Development Trend of NC Machining Accuracy Control Technology for Aeronautical Structural Parts

High-performance five-axis computer numerical control machine tools are widely used in the processing of Aeronautical Structural parts. With the increase of service life, the precision of CNC machine tools equipped by aeronautical manufacturing enterprises is declining day by day, while the new generation of aircraft structural parts are developing towards integration, large-scale, complexity, thin-walled and lightweight. It is very easy to produce dimension overshoot and surface quality defects due to unstable processing technology. The machining accuracy of aircraft structural parts is also affected by complex factors such as cutting load, cutting stability, tool error, workpiece deformation, fixture deformation, etc. Because of the complexity of structure and characteristics of Aeronautical Structural parts, the consistency and stability of cutting process are poor. It is easy to cause machining accuracy problems due to tool wear, breakage and cutting chatter. Relevant scholars have carried out a lot of basic research on NC machining accuracy control and achieved fruitful results, but the research on NC machining accuracy control of Aeronautical structural parts is still less. This paper elaborates from three aspects: error modeling method of NC machine tools, error compensation method, prediction and control of machining accuracy, and combines the characteristics of Aeronautical Structural parts, the development trend and demand of NC machining accuracy control technology are put forward.

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.

An allowance allocation method based on dynamic approximation via online inspection data for deformation control of structural parts

Deformation resulting from residual stress has been a significant issue in machining.As allowance allocation can directly impact the residual stress on part deformation,it is essential for deformation control.However,it is difficult to adjust allowance allocation by traditional simulation methods based on residual stress,as the residual stress cannot be accurately measured or predicted,and many unexpected factors during machining process cannot be simulated accurately.Different from traditional methods,this paper proposes an allowance allocation method based on dynamic approximation via online inspection data for deformation control of structural parts.An Autoregressive Integrated Moving Average(ARIMA)model for dynamic allowance allocation is established so as to approach the minimum deformation,which is based on the in-process deformation inspection data during the alternative machining process of upside and downside.The effectiveness of the method is verified both by simulation cases and real machining experiments of aircraft structural parts,and the results show that part deformation can be significantly reduced.