3d打印機(jī)英文論文

1、TSINGHUA SCIENCE AND TECHNOLOGY ISSN 1007 -0214 04/38 pp24-28Volume 14, Number S1, June 2009Perusing Piezoelectric Head Performance in a New3-D Printing DesignRAHMATI Sadegh,SHIRAZI Farid?,**, BAGHAYERI Hesam?Mechani

2、cal Engineering Group, Faculty of Engineering, Azad Islamic University, Majlesi Branch, Iran;? Mechanical Engineering Department, Khaje Nasir Toosi University, Tehran, IranAbstract: Rapid prototyping (RP) is a computeriz

3、ed fabrication technology that additively builds highly com-plex three-dimensional physical objects layer by layer using data generated by computer, for example CAD or digital graphic. Three-dimensional printing (3DP) is

4、 one of such technologies that employ ink-jet printing technology for processing powder materials. During fabrication, a printer head is used to print a liquid on to thin layers of powder following the object's profi

5、le as generated by the system computer. This work looks at redesigning 3DP machine, using piezoelectric demand-mode technology head in order to improve accuracy, surface finishing and color quality of constructed models.

6、 The layers created with aforesaid system are be-tween 25 to 150 µm (steps of 25 µm).Key words: prototyping; three-dimensional printing (3DP); piezoelectric headIntroductionSolid freeform fabrication (SFF) tech

7、nologies are manufacturing/prototyping technologies that are char-acterized by layer-by-layer addition of material to fab-ricate components. These techniques are also known as layered manufacturing and rapid prototyping.

8、 The layer-by-layer building approach allows significantly more complex parts to be built in one fabrication step than was previously possible thus simplifying process planning.SFF technology therefore can automate the p

9、rocess planning and fabrication of a part under computer con-trol so that the only input needed is a solid model of the part[1,2].Over the last decade, many different technologies for SFF have evolved. Broadly, the SFF t

10、echniques available currently can be classified as stereo lithogra-phy, solid fusion and solidification, laminated objectReceived: 2008-11-09; revised: 2009-03-30**To whom correspondence should be addressed. E- mail: s_f

11、arid_sh@yahoo.com; Tel: 98-912-1350938manufacturing, and powder-based techniques. The ste-reo lithography technique selectively solidifies a liquid photopolymer while solid fusion and solidification fuse/melt the materia

12、l and deposit it layer-by-layer. The laminated object manufacturing technology cuts out laminates from sheets of part material and glues or fuses them together. In most methods of SFF, specialsupport structures are neede

13、d to support overhanging features of the part[1,3].The two main powder-based techniques that have been commercialized are selective laser sintering and three-dimensional printing (3DP) printing. For powder-based methods,

14、 no support structures are typically re-quired to create complex shapes. Powder is selectively consolidated into a part and the remaining powder can be removed. In the SLS process, a thin layer of powder is deposited in

15、a workspace container and the powder is then fused together using a laser beam that traces the shape of the desired cross-section. The process is re-peated by depositing layers of powder thus building the part layer-by-l

16、ayer. In the 3DP process, a binder material selectively binds powder deposited in layers.26create thermal stress on the fluids which is being jetted from the nozzles of head. Meantime, the diversity of fluids that can

17、be jetted by the piezoelectric heads grows vastly[6]. In addition, some thermal ink-jet sys-tems in comparison with piezoelectric type produce more inconsistent droplets with satellite and misting, which causes dimensi

18、onal error, rough surface finish-ing, and low color quality in constructed models[9].2 Control of the Ejection and Impact PhenomenaAs the ink-jet printed models structures strongly de-pend on the velocity, the initia

19、l size and the path of the droplet just before spreading, it is essential to controlthese different characteristics as a function of the driv-ing parameters of the printing head[10]. To obtain this data, the mathematical

20、 equation was used based on two different voltages (5 and 12 V). This reveals that the increase of the amplitude (up to 12 V) leads to the formation of a satellite droplet, which catches up with the main one later. Moreo

21、ver, this shows that the final volume increases with the amplitude of the pulse (Fig. 5).Fig. 5 Resonance frequency vs. droplet volumeThe equation is given as[10]V ? πr 2V /(2 f ) (1)dwhere Vd is the volume of droplet,

22、 r is the radius of the nozzle, V is the velocity of droplet, and f is the reso-nance frequency. As can be inferred from Eq. (1), when Vd is increased, the necessary velocity of droplet in-creases rapidly. Also, the fre

23、quency of head movement to print the layers decreases contemporary. Consider-ing these conditions, accurate dimensional layers of model are possible to be made. The only downside to these attitudes is the rate of bui

24、lding layers because theTsinghua Science and Technology, June 2009, 14(S1): 24-28frequency of working head has direct effect on the ve-locity of printing layers.3 NozzlesAnother important parameter to build accurate lay

25、ers is the inner nozzle diameter. When a nozzle diameter is decreased, the droplet volume decreases, however, the viscous resistance in the nozzle is greatly increased, and the energy loss grows rapidly. Figure 6 shows t

26、he relationship between the nozzle diameter and the drop-let velocity.Fig. 6 Nozzle diameter vs. droplet velocity at differ-ent viscosityIn a situation where the binder viscosity is increas-ing, if nozzle throat area get

27、s smaller, velocity drop is significant. In other words, increasing binder viscosity has predominant effect on velocity drop compared with increasing velocity by changing nozzle cross sectional area. The relation between

28、 inner nozzle diameters, droplet size, and droplet volume is shown in Table 1.Table 1 Relation between inner nozzle diameter, drop-let size, and droplet volume[11]Inner nozzle diameter Droplet size Droplet volume(µm

29、) (µm) (pL)30 35 2050 55 9070 70 1804 Binder PropertiesTo adjust the fluid properties of the organic suspen-sions to be compatible with the type of printing head, viscosity and surface tension must be 5-20 mPa s an