In recent old ages, fused deposition mold ( FDM ) has become a widely used engineering in rapid prototyping procedure. Typically polymer stuffs used are acrylonitrile butadiene cinnamene ( ABS ) and polycarbonate ( Personal computer ) . The polymer is fed into equipment as a 1.6mm diameter, which is heated and extruded onto a edifice platform. The ABS fibril sold by the equipment providers is really expensive at aroundi??270 per kilogram [ 1 ] . Besides, during the FDM procedure, some of this stuff is used as build supports and which is merely thrown off after being removed from the parts. This undertaking aims to utilize alternate stuffs for the FDM procedure.
1.2 Previous Work of Undertaking
This undertaking is followed by a summer 2009 undertaking that Yifei Zhang did. In Zhang ‘s undertaking, one class of virgin ABS has similar thaw and flow belongingss to the benchmark stuff, but due to the restrictions of research lab equipment and undertaking financess, Zhang can non acquire the consequence. Zhang besides try to utilize WEEE ABS as a possible beginning, but the grade of pureness ( 98 % ) could non be accepted in FDM operation. In add-on, a nylon strimmer line was found which had the suited fibril diameter, but it besides failed because of the viscousness of the stuffs.
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1.3 Aims of Undertaking
After sum up the Zhang ‘s experience, the mark of undertaking is to place the inexpensive alternate polymeric stuffs to ABS. Before the undertaking, a farther polymer apprehension of the thaw and flow belongingss should be reviewed. Some jobs Zhang met demand to be solved to successfully bring forth the merchandise. Some experiments, which Zhang did, necessitate to be repeated to hold a better apprehension of this undertaking. Some test stuffs are aimed to bring forth the merchandises, and so the belongingss of merchandise are evaluated.
2. Literature Survey
2.1 Why usage rapid prototyping methods?
Rapid Prototyping ( RP ) is defined as “ the usage of a computing machine aided design ( CAD ) -based automated linear fabrication procedure to build parts that are used straight as finished merchandises or constituents ” [ 2 ] . By and large, it is a speedy manner to turn a practical design to a existent theoretical account. There are many intents for a prototyping, for illustration, validate system specification or present early cogent evidence of construct or make a market demo [ 3 ] . The best grounds to rapid prototyping is to salvage clip and salvage money. A complete merchandise design rhythm is really long, and there are a batch of tests and mistakes in the processing. The rapid prototyping processing can be used to modify the test and debug the paradigm in a short clip. In add-on, the resources can be saved by bring forthing cut down scale theoretical account.
2.2 Rapid prototyping equipment
With the development of modern scientific discipline and engineering, techniques of rapid prototyping engineering progressively diversified, such as stereo lithography ( SL ) , laminated object fabrication ( LOM ) , selective optical maser sintering ( SLS ) , selective optical maser thaw ( SLM ) , fused deposition mold ( FDM ) , ink jet printing ( IJP ) , 3-D printing ( 3DP ) [ 4 ] . There are three classs harmonizing to the natural stuff used in these processing. They are liquid-based system, powder-based system and solid-based system [ 2 ] [ 3 ] . FDM belongs to solid-based RP procedures. The merchandise made by FDM operation can be used as test trials or for farther surveies, which reduces the hazard of planing errors.
2.2.1 Stratasys FDM System
Fused Deposition Modeling ( FDM ) , which invented by Stratasys Inc, is used in the undertaking. Generally, FDM is a typical PR procedure, which contains a computing machine controlled, and micro-extrusion system. In the procedure, the polymer is fed into the equipment as a 1.6 diameter fibril, which is heated and extruded through a dice as a 0.5mm fluid fibril. By puting down of the thaw fibril from nose, certain thickness of 2-D beds construction is formed, so by reiterating the procedure for the 2nd bed, repetition this procedure bed by bed, so a complex 3-D construction is formed. As can be seen in Fig 1, the treating path follows the design, forming and coatings these three stairss.
Fig 1 treating path via Stratasys Fused Deposition Modeling equipment [ 5 ]
In the path of this industry, pre-process CAD file is designed by FDM Quickslice package and saved as STL format [ 6 ] , and so during the industry portion, the thermoplastic stuff is extruded and formed bed by bed on precise waies. Remove the support structures so the concluding merchandise is completed.
Bulge procedure is a cardinal measure in the FDM fabrication [ Fig 2 ] . By and large talking, the polymer fibril is in solid province when feeding into the FDM machine. The fibrils of liquefied thermoplastic are extruded from a het nose. The procedure lays down both support stuff fibril and construct material fibril for one bed at a clip. The diameter of the fibril is about 1.67mm, and the scope of diameter of different tips is from 0.025mm to 0.4mm.
