FPGA-based hardware CNC interpolator of Bezier,splines, B-splines and NURBS curves for industrial applications

Tool path interpolation is an important part of Computerized Numerical Control (CNC) systems because it is related to the machining accuracy, tool-motion smoothness and overall efficiency. The use of parametric curves to generate tool-motion trajectories on a workpiece for high accuracy machining has become a standard data format that is used for CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) and CNC systems. Splines, Bezier, B-splines, and NURBS (Non-Uniform Rational B-splines) curves are the common parametric technique used for tool path design. However, the reported works bring out the high computational load required for this type of interpolation, and then at best only one interpolation algorithm is implemented. The contribution of this paper is the development of a hardware processing unit based on Field Programmable Gate Arrays (FPGA) for industrial CNC machines, which is capable of implementing the four main interpolation techniques. It allows the selection of the required interpolation technique according the application. Two CAD models are designed for test the CNC interpolations; experimental results show the efficiency of the proposed methodology.     

Tool life and other process constraints for NC path planning

The path of the cutter in a face milling operation is a critical parameter that governs the total production time. Computer Aided Design (CAD) systems allow for the careful planning of the cutter path without physical verfication. Optimization of cutter path for generic shapes is still an unsolved problem. Moreover, while planning the path of the cutter analytically, many real time process effects get neglected. Of chief mention is a variable that affects the non-machining time, Viz., tool life. Often the optimal path is insignificant in the light of the damage the tool will suffer if it follows this path.

Tool life in face milling depends on the entrance and exit conditions of the cutter into the workpiece (among other variables). Using the actual (trochoidal) path of the cutter tip (compared to the commonly used circular path) allows for a better evaluation of cutter entances and exits. In this research, an attempt is made to point out the importance of “process effects” in NC verification. Further, a program is developed to study the above mentioned variables in relation to the tool path. Preliminary testing of this program proved the validity of the proposal.     

The Impact of High Speed Machining on Computing and Automation

Machine tool technologies, especially Computer Numerical Control (CNC) High Speed Machining (HSM) have emerged as effective mechanisms for Rapid Tooling and Manufacturing applications. These new technologies are attractive for competitive manufacturing because of their technical advantages, i.e. a significant reduction in lead-time, high product accuracy, and good surface finish. However, HSM not only stimulates advancements in cutting tools and materials, it also demands increasingly sophisticated CAD/CAM software, and powerful CNC controllers that require more support technologies. This paper explores the computational requirement and impact of HSM on CNC controller, wear detection, look ahead programming, simulation, and tool management.     

Intelligent Programming of CNC Turning Operations using Genetic Algorithm

CAD/CAM systems are nowadays tightly connected to ensure that CAD data can be used for optimal tool path determination and generation of CNC programs for machine tools. The aim of our research is the design of a computer-aided, intelligent and genetic algorithm(GA) based programming system for CNC cutting tools selection, tool sequences planning and optimisation of cutting conditions. The first step is geometrical feature recognition and classification. On the basis of recognised features the module for GA-based determination of technological data determine cutting tools, cutting parameters (according to work piece material and cutting tool material) and detailed tool sequence planning. Material, which will be removed, is split into several cuts, each consisting of a number of basic tool movements. In the next step, GA operations such as reproduction, crossover and mutation are applied. The process of GA-based optimisation runs in cycles in which new generations of individuals are created with increased average fitness of a population. During the evaluation of calculated results (generated NC programmes) several rules and constraints like rapid and cutting tool movement, collision, clamping and minimum machining time, which represent the fitness function, were taken into account. A case study was made for the turning operation of a rotational part. The results show that the GA-based programming has a higher efficiency. The total machining time was reduced by 16%. The demand for a high skilled worker on CAD/CAM systems and CNC machine tools was also reduced. Received: September 2004 / Accepted: September 2005     

Tool path planning for 5-axis flank milling of ruled surfaces considering CNC linear interpolation

This paper investigates tool path planning for 5-axis flank milling of ruled surfaces in consideration of CNC linear interpolation. Simulation analyses for machining error show insights into the tool motion that generates a precision machined surface. Contradicting to previous thoughts, the resultant tool path does not necessarily produce minimal machining error when the cutter contacts the rulings of a developable surface. This effect becomes more significant as the distance between two cutter locations is increased. An optimizing approach that adjusts the tool position locally may not produce minimal error as far as the entire surface is concerned. The optimal tool path computed by a global search scheme based on dynamic programming supports this argument. A flank milling experiment and CMM measurement further validate the findings of this work.     

