Machining Tool Path Research Articles

Development of Embedded Linux CNC System Based on ARM9

Five-axis machining area of free surface is proposed by based on ARM9 and Linux open CNC system's overall structure of the CNC system hardware and software architecture. The system adopts the mode of the host computer PC, the lower computer ARM9 development board. PC completes the model of space surface and generates tool path by Simultaneous Multi-objective Optimization Algorithm on Free-form Surface Five-Axis Machining Tool Path and Tool Posture. The lower computer applies MYSQL database to storage and manage cutter location point information. Other modules access the database through ODBC standard interface. ARM9and PC utilize the way of cross-platform socket data transmission, the stepper motors is controlled by the way of constant acceleration - deceleration.

Tool Path Design Methods for High Efficiency Die Cavity Machining with CAD/CAM Technology

In this research, high efficiency machining tool path design of die cavities were developed using CAD/CAM and plunge roughing technology. The algorithms of cutting tool path design for ideal and non-ideal rouging area were proposed to improve the material removal rate (MRR). The proposed tool path design methods are based on the minimum numbers of rectangular or triangular patterns to cover the roughing areas. The cutting results of the traditional Z-plane and the plunge roughing were compared to show the improvement of the cutting efficiency with the proposed methods. Design of experiments (DOE) method was adopted to optimize the tool path designs and cutting conditions. Cutting experiments were carried out to verify the proposed cutting path design methods. The better material removal rate was obtained using the proposed plunge roughing method compared to the traditional Z-plane roughing. Both of the cutting simulations and the cutting experiments also showed the cutting efficiency of plunge roughing is increased with increase of cutting depth. The proposed hybrid tool path design method can further improve the cutting efficiency of plunge roughing process.

Free-Form Surface Five-Axis Machining Tool Path and Tool Posture Simultaneous Multi-Objective Optimization Theory Research

In view of all sorts of questions existing in CNC machining, such as machining vibration, so proposed a new simultaneous multi-objective optimization algorithm on free-form surface five-axis machining tool path and tool posture based on constant scallop height. In the algorithm, we first complete the surface fitting on the base of feature points obtained. Secondly calculate principal curvatures of the surface, select tools, and at the same time generate tool axis vector in the current cutter-contact point tool axis. Once again get the maximum spacing and surface curvature in accordance with the tool effective cutting radius, discrete into cutter-contact point, and calculate the cutting depth to adjust the machine feed rate. And finally connect adjacent curve path using the diagonal to achieve a continuous cutting scallop height tool path. This algorithm can achieve the goals such as the same precision, improving processing efficiency, reducing the number of tool cutting in and out, reducing cutting vibration and tool wear and so on. That is the algorithm can achieve simultaneous multi-objective optimization of the free-form surface NC machining finally.

工具姿勢と姿勢変化の影響を考慮した５軸制御ＣＡＭシステムの開発

5-axis control machining can realize high performance machining by considering the relative attitude between a tool and a workpiece. Thus, it enables to avoid the abnormal tool wear and the deterioration of machined surface quality. The influence that the tool attitude gives the machined surface has been investigated by some researchers, and the tool attitude to obtain good surface quality has been already proposed in previous studies. On the other hand, the tool attitude in 5-axis control machining cannot but change inevitably with the rotational axis motion, while keeping the relative attitude constant. The influence of not only the tool attitude to the machined surface but also the variation in tool attitude should be evaluated to obtain good surface quality, based on 5-axis control machining experiments. The study deals with the proposal of an evaluation formula by considering the influence of both the tool attitude and the variation in tool attitude. It is experimentally recognized that the devised CAM system can generate appropriate 5-axis control tool paths for finish machining by utilizing the evaluation formula.

Tool Positioning Algorithm Based on Smooth Tool Paths for 5-axis Machining of Sculptured Surfaces

The current research of the 5-axis tool positioning algorithm mainly focuses on searching the local optimal tool position without gouging and interference at a cutter contact(CC) point, while not considering the smoothness and continuity of a whole tool path. When the surface curvature varies significantly, a local abrupt change of tool paths will happen. The abrupt change has a great influence on surface machining quality. In order to keep generated tool paths smooth and continuous, a five-axis tool positioning algorithm based on smooth tool paths is presented. Firstly, the inclination angle, the tilt angle and offset distance of the tool at a CC point are used as design variables, and the machining strip width is used as an objective function, an optimization model of a local tool positioning algorithm is thus established. Then, a vector equation of tool path is derived by using the above optimization model. By analyzing the equation, the main factors affecting the tool path quality are obtained. Finally, a new tool position optimization model is established, and the detailed process of tool position optimization is also given. An experiment is conducted to machine an aircraft turbine blade by using the proposed algorithm on a 5-axis blade grinding machine, and the machined blade surface is measured with a coordinate measuring machine(CMM). Experimental and measured results show that the proposed algorithm can ensure tool paths are smooth and continuous, improve the tool path quality, avoid the local abrupt change of tool paths, and enhance machining quality and machining efficiency of sculptured surfaces.

