Tool Orientation Planning in Milling With Process Dynamic Constraints: A Minimax Optimization Approach

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Tao Huang ◽  
Xiao-Ming Zhang ◽  
Jürgen Leopold ◽  
Han Ding
Keyword(s):  
Tool Path ◽  
End Milling ◽  
Tool Path Generation ◽  
Optimization Approach ◽  
Path Generation ◽  
Tool Orientation ◽  
Minimax Optimization ◽  
Ball End Milling ◽  
Dynamic Constraints ◽  
Five Axis

In five-axis milling process, the tool path generated by a commercial software seldom takes the dynamics of the machining process into account. The neglect of process dynamics may lead to milling chatter, which causes overcut, quick tool wear, etc., and thus damages workpiece surface and shortens tool life. This motivates us to consider dynamic constraints in the tool path generation. Tool orientation variations in five-axis ball-end milling influence chatter stability and surface location error (SLE) due to the varying tool-workpiece immersion area and cutting force, which inversely provides us a feasible and flexible way to suppress chatter and SLE. However, tool orientations adjustment for suppression of chatter and SLE may cause drastic changes of the tool orientations and affects surface quality. The challenge is to strike a balance between the smooth tool orientations and suppression of chatter and SLE. To overcome the challenge, this paper presents a minimax optimization approach for planning tool orientations. The optimization objective is to obtain smooth tool orientations, by minimizing the maximum variation of the rotational angles between adjacent cutter locations, with constraints of chatter-free and SLE threshold. A dedicated designed ball-end milling experiment is conducted to validate the proposed approach. The work provides new insight into the tool path generation for ball-end milling of sculpture surface; also it would be helpful to decision-making for process parameters optimization in practical complex parts milling operations at shop floor.

scholarly journals Minimizing Flute Engagement to Adjust Tool Orientation for Reducing Surface Errors in Five-Axis Ball End Milling Operations

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
M. Habibi ◽  
Z. M. Kilic ◽  
Y. Altintas
Keyword(s):  
Optimization Problem ◽  
Tool Path ◽  
End Milling ◽  
Contact Point ◽  
Geometrical Approach ◽  
Tool Orientation ◽  
Ball End Milling ◽  
Surface Errors ◽  
Five Axis ◽  
Path Modification

Abstract Surface errors due to force-induced tool and workpiece deflections are one of the major errors in multi-axis machining of parts especially with thin-walled structures. Dominant approaches to reduce these surface errors are re-machining the part, feed scheduling, and tool path modification. These methods are time consuming and computationally costly, and they rely on experimental data which is used in cutting force and deflection predictions. The present paper introduces a pure geometrical approach to reduce surface errors drastically by minimizing the engagement lengths of flutes’ cutting edges when a point on the flute’s cutting edge is in contact with the design surface. The total engagement length of the flutes’ cutting edges when one of them generates a contact point on the workpiece surface is formulated and considered as the minimization objective function of an optimization problem. Tilt and lead angles, which define the tool orientation, are the design variables of the optimization problem subjected to constraints based on the geometrical requirements of the ball end milling process. The optimization problem uses the nominal tool path to generate an optimal tool path with adjusted tool orientations. The presented method is computationally inexpensive and does not need any experimentally calibrated coefficients to predict cutting forces because of the pure geometrical nature of the approach. The method is experimentally validated through five-axis ball end milling experiments in which more than 90% surface error reduction is achieved.

Study of The Tool Path Generation Method of an Ultra-Precision Spherical Complex Surface Based on a Five-Axis Machine Tool

2021 ◽  
Author(s):  
Tianji Xing ◽  
Xuesen Zhao ◽  
Zhipeng Cui ◽  
Rongkai Tan ◽  
Tao Sun
Keyword(s):  
Surface Roughness ◽  
Tool Path ◽  
Spherical Surface ◽  
Tool Path Generation ◽  
Path Generation ◽  
Tool Paths ◽  
Spherical Surfaces ◽  
Spherical Complex ◽  
Ultra Precision ◽  
Five Axis

Abstract The improvement of ultra-precision machining technology has significantly boosted the demand for the surface quality and surface accuracy of the workpieces to be machined. However, the geometric shapes of workpiece surfaces cannot be adequately manufactured with simple plane, cylindrical, or spherical surfaces because of their different applications in various fields. In this research, a method was proposed to generate tool paths for the machining of complex spherical surfaces based on an ultra-precise five-axis turning and milling machine with a C-Y-Z-X-B structure. Through the proposed tool path generation method, ultra-precise complex spherical surface machining was achieved. First, the complex spherical surface model was modeled and calculated, and then it was combined with the designed model to generate the tool path. Then the tool paths were generated with a numerically controlled (NC) program. Based on an ultra-precision three-coordinate measuring instrument and a white light interferometer, the machining accuracy of a workpiece surface was characterized, and t[1]he effectiveness of the provided tool path generation method was verified. The surface roughness of the machined workpiece was less than 90 nm. Furthermore, the surface roughness within the spherical region appeared to be less than 30 nm. The presented tool path generation method in this research produced ultra-precision spherical complex surfaces. The method could be applied to complex spherical surfaces with other characteristics.

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