Experimental Investigation On The Machining Accuracy Of Silicon Aluminum Alloy Piston's Outer Diameter

Piston usually works under unfavorable working conditions during engine service.It provides high speed reciprocating movement for the whole engine to transmit the prime power,and bear quite high mechanical load and thermal load.Piston is one of the critical components to influence engine performance.Piston deforms under the effects of thermal and mechanical loads.This deformation influences the dimensional accuracy of piston and cylinder.It further exerts impact on the motion accuracy,service performance and reliability of the engine.The piston structure is complex in shape,the requirement of dimensional accuracy is high,and piston's outer diameter is difficult to control,thus piston's scrap rate and manufacturing costs are relatively high.Based on the structure characteristics of the silicon aluminum alloy piston,the first reasonable process is to machine counter bore,and then machine its pinbore.This study confirms that PCD cutting tools are suitable for machining piston outer diameter.Four process parameters are determined as spindle speed,feed rate,depth of cut and coolant to influence piston outer diameter precision.In terms of piston machining process,it is reasonable to define counter bore as location datum of the piston.The cutting depth of the top surface has great influence on the deformation of the counter bore.Experimental method and balanced production cycle time are optimized by selecting the cutting depth of 2mm per cycle.By analyzing the experimental data,the relevant process data are optimized.In piston outer diameter machining process,four key parameter is improved.Spindle speed is 2500 rpm,feed rate is 0.25mm/r,final turning out diameter process signal side cutting depth is 0.1mm and clamping mode is according to the piston top surface shape with the long axis direction symmetrical clamping or circumferential direction of the uniform clamping,coolant concentration range is from 5% to 7%.The piston outer diameter machining precision can be increased from ±0.009 mm to ±0.003 mm and the scrap rate decreased obviously.Based on the study of the effect on the top surface of the clamping force on the piston diameter machining of piston skirt deformation,five experiments are designed to investigate the effect of the top clamping force on the skirt profile deformation.The five groups include the minimum value,the small value,the middle value,the large value and the maximum value.The experimental results reveal that the clamping force of 830 N has minimal impact on the skirt profile to ensure the piston outer diameter machining precision requirements.The accuracy of the machining parameters is verified by experiments.