Papers by Author: Li Qiang Zhang

Abstract: Aiming at the corner connection speed of continuous small blocks caused by their angle influences, the speed of transition is low and easy to cause vibration of machine tool. Research on the mathematical model of constant-speed linking of multiple periods is established by using the arc to smooth continuous small blocks, combined with the transition’s geometrical constraint, motion constraint, parameter calculation, the theory is to realize the method of high-speed interpolation of constant-speed linking of multiple periods. The result reveals that the effectiveness and practicability of the proposed method.

Abstract: Five-axis high speed machining can improve the efficiency and accuracy obviously, but the machining errors and tool interference are likely to happen due to the complexity of tool motion. So the collision detection and verification of tool path are very important and necessary before machining the part. Using a combination of process simulation and collision detection based on image analysis, a rapid detection approach is developed in this research. The geometric model provides the cut geometry for the collision detection and records a dynamic geometric information for in-process workpiece. For the precise collision detection, a strategy of image analysis method is developed in order to make the approach efficient and maintian a high detection precision. An example of five-axis machining propeller is studied to demonstrate the proposed approach.

Abstract: Collision detection is a critical problem in five-axis high speed machining. Using a combination of process simulation and collision detection based on image analysis, a rapid detection approach is developed. The geometric model provides the cut geometry for the collision detection and records a dynamic geometric information for in-process workpiece. For the precise collision detection, a strategy of image analysis method is developed in order to make the approach efficient and maintian a high detection precision. An example of five-axis machining propeller is studied to demonstrate the proposed approach. It has shown that the collision detection task can be achieved with a near real-time performance.

Abstract: This paper presents process optimization for the five-axis milling based on the mechanics model explained in Part I. The process is optimized by varying the feed as the tool-workpiece engagements. The linear and angular feedrates are optimized by sequential quadratic programming. Sharp feedrate changes may result in undesired feed-marks on the finished surface. The adopted step is to update the the original CL file with optimized and filtered feedrate commands. The five-axis milling process is simulated in a virtual enviroment, and the resulting feedrate outputs are stored at each position along the tool path. The new feedrate profiles are shown to considerably reduce the machining time while avoiding process faults.

Abstract: In free-form surface machining, it is essential to optimize the feedrate in order to improve the machining efficiency. This work is the first of a two part paper on cutting force prediction and feedrate optimization for five-axis milling. Conservative cutting parameters have been mostly used since there was a lack of physical models and optimization tools. Part and tool deflections under high cutting forces may result in poor part quality. The extracted cutter workpiece engagements are used as input to a force prediction model. The predicted cutting forces are shown to be in reasonable agreement with those collection during a roughing operation on a dual blades part.

Abstract: 5-axis milling operations are used in industries such as aerospace, automotive and mold for free-form surface machining. In these process, surface quality and material removal rate are of very important. Conservative cutting parameters have been mostly used since there was a lack of physical models and optimization tools. Part and tool deflections under high cutting forces may result in unacceptable part quality. The overall goal of this research is the integration of geometric and mechanistic models for cutting process simulation and feedrate optimization. The extracted cutter workpiece engagements are used as input to a force prediction model. The model predictions for cutting forces and feedrate optimization are compared and verified by experimental results.

Abstract: In free-form surface machining, it is essential to optimize the feedrate in order to improve the machining efficiency. Conservative constant feedrate values have been mostly used since there was a lack of physical models and optimization tools for the machining processes. The overall goal of this research is the integration of geometric and mechanistic milling models for force prediction and feedrate scheduling for free-form surface machining. For each tool move a geometric model calculates the cutting geometry parameters, then a mechanistic model uses this information with the constraint force to calculate desired feedrates. The feedrate is written into the part program. When the integrated modeling approach was used, it was shown that the machining time can be decreased significantly along the tool path. Production time in machining propeller example was reduced to 35% compared to constant feedrate cases.

Abstract: Five-axis NC machining tools can improve the efficiency and accuracy obviously in today’s machining industries, but the machining errors and tool interference are likely to happen due to the complexity of tool motion. So the verification of the tool path is very important and necessary before machining the part. A new algorithm for 5-axis machining verification based on the swept volume has been presented in the paper. Based on the machine tool path and the cutter geometry, the cutter’s instantaneous swept profile is determined. By integrating the intermediate swept volume, the cutter’s swept envelope can be constructed and applied to NC verification. The algorithm has been implemented through Visual C++ and OpenGL language on Windows XP platform; a few examples are to verify the reliability of the proposed algorithms effectively. The experiment results indicate that the proposed method is superior to the traditional methods on the processing time and image quality. This proposed algorithm can be further applied to machining error analysis, collisions interference and NC path optimization, etc.

Abstract: Five-axis CNC machining tools can improve the efficiency and accuracy obviously in machining industries, but the machining errors and tool interference are likely to happen due to the complexity of tool motion. So the verification of the tool path is very important and necessary before machining the part. A new algorithm for 5-axis machining verification based on the stencil buffer has been presented in the paper. Based on the tool path and the cutter geometry, the cutter’s swept profile is determined. The swept envelope is subtracted from the sliced blank part model by using the stencil buffer. Considering the complexity of five-axis tool motions, examples are necessary to verify the reliability of the proposed algorithms. The experiment results indicate that the method is superior to the traditional methods on the processing time and the image quality. This proposed method can further be applied to machining error analysis, collisions interference.