Cutter Location Research Articles

5-axis machining using a curvilinear tool path aligned with the direction of the maximum removal rate

Machining large complex industrial parts with a high accuracy often requires tens, hundreds of thousands, or even millions of cutter location points and hundreds of hours of machining. That is why reducing the machining time is one of the most important topics in the optimization of CNC codes for 5-axis milling machines. We propose and analyze a new method of constructing curvilinear tool paths which partly or even entirely align with the direction of the maximum material removal rate. The alignment based on the curvilinear elliptic grid generation allows minimization of the machining time while keeping the convenient zigzag-like topology of the path. The method is applicable to a variety of cost functions such as the length of the path, the machining speed, the material removal rate, the kinematic error, etc., generating different machining strategies. The method has been combined with a new version of the adaptive space-filling curves. The approach has been tested against the standard iso-parametric zigzag, MasterCamX5, “Follow Periphery”/“Helical or Spiral” options of Unigraphics as well as the conventional space-filling curves. The material removal rate cost function has been tested against the tool path length minimization. The numerical and machining experiments demonstrate a considerable advantage of the proposed method.

Parametrically automated 3D design and manufacturing for spiral-type free-form models in an interactive CAD/CAM environment

For product lifecycle management reasons, research trends impose the need of automated engineering tasks, such as computer-aided design and manufacturing. This paper proposes a novel approach of automating both the design and manufacturing processes of impeller-type geometries, when CAD/CAM technology is employed. To do so, a newly developed application was built; exploiting application programming interface objects of parametric instances, in order to automate time-consuming repetitive tasks for the preparation of 3D models and their direct manufacturing process. The developed application incorporates Simpson’s method, Bezier-Bernstein equation and Non-Uniform Rational B-Spline for curve approximation describing blades of centrifugal impellers, as a representative case study. The machining technology is that of 3-axis CNC, thereby; each curve extends along a constant x-y plane. In the first step of the application, the entire 3D model of the impeller-type model is automatically generated according to variable values taken as user-defined entities from the interface. The application then carries on by automatically modeling the manufacturing process and ultimately generating the NC program from the cutter location data for a given CNC machine tool.

Generation of kinematic smooth tool-paths in 5-axis milling of sculptured surfaces

This paper addresses the issues of tool-path smoothness and tool-path length (machining efficiency) in the generation of cutter location (CL) paths of 5-axis point milling of sculptured surfaces. In the proposed method, the joint movement between two neighbouring CLs in the machine frame is used to measure the tool-path smoothness and the cutting strip-width to measure tool-path length. In order to generate tool-paths with satisfactory smoothness and good efficiency, two approaches are proposed: 1) a fast repairing approach that modifies CL segments with drastic joint movement; 2) a holistic optimisation approach that considers both objectives simultaneously. For both approaches, corresponding algorithms based on evolutionary algorithms (EAs) have been developed to search for the best posture sequence for the CLs on each path. A case study is presented to show the performance comparison between the two approaches. [Received 18 August 14; Revised 30 April 5; Accepted 18 May 2015]

2A2-T03 産業用ロボットのためのCAMシステムを用いた発泡スチロール切削加工における最適な加工条件の実験的検討

Polystyrene mold used in full mold casting is usually machined by a CNC machine. On the other hand, an articulated industrial robot costs lower and can move more flexibly. Efficient machining will be accomplished by attaching a spindle motor with a ball end mill to the tip of the robot. A trajectory following control system based on CL (Cutter Location) data has been developed for a machining robot. In the system, the discrete trajectories at each sampling time are generated from position and orientation information in CL data made by post processor in CAM system. Many machining experiments were carried out using the machining robot incorporated with the controller, so that it was confirmed that the quality of machined surface of foamed polystyrene depended on machining conditions. In this paper, the effects of rotation speed of an end mill and small vibration control on quality of machined surface are compared.

Prediction of Cutting Force in 3-Axis CNC Milling Machines Based on Voxelization Framework for Digital Manufacturing

A new digital-based model is presented for the prediction cutting forces in 3-axis CNC milling of surfaces. The model uses an algorithm to detect the work-piece/cutter intersection domain automatically for given cutter location (CL), cutter and work-piece geometries. The algorithm uses a voxelization framework to voxelize the cutter helix as well as the work-piece and based on voxel intersections between them can detect the tool engagement. Furthermore, an analytical approach is used to calculate the cutting forces based on the discretized model. The results of model validation experiments on machining PMMA and Aluminum 6061 are also reported. Comparisons of the predicted and measured forces show that this digital approach can be used to accurately predict forces during machining.

