A Curve-Based Approach for Clean-up Machining

Geometric Modelling, 2001

Presented in the paper is a new approach to tool-path generation for sculptured surface machining. In the proposed C-space approach, the geometric data describing the design-surface, stock-surface and tool shape are transformed into C-space elements, and then, all the tool-path generation decisions are made in the configuration space (C-space). The C-space approach provides a number of distinctive features suitable for sculptured surface machining, including: I) gouge-free tool-paths; 2) uncut handling; 3) balanced cuttingload; 4) smooth cutter movement; 5) collision-free tool-path. F. Kimura (ed.), Geometric Modelling

The International Journal of Advanced Manufacturing Technology, 2009

This paper presents a new tool-path-generating methodology for five-axis machining of 3D curves that are projected from 2D planes onto free-form part surfaces. In our approach, the scanning for mapping is planned directly on parameter domain. The DXF pattern was scaled to parametric dimension and transferred to parametric domain, and thus, all entity coordinates were transferred from X,Y to (u,v). By using a B-spline surface equation algorithm, the projected curves were obtained on a free-form surface for tool path generation. 2D pattern models were delineated with the DXF format; 3D free-form surfaces were delineated with the STEP-AP214 format and the "B_Spline_-surface_with_knots" entity was used to define the free-form B-spline surface geometry. Windows® based software written in Borland® Delphi has been developed according to the presented algorithm. Cutter contact (CC) data and surface normals for CC points were obtained with this software. The obtained CC data and surface normal data were transferred to cutter location (CL) data and the tool path verification is obtained by simulation successfully.

Machining Impossible Shapes, 1999

Presented in this paper is a new approach to three-axis NC tool path generation for sculptured surfaces. In the proposed curve-based approach, the gouge-free tool paths are generated from a polyhedral model ofSTL form. The polyhedral model is offset using loealoffsetting scheme. Then, the offset elements such as triangular facets, trimmed cylinders, and trimmed spheres are sliced by a series of drive planes. The curve segments on a drive plane are sorted, trimmed and linked, while the concave gouge is removed during the trimming process. The method is implemented on a PC, and some illustrative examples are provided in this paper. The main advantage of the proposed method is that a polyhedral model can be machined without any concave and convex gouge, especially on a NC machine supporting NURBS interpolation.

The paper presents a new combination of two methods for tool path generation for five-axis machining proposed earlier by the authors. The first method is based on the grid generation technologies whereas the second method exploits the space-filling curve approach. Combination of the two techniques is superior with regard to the conventional methods and with regard to the case when the two methods are applied independently. In particular the algorithm allows us to generate tool paths for workpieces with complex boundaries as well as when the scallop and gouging constraints are changing sharply and irregularly. In this case the conventional methods are inefficient, whereas the proposed algorithms construct the required tool path and reduce the length of the path and the time of the machining. The numerical experiments are complemented by the real machining as well as by the test simulations on the Unigraphics 18.

Procedia CIRP, 2015

This paper gives a detailed explanation of the project, related to reverse engineering, which was conducted by the authors of this paper. The project was based on direct machining, which is done by generating efficient tool paths directly from point cloud data, stored in STL format. The primary objective was to achieve high efficiency in the machining of free-form surface geometries, having complex machining areas. Reverse engineering traditionally involves surface fitting. However, it has several drawbacks. To overcome these drawbacks, the concept of direct machining is used. This skips the surface fitting process and consists of three main steps: digitizing, tool path generation and machining. Therefore, an algorithm to generate tool paths for direct machining was developed. The algorithm works for three-axis milling, using a ball-end mill cutter. It includes dividing the surface into ranges and generating B-spline curves which are best fit curves within each range. These curves are the required tool paths. A few case studies have also been conducted using this algorithm.

