Cutting Parameters Optimization Of Spiral Groove Processing On Liquid Rocket Engine Nozzle

Combustion chamber and nozzle are important components of liquid rocket engines. The spiral cooling channels on the nozzles can be difficult to be machined by common milling machine or CNC center in view of its complex space geometry, large height-width ratio and quantities. So a production miller with double disc-milling cutters is designed to process the loxodromic groove of rocket nozzle currently. It’s found that the cutting load changes frequently and in a wide range during a single feeding process by season of the change of chipping allowance and machining interference. To reduce the influence on processing quality and prevent overloading of the system, the machine tool should be kept running in a low level of feedrate which can only be modified via experience. However, it’s not the fundamental solution to the problem but a limit of the performance of the equipment. Therefore, it’s necessary to study the source of the cutting load and the method to keep it stable. On this basis, the optimization of cutting parameters can be researched to improve production efficiency.In this paper, processing technique of the equipment was studied firstly to conclude the uncontrolled geometric factor which leads to the change of the cutting load. Then numerical method of the factor was presented after the geometric model of the spiral groove was built.Indirect cutting load acquisition method based on the measurement of spindle motor currents and eigenvalue extraction via wavelet analysis was developed, because it’s unlikely to measure the cutting force by dynamometer in this machine tool. Then mathematical model between eigenvalue of spindle current and factors that influence the cutting load was established. Multiple linear regression model was used to process orthogonal experiment data, by which the model parameters were calculated.Multi-objective optimization model for maximum productivity and minimum cost was presented and an approach to get the optimal solution by MATLAB programming was developed based on the study of GA. Then zoning federate scheduling strategy was designed when processing.At last, a new CAM matched the slotting machine was developed using the established model and optimization method, within which the cutting parameters were scheduled. Then a given workpiece was machined by NC codes separately generated by new CAM and an amended old one. The results showed that the cutting load was more stable using the NC code modified by new CAM and the processing time was drastically reduced. It shows that this research has a great value in practical engineering.