Mechanistic Model for Prediction of Cutting Forces in Turning of Non-axisymmetric Parts

Most of the existing mechanistic (semiempirical) models for turning are orientated towards continuous cut and are applicable neither to non-axisymmetric parts, nor to the particular case of interrupted turning, so common in real workpieces. Some commercial software packages which simulate machining process by FEM enable to calculate interrupted cut. However, their high computational cost limits the simulations to a very short length of cut, hardly completing one cutting revolution.By contrast, mechanistic models are not as computationally expensive as FEM ones. Despite their limited accuracy, they give approximate estimations of cutting forces during a whole tool path. Consequently, they are extremely useful to detect critical tool path steps, adapt cutting parameters and avoid machine overload.This study presents a mechanistic model to predict orthogonal turning forces in 3 directions (XYZ), torque and power consumption along the machining path of non-axisymmetric parts. The model communicates with CAM software by automatically transferring information about tool path and geometry from the CAM to the mechanistic model in standard format, contained in CL (Cutter Location) and STL (Stereolithography) files, respectively. Thus, the model is suitable to be integrated into any commercial CAM software. The simplicity of the model, the communication with CAM and an easy-to-use interface aim to spread out the applicability of the model among machining companies. The results of the study are validated by comparing simulations to experimental turning tests.

A combined approach to tool path generation for flank milling of impeller blades with non-developable ruled surfaces

Impeller blades are often constructed by non–developable ruled surfaces. Due to their twisted feature, the application of flank milling to these blades would inevitably cause significant interference between the cutter edge and the machined surfaces. In view of the advantages of flank milling operations, this paper proposes a combined approach to flank milling these blade surfaces with acceptable precision and fairly high efficiency. Centring on the minimisation of the interference, the non–developable blade surface is divided into a number of strips, the cutter profile is modified accordingly, and then the tool paths are calculated strip by strip. Along with the basic idea, related issues are investigated in detail focusing on the strip width determination, cutter profile modification, and cutter location calculation. For practical use of the proposed approach, necessary algorithms are also provided. Finally, a case study is presented, together with numerical simulation of the cutting process. The results show that the proposed approach is not only feasible but also much more efficient than the conventional point milling method. [Received 6 November 2013; Revised 16 June 2014; Accepted 2 October 2014]

A five-axis tool length compensation method using the numerical control program with macro variable

Most of the early five-axis computer numerical control systems do not have the function of five-axis tool length compensation. When the tool length changes in five-axis machining, the original numerical control program will not be able to continue to be utilized. At the moment, the cutter location file needs to be post-processed again to generate the new numerical control program through modifying the value of the pivot length. In order to solve the above problem, this article proposes a five-axis tool length compensation method using the numerical control program with macro variable for five-axis machine tools with dual rotary heads or with a rotary head and table. First, by analyzing the structure of the specific five-axis machine tool, a kinematics model of the five-axis machine tool was established and solved. Second, a post-processor for the five-axis machine tool was developed, and the pivot length as a macro variable was written into the numerical control program through the post-processor. Moreover, the five-axis tool length compensation was implemented by modifying the macro variable of pivot length in the numerical control program. Finally, a turbine blade was machined on a five-axis machine with a rotary head and table, the generated cutter location file was converted into the numerical control program with macro variables by using the proposed method, and the generated numerical control program was simulated on the solid cutting simulation software. Simulated results verify the effectiveness of the proposed method. In addition, the proposed method can be widely applied to early five-axis machine tools without the function of five-axis tool length compensation.

Optimization of the setup position of a workpiece for five-axis machining to reduce machining time

Five-axis machining is commonly used for complicated features due to its advantage of rotary movement. However, the rotary movement introduces nonlinear terms in the kinematic transform. The nonlinear terms are related to the distance between the cutter location (CL) data and the intersection of the two rotary axes. This research studied the possible setup positions after the toolpaths have been generated, and the objective was to determine the optimal setup position of a workpiece with minimal axial movements to reduce the machining time. We derived the kinematic transform for each type of five-axis machines, and then, defined an optimization problem that described the relationship between the workpiece setup position and the pseudo-distance of the axial movements. Eventually, an optimization algorithm was proposed to search for the optimal workpiece setup position within the machinable domain, which is already concerned with over-traveling and machine interference problems. In the end, we verified the optimal results with a case study with a channel feature, which was real cutting on a table-table type five-axis machine. The results show that we can save the axial movements up to 16.76% and the machining time up to 10.70% by setting up the part at the optimal position.