Computer-Aided Design, 1997

Presented in the paper is a new approach to 3-axis NC tool-path generation for sculptured surface machining. In the proposed Cspace approach, the geometric data describing the design-surface and stock-surface are transformed into C-space elements, and then, all the tool-path generation decisions are made in the co&urution space (C-space). The C-space approach provides a number of distinctive features suitable for high speed machining of dies and moulds, including: (1) gouge-free and collision-free tool-paths; (2) balanced cutting-loads; (3) smooth cutter movements; and (4) verification mechanisms. It is suggested, with some supportive results, that the Z-map model might be a suitable representation scheme for implementing the Cspace method. Also discussed are other implementation as well as future research directions.

Computer-Aided Design, 2004

This article presents a new format of tool path polynomial interpolation in 5-axis machining. The linear interpolation usually used produces tangency discontinuities along the tool path, sources of decelerations of the machine tool whereas polynomial interpolation reduces the appearance of such discontinuities. The new format involves a faster tool path and a better surface quality. However, it imposes a modification of the process so as to take the interpolation format and the inverse kinematics transformation (necessary to 5-axis machining) into account. This article deals with the geometrical problem of tool path calculation. Validation tests are detailed. They show that profits concern the reduction of machining time as well as the quality of the machined surfaces. Indeed, the trajectory continuity avoids the appearance of marks and facets. q

International Journal of Production Research, 2016

We propose a new framework for toolpath generation for five-axis machining of part surfaces represented by the StereoLithography (STL) format. The framework is based on flattening the STL part and generation of adaptive curvilin-ear toolpaths. The corresponding cost functions, designed to represent the accuracy and the efficiency of the toolpath, are scalar functions, such as the curvature, kinematic error, rotation angles, machining strip or material removal rate or a vector field when the tool moves along a curvilinear path partly or even entirely aligned with directions considered to be optimal. The adaptive toolpath exploits grid generation methods and biased space-filling curves, combined with adaptation to the boundary and the domain decomposition. The proposed methodology of the adaptive curvilinear toolpath (ACT) has been tested on a variety of STL surfaces, including a case study of STL dental parts. Machining crowns/ implants for four basic types of human teeth, molar, premolar, canine and incisor, has been considered and analysed. The reference methods are the standard iso-parametric path, MasterCam toolpath, and advanced methods of NX9 (former UG). The experiments show that there is no universal sequence of steps applicable to every surface. However, a correct choice of the tools available within the proposed ACT-framework always leads to a substantial improvement of the tool-path, in terms of its length and the machining time.

The International Journal of Advanced Manufacturing Technology, 2014

The aim of this study is to propose a five-axis toolpath smoothing method in order to improve the quality of machined surfaces. Currently, toolpaths are commonly computed from CAD models presenting small geometrical discontinuities. These discontinuities may be caused by an insufficient quality of the CAD model (geometrical discontinuities) and the use of meshed surfaces (e.g., stereolithography (STL) files). Normally, CAM systems generate linearly interpolated toolpaths. CNC options are then used on the machine to smooth the toolpath. The geometrical discontinuities of CAD models and linear toolpath interpolation may induce an unsmooth toolpath. This type of toolpath causes marks on the machined workpiece even if classical enhanced CNC options are used. Generally, these marks are unacceptable for the functionality of the workpiece. To reduce this problem, this study proposes a method to efficiently smooth toolpaths and consequently improve the obtained surface quality. The proposed method may be employed with high-end controllers commonly used on five-axis CNC machines. First, a five-degree polynomial interpolation method is presented. This interpolation is computed to ensure geometrical continuity in the slope and curvature of the obtained toolpath. Next, a concatenation method is proposed to reduce the size of the CNC program and to improve the toolpath smoothness. Moreover, the purpose of this concatenation is to obtain an optimized repartition of points along the toolpath. Furthermore, in a reverse engineering process, this method avoids surface reconstruction, decreasing the process time and improving the quality of the obtained surface. The efficiency of these methods is validated by the machining of biomedical prostheses. The CAD model used for the test is a meshed surface.

International Journal Advanced Manufacturing Technology , 2015

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.