On-Machine Inspection Planning And Evaluation Of Form Error For Case Workpieces

Design,manufacturing and inspection are the three main producing procedures in any industrial area.Relying on the CAD/CAM system,modern technology have transformed the tedious manual drawing into computer-aided design and replace manual operations as much as possible by the CNC machining.With the increasingly fierce competition of the global market,quality control for products in the manufacturing sector has become one of the most prominent problem.Usually at the end of processing,workpieces need to be measured with the help of auxiliary equipments,but due to the second clamping,it will inevitably reduce the manufacturing precision and extend the processing time.In view of this,the concept of on-machine measurement comes into being.In this thesis,taking the form error of case workpieces as the research object,the following contents are studied in order to plan their inspection strategy and develop the error evaluation approach:Firstly,the touch trigger probe and its working principle were analyzed,after summing up a number of factors which affected the accuracy,based on the internal structure of probes,the mathematical model of pre-travel error whose influencing power was larger was established,and on this basis,the main parameters of this model were analyzed by simulation;then the theory of probe calibration and radius compensation was buildt up.Also,the calibration program codes and a work interface were developed on VB6.0.Secondly,the main extraction information of basic geometric elements for on-machine measurement was defined,also operating parameters of the probe were set,and under the condition of basic geometric elements' fitting,the method of establishment and alignment for the workpiece coordinate system was proposed;then the relevant sampling strategy was studied,and through mathematical statistics,Hammersley sequence and Ant Colony Algorithm,the determination of number,the arrangement of distribution and path optimization for measurement points were finished;for general prismatic and cylindrical workpieces,the corresponding avoidance strategy was put forward.Then,based on VB6.0,the secondary system development of SolidWorks was realized,and planning system codes for the two-dimensional form error of case workpieces were completed,also,an overall design of the software system was highlighted,ie,functional analysis,function module design and related procedures;additionally a virtual CNC simulation measuring platform was built up.In addition,the error evaluation of flatness and cylindricity was carried out by means of plant growth simulation algorithm,later,the basic theory of this algorithm was explained,and an mathematical model based on the minimum-area principle of error evaluation was established;th-en based on Matlab and VB6.0,the corresponding software codes and user's interface were developed,also,the evaluation results were analyzed;at last,the effectiveness of related algorithms were verified by the experiment of milling and on-machine measurement for planes.Finally,a summary and a prospect for this thesis were made.