Current State of the Art of Multi-Axis Control Machine Tools and CAM System

<div class=""abs_img""><img src=""[disp_template_path]/JRM/abst-image/00260005/01.jpg"" width=""300"" />Asymmetric curved grooving</div> Multi-axis numerical control (NC) machine tools such as 5-axis control machining centers and 5-axis control multi-tasking machines are widely used in machine shops. NC data, which are prepared using computeraided manufacturing (CAM) systems, are used with multi-axis control NC machine tools that have a variety of advantages. This article describes the advantages ofmulti-axis control machining. The structure of CAM systems used for multi-axis control machining and the important role of collision avoidance in generating cutter location (CL) data are then explained. The transformation of CL data to NC data for use in machining, which is performed by a post-processor, is presented. Finally, an efficient machining method and unique shape creation via 6-axis control machining are explained. </span>

Post Processing for Five-Axis Machine Tools with Pose Error Compensation

This paper describes the enhancement of the machining precision of 5-axis machine tools. Most post-processors did not consider the pose errors so that the processing error was increased invisibly. A post processing method with pose error compensation was proposed for table/spindle-tilting type machine tools.12 position errors and 12 rotation errors were compensated by the proposed method. Mathematical model contained pose errors which converted cutter location data into machine motion coordinates was established based on inverse kinematics and the analytical solutions of NC code were derived. The tool paths of the freeform surface machining were posted with the presented method. And the simulation experiment was carried out which verified the feasibility of the post processing method with pose error compensation. Comparison of processing error shows that the post processing with pose error compensation can effectively improve the machining accuracy by approximately 50%.

A new plunge milling tool path generation method for radial depth control using medial axis transform

A new plunge milling tool path generation method using medial axis transform is proposed to control the radial depth to improve the cutting efficiency and cutter life. Radial depth have great influences on cutting force and cutter life. Traditional plunge milling tool path generation methods such as zigzag may lead to large radial depth on some cutter locations. It is hard for these methods to judge and adjust the real radial depth. The method proposed in this paper is based on the inscribed circle of the offset contour generated by medial axis transform. Radial depth can be easily controlled in this method. Experiments showed that both the cutting efficiency and the cutter life were improved.

Study on Five-Axis NURBS Path Generation Method and Direct-Interpolation for CNC System

In this article, a new method with Non-Uniform Rational B-Spline (NURBS) technology is presented and realized in a location and federate controlling system. In the method, the tool paths and the cutter locations (CL) were represented into NURBS curves based on the same knot vector. The above CL data was firstly calculated and then transformed to five motion commands of five axes of machine through the real-time post-procession algorithm. The acceleration/deceleration controlling method is also presented to avoid the impact of machine. The proposed 5-axis spline interpolation method is realized and the experimental result of machining shows that the method is valid.

Toolpath Planning and Simulation for Cutting Test of Non-Orthogonal Five-Axis Machine Tool

Owing to NAS 979 describes a cutting test for five-axis machine center with a universal spindle, several conditions for C-type machine tool have not been defined yet. This paper proposes a cutting test for a non-orthogonal swivel head and a rotary table type five-axis machine tool (C type) to evaluate its performance. The workpiece consists of 10 machining features. These features include the multi-axis simultaneous machining patterns and the positioning machining patterns. The flat end mill cutters are applied in each machining feature. Cutter location data for the test piece was generated using a commercial CAD/CAM system (UG) and converted to five-axis NC code using a postprocessor created in UG Post Builder. This UG postprocessor is verified through the developed postprocessor utilizing the modified D-H notation. It is also verified using VERICUT® solid cutting simulation software demonstrated the veracity of the generated five-axis NC code. The machining test is applicable for a variety of five-axis machine tool configurations.

Inequity in the Face of Death.

