加工行业，但是传统的数控加工中心只有一个刀库，换刀时间较长。本文复合式镗铣加工中心采用的是双刀库的自动换刀设计思想，即固定换刀刀库和随机换刀刀库主要是为方便镗床和铣床在机加工过程换刀效率从而提高机床的加工精度并且提高机床的加工效率从而提高整个加工中心的工作效率。一般加工中心的刀库都是封闭的，但是在加床加工的过程中尤其是随机换刀刀库看不刀机床中主轴和刀库中各个刀座上具体是存放的哪种刀具，本文针对此问题使用vb6.0编程语言研究设计了复合镗铣加工中心双刀库可视化的人机界面，实现机床随机换刀刀库的可视化控制，实时监控机床随机换刀的运行状态，通过实验运行证明，该运行系统具有有效稳定性，精确性，实时性。 Composite boring milling machining center which has complete function is the NC machine. The processing efficiency is 5 to 10 times than the ordinary machine tool. So far, it has been widely used in the machining industry, but the traditional CNC machining center with only a Knife Bank spends longer time of changing knife. In this paper, automatic changing tool thought of double tool bank was applied in composite boring milling machining center. Namely, fixed knife bank and random changing knife bank were used to improve the efficiency of changing knife in the machining process. At the same time, machining efficiency and machining precision were improved. Generally, the knife bank of machining center was sealed. But for the random knife bank, the knife type on the knife seat which was installed on the spindle and knife bank couldn’t be identified in the machining process. According to above problems, by means of VB6.0 programming language, the visual human computer-interface of double knife bank was designed in the machining center. And the visual control of random changing knife bank was accomplished. At the same time, running state of random changing knife was controlled in the real time. The experiment showed that the system was stable, accurate and real-time.

Research on geometric error measurement system of machining center BV75 based on laser interferometer

This paper measures the twenty one geometric errors of numerical control machining center with parameter identification through laser interferometer, the main contents illustrate the measurement system, measurement model and some testing results combined with specific experimental conditions, at the same time provide particular reference value on numerical control machine tool(NC machine tool) geometric precision detection.

NC Machining Program Simulation and Experiments for Pelton Runner

With pelton turbines and other complex three-dimensional structure cavities that contains various shaped surfaces and all kinds of larger curvature, the three-axis CNC machine with a tool rotary to achieve the four coordinate overall Pelton CNC machining. According to processing characteristics of pelton runner, the paper determines the selection of materials and the overall structure of the tool. And the appropriate way of milling and milling parameters are made. The overall processing program and processing parameters of pelton runner are designed on this basis. The feasibility of the process and cutting route are verified by the simulation of cutting route and experiments.

Effect of Tool Rotation Erroron the Topography of Flank Machined Surface

In the flank milling process, processed metal surface is formed by the edge of the cutting tool and affected by errors of it in the manufacturing process. Among those errors, the error of tool rotation movement has the most significant effect on machined surface. This article focuses on the machining process influenced by cutting tool rotation errors in the NC machining process. In this paper, a mathematical model of machining process is built. The effect of tool offset error and tool tilt error on tool deflection error is studied. A method of detecting tool rotation errors through machined surface topography is presented in the paper.

The Research on Intelligent Monitoring Technology of NC Machining Process

According to the current situation and problems of CNC machine tool monitoring technology, we discuss the intelligent monitoring technology development and CPS features, and propose a four-layer architecture CPS NC machining process intelligent platform which realizes the real-time monitoring and three-dimensional display of machine tools. And we discuss the system composition and realization of the developing platform.

Reliability Evaluation of NC Machine Tools considering Working Conditions

Reliability evaluation is the basis for reliability design of NC machine tools. Since traditional reliability evaluation methods do not consider the working conditions’ effects on reliability, there is a great error of a result of a traditional method compared with an actual value. A new reliability evaluation model of NC machine tools is proposed based on the Cox proportional hazards model, which describes the mathematical relation between the working condition covariates and the reliability level of NC machine tools. Firstly, the coefficients of working condition covariates in the new reliability evaluation model are estimated by the partial likelihood estimation method; secondly, the working condition covariates which have no effects on the reliability of NC machine tools are eliminated by the likelihood ratio test; then parameters of the baseline failure rate function are estimated by the maximum likelihood estimation method. Thus, the reliability evaluation model of NC machine tool is obtained under different working conditions and the reliability level of NC machine tools is obtained. Case study shows that the proposed method could establish the relation between the working condition covariates and the reliability level of NC machine tools, and it would provide a new way for the reliability evaluation of NC machine tools.

Trends in Control of NC Machines

The paper comments on the new possibilities of utilizing the inertial navigation system in robototechnics. It deals with the application of a new inertial measurement system for a robotic workplace calibration. The calibration is necessary so that the simulation model of the production device can adjust to the real geometric conditions. The aim is to investigate and develop a new combined inertial navigation system based on electronic gyroscopes, magnetic and barometric sensors. The crucial activity is focused on three basic fields: 1. the first goal is to analyze accelerometer and gyroscopic sensors and their possibilities of utilization for inertial navigation. The simulation of the effect of sensors with different metrological parameters and their effect on the properties of the proposed combined navigation system, 2. the second goal is to optimize a specialized processor system for processing the data from the defined sensors in connection with controlling items of an industrial robot. The proposal of an algorithm of combined navigation with respect to the used processor system and 3. the third goal is to verify experimentally the proposed inertial navigation system in real conditions of the industrial robot operation.

