| With the intensified economic competition in the global market,the United States,in the Sino-US trade war,ignoring the WTO rules and arbitrarily cracking down on my country's high-end manufacturing industry,intends to interrupt the upgrading of my country's manufacturing industry.In order to counter the United States,my country is cultivating high-tech manufacturing enterprises based on "Made in China 2025",eliminating outdated production capacity,promoting industrial upgrading and development,and seizing the commanding heights of science and technology.My country's traditional foundry industry must take the road of high-quality,green,healthy and sustainable development.Efficient,low-pollution,and flexible moldless casting technology provides a new way for the transformation and upgrading of the foundry industry.The related technology of moldless casting is still under development and needs to be further promoted and applied.In this paper,the casting process design,numerical simulation and trial production research based on moldless casting technology are carried out for the key part of a printing prototype-the impression cylinder.The material of the impression cylinder is QT500,the weight is 3100 kg,the maximum diameter is 809 mm,the height is 842 mm,the average wall thickness is 115 mm,the inner cavity is more complicated,the production quantity is small,the cycle is short,the casting quality requirements are high,and the casting is difficult.According to the design principles and requirements of the casting process,the pouring position,parting surface and other process design are carried out,and the process parameters such as casting tolerance,shrinkage rate,draft angle,machining allowance,and negative number of split core(mold)are selected and determined;The structural characteristics of the castings,the relevant data in the foundry process manual and the relevant design experience,firstly design three gating systems of top-injection,stepped,and bottom-injection rain showers,and then calculate and select three gating systems that are more appropriate,the parameters are checked by Ozan's formula,and finally the 3D model design of the pouring scheme is carried out based on this.Based on Pro CAST software,three different pouring schemes were simulated numerically.According to Pro CAST's simulation calculation of flow field,temperature field,solid phase rate field and other aspects during the filling and solidification process of castings,it is found after analysis that the pouring time of the top-pouring rain pouring scheme is too short,the pouring speed is too fast,and there is entrainment.Phenomenon: The stepped pouring scheme has too long pouring time and slow pouring speed;the bottom casting rain shower pouring scheme has a middle pouring time and a moderate pouring speed.Further research and analysis found that: the top-injection rain pouring scheme has a large erosion of the cavity,easy to produce defects such as sticky sand,and shrinkage and porosity defects are all over the corners of the casting;the stepped pouring scheme is complicated in shape and is not suitable for prototype production.The upper inner runner and the casting form a new hot joint,resulting in new shrinkage and shrinkage defects;the bottom-injection rain pouring scheme is stable in filling,smooth exhaust,less scouring to the inner cavity,and it is not conducive to the sequence Solidification is not conducive to the shortcomings of feeding,but it can be adjusted and optimized by means such as risers and chilled iron.According to the numerical simulation results of the first two pouring schemes,it is found that the effect of the cold iron at the hot joint of the casting is not obvious,and the feeder position is not obvious due to the upper position of the riser.Based on this,the position of the riser and the the position of the cold iron was adjusted,and the final simulation result was better than the first two schemes.The shrinkage was basically concentrated at the riser,so the bottom-injection rain pouring scheme was used for trial production.During the trial production,the cavity of the impression cylinder casting shape is still shaped by a wooden mold,which is more efficient and economical;the complex sand core is quickly manufactured based on the CNC machining of moldless casting technology.The modelling test shows that the sand core made by the moldless casting technology and the cavity made by the wood mold are dropped and closed,and the relevant mold size meets the technical requirements.The alloy is smelted in an intermediate frequency induction furnace,the spheroidizing temperature is 1450°C,the pouring temperature is 1370°C,and the pouring time is 90 s.After the trial production,according to the single-piece manufacturing cycle and manufacturing cost of the impression cylinder,the economic analysis of the moldless casting process and the traditional casting mold-making process was carried out.The use of the moldless casting process saved about 35,000 yuan in cost and shortened the production cycle by about 47 days per person.Under the traditional casting mold making process,the mold can be reused,and the cost of the mold after producing the second piece is zero.However,each piece produced by the moldless casting process will produce a sand core manufacturing cost of 12,000 yuan.The critical output of the same production process plan cost is 4?5 pieces.Therefore,the concept of the critical output of the two schemes can be drawn.When the critical output is less than the critical output,choosing the moldless casting process has the advantages of speed and economy.In short,the application of moldless casting technology and numerical simulation technology can quickly realize the development of new product production processes,meet the needs of enterprises in the sample production stage,and avoid time-consuming and labor-intensive production verification.The rapid production and market launch of samples can enable enterprises in an advantageous position in market competition. |
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