Cutter Location Surface Research Articles

Tool-path Generation of Multi-axis Machining for Subdivision Surface

An algorithm of multi-axis NC tool-path generation for subdivision surfaces is proposed. The algorithm includes two steps: model building and tool path generation. In the section of model building, in order to obtain the deformed surface, the deformation vector is computed which is associated with the curvature and the slope of cutter location surface. In the procedure of tool path generation, the slicing procedure is adopted to get the CL points. In addition, the inversely converted method is used. The method is tested by some examples with actual machining. The results show that the method can effectively reduce the error of the scallop height for subdivision surface and obtain the better shape and quality. In addition, the computational complexity and is scalable and robust.

Iso-Scallop Controlled Tool Path Generation for Free-Form Surfaces Based on Level Set Method

The proposed tool-path planning algorithm in this paper is based on the data generated by Level Set Method, which can naturally eliminate self-intersections of the offset surface during ball-end milling. The offset Cutter Location (CL) surface can be represented by a set of discrete points which can be obtained from linear interpolation of the Signed Distance Function. Parts of the points on CL surface are filtrated according to the fitting error to form CL paths, while the path intervals are determined according to the iso-scallop rule. This strategy will guarantee perfect surface quality with good uniformity as well as high efficiency. The determination and checking algorithms of CL points are both comprehensive and concise, which can be easily implemented.

Study on discrete form algorithm of cutter location surface in CNC milling of freeform surface

A novel discrete form algorithm of cutter location surface is proposed to produce 3D tool paths in computer numerical control (CNC) 3-axis milling of freeform surface. As compared with the normal form algorithm, it can be applied to the complex curve surface and irregular shape cutter. The research objective is to identify the discrete form algorithm of cutter location surface. First, the cutter working surface and the machined curve surface were dispersed to be two-point clouds, respectively. Next, the tangency mode of their point clouds was established to produce the cutter location surface. Then, CNC milling experiments were carried out to identify the machined form errors for discrete and normal form algorithms. Finally, the effects of discrete form parameters and workpiece surface posture were investigated on the discrete form accuracy. Experimental results show that the machined form errors for the discrete form algorithm is identical to that for normal form algorithm, but its large form errors are mainly distributed on the large workpiece slope location. On decreasing searching interval and lattice grid size, the discrete form accuracy increases. Moreover, the workpiece surface posture greatly influences the discrete form accuracy, but there exists such a workpiece surface posture that the best discrete form accuracy may be achieved. It is concluded that the discrete form algorithm is feasible to produce the cutter location surface for CNC milling of freeform surface by controlling lattice grid size and searching interval and choosing a suitable workpiece surface posture.

Study on Computer-Aided Process Planning of Mold Part Machining

In this paper, an algorithm for projecting the machining remained area in a prior machining to the cutter location surface for the next machining is proposed. This projection is useful for automating some process planning task of mold machining, such as the determination of the milling region in the following machining operations. In our proposed algorithm, the milling simulation and the inverse offsetting of the result shape of the simulation is required. Most milling simulation programs use discrete Z-map models for representing the workpiece shape. In this paper, an algorithm for inverse offsetting the Z-map model is discussed. Our algorithm computes dense zig-zag curves covering the Z-map model, then it generates the swept volume of the inversed cutter moving along the curves to obtain their Minkowski sum shape. Proposed algorithm is implemented and an experimental process planning assistance program using this technology is demonstrated.

CL surface deformation approach for a 5-axis tool path generation

In this paper, the 5-axis tool path that has been generated on the cutter contact (CC) surface is generated on the cutter location (CL) surface, and the CL surface deformation approach that inversely deforms the 3-axis tool path generated on the deformed CL surface to a 5-axis tool path is introduced. The CL point computation and interference check based on the CL surface is faster and more robust than that based on the CC surface. The proposed CL surface deformation approach can be used if the orientation of the cutter is predefined. By the CL surface deformation approach, the 5-axis tool path generation time can be reduced to that of a 3-axis, since the complexity of a CL surface deformation is linear and because the 3-axis tool path generation and gouge removal algorithms are used at the deformed CL surface .

A CL surface deformation approach for constant scallop height tool path generation from triangular mesh

In this paper, we present a cutter location (CL) surface deformation approach for constant scallop height tool path generation from triangular mesh. The triangular mesh model of the stereo lithography (STL) format is offset to the CL surface and then deformed in accordance with the deformation vectors, which are computed by the slope and the curvature of the CL surface. In addition, the tool path, which is computed by slicing the deformed CL surface, is inversely deformed by those same deformation vectors to a tool path with a constant scallop height. The proposed method is implemented, and a tool path is generated and tested by simulation and by numerical control (NC) machining. The scallop height was found to be constant over the entire machined surface, demonstrating much better quality than that of mesh slicing, under the same constraints for machining time.

