Thermally Stable Instantaneous Cutting Amount Planning Method For Titanium Alloy Surface Milling

Titanium alloy(Ti-6Al-4V)is widely used in parts manufacturing materials in various key fields such as aerospace,automobile manufacturing,etc.due to its excellent mechanical properties such as high strength,low density,high temperature resistance and high corrosion resistance.Such parts often have complex curved surface geometric characteristics,and the processing precision is demanding,so as to meet the extreme working environment such as high temperature and high pressure.In order to meet the requirements of cutting performance,economic benefits and environmental protection at the same time,for such titanium alloy curved surface parts,a ball-end milling cutter combined with a three-axis CNC machine tool is generally used for high-speed dry milling.However,titanium alloys are difficult-to-machine materials,and have poor cutting performance and low thermal conductivity.Therefore,the milling heat under the above milling conditions will quickly accumulate and not be easily discharged.The specific performance is that the milling temperature increases sharply during the milling process,which exacerbates the tool wear and reduce the surface integrity of the workpiece.The current milling process planning for titanium alloy curved surfaces is to select reasonable cutting parameters in order to reduce the impact of milling temperature.However,the influence of milling heat fluctuations caused by the temporal variability of the instantaneous cutting amount on milling processing is less analyzed,and there is a lack of a milling thermal theoretical analysis method for surface milling of difficult-to-machine materials.In the process of three-axis numerical control machining of titanium alloy curved surfaces,when the cutting parameters that meet the requirements of high-speed milling are selected for machining experiments,the material removal rate of the workpiece is unstable.It shows that the instantaneous cutting amount during milling is time-varying,which directly affects the fluctuation of milling heat.In this paper,by establishing the theoretical calculation model of the instantaneous cutting amount in the surface milling process of the three-axis ball head milling cutter,the indirect relationship between the cutting parameters and the milling heat is established,and the instantaneous cutting amount planning method for surface redesign is innovatively proposed.Planning to achieve the stability of milling heat during the machining process.Firstly,taking the three-axis milling of the sine curved surface of titanium alloy TC4 as an example,through the geometrical characteristics of the curved surface and the cutting contact of the tool contour,with the curvature radius of the sinusoidal curved surface as a variable,the theoretical calculation model between three instantaneous milling amount: the instantaneous cutting area,the maximum effective cutting radius,the maximum unreformed cutting thickness and three cutting parameters: cutting depth,cutting speed,feed per tooth were constructed respectively.Take discrete feature points at equal intervals on the surface contour equation,calculate the three instantaneous cutting amounts corresponding to each feature point in MATLAB and draw corresponding images for analysis.Secondly,the aim is to improve the stability of the milling temperature,that is,by reconstructing the coordinates of the tool point of the sinusoidal surface contour,the corresponding instantaneous milling amount at each tool point is planned.According to the shape of the curved surface: convex curved surface,concave curved surface and milling direction: curved surface upward milling,curved surface downward milling,plan different tool point reconstruction methods,and redesign the curved surface of the finishing process and the semi-finishing process respectively.Finally,reasonable cutting parameters were designed according to high-speed milling conditions,and a three-axis milling experiment of titanium alloy curved surfaces was carried out.Real-time high-speed milling temperature acquisition by infrared thermal imaging camera,and analysis of experimental results.The results show that the fluctuation of the cutting temperature in the stable area after planning is reduced by 75.81% compared with the conventional machining method,and the machining effectiveness of the instantaneous milling amount adjustment method based on the surface redesign theory is verified.Taking the variance of the milling temperature as the measurement target,comparing the planned machining trajectories corresponding to the three instantaneous milling quantities,the machining trajectory corresponding to the instantaneous cutting area is analyzed as the optimal adjustment method.The results verify the feasibility of improving the thermal stability of milling in the process of milling by the instantaneous milling amount in the process of planning machining,and realize the surface redesign method of improving the thermal stability of milling by adjusting the allowance,which provides theoretical guidance for the production of difficult-to-machine materials curved surface workpiece.