Efficient CNC Machining of Freeform Surfaces From Point Cloud

Author(s):  
Mandeep Dhanda ◽  
S. S. Pande

This paper reports the development of an efficient tool path planning strategy for CNC machining of freeform surfaces directly from their representation in the form of point cloud. A grid based adaptive isoplanar tool path planning system has been designed and implemented for 3axis CNC machine using ball end mill. Inverse tool offset algorithm (IOM) is used to compute initial uniform CL (Cutter Location) grid points. From these CL points, surface slope and curvature are estimated and the forward and side step errors likely to be produced during machining are computed. The grid is subsequently refined through segmentation if the error values exceed the user defined tolerances. Adaptive grid refinement is continued iteratively till the error values converge below the prescribed tolerance limits. The grid (CL) points are sequenced to generate the final tool path. The software system developed takes the input part model as point cloud and generates post-processed CNC part program in the ISO format. The CNC part programs were extensively tested for various case studies on the commercial CNC simulator as well on the actual CNC machine. The results were compared with those from the commercial software for the same process conditions. Our system was found to generate more efficient tool paths in terms of enhanced productivity, part quality and reduced memory requirement.

Author(s):  
Mandeep Dhanda ◽  
Aman Kukreja ◽  
Sanjay Pande

Abstract This paper presents an efficient tool path planning strategy for three-axis CNC machining using curvature based segmentation (CBS) of freeform surface from its representation in the form of a point cloud. Curvature parameters estimated over the point data are used to partition the surface into convex, concave, and saddle like regions. Grid based adaptive planar tool path planning strategy is developed to machine each region separately within its boundaries. In addition to the region by region machining, strategy to stitch the obtained regions is also developed to minimize the tool lifts and tool marks. The developed region based tool path planning strategy is compared with the point cloud based adaptive planar strategy, iso-scallop strategy and commercial software for parts with various complexities. The result shows significant improvement in terms of performance parameters viz. machining time, tool path length and code length while maintaining the desired part surface quality. The proposed method is also tested by machining a real surface and analyzing its surface quality.


Author(s):  
Zezhong C. Chen ◽  
Zuomin Dong ◽  
Geoffrey W. Vickers

Some sculptured parts with complex free-form surfaces usually require expensive 5-axis CNC machining. In this work, a cost-effective and practical solution to the 5-axis sculptured part machining – 3-1/2-1/2-axis CNC machining scheme – is discussed. An automatic and optimal tool path planning system for 3-1/2-1/2-axis CNC machining is introduced. The system uses fuzzy pattern recognition method and Voronoi diagram to subdivide a complex sculptured surface into an optimal number of uniform surface patches, finds the optimal cutter/part orientation for each surface patch, and plans 3-axis CNC tool paths for them. This type of machining is carried out by rotating the part to the cutter/part orientations discretely and sequentially using a tilt-rotary table attached to the 3-axis CNC machine. Under each orientation, the corresponding surface patch is machined using the 3-axis CNC tool paths. This tool path planning system can automatically generate efficient tool paths for sculptured parts and make the 3-1/2-1/2-axis CNC machining scheme as an applicable alternative of 5-axis CNC machining method.


Author(s):  
Sumedh Ghogare ◽  
S. S. Pande

This paper reports the development of an efficient iso-scallop tool path planning strategy for machining of freeform surfaces on a three axis CNC milling center using the point cloud as the input. Boundary of the point cloud is chosen as the Master Cutter Path, using which the scallop points are computed. Adjacent side tool paths are computed using these scallop points and the path planning process is completed till the entire surface is covered. The system generates post-processed NC program in ISO format which was extensively tested for various case studies. The results were compared with the iso-planar tool path strategy from commercial software. Our system was found to generate efficient tool path in terms of part quality, productivity and storage memory.


2010 ◽  
Vol 97-101 ◽  
pp. 3382-3386 ◽  
Author(s):  
Juan Du ◽  
Xian Guo Yan ◽  
Zhi Chen

Today a new model of data transfer between CAD/CAM systems and CNC machines, called STEP-NC, is being developed by the ISO technical Committees. It overcomes the shortcomings of ISO 6983 by specifying machining processes rather than machine motion, using the object-oriented concept of working step. Although the STEP-NC contains abundant geometry information of part and associated process parameters, the tool path is general not included in the STEP-NC program. So before the beginning of the STEP-NC-compliant CNC machining, the tool path should be firstly designed. By analyzing the characteristic of STEP-NC data model for milling, a working step-oriented tool path planning method for milling was proposed in this paper, and the distributed artificial intelligence methods, namely collaborative multi-agent was employed to accomplish tool path planning. Firstly a multi-agent architecture was constructed to allow multiple agents to work cooperatively to realize automation of tool path planning, and then, the function of every kind of agent and the communication between the agents were all described in detail. At last, one test component was designed and simulated to demonstrate the capabilities of this research in the paper.


1996 ◽  
Vol 118 (1) ◽  
pp. 20-28 ◽  
Author(s):  
Rong-Shine Lin ◽  
Y. Koren

This paper presents an analytical method for planning an efficient tool-path in machining free-form surfaces on 3-axis milling machines. This new approach uses a nonconstant offset of the previous tool-path, which guarantees the cutter moving in an unmachined area of the part surface and without redundant machining. The method comprises three steps: (1) the calculation of the tool-path interval, (2) the conversion from the path interval to the parametric interval, and (3) the synthesis of efficient tool-path planning.


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