A new approach to z-level contour machining of triangulated surface models using fillet endmills

Precision z-level contour machining is important for various computer-aided manufacturing (CAM) applications such as pocket machining and high-speed machining (HSM). This paper presents a new z-level contour tool-path generation algorithm for NC machining of triangulated surface models. Traditional approaches of z-level machining rely on the creation of accurate CL (cutter location) surfaces by surface offsetting or high-density z-map generation, which is computationally expensive and memory demanding. In contrast, this paper presents a novel approach to the generation of CL data directly from the section polygon of a triangulated surface model. For each polygon vertex of the contour, the offset direction is determined by the normal to the edge, while the offset distance is not fixed but is determined from the cutter shape and the part surface. An interference-free tool-path computation algorithm using fillet endmills is developed. Since there is no need to create a complete CL surface or high-density z-map grids, this proposed method is highly efficient and more flexible, and can be directly applied to triangulated surfaces either tessellated from CAD models, or reconstructed from 3D scanned data for reverse engineering (RE) applications.

Triangular mesh offset for generalized cutter

In 3-axis NC (Numerical Control) machining, various cutters are used and the offset compensation for these cutters is important for a gouge free tool path generation. This paper introduces triangular mesh offset method for a generalized cutter defined based on the APT (Automatically Programmed Tools) definition or parametric curve. An offset vector is computed according to the geometry of a cutter and the normal vector of a part surface. A triangular mesh is offset to the CL (Cutter Location) surface by multiple normal vectors of a vertex and the offset vector computation method. A tool path for a generalized cutter is generated on the CL surface, and the machining test shows that the proposed offset method is useful for the NC machining.

Sculptured surface machining using triangular mesh slicing

In this paper, an optimized procedure for tool path generation in regional milling is presented. The proposed procedure computes tool paths by slicing a CL-surface (Cutter Location surface), which is a triangular, mesh containing invalid triangles. Tool path generation consists of two steps: firstly, it obtains a set of line segments by slicing the triangular mesh with two-dimensional geometric elements (slicing elements), and, secondly, it extracts a valid tool path from the line segments by removing invalid portions. Two algorithms based on the slicing elements are presented: a ‘ line projection’ algorithm based on the plane sweeping paradigm, which works efficiently by using the characteristics of a monotone chain; and a ‘ curve projection’ algorithm for the projection of curves, which transforms the curve projection problem into a line projection problem by mapping the XYZ-space of the cylinder surface to the TZ-plane of the unfolded cylinder. The proposed procedure has been implemented and applied to tool path generation in regional milling. Performance tests show the efficiency of the proposed procedure.

Tool-path generation from measured data

Presented in the paper is a procedure through which 3-axis NC tool-paths (for roughing and finishing) can be directly generated from measured data (a set of point sequence curves). The rough machining is performed by machining volumes of material in a slice-by-slice manner. To generate the roughing tool-path, it is essential to extract the machining regions (contour curves and their inclusion relationships) from each slice. For the machining region extraction, we employ the boundary extraction algorithm suggested by Park and Choi (Comput.-Aided Des. 33 (2001) 571). By making use of the boundary extraction algorithm, it is possible to extract the machining regions with O(n) time complexity, where n is the number of runs. The finishing tool-path can be obtained by defining a series of curves on the CL (cutter location) surface. However, calculating the CL-surface of the measured data involves time-consuming computations, such as swept volume modeling of an inverse tool and Boolean operations between polygonal volumes. To avoid these computational difficulties, we develop an algorithm to calculate the finishing tool-path based on well-known 2D geometric algorithms, such as 2D curve offsetting and polygonal chain intersection algorithms.

Fast inverse offset computation using polygon rendering hardware

Mold and die parts are usually fabricated using 3-axis numerically controlled milling machines with ball-end, flat-end or round-end cutters. The cutter location (CL) surface representing a trajectory surface of the cutter's reference point when the cutter is slid over a part is important for preventing the gouging problem. This surface is equivalent to the inverse offset shape of the part, which is the top surface of the swept volume of the inverse cutter moving around the part surface. The author proposes a fast computation method of the inverse offset shape of a polyhedral part using the hidden-surface elimination mechanism of the polygon rendering hardware. In this method, the CL surface is obtained by simply rendering the component objects of the swept volume. An experimental program is implemented and demonstrated.