High-Speed Milling Toolpath Planning for Aviation Engines Impeller Using POWERMILL Software

In this paper, the machining process of integrated impeller is customized basing on the geometry feature, function characteristics and the processing difficulties. Considering the working performance and machining rigidity, the rough machining and finish machining toolpath of the hub are generated in surface projection manner and the finish milling toolpath of blade is created in driver surface manner providing by the POWERMILL software. After simulating the machining toolpath, an integrated impeller is machined by 5-axis machining center of HSM 600U.

Geometric Modeling for Five-Axis CNC Machining of Mold Surface with Flat-End Tool

This paper taken the flat-end tool and machined surface as a pair of mutually conjugate space contact tooth envelope surface and used the Frenet frame of differential geometry to describe the NC machining tool path in five-axis CNC machining of mold surface with flat-end tool. Thus the geometric model in five-axis CNC machining of mold surface with flat-end tool was established.

Optimization of Machining Process for Aluminum Alloy Thin-Walled Supporting Part on UG NX

According to the structural features of the supporting part, the manufacturing process plan of it is made and the fixtures are designed. The process parameters are optimized by the means of setting up multi-objective function that cover productivity, cost of production, processing efficiency; The NC Programs of supporting part are drawn with UG CAM and the machining tool-path is optimized through machining simulation.

Tool Path Generation Method of Equal Approximation Error for Free-Form Surface in High Speed Machining

The development of surface high-speed machining has put forward higher demands for uniform cutting load and smooth cutting tool path. Most current tool-path planning methods are based on constant scallop height, but they have the disadvantage of path point redundancy during the path discretization process. To overcome the problem, a tool path generation method of equal approximation error in each step for free-form surface is presented based on geodesic principle and curvature judgment. In this method, the NURBS curve is employed to realize smooth transition for adjacent two tool paths in high-speed machining. A certain angle of inclination of flat-end milling cutter during multi-axis machining improves the machining efficiency. Because of the advantage of this machining condition, the cutter location point generation algorithm during the machining condition is given by the method. The method is verified and simulated by C++. Experiment results proved that it can obtain uniform cutting load and continuous smooth cutting tool path during surface high-speed machining by the proposed method.

Toolpath Algorithm for Complex Pocket on the Network Optimization

On the consideration of connection of offset contour, deletion of interferential contour loop and accurate generation of toolpath in pocket machining, the linking of the pocket toolpath is paid close attention to, and an algorithm based on network optimization for complex pocket is brought forward. The introduced Dijkstra algorithm which is positive cost and directed cycle can accurately connect the vertexes of line segment and arc graph elements, and generate the shortest toolpath. The contour parallel toolpath algorithm can deal with linking of pocket with islands. Based on the techniques, experimental results are given to verify the proposed approach.

Tool path generation for five-axis sculptured surface machining with a toroidal cutter

This paper presents an algorithm to generate tool paths for five-axis sculptured surface machining with a toroidal cutter based on optimal tool position and orientation. The toroidal cutting surface offers a large range of radius of curvatures. Furthermore, the cutter orientation varies depending on the curvature of surface. Thus, the proposed method is much better than the conventional method with a fixed orientation. To verity the usefulness of the developed algorithm, a computer simulation program is coded using C++ language. The proposed method can be integrated into CAM systems to improve five-axis sculptured surfaces machining.

Five-axis machining: technologies and challenges

Typical applications of 5-axis machining have been found in many industries. However, 5-axis machining still faces a number of challenges. It introduces further complexity as well as flexibility owing to the additional degrees of freedom compared to 3-axis machining. The focus of this review is to provide a perspective view of the research effort towards 5-axis machining that has been carried out over the last ten years. It centres on machine tools including topics such as 5-axis machine tool structures, 5-axis machining tool paths, modelling and compensation of process errors, modelling of 5-axis machine tools and emerging parallel kinematics machines. [Received 18 October 2009; Revised 27 January 2010; Accepted 1 February 2010]

High speed machining tool path generation for pockets using level sets

With the increasing application of high speed machining for pockets, the conventional methods of tool path generation show their limitations, such as the existence of a high curvature region along the tool path. This paper presents a level set approach of tool path generation for high speed machining of pockets. Pocket boundary is first embedded into a higher dimensional function, namely, the level set function. Then the tool paths are realised by the propagation of the pocket boundary. The topological changes of tool path can be naturally handled during the evolution of moving fronts. In order to avoid the appearance of high curvature corners along tool paths, a curvature-dependent term is adopted to regulate the velocity function of the level set equation. At the same time, the curvature flow motion is used to identify the machinable region of pockets. The vector level-set functions are utilised to handle complex pockets with multiple islands. The simulation of material removal rate based on the implicit description is also discussed. Numerical examples are presented to demonstrate the robustness of the proposed approach on different kinds of pockets with islands.

