Deposition Forming Technology Based On Mono-sized Metal Droplets Prepared By Pulsated Orifice Ejection Method (POEM)

Deposition forming technology based on mono-sized metal droplets is a new member of rapid prototyping technology. The principle of this method is to prepare uniform droplets which are deposited one by one on the motion platform to fabricate3D complex shaped prototyping. The technique breaks through the limitation of the materials of traditional rapid prototyping technology, and the molding material used can be not only the non-metallic material but also metal material. Compared with the traditional rapid prototyping methods, it has the advantages of simple structure equipment, high machining accuracy, and suitable to materials in a wide range. The precision of the droplet spray is the key technology that determines the quality of the molded parts. As a kind of drop-on-demand (DOD) method Pulsated Orifice Ejection Method (POEM) allows the preparation of droplets with very narrow size distribution and very small standard deviation of the mean droplets size. The rectangular pulse waves generated by a function generator are used for controlling the output wave of a power amplifier, which was applied to the piezoelectric actuator to drive the rod in reciprocating motion in corresponding with the rectangular waves. The displacement is transmitted by rod to the local melt near the orifice at the bottom of crucible, breaking the balance of surface tension and static pressure of melt, and leading a certain volume of liquid ejected out of crucible to form a droplet. POEM can realize the accurate control of in desired size spraying and can be considered as a real sense of controllable drop-on-demand ejection.In this paper, the deposition forming technology is developed based on rapid prototyping technology in combination with mono-sized droplets prepared by POEM. The device mainly includes mono-sized droplets generation system, platform motion system, control system, image acquisition system and vacuum system. Also, the mono-sized droplets generation system consists of the pressure control system, temperature control system, piezoelectric actuator driving system.Droplets spray experiments were carried out using eutectic alloy of Sn63Pb37on the independently developed molding system. The influence of experimental parameters on the droplet spraying were carried out and the conclusion can be drawn:the droplets size presents a linear growth with piezoelectric actuator applied voltage and differential pressure between the crucible and chamber; The relationship between the droplets size and heating temperature piezoelectric actuator vibration frequency and injection time of droplet is not obvious; The diameter of orifice is the main factor on the droplet size. The dynamic behavior and thermal behavior of the droplets during the falling is carried out. The results showed that no solidification occurred at the falling height of150mm. The deposition molding process was carried out at different velocity of working platform at the deposition frequence of2Hz and the deposition height of80mm, the adjacent droplets have ideal overlapping at the speed of600um/s of work platform; Excessive overlap occurred when working platform is too slow, while no overlap was obtain when is too fast; The three-dimensional metal parts with a perfect metallurgical bond status were fabricated by independently developed molding system.