NC工作機械の送り軸のための2慣性系モデルによる低周波振動抑制制御の研究

Large NC machine tools or NC machine tools with elastic parts such as reducers tend to have mechanical low frequency vibration. With high gain servo control, low frequency vibration appears as machining point vibration, and results in deterioration of machining surface. In this article, two anti-vibration control methods to suppress machining point vibration are proposed based on two-mass model; one is for semi-closed control and the other is for full-closed control. The basic idea of the proposed control laws is to regard the position reference from NC not as for motor but as for load of two-mass system. Experiments were done and it is shown that both proposed laws effectively suppress the load angular error by allowing motor angular error.

振動操作関数によるＮＣ工作機械送り系軌道の離散サンプル値制御（減衰を考慮しない場合について）

振動操作関数によるＮＣ工作機械送り系軌道の離散サンプル値制御（減衰を考慮しない場合について）

Trade-off analysis between machining time and energy consumption in impeller NC machining

Electrical energy is directly linked to society's prosperity across the globe; much of this due to the diverse innovations on manufacturing processes. Keeping pace with the high energy demand growth will require constant efforts in terms of investment and research in order to bring new alternatives of usage. This paper outlines the application of multiple response optimization in order to analyze the trade-off between machining time and energy consumption in 5-axis impeller rough machining to find a possible balance between them. It is well known that a higher speed reduces machining time but increases energy consumption, and vice versa. A quantitative form of the relationship between the involved factors was obtained by utilizing response surface methodology (RSM) together with the desirability function method. Four independent factors were selected, namely, spindle speed, feed rate, depth and width of cut. The responses are the consumed energy and the machining time. The results showed that selecting an appropriate feed rate is crucial to balance the trade-offs between energy and time. Spindle speed is the major factor for energy consumption, while width of cut is the most influential factor for machining time. Multiple response optimization of the cutting conditions for impeller roughing.Substantial improvement by balancing the factors in machining processes.Balancing factors can be the best optimization for a multiple response problem.2.7mm of width, 1.8mm of depth, 8,000 rpm, and feed 740 mm/minprovide best balance.The proposed model showed congruence between theoretical and practical results.

Free Surface NC Machining Tool Path Optimization Algorithm Based on the Iso-Scallop Method

In order to solve the problem of free surface processing of tool redundancy,the tool lack problem, and the demerit of low machining efficiency, etc., based on the iso-scallop method, based on the iso-scallop method, we put forward a kind of free surface NC machining tool path optimization algorithm,make the surface boundary discrete point set, which is generated by point set ring machining path, diagonal connection and then use the path of the adjacent curve, forming cutting tool machining line.finally, the calculation of step size and line spacing in machining path based on the iso-scallop method and the process of feeding direction is optimized. Proved by the simulation process, the algorithm is feasible and can effectively avoid tool redundancy and tool lack problems,concesquently, processing efficiency improved significantly.

Makespan estimation of a production process affected by uncertainty: Application on MTO production of NC machine tools

In this paper we address the estimation of the duration of the production process of a complex product in a Make-To-Order (MTO) or Engineering-To-Order (ETO) environment, a common situation in the manufacturing sector, specifically when production operations are executed by human operators. The addressed products, due to their complexity and high degree of customization, are specifically designed for a customer, together with their production process. On the other hand, the uncertainty affecting the production problem must be considered due to the presence of operations executed by human operators, the high level of customization entailing the need to cope with new products and processes and the behavior of the production environment.The proposed approach deals with the estimation of the duration of a production process modeled through a project network whose activities have an uncertain duration. It can provide support to a manager in the estimation of the makespan of the production of a product to provide a realistic and competitive due date to the customer, as well as to manage the scheduling of production and supplying operations and the resources assignment within the plant.The proposed approach is described, validated and compared with existing approaches through an ideal case. Moreover, a real case application is provided, related to the assembly process of a NC machine, to demonstrate its industrial viability.

The Modeling Methods of Heavy NC Machine Tool Bolt Joint Based on Virtual Media

The Modeling Methods of Heavy NC Machine Tool Bolt Joint Based on Virtual Media

Effects of transient slamming and harmonic swings on the marine compound NC machine tool

To study structural seakeeping stability of the marine compound NC machine tool in the ship environment, this research analyses the effects of extreme wave loads including transient slamming and harmonic swings on the machine tool, and the coupling methods of transient reaction, static structural analysis and harmonic response are used to solve the problems. The results show that the major guide pairs of the column are the weakest parts in the machine tool in a ship environment, so the column working deflection angle of the machine tool should be consistent with the ship heading angle to reduce influence of wave loads on dynamic stability of the machine. The data indicate that the minimum safety factor is 3.43 under an extreme surge acceleration of 41.8m/s2, and the normal safety factor of 3.0 shows that the guide pairs are able to endure extreme slamming wave loads of H1/3=7.6m at the maximum velocity of the ship. In addition, the machine tool has a maximum deformation of 0.032mm and a peak stress of 5.07MPa under extreme harmonic wave excitation. Importantly, the machine's cutting accuracy was suitable for the rapid manufacturing requirement to maintain a ship's broken components.

