| Precision seeding is the mainstream means of the modern seed industry,which has many advantages,such as the short sowing time,high efficiency,and increasing production.At present,in seedling stage,the means of precision seeding are so many,but the main planting pattern is through manual operation,and the labor intensity is very high and the sowing quality is discrepant and inefficient.Efficient,accurate and practical seedling planting machine is urgently needed.Pneumatic cylinder precision seed-metering device is the key equipment to the implementation of precision seeding,the existing gas suction drum metering device without positive pressure cavity of cast seed is some kind of question,such as complex assembly,difficult sealing,and the single negative pressure cavity without positive pressure to throw cavity means no positive pressure for gas chamber,poor sealing,and it is hard to achieve positive pressure for unblock the function,unable to achieve positive pressure for air,due to its high seed sowing leakage rate,directly restricting the application and promotion.So the design of negative pressure suction kinds of positive pressure to throw and drum cavity of rows kind of roller structure scheme,double cavity theory,processing and assembling process,doing the test to obtain the optimal working parameters affecting metering performance has a certain reference value to the research and development of suction drum precise metering instruments.Therefore,the new idea of using 3d printing to print double cavity metering roller is put forward.Main contents and results of the research include:1.In view of technical problems exiting in single cavity seed-metering roller,such as the assembly of positive pressure zone of metering is very difficult,poor sealing,no positive pressure for gas chamber,and it is hard to achieve positive pressure for unblock the function,directly causing the technical problem of high metering device leakage rate.For the reasons,this paper puts forward a new idea of using 3d rapid prototyping technology to print the roller,and innovatively designs the double cavity seed-metering roller.This paper analyzes the seed filling,seed absorbing,seed carrying,and seed dropping.The mechanical models are build.The interrelationships of every factor is clear.Then the key components are designed,and the working process is also defined.This is the foundation of the following researches.2.Simulated analysis of negative pressure cavity and positive pressure to throw cavity was ana lyzed by the computational fluid dynamics(CFD)software,the main factors of impacting internal flow field uniformity of drum cavity and determining the structure of the double cavity metering r oller and size parameters ware found.The optimal combination was: the way of positive and nega tive pressure choices single-ended air inlet gas,and cylinder diameter was 160 mm,and the drum l ength was 300 mm.The suction hole structure shape was the taper hole structure,and suction hole diameter was 1.5mm,without barrier of drum cavity internal structure.3.Based on double cavity metering roller core parts of the structure features and technical re quirements,this paper uses 3d printing rapid prototyping technology and the method of modular d esign to manufacture the double row of kind of drum cavity modular,which greatly simplifies themanufacturing process.4.The qualified index,the multiple index,and the missing index were chosen for sowing object.Based on the three-factor three-level orthogonal regression test method,the influences of Kind of positive pressure cavity chamber,negative pressure of roller and rotate speed on sowing performance were explored.The regression equations of the 3 factors were fitted through the processing by Design-Expert(experimental design expert)software.The experimental results showed the significant influence of positive pressure of air chamber,negative pressure of roller and rotate speed.Based on the results of examination,we found that the fitting of the equations was good,the best parameter combination was kind of positive pressure cavity chamber of 2.2 kPa,negative pressure value of 2.4kPa,and speed of 16 r/min,and under the optimal condition,the qualified index was 93.2,the multiple index was 4.3,and the missing index was 2.5,the double cavity metering roller met the standard and requirements by comparing the results with the national standard and planting requirements. |
