Modeling And Analysis For Rapid Freeze Prototyping Of Ice Parts

Rapid Prototyping Technology(RP)is another revolution of manufacturing industry after the numerical control technology.RP and VM have been regarded as the two pillars of the future manufacturing technology.RP builds a three-dimensional part on discrete-collecting principle according to a CAD model by depositing droplets layer by layer.RP is a new type of die less and cutting tool less manufacturing process.It offers a solution for the problem that can’t be solved through traditional manufacturing process,while the production process and production cycle are greatly reduced.Especially for that complicated parts,RP can fully take its advantages.The objective of this paper is to explore the variable parameters in Rapid Freeze Prototyping(RFP)and show the relationships between these parameters and the effects they have on fabricating ice parts.It further provides theoretical basis and control methods for making other water-based materials forming process.Therefore,it is very significant to understand forming principle and improve the dimensional accuracy and surface roughness of parts.The paper based on jet theory of fluid dynamics theory,a linear instability analysis is presented for non-viscous and viscous liquid jet.According to the physical model,the general solution of pressure and velocity are obtained.The nozzle spray process is analyzed based on the Bernoulli’s equation and continuity equation in detail.The theoretical value of optimal frequency and jet velocity at different spray pressures are gained so as to realize the theoretical prediction for spray result.Some physical characters of RFP are analyzed,and the model of ice line is built.The effects of technical parameters in RFP on product properties are discussed mainly.A surface roughness empirical formula was deducted based on experiments,which can forecast practical roughness under different process parameters.The result might provide science foundation for the quality control of ice parts.Use of support material in RFP is necessary for building complex ice parts with features such as internal holes or overhung areas.This paper studies on the support material.A possible solution at the top of the list for a support material was a eutectic dextrose solution which successfully used in the ice wall parts manufacturing process.In order to understand the interaction of the diffusion phenomenon and predict the amount of diffusion that is occurring around the interface of the two miscible materials due to the diffusion of the dextrose from the support material section of the wall into the water section,two basic concentration models are developed.This paper presents a one-dimensional transient heat transfer model for a thin ice wall built by the RFP according to the basic theory of heat transfer.Closed-form solutions for temperatures of the ice wall during solidification of a layer of water are derived,which can be used to estimate the solidification time for the semi-infinite ice wall.It shows that the solidification time is proportional to the square of layer thickness and inversely proportional to the square of temperature difference.The results are useful for improving the produce efficiency of ice parts.The heat transfer is also considered in the natural cooling process of a semi-infinite ice wall just after solidification of a layer of water.Using Laplace Transformations the final temperature distribution function is got by considering the boundary condition and initial condition.The results provide an important theoretical basis for further detailed analysis of fabrication process thermodynamics phenomenon.