Nanjing University of Aeronautics and Astronautics

Haoqin Yang

Zhongde Shan

Jianpei Shi

Jun Wang

Yaoyao Wang

Qinjiang Liu

Chao Li

Xiaokang Ma

Shijie Dong

Dandan Yan

Yufeng Dai

Wanneng Liao

An ultrasonic-assisted permeation and homogenization molding device and method for frozen printing liquid drops are provided. The device includes an ultrasonic generator, a transducer and an amplitude-change pole. The ultrasonic generator generates 20 KHz low-frequency ultrasonic waves, and a flange plate is arranged on a pitch surface of the amplitude-change pole and connected with an outer cavity wall of the low-temperature molding chamber by threads. According to the ultrasonic-assisted permeation and homogenization molding method for frozen printing liquid drops, pre-paved molding sand particles are homogenized and distributed under ultrasonic vibration by adjusting the frequency of the ultrasonic generator in a sand paving process. When a pure water binder is sprayed, liquid drops are sprayed to the surface of premixed molding sand, and then permeate to the bottom of pre-cooled molding sand under the assistance of low-frequency ultrasonic waves to freeze and solidify.

Ultrasonic-assisted permeation and homogenization molding device and method for frozen printing liquid drops

A method for preparing a negative pressure film-covering frozen sand mold includes: directly obtaining a mold cavity of a sand mold through numerically controlled machining of a frozen sand blank; covering a surface, brushed with a thermal insulation coating, of the mold cavity of the sand mold with a softened thin film, and covering an outer surface of the sand mold with a back film to seal a sand box; fixing the frozen sand mold in an air extraction sand box with a vacuum chamber, and extracting air through a vacuum pump, so that the thin film tightly adheres to the sand mold through vacuum suction force; and closing the box to obtain an integral sand mold, and pouring a casting at room temperature or low temperature under negative pressure. The method is environment-friendly, and the prepared frozen sand mold has high strength and is convenient for sand cleaning.

Method for preparing negative pressure film-covering frozen sand mold

A multi-path internal microporous efficient refrigeration method and device for a frozen sand mold is provided. The device includes a frozen sand molding chamber, an electric lifting platform, a teflon porous lining, a removable porous aluminum plate, a frozen sand mold refrigeration device box, a sealing cover plate, an ultrasonic piezoelectric sheet, a U-shaped condenser tube, an ultrasonic generator, and a low-temperature refrigeration system. The teflon lining and the removable porous aluminum plate are provided with through hole structures of the same size and shape for rapid cooling from the surface to core of molding sand. The lifting platform is opened and the bumpy-ridge teflon lining rises to a highest point to facilitate demolding. The high- and low-frequency dual mode of the ultrasonic piezoelectric sheet can be used for vibrating and compacting the frozen sand mold, and can also assist in cutting forming.

Multi-path internal microporous efficient refrigeration method and device for frozen sand mold

An interlayer pre-cooling apparatus for a sand mold freezing printing includes a sand paving apparatus. The sand paving apparatus is located above a negative-pressure low-temperature forming chamber, and the sand paving apparatus includes several independent sand paving grooves, a hollow sand paving roller, a cooling chamber, a sand scraping plate, and an openable and closable baffle. The openable and closable baffle is rotationally arranged at a discharge port of each sand paving apparatus, and the openable and closable baffle is used for paving low temperature premixed sand on demand. The premixed molding sand is further cooled during the process of scraping and compacting low-temperature molding sand. When the apparatus is adopted for sand mold freezing 3D printing, the low temperature of the premixed molding sand is precisely controllable, which has great significance for realizing interlayer pre-cooling of the sand mold freezing printing.

Interlayer pre-cooling apparatus for sand mold freezing printing

A mechanism for radially inserting a yarn into a 3D braided preform, including a first bracket, an upper linear actuator, a support mechanism, an upper yarn insertion device, a yarn carrying device, an upper gear ring, a lower yarn insertion device, a lower linear actuator, a second bracket, a lower gear ring, a lower gear, a lower motor, a lower circular track, an upper circular track, a base, an upper gear, a pneumatic transmission and control device and an upper motor.

Mechanism for radially inserting yarn into three-dimensional braided preform

An automatic circumferential insertion apparatus and method for a complex rotary preform. The apparatus includes a double-hinge yarn carrier and a U-shaped bracket. Two ends of the double-hinge yarn carrier are respectively provided with a cylindrical hinge structure. One cylindrical hinge structure is in revolving pair connection with an outer clamping buckle at one end of the U-shaped bracket, and the other cylindrical hinge structure is in revolving pair connection with an inner clamping buckle at the other end of the U-shaped bracket. Two sides of the U-shaped bracket are provided with an electromagnet, respectively. The outer clamping buckle is provided with a pin, which is controlled by triggering, and is triggered simultaneously with the electromagnet at the side where the outer clamping buckle is arranged.

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Nanjing, China

Haoqin Yang