19-01-2016, 12:07 PM
Micro thin-walled metal parts are much difficult to be fabricated, because they are very easy to deform under the action of stress, heat and vibration in manufacturing process. At present, the traditional forming methods are mainly used to manufacture the normal size and simple shape thin-walled metal parts. Some novel forming methods have been studied by researchers in recent years. It includes selective laser melting (SLM), laser cladding forming, Direct laser fabrication (DLF) technology, three dimensional micro-welding (3DMW), electron beam selective melting (EBSM).
However, the above forming methods are not very mature and also need to be further improved. For example, the equipments of SLM and DLF are very expensive, and the preparation of powder material is difficult. The 3DMW uses wire as material, so the forming accuracy needs to be improved. Therefore, it is necessary to develop a new forming method to fabricate micro thinwalled metal part. Metal micro-droplet deposition manufacture is a novel direct metal rapid prototyping, which has the advantage of high efficiency, low cost, and simple process. Because the droplet diameter can be controlled in the range of 30–1000 µm, the forming process can be used to build the complicated and porous micro thin-walled metal structures. In process of fabricating micro thin-walled metal parts, the formed wall thickness and deposition accuracy of droplet are two key control objects, which determine the forming qualities of parts.
If they are not appropriate to be controlled the formed parts are hard to satisfy the design requirement. Thus, it is very important to investigate the influences of process parameters on the forming thickness of wall and deposition accuracy of droplet. In this paper, a direct droplet fabrication experimental system was developed based on the forming principle. The effect of deposition distance Hs on deposition accuracy of droplets was researched by analysing the spraying process of droplet and measuring the deposited experimental results of vertical micro columns. The relationship between the formed wall thickness W, the nozzle diameter D and formed angles of deposited droplet ϴ was investigated by comparing the experimental and theoretical results of Sn60-Pb40 single-pass wall.