Automated path planning for face milling of N-sided convex polygonal surfaces using staircasing strategy

In a manufacturing environment, many times, it is difficult to have NC physical effort with actual machining. This effort can be considerably minimized by analytical modeling of tool path. The path selected for face milling of flat convex polygonal surfaces can significantly affect the cutter travelling distance. Past studies have identified that efforts were made to minimize the path selected for maching these surfaces. However, not much information is available on machining convex polygonal parts for N-sides. An object oriented software package was developed in Turbo C++ to graphically simulate the tool path while face milling different N-sided polygonal surfaces following staircasing path. The staircasing strategy was adopted since the shortest length of cut generated is better than that generated by window frame milling. Pop Up menus were created so that the software developed is interactive, user friendly and completed with error handling.     

Neural networks for estimating the tool path length in concurrent engineering applications

This paper deals with the development of a neural computing system that can predict the cutting tool path length for milling an arbitrary pocket defined within the domain of a product design, in a computer numerically controlled (CNC) setting. Existing computer aided design and manufacturing systems (CAD/CAM) consume significant amounts of time in terms of data entry pertaining to the geometries and subsequent modifications to them. In the concurrent engineering environment, where even the designer needs information from the CAD/CAM systems, such time-consuming processes can be expensive. To alleviate this problem, a neural network system can be used to estimate machining time by predicting cost-dependent variables such as tool path length for the pocket milling operation. Pockets are characterized and classified into various groups. A randomized design is described so that the training samples that have been chosen represent the domain evenly. An appropriate network was built and trained with the sample pocket geometries. The analysis of the performance of the system in terms of tool path length prediction for new pocket geometries is presented.     

Problems associated with the off-line programming of robots

The introduction of robots into any organization forms part of a considerable investment in new technology over a range of applications in the search for efficiency and increased productivity. The greater consistency and quality associated with robot operations, compared with that of the human operator, is regarded as an advantage both in relation to the manufacturing process and to the product. However, in order to make the most efficient use of robots, the ability to generate good robot programs must be developed. Traditional robot programming techniques are extremely slow and laborious. Off-line programming by textual input alone is an equally tedious process. In this paper, existing and potential problems associated with off-line programming are examined. Various commercial and experimental robot languages and their relative important features are described. Opinions of manufacturers of CNC (Computer Numerically Controlled) machines and robots concerning both user interfaces and potential candidate users are discussed. Both the training and the abilities of the candidate robot programmers are important aspects of any robot programming system, although obviously much will depend on the sophistication of the particular application. Recommendations are made concerning issues that should be taken into account when developing future off-line programming systems.     

Integration of calculation models and CAD systems in building services design

Computer programs for analysing flow in pipework and in mains electrical distribution systems are well known. Computer-aided drafting is commonly used to produce working drawings of such systems. This paper looks at the integration of calculation models and CAD systems, particularly for the building services industry. Two types of networks generally occur in building services engineering. These are trees and circuits. They have certain features that allow the calculation model to be built up from geometrical data with minimum additional user input. The specific cases of closed circuit pipework and electrical wiring are dealt with in more detail.     