Fig 2 the extrusion-based procedure in FDM operation [ 7 ]
Functional prototyping is used via an linear fiction system. Fabrication tools and End-Use parts besides can be produced with FDM system. There are many advantages including streamlining the development procedure, cut downing the cost and acquiring to the market faster [ 7 ] .
The disadvantage is obvious, the monetary value of cartridge is really expensive, and ABS build ( including the breaking away stuffs ) is ?275.00 per kilogram. So find the inexpensive alternate stuff is the mark of the undertaking.
2.2.2 Mesostructure of FDM ABS [ 8 ]
There are two sorts of mesostructure during the FDM processing [ Fig 3 ] . The aligned mesostructure is the standard theoretical account of the machine. Another skew mesotructure uses the jumping “ jogs ” of length 0.5 ( W+g ) in the ProEngineer pulling [ Fig 4 ] . A rectification in the nozzle tallness scene, I? z ( see equation 1 ) , utilizing the z-direction shrinking factor, is set in the QuickSlice plan.
Fig 3 two sorts of mesostructure in FDM processing
Fig 4 the mesostructure of Skewed Configuration
aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦ [ 1 ]
The null denseness on the stuff plane I is defined as: ( see equation 2 ) . The extent of circumferential fiber-to-fiber bonding is quantified utilizing a cross-section norm of the fiber-to-fiber interface bond length densenesss. For a individual fibre, it is defined as: ( see equation 3 )
aˆ¦aˆ¦aˆ¦ . [ 2 ]
aˆ¦aˆ¦aˆ¦aˆ¦.. [ 3 ]
Harmonizing to Jose, James and John, the same fibril stuffs ( ABS P400 ) and the same consecutive FDM machine were used to prove. So the informations have the mention value.
Fig 5 nothingness denseness with increasing of fibre spread and flow rate
Fig 6 Bond length denseness with increasing of fibre spread and flow rate
Fig 7 Void denseness with increasing of fibre spread and flow rate in a broad scope
As can be seen in Fig 5, the lowest nothingness denseness value is the skewed constellation construction. From the chart above ( Fig 5 Fig 6 and Fig 7 ) , Fiber spread ( g ) and flow rate are two cardinal factors on mesostructure while temperatures ( Te and TL ) had really small influence. So for the best belongingss, lower limit nothingness and maximal bond length are needed.
2.3 Alternate stuff
2.3.1 Standard Material
The current stuffs utilizing for the FDM fabrication procedure are supplied by Stratasys Inc, which could be ABS plastic, Personal computer and wax [ 9 ] . The P400 ABS, whose chief mechanical belongingss can be clearly know in Fig 8, bought from the machine seller was used as benchmark this undertaking, provided as white fibril with a diameter of 1.67mm and a A± 0.02 millimeter tolerance, measured by research lab ‘s callipers.
Fig 8 mechanical belongingss of ABS P400 [ 10 ]
2.3.2 Recycled ABS
Recycled ABS, I think, still is the most ideal choose in this undertaking. The recycled WEEE industry is turning by more attending today. Compared to virgin ABS, the monetary value of WEEE ABS is instead inexpensive. Due to the job of the grade of pureness in former undertaking, one solution of undertaking is to look into methods of filtrating recycled ABS for FDM.
During recent old ages, some researches about WEEE have been carried out [ 11 ] [ 12 ] .
There are similar consequences on their studies. With the regard to the belongingss of virgin ABS, a lessening in mechanical belongingss ( except the modulus of snap ) was recorded for both PC/ABS and ABS/HIPS mixtures [ 11 ] .
One attack to different features of recycled polymer was reported by Liang [ 13 ] . The contaminations of these recycled polymers are showed in Fig 11.
Fig 11 the contaminations of different recycled polymeri?»13i??
Previous debasement degrees ABS and WEEE ABS
FTIR spectra for WEEE ABS can be compared with virgin ABS to gauge differences. Harmonizing to Balart ‘s research, little debasement in ABS was evaluated in the FTIR spectra ( Fig 12 ) . The hydroxyl groups which absorb near 3250cm-1 shown, and the carbonyl groups, which absorb near 1750cm-1 missed in the spectra [ 11 ] .
Fig 12 Comparison between FTIR spectra of ( a ) recycled ABS and ( B ) a commercial ( Polylac PA-714C ) virgin ABS rosin [ 11 ]
2.3.4 Mixture of ABS/PC system
Harmonizing to Balart [ 11 ] , Equivalent Box Model ( EBM ) was carried out to analysis the mechanical behaviour of ABS/PC blends. EBM can obtain a scope of tensile values of blends. Fig 13 shows different curves with the critical values and different A values which is an experimental parametric quantity related to the assorted interaction forces along the interface.
Fig 13 Variation of tensile strength with ABS/PC blends composing compared with predicted values based on EBM [ 11 ]
As Balart pointed, the optimal scope between10wt % and 20wt % Personal computer in mixture shows an industrial stuff with balanced belongingss [ 11 ] . One ground is that mechanical ductile belongingss do non diminish [ 11 ] .
Furthermore, harmonizing to Arnold, the mechanical belongingss of recycled ABS, particularly ductileness, are significantly affected by gas development during the procedure of ABS from WEEE [ 14 ] .
Tarantill and Mitsakaki have done some trials about the propernesss of ABS/PC blends.
( Fig 14 Fig 15 Fig 16 )
Blend Composition ( w/w )
MFI ( g/10min )
MFI agreement. To regulation of mixtures
Fig 14 MFI measurings of ABS/PC blends [ 12 ]
Fig 15 Tensile trial consequences for ABS/PC blends [ 12 ]
Fig 16 DSC analysis of ABS/PC blends [ 12 ]
In this undertaking, more can be dig deeper in ABS based on the Zhang ‘s work.
First, FTIR spectra can be used to compare the virgin ABS, after treating ABS and WEEE ABS. The relationship between WEEE ABS, after treating ABS and standard ABS should be clear in this undertaking.
Second, ABS/PC mixture is one manner to look into. In Balart ‘s study, the optimal scope is 10wt % to 20wt % ; the mechanical belongingss of this scope besides have a good public presentation.
Furthermore, to polish the WEEE ABS is besides one manner, but due to the current state of affairs ; it is difficult to happen a procedure to increase the pureness of WEEE ABS ( 98 % ) .
Simply mix one tantamount portion of pureness ABS and one tantamount portion of WEEE ABS may be possible. Higher pureness of WEEE ABS may hold better belongingss.
2.3.5 Alternate Nylon Beginning
Harmonizing to Zhang ‘s research, Nylon could be an alternate stuff to replace the ABS P400. Compared to the ABS, Nylon have lower monetary value. In the research lab, nylon strimmer line has already been produced into fibril with the same diameter as benchmark P400 ABS. It is easier to acquire the natural stuff. One cardinal factor for this alternate stuff is melt temperature when nylon as a sample. The recommend FDM operation on standard P400 ABS was 100oC higher than the thaw point. Among the nylon-6, nylon-12 and nylon-66, nylon-12, which could be a possible stuff, has the lowest thaw point 179oC [ 15 ] . Compared to P400 benchmark, the thaw mass flow rate can be a sensible scope from 7.0 to 20 [ 16 ] . During the Zhang ‘s test of nylon stuff, 300oC is the highest temperature restriction for liquefying the FDM machine, but nylon-6 demand higher. So glue gun can be used for higher FDM operation temperature. The farther belongingss of the Nylon merchandise demand to be evaluated in the experiment.
2.4 Measuring Instruments
The mark of the undertaking is to happen the alternate stuff to replace the ABS-P400, before that, the belongingss of ABS-P400 and after treating ABS should be investigated. By comparing the differences of these two stuffs, the possible of re-used after treating ABS is demonstrated. Furthermore, the information of the standard stuff can be the mention of the alternate stuffs. The chief equipments and trials may be used below.
2.4.1 Melt Flow Index ( MFI )
Harmonizing to Zhang ‘s study, syrupy flow of the stuff is the key to this undertaking. Low viscousness merely means that the stuffs are able to flux easy [ 2 ] . Viscosity is lowered significantly by increasing temperature harmonizing to the equation 4:
aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦ ( 4 )
Where 0 is a changeless, Q is the activation energy for flow, R is the cosmopolitan gas invariable and T is absolute temperature. In this undertaking, MFI is used to mensurate the syrupy flow.
Harmonizing to Zhang, the some MFI consequences were obtained.
( g/10min )
( Recycled )
Table 1 MFI consequences under injection molding and FDM conditions
The Melt Flow Index ( MFI ) is a manner to mensurate the easiness of flow of the thaw of a thermoplastic polymer. In Farlex ‘s free lexicon, it is defined as “ the weight of polymer in gms fluxing in 10 proceedingss through a capillary of specific diameter and length by a force per unit area applied via prescribed alternate hydrometric weights for alternate prescribed temperatures ” [ 17 ] . One decision of Balart is that bulge and injection molding procedure are really of import to guarantee good commixture conditions and homogeneousness. MFI measurings were used with an bulge plastometer [ 11 ] . Flow rate, whose unit is g/10mins, reflects the thaw polymer ‘s characteristics. In this undertaking, there are two standards for different classs of ABS plastic