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Adaptive ball drop algorithm for toolpath generation of axisymmetric triangulated parts to eliminate overcutting

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Computer Numeric Control (CNC) milling lathes are used for pseudo-symmetric ornamental woodworking. A stereolithography (STL) part model is used for gouge-free toolpath generation using methods such as the geometry offset method and the ball drop method. The tool movement between cutter location (CL) points results in gouging of the STL part at convex intersections of triangles (path-gouging). This path-gouging can be controlled to be within user-specified tolerance, with large number of equispaced points in forward and sidestep directions. The resulting toolpath with large number of tool positions considerably slows the machining process. There exists a need for a universal method for efficiently eliminating this gouging and slowdown. In this work, a refined ball drop method is presented that eliminates path-gouging and reduces slowdown by automatically generating a variable step size in the side step and forward directions. To further optimise the number of side steps generated by the presented method, banding is used to reduce machining time while minimising un-machined material and eliminating gouging. The developed algorithm was tested on sample parts and verified by simulation and machining of wooden parts.

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The help by Mr. Mukhmeet Singh in various processes is appreciated.


This research used the facilities of State Initiated Design Centre (SIDC) for ornamental woodworking, set up under financial support from Handicrafts Division of Ministry of Textile, Government of India [Grant in Aid page no. 48 SI.No. 320]; FIST-II by Department of Science and Technology (DST), Ministry of Science and Technology, Government of India [FIST SI.No. 104 dated 30.08.2013, 3D scanner].

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Correspondence to Sanjeev Bedi.

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Jawanda, A.S., Batish, A. & Bedi, S. Adaptive ball drop algorithm for toolpath generation of axisymmetric triangulated parts to eliminate overcutting. Int J Adv Manuf Technol 99, 461–474 (2018). https://doi.org/10.1007/s00170-018-2507-7

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  • Toolpath planning optimisation
  • Three-axis CNC milling lathe
  • STL sculptured surface machining
  • Overcutting
  • Undercutting