An integrated manufacturing planning assistant — IMPA

In this paper, we describe our development of a fully integrated manufacturing planning assistant (IMPA) system, which is able to: (1) interpret the finished part requirements directly from the designer's CAD systems or solid modelers without user intervention or special feature coding; (2) check the machinability of a designed part; (3) automatically generate a process plan, a tool path and an NC (numerically controlled) code, and (4) support interactive user modification of the resulting plans, tool paths and NC code. A demonstration version of the system was designed to provide automated assistance for the planning of machining processes on three-axes NC machine tools. The underlying architectural concepts and reasoning algorithms can be extended to more complex machines such as four-or-more-axes NC machines. CAD, CAE, and CAM including robotic, FMS (flexible manufacturing system) and NC machines are widely used in industry today. There is increasing interest in automation of factory control software Merchant, (1988); this includes automating the generation of the control programs — that is, in developing systems which will automatically produce the NC code for machining the part, given a model of the part, the shape of the raw material, and the machine specifications. With such systems, there are several difficulties in the manual preparation of an NC program code such as, long and tedious calculations, high risk of error in data preparation, etc., which need to be eliminated. This is a critical step toward the integration of CAD and CAM into a truly concurrent engineering and manufacturing environment.     

Optimize tool paths of flank milling with generic cutters based on approximation using the tool envelope surface

This paper presents a global optimization method to generate a tool path for flank milling free-form surfaces with a generic cutter based on approximation using the tool envelope surface. It is an extension of our previous work [Gong Hu, Cao Li-Xin, Liu Jian. Improved positioning of cylindrical cutter for flank milling ruled surfaces. Computer Aided Design 2005; 37:1205–13]. First, given initial tool path or tool axis trajectory surface, the grazing points of the tool envelope surface can be calculated. Second, the errors between the tool envelope surface and the designed surface along the normal direction of the tool envelope surface are calculated. Based on this new definition of error, an optimization model is established to get the global optimized tool axis trajectory surface. In order to simplify the calculation, two variants of this method based on the least square criterion are proposed to solve this model. Since this method is really based on the tool envelope surface, it can reduce the initial machining errors effectively. The proposed method can be used not only for cylindrical cutters and conical cutters, but also for generic cutters with a surface of revolution. In addition to ruled surfaces, it also can be used for machining non-ruled surfaces. Finally, several examples are given to prove its effectiveness and accuracy. The generated tool paths and calculated grazing points for test are available in supplementary files for the readers’ convenience in verifying this work in different CAD/CAM systems.     

The design of a user friendly interactive personal computer package for quality control charts, project management, and linear programming applications

This paper describes the design of a user friendly interactive software package which can easily be used in both educational and industrial environments. The package contains applications for Quality Control Charts, Project Management, and Linear Programming. It is written in the BASIC programming language using the IBM Disk Operating System (DOS version 3.1). An IBM Personal Computer (PC, XT or AT) or compatible with one disk drive, a monochrome VDT and a line or dot matrix printer are required. The programs incorporate human factors considerations and the user is not required to have any previous computer programming experience. The package has data management options for adding new data, deleting data, listing data, storing data on a disk file and printing data collection forms for each program. The programs have been extensively validated using text book examples and comparisons with similar packages on main frame computer systems (such as EZLP, PPERT, LPRG, etc.). Based upon testing, this package was found to be easier to use and produced the desired results in approximately one third of the total time required by using the main-frame packages.     

基于dyna971的数控镗铣机床动态模拟仿真

落地式数控镗铣机床结构复杂,为保证机床具有良好的动态性能,在开发设计该类机床时要进行整机的动态模拟仿真分析。针对这一要求,提出一种实际设计中实用化程度较高的机床动态模拟仿真思路,首先对数控落地镗铣机床样机进行模态试验,获取床身〖CD*2〗滑座、滑座〖CD*2〗立柱、立柱〖CD*2〗主轴箱等结合面的模态参数,在对模态参数进行有限元方法优化识别后,利用COMBIN14单元模拟优化后的结合部参数建立机床整机有限元模型。在dyna971软件平台对整机有限元模型进行动态模拟仿真,从模拟仿真分析结果可以看出机床在受到外界作用力时,其输出的应力和应变变化波形平稳,说明经过上述分析而设计出的机床具有良好的动态性能。目前,该研究成果已应用于此类型机床的批量生产。     

