Research On Low Pressure Casting Forming Method Of Complex Surface Air Compressor Rotor

Screw air compressor is widely used in aerospace,petrochemical,metal smelting,weaponry and other fields.As a key component of the air compressor,the screw rotor has the characteristics of complex surface,difficult design and manufacture,and high precision requirements,and its machining accuracy directly determines the working performance of the compressor.At present,the mechanical processing method used to produce screw rotor has the defects of complex process,large number of required equipment,high precision of equipment requirements,long manufacturing cycle,high cost and low efficiency.In this paper,a low pressure casting method of screw rotor with complex surface is proposed to realize the forming of screw rotor,and the casting forming process and die of screw rotor are studied.The research contents are as follows :(1)According to the profile data of the positive rotor end face of the twin screw air compressor,the three-dimensional model of the rotor was established by UG software.Combined with the structural characteristics of the screw rotor,the casting model and gating system were designed,and the ingate,runner and riser of the mold were refined.The three-dimensional model of the mold gating system was established in the UG environment.(2)According to the requirements of low pressure casting process parameters,the boundary conditions of simulation such as process parameters and filling pressure range of rotor casting filling stage are calculated.The temperature distribution,solidification time and shrinkage defect distribution of screw rotor in low pressure casting process were obtained by simulation.According to the simulation results of filling and solidification of the initial gating system,the structure of the gating system was optimized.(3)The optimal process parameters of low pressure casting were obtained by response surface test method.The casting quality prediction model including pouring temperature,mold preheating temperature,filling pressure,solidification time and shrinkage volume was established.The influence of pouring temperature,mold preheating temperature and filling pressure on solidification time and shrinkage volume on rotor quality was obtained.The optimum process parameters of rotor casting were determined by combining casting quality and solidification time.(4)Combined with the simulation results of screw rotor and the characteristics of the model,the low pressure casting mold of screw rotor was designed,and the parting surface,machining allowance,pattern draft,metal mold size,cooling system,exhaust system and casting demoulding mechanism were determined.According to the characteristics of the screw rotor,the demolding force and demolding height were calculated,and the overall structure of the mold was virtually assembled.