Research On The Tool Path Generation Of Freeform Surfaces’ Off-axis Machining With Chip-load Constraints

Freeform optics has a good future in Electro-Optics system. And as a result, studyon the processing method of freeform optics has obtained high attentions. It is widelybelieved that diamond turning is a cost-effective and efficient new approach forprocessing freeform optics in the existing ones. However, how to raise processedquality and simultaneously get high processing efficiency is still a difficult problem fordiamond turning.The existing freeform optical surface machining mainly adopts coaxial machining,and the research on off-axis machining is rarely reported, with a number of problems tobe researched and solved. Due to the nearly zero machining speed in the rotary centerof traditional coaxial machining, there are larger shape errors and surface roughness inthe rotary center. So comes the off-axis machining of freeform optical surfaces inacademic circles to avoid the emerging of zero machining speed in coaxial machining.However,chip-load with larger variations will case larger change in cutting force. Andas a result,the shape errors and surface roughness will increase. This paper willprovide a tool path generation approach of freeform surfaces’ off-axis machining forchip-load constraints, which is studied to restrain the deterioration of surface qualityand accuracy caused by chip-load and to control the variety of chip-load in a expectedrange in the whole machining process.The main researches in this paper are as following. Firstly, algorithms of constantradial feeding tool path of off-axis machining and off-axis machining tool path forchip-load constraints are provided. Then, the instantaneous chip load calculating withnon-zero hook angle is studied. And we also discuss a machined.Surface topography meshing generation approach in polar coordinates. We takeinto account the Fast Tool Servo’s low-rigidity influence on machining error. Two dimension wavelet analysis is used to verify the three-dimension surface topographygenerated by simulation. The component of surface roughness and surface error isobtained by decomposition and re-construction of the three-dimensional data of thepart surface. Also the influencing rule of off-axis machining parameters and differentlateral displacement on the surface quality and process accuracy is studied byemulation analysis. By contrast, the influence on the surface topography is discussed ofconstant radial feeding tool path of off-axis machining and off-axis machining toolpath for chip-load constraints. The improvement of processing efficiency by off-axismachining tool path for chip-load constraints is also studied. In the experiment offreeform surfaces’ diamond turning by FTS, many freeform surfaces are obtainedwhile clamping and cutting once. What’s more, the surface roughness of the surfacesmachined is measured and verified.The results of the simulation analyses and experimental research show that theinfluence of off-axis machining on freeform surface morphology is related to thelateral displacement of the machining. According to the analyses of loop surfaces, it isnot hard to find that with the increment of the lateral displacement, the surface qualityand machining accuracy improves at first and then decreases. Another findings is thatthe processing efficiency of off-axis machining is dramatically higher than that ofcoaxial machining. What’s more, the tool path generation approach of off-axismachining for chip-load constraints improves the surface quality and machiningaccuracy significantly. It follows that the processing efficiency of tool path generationapproach of off-axis machining for chip-load constraints improves dramatically higherthan the traditional ones while processing the same surface morphology. In conclusion,compared with the traditional machining tool path generation approach, the tool pathgeneration approach of off-axis machining for chip-load constraints improvesobviously in surface morphology quality and processing efficiency.