Software-based tool path evaluation for environmental sustainability

Currently available life cycle assessment (LCA) tools provide only a rough estimation of the environmental impact of different manufacturing operations (e.g. energy consumption). To address this limitation, a web-based and application programming interface (API) based process analysis software tools were developed to estimate the energy consumption of a computer numerically controlled (CNC) machine tool operation and to evaluate its environmental impact as a first step towards sustainable manufacturing analysis. Acceleration/deceleration of machine tool axes and the direction of axes movement were considered to estimate the total energy demand and processing time of the machine tool operation. Several tool path generation schemes were tested to analyze the energy consumption and resulting green house gas emission of CNC machine tool operation. It showed that tool path generation schemes affect the amount of energy and the processing time required to machine the same part, and location of the machining resulted in different amount and characteristics of green house gas emission.     

Something to smile about: 3D graphics are revolutionizing oralhealth care

Computer graphics and all the computer-aided drawing and manufacturing (CAD/CAM), scanning, and imaging technology is changing dentistry. Invisalign is a technology that straightens adult teeth using a series of clear, plastic, nearly invisible aligners. Though proprietary CAD/CAM software that does 3D modeling, the company creates the fixtures for orthodontists. For dental implants dentists make a study cast of the area where the abutment will be placed. They then scan the cast into the computer using a 3D optical scanner, creating a 3D point cloud. Technicians create a polygonal surface from the point cloud. They use proprietary software to virtually assemble the digital teeth data with an unmodified (or template) version of their product. This template is a 3D model of an ideally shaped dental abutment. The computer generates the tool path and sends it to the milling machines that create the titanium abutment. Maxillofacial surgery repairs physical malformations resulting from disease, injury, burns, birth defects, or aging. In these cases, a maxillofacial surgeon must make changes that often include removing bone and replacing it with modeled implants. A surgeon uses computer graphics to solve these problems in his practice. The common thread among the examples of oral health care techniques discussed is the CAD/CAM software they use from Raindrop Geomagic     

MasterCAM编程和CNC数控铣床巧妙结合在雕刻加工中的应用

该文通过对圆弧曲面数控雕刻加工的实例表述,给出了圆弧曲面数控雕刻的编程加工应用步骤,在圆弧曲面数控雕刻加工中,针对于编程软件的特点和数控铣床的特点,采用了灵活实用编程方案和可靠有效的数控加工工艺,从而保证零件加工质量和加工效率,也使企业经济效益和生产水平得以提高。     

A corner-looping based tool path for pocket milling

In milling around corners, cutting resistance rises momentarily due to an increase of cutter contact length. NC tool path generation in dealing with sharp corners thus requires special consideration. This paper describes an improved NC tool path pattern for pocket milling. The basic pattern of the improved tool path is a conventional contour-parallel tool path. Bow-like tool path segments are appended to the basic tool path at the corner positions. When reaching a corner, the cutter loops around the appended tool path segments so that corner material is removed progressively in several passes. By using the corner-looping based tool path, cutter contact length can be controlled by adjusting the number of appended tool path loops. The procedures of creating the improved tool path for different corner shapes are explained. The proposed tool path generation was implemented as an add-on user function in a CAD/CAM system. Cutting tests were conducted to demonstrate and verify the significance of the proposed method.     

Advances in software engineering

Software is the key technology in applications as diverse as accounting, hospital management, aviation, and nuclear power. Application advances in different domains such as these-each with different requirements-have propelled software development from small batch programs to large, real-time programs with multimedia capabilities. To cope, software's enabling technologies have undergone tremendous improvement in hardware, communications, operating systems, compilers, databases, programming languages, and user interfaces, among others. In turn, those improvements have fueled even more advanced applications. Improvements in VLSI technology and multimedia, for example, have resulted in faster, more compact computers that significantly widened the range of software applications. Database and user interface enhancements, on the other hand, have spawned more interactive and collaborative development environments. Such changes have a ripple effect on software development processes as well as on software techniques and tools. In this article, we highlight software development's crucial methods and techniques of the past 30 years