Generation of offset surface for tool path in NC machining through level set methods

Surface offset is always necessary for ball-end milling during computer-aided manufacturing period. Self-intersection may occur in offsetting complex surfaces. Many solutions for surface self-intersection are always complicated with algorithms for approximation, and they are always based on surfaces which are represented by special mathematical expressions. This paper proposes level set methods in the surface offsetting progress. The surface offset problem is regarded as the generation of a new interface from a dynamic initial surface with constant normal speed. Numerical computing results demonstrate that accurate solutions can be obtained through the level set methods with an appropriate numerical flux. The self-intersections are naturally eliminated while topology stability is kept.

A smooth spiral tool path for high speed machining of 2D pockets

We introduce a new algorithm for generating a spiral tool path for high-speed machining of pockets without islands. The pocket may be an arbitrary simply-connected 2D shape bounded by straight-line segments and circular arcs. The tool path is generated by interpolating growing disks placed on the medial axis of the pocket. It starts inside the pocket and spirals out to the pocket boundary. The tool path is guaranteed to be free of self-intersections and allows machining of the pocket without tool retractions. The start point of the spiral may be chosen freely by the user anywhere within the pocket. Most importantly, the spiral tool path complies with a user-specified maximum cutting width. The output of our algorithm is a G 1 -continuous spiral path. However, in a post-processing step, a properly adapted variant of the recent “ PowerApx” package [Heimlich M, Held M. Biarc approximation, simplification and smoothing of polygonal curves by means of Voronoi-based tolerance bands. International Journal of Computational Geometry & Applications 2008;18(3):221–50] can be used to boost the tool path to C 2 -continuity. Our new algorithm was implemented and tested successfully on real-world data. We conclude our paper by an analysis of sample tool paths produced by our implementation.

Study of Virtual Numerical Control Milling Simulation System

Virtual numerical control milling simulation system, based on UG, is studied oriented to low utilization of NC machines. A virtual machine tools library, standard fixture library and visual machine tool processing environment were established by the second development techniques of UG and VC++. Through the example of XH715 NC machine center, tool path and motion of miller were simulated separately; at last processing scheme was evaluated and optimized. The experimental results show this system possesses good utility, and the utilization of machine tools could thus be improved.

C1 Tool Path Generation for 5-Axis Control Machining Considering the Quality of Machined Surface(Multi-axis control machining)

The frequent change in tool attitude makes the quality of machined surface worse. In the study, the influence of the change in tool attitude is evaluated, based on the experiment. Then, an evaluation formula is proposed, considering the influence of both the tool attitude and the change in tool attitude against the machined surface. Machining experiments are performed to confirm the validity. Moreover, the method that generates appropriate tool path for finish machining is devised by utilizing the evaluation formula. It is confirmed that the tool path generation method is useful to improve the quality of machined surface.

Study of Virtual Numerical Control Milling Simulation System

Virtual numerical control milling simulation system, based on UG, is studied oriented to low utilization of NC machines. A virtual machine tools library, standard fixture library and visual machine tool processing environment were established by the second development techniques of UG and VC++. Through the example of XH715 NC machine center, tool path and motion of miller were simulated separately; at last processing scheme was evaluated and optimized. The experimental results show this system possesses good utility, and the utilization of machine tools could thus be improved.

The Domain of Admissible Orientation concept: A new method for five-axis tool path optimisation

This work deals with the optimisation of tool paths in five-axis machining. The objective is to improve the kinematic behaviour of machine tools during milling. The orientation of the tool axis at each point of a tool path is optimised while ensuring quality constraints. These are modelled using the Domain of Admissible Orientation (DAO) concept expressed in the P-System and transformed into the M-System. This article aims at defining the DAO and presents an example of optimisation using this concept. This optimisation is a minimisation of the movement generated by each rotation axis and is applied to two test parts.

An Efficient, Accurate Approach to Representing Cutter-Swept Envelopes and Its Applications to Three-Axis Virtual Milling of Sculptured Surfaces

To address a major technical challenge in simulating geometric models of machined sculptured surfaces in three-axis virtual machining, this paper presents an efficient, accurate approach to representing the 3D envelopes of a cutter sweeping sequentially through cutter locations; these envelopes embody the furrow patches of the machined surfaces. In our research, the basic mechanism of removing stock material in three-axis computer numerically controlled (CNC) milling of sculptured surfaces is investigated, and, consequently, an effective model is proposed to represent the 3D envelopes (or furrow patches). Our main contribution is that a new directrix (or swept profile) of the furrow patches (mathematically, ruled surfaces) is identified as a simple 2D envelope of cutting circles and is formulated with a closed-form equation. Therefore, the 3D cutter-swept envelopes can be represented more accurately and quickly than the existing swept-volume methods. With this innovative approach, a method of accurate prediction of the machining errors along tool paths in three-axis finish machining is provided, which is then applied to the optimization of tool-path discretization in two examples. Their results demonstrate the advantages of our approach and verify that the current machining-error-prediction methods can cause gouging in three-axis sculptured surface milling.