A real-time and look-ahead interpolation methodology with dynamic B-spline transition scheme for CNC machining of short line segments

Tool path is presented as continuous small line segments in some existing NC machining programs. To achieve high machining speed and smooth machining quality, the tool path needs to be processed. This study presents a real-time and look-ahead interpolation methodology with dynamic B-spline transition scheme for short line segments machining. In the methodology, transition curve is adjusted to avoid intersection and keep high machining speed. Firstly, the unit length of every B-spline transition curve is calculated depending on tool path and NC system requirements; then, the maximum allowable velocity of the curve which is called threshold velocity can be got. Secondly, transition curve is determined according to the unit length and two consecutive threshold velocities, and time optimization function makes the transition curve take less machining time. Thirdly, the 7-phase velocity planning algorithm and static look-ahead algorithm are adopted to generate smooth machining feedrate and fine machining quality. Lastly, the curve interpolation is performed on the processed tool path. The simulations and experiments demonstrated that the proposed algorithm is able to achieve high machining speed and generate fine machining quality.

An approach to optimize the machining accuracy retainability of multi-axis NC machine tool based on robust design

Machining accuracy retainability is considered to be one of the most important aspects in the process of performance evaluation and optimization design of the machine tools. Reliability based design optimization (RBDO) and robust design optimization (RDO) are the tools that search for safe structural systems with minimal variability of response when subjected to uncertainties in design parameters. The aim of this paper is to propose an approach that simultaneously considers reliability and robustness to allocate geometric accuracy of components for improving machining accuracy retainability under certain design requirements. Based on homogenous transformation matrices (HTMs), a comprehensive volumetric model explaining how individual errors in the components of a machine affect its volumetric accuracy (the coupling relationship) was established. By applying high-order moment standardization technique (HOMST), reliability and sensitivity with single failure mode were obtained and then the reliability model and the sensitivity model with multiple failure modes were developed and common methods such as Narrow bounds, AFOSM and Monte Carlo were used for verification and comparison. Meanwhile, a cost model taking manufacturing cost and present worth of expected quality loss into consideration was introduced. By taking the minimum possibility of failure and cost of machine tools as criterions and taking the reliability of machine tools as constraint of optimizing the basic parameters of machine tools, an approach to optimize the machining accuracy retainability of multi-axis NC machine tool based on robust design was developed and an example of improving the machining accuracy retainability for a five-axis NC machine tool was used to demonstrate the effectiveness of this approach. This study implies that it is possible to obtain the relationships between geometric errors and specify the accuracy grades of main feeding components of mechanical assemblies.

A GENERAL CAD/CAM MODEL FOR APT-LIKE ROTARY MILLING CUTTERS

This paper presents a general mathematical model for NC-machining an APT-LIKE rotating cutter. The design model of cutting-edge and helical groove is also developed by using the principles of differential geometry and kinematics. Based on the envelope condition, approaches for solving the inverse problems that are related to the manufacturing models are also presented. The velocities of the cutter in the radial and axial directions are then determined based on the gouging avoidance of grooves. The results of the numerical experiment indicate that the proposed systematic design method by using 2-axis NC machine setup is feasible and reliable.

Research on five axis NC Machining Simulation Based on VERICUT

The structure of five axis machine tool is complex and expensive, especially in the processing of complex and sophisticated parts. It is prone to produce the phenomenon of overcutting or undercutting between the machine parts and the knives or the machine tool , which will cause serious damage or even grievous scrap on the machine tool . With the help of VERICUT 7.0 Simulation of NC machine tool, you can modify and optimize the NC program code, shortening the real processing time required and improving the economic benefit of the company remarkably.

Exploratory study of spiral NC tool path generation on triangular mesh based on local subdivision

As a representation of free-form surface, triangle mesh model (commonly with the stereo lithography format) has gained wide application in CAD and CAM recently because of its simple geometric computation, superior robustness, and high efficiency in tool path generation. However, conventional tool-path generation methods for NURBS surface are incapable of direct application to mesh models. Development of a tool-path generation method based on mesh model with high machining precision is becoming a key problem for NC machining. In this paper, a spiral tool-path generation method in finish-cut process is developed based on the offset-surface method (also called cutter location method). A novel local subdivision method is proposed firstly to guarantee edges of the offset-mesh within the required tool-path interval, and then gouge-free tool-path is generated by organizing path through vertex of the offset-mesh. Therefore, all the path intervals are under precise control by the local subdivision, allowing the mesh surface with both steeper and flatter areas to be machined with high-precision. Besides, tool-path naturally runs along the boundary of the triangle mesh model, ensuring continuous cut for reducing the fluctuation of cutting load. At last, tool-paths with multiple connective areas are generated for several complex mesh surfaces to clarify efficiency and robust of proposed method.