The aim of tool path planning is to maximize the efficiency against some given precision criteria. In practice, scallop height should be kept constant to avoid unnecessary cutting, while the tool path should be smooth enough to maintain a high feed rate. However, iso-scallop and smoothness often conflict with each other. Existing methods smooth iso-scallop paths one-by-one, which make the final tool path far from being globally optimal. This paper proposes a new framework for tool path optimization. It views a family of iso-level curves of a scalar function defined over the surface as tool path so that desired tool path can be generated by finding the function that minimizes certain energy functional and different objectives can be considered simultaneously. We use the framework to plan globally optimal tool path with respect to iso-scallop and smoothness. The energy functionals for planning iso-scallop, smoothness, and optimal tool path are respectively derived, and the path topology is studied too. Experimental results are given to show effectiveness of the proposed methods.
Last decade has seen a great deal of literature on tool path planning for free-form surfaces, such as iso-parametric method @cite_25 @cite_12 @cite_1 , iso-planar method @cite_19 @cite_9 @cite_18 , iso-scallop method @cite_23 @cite_32 @cite_13 @cite_17 @cite_3 @cite_8 @cite_21 , iso-phote method @cite_4 and C-space method @cite_33 , to name a few. Surveys of much more work about tool path planning research can be found in @cite_0 @cite_30 . Since we aim at optimal tool paths with respect to iso-scallop and smoothness, we put special interest in the iso-scallop method, which means the height of the points at the scallop curves remains as high as a given value so that the tool path has no unnecessary cutting. Conventionally, constant scallop height is obtained by varying the offset magnitude along each path. A mathematical method for generating iso-scallop tool paths following such strategy was first proposed by @cite_23 . Afterwards, methods to improve the computing efficiency @cite_2 @cite_3 and accuracy @cite_16 @cite_17 @cite_21 were proposed. In 2007, Kim @cite_27 reformulated the iso-scallop tool path as geodesic parallel curves on the design surface by defining a new Riemannian metric.
@cite_30 @cite_3 @cite_2 @cite_18 @cite_4 @cite_8 @cite_21 @cite_23 @cite_17 @cite_32 @cite_19 @cite_27 @cite_16 @cite_25 @cite_12 @cite_33 @cite_9 @cite_1 @cite_0 @cite_13
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A novel approach for the NC tool-path generation of free-form surfaces is presented. Traditionally, the distance between adjacent tool-paths in either the Euclidean space or in the parametric space is kept constant. Instead, in this work, the scallop-height is kept constant. This leads to a significant reduction in the size of the CL (cutter location) data accompanied by a reduction in the machining time. This work focuses on the zig-zag (meander) finishing using a ball-end milling cutter. This paper presents a novel approach for generating efficient tool paths in machining free-form surfaces. Concept of iso-phote is used to facilitate tool-path generation. An iso-phote is defined as a region on a surface where the normal vector does not differ by more than a prescribed angle from a fixed reference vector. The boundary curves of the iso-phote, called iso-inclination curves, are numerically generated and are served as the initial master tool paths. These iso-inclination curves are then projected to a 2D plane which is perpendicular to the fried reference vector. 2D curve offsetting of the projected iso-inclination curve is then performed. The resulted 2D offset curves are projected back to 3D surface to form final tool paths. The resulted tool paths can guarantee the satisfaction of machining tolerance requirements. A comparison study of this iso-phote based machining with the conventional iso-parametric machining and the iso-planar machining shows favorite result for the new approach. Numerically controlled milling is the primary method for generating complex die surfaces. These complex surfaces are generated by a milling cutter which removes material as it traces out pre-specified tool paths. The accuracy of tool paths directly affects the accuracy of the manufactured surface. The geometry and spacing of the tool paths impact the scallop height and time of manufacturing respectively. In this paper we propose a new method for generating NC tool paths. This method gives the part programmer direct control over the scallop height of the manufactured surface. The method also provides options to the part programmer for generating a variety of tool paths based on practical metrics such as tool path length, tool path curvature and number of tool retractions. An algorithm for three-axis NC tool path generation on sculptured surfaces is presented. Non-constant parameter tool contact curves are defined on the part by intersecting parallel planes with the part model surface. Four essential elements of this algorithm are introduced: initial chordal approximation, true machining error calculation, direct gouge elimination, and non-constant parameter tool pass interval adjustment. A software implementation of this algorithm produces graphical output depicting the tool path superimposed over the part surface, and it outputs cutter location (CL) data for further post-processing. Several applications examples are presented to demonstrate the capabilities of the algorithm. The results of this technique are compared to those generated from a commercially available computer-aided manufacturing program, and indicate that equivalent accuracy is obtained with many fewer CL points.