We apply the theory of inequality of opportunity to the measurement of inequity in mortality. Using a rich data set linking records of mortality and health events to survey data on lifestyles for the Netherlands (1998-2007), we test the sensitivity of estimated inequity to different normative choices and conclude that the location of the responsibility cut is of vital importance. Traditional measures of inequity (such as socioeconomic and regional inequalities) only capture part of more comprehensive notions of unfairness. We show that distinguishing between different routes via which variables might be associated to mortality is essential to the application of different normative positions. Using the fairness gap (direct unfairness), measured inequity according to our implementation of the 'control' and 'preference' approaches ranges between 0.0229 and 0.0239 (0.0102-0.0218), while regional and socioeconomic inequalities are smaller than 0.0020 (0.0001). The usual practice of standardizing for age and gender has large effects on measured inequity. Finally, we use our model to measure inequity in simulated counterfactual situations. While it is a big challenge to identify all causal relationships involved in this empirical context, this does not affect our main conclusions regarding the importance of normative choices in the measurement of inequity. Copyright © 2014 John Wiley & Sons, Ltd.

Research on the Interference Correction in the CNC Incremental Forming Based on Iterative Algorithm

Aiming at the problem of the interference of extrusion tool handle and workpiece in the process of 5-axis CNC sheet forming, an interference correction method based on one-dimensional searching algorithm of iterative of optimal design is presented in this paper. Using the iterative algorithm, the optimal critical posture of extrusion tool which the interference is corrected with the given accuracy requirement is found out, and then the interference correction angle is calculated. Taking the cutter location point (CLP) as a rotation center, the extrusion tool is rotated the correction angle to achieved interference correction. The case study shows that this method is simple, effective and it can correct the interference with the given accuracy value.

Prediction of Cutter-Workpiece Engagement for Five-Axis Ball-End Milling

Five-axis ball-end milling technology is widely used in many industries such as aerospace, automotive and die-mold for complex surface machining. Despite recent advances in machining technology, productivity in five-axis ball-end milling is still limited due to the high cutting forces and stability. Moreover, cutting forces in machining is determined by extracting the cutter workpiece engagement (CWE) from the in-process workpiece. A discrete boundary representation method is developed. Cutter is firstly divided into disk elements along the tool axis. And in each disk element, boundary representation based exact Boolean method is introduced for extracting complex cutter-workpiece engagements at every cutter location due to its efficiency and speed over other discrete methods. Developed engagement model is proved to calculate complex engagement regions between tool and workpiece efficiently and accurately.

Study on Milling Deformation of Ruled Surface Blade

Integral impeller is the key component in aviation, aerospace and other fields, and the deformation has an important effect to the machining quality and precision of the integral impeller. Because of the complexity of the geometry and surface curvature changes for the integral impeller, and the semi suspended state during the processing, force analysis and control technology for the deformation have become the key and difficulty to realize high quality processing. In this paper, the situation about the blade machining with the finite element analysis is introduced, and the factors about the blade machining deformation is also summarized. The deformation of a single cutter location point are computed and analyzed with finite element method, and the application problems to the machining deformation with the finite element are presented.

Detecting corn tassels using computer vision and support vector machines

An automated solution for maize detasseling is very important for maize growers who want to reduce production costs. Quality assurance of maize requires constantly monitoring production fields to ensure that only hybrid seed is produced. To achieve this cross-pollination, tassels of female plants have to be removed for ensuring all the pollen for producing the seed crop comes from the male rows. This removal process is called detasseling. Computer vision methods could help positioning the cutting locations of tassels to achieve a more precise detasseling process in a row. In this study, a computer vision algorithm was developed to detect cutting locations of corn tassels in natural outdoor maize canopy using conventional color images and computer vision with a minimum number of false positives. Proposed algorithm used color informations with a support vector classifier for image binarization. A number of morphological operations were implemented to determine potential tassel locations. Shape and texture features were used to reduce false positives. A hierarchical clustering method was utilized to merge multiple detections for the same tassel and to determine the final locations of tassels. Proposed algorithm performed with a correct detection rate of 81.6% for the test set. Detection of maize tassels in natural canopy images is a quite difficult task due to various backgrounds, different illuminations, occlusions, shadowed regions, and color similarities. The results of the study indicated that detecting cut location of corn tassels is feasible using regular color images.

Study on Tool Path Generation and Direct Interpolation Method

At present, Non-Uniform Rational B-Spline (NURBS) curves are mostly used to generate arbitrary contour of a complex shape in the CAD field. In this article, a new method with NURBS technology is presented and realized in a location and federate controlling system. In the method, the tool paths and the cutter locations (CL) were represented into NURBS curves based on the same knot vector. The above CL data was firstly calculated and then transformed to five motion commands of five axes of machine through the real-time post-procession algorithm. The acceleration/deceleration controlling method is also presented to avoid the impact of machine. The proposed 5-axis spline interpolation method is realized and the experimental result of machining shows that the method is valid.