High precision and efficiency robotic milling of complex parts:Challenges,approaches and trends

Due to the advantages of large workspace,low cost and the integrated vision/force sensing,robotic milling has become an important way for machining of complex parts.In recent years,many scholars have studied the problems existing in the applications of robotic milling,and lots of results have been made in the dynamics,pose planning,deformation control etc.,which provides theoretical guidance for high precision and high efficiency of robotic milling.From the perspective of complex parts robotic milling,this paper focuses on machining process planning and control techniques including the analysis of the robot-workspace,robot trajectory planning,vibration monitoring and control,deformation monitoring and compensation.As well as the principles of these technologies such as robot stiffness characteristics,dynamic characteristics,chatter mechanisms,and deformation mechanisms.The methods and characteristics related to the theory and technology of robotic milling of complex parts are summarized systematically.The latest research progress and achievements in the relevant fields are reviewed.It is hoped that the challenges,strategies and development related to robotic milling could be clarified through the carding work in this paper,so as to promote the application of related theories and technologies in high efficiency and precision intelligent milling with robot for complex parts.

CA Investment Casting Process of Complex Castings

CA (Computer aided) investment casting technique used in superalloy castings of aerospace engine parts was presented. CA investment casting integrated computer application, RP (Rapid Prototyping) process, solidification simulation and investment casting process. It broke the bottle neck of making metal die. Solid model of complex parts were produced by UGII or other software, then translated into STL(Stereolithography) file, after RP process of SLS(Selective Laser Sintering), wax pattern used in investment casting can be acquired without metal die in short time. These can reduce period and cost greatly of complex superalloy parts development of engine. The key processes of CA investment casting were discussed. The accuracy of model translation should match that of RP system. Choice of RP material, surface polishing, sintering parameter plays important role in RP process. Other processes, like solidification simulating and optimization of gate system were introduced. The conclusion was that complex parts can be produced by CA investment casting with lots of advantages. The accuracy of castings can reach CT5～7,and the smoothness can get Ra3～13 mm. These parts of engines worked well.

Additive manufacturing of pure copper via vat photopolymerization with slurry

Stereolithography(SLA)combined with a two-step post-processing method“oxidation−reduction”was developed to fabricate pure copper with high complexity.The copper slurries for SLA were prepared,and particularly the influence of volume fraction of copper on the properties of copper slurries was investigated.In the two-step post-treatment process,organics were removed by oxidation and copper powder was oxidized simultaneously,and then the oxidized copper was reduced into highly reactive copper particles,improving the sintering activity of the copper green body and enhancing the relative density of the sintered part.The results show that curing depth of the copper slurries decreased with the increase of volume fraction of copper.The viscosity of the pure copper slurry rises exponentially as the volume fraction of copper exceeded 50%.The highest volume fraction of pure copper slurry for SLA is 55%.The specimens exhibited an increase in hardness and electrical conductivity with the increase of volume fraction of copper.Specifically,the maximum values of hardness and conductivity of samples with 55 vol.%copper were HV 52.7 and 57.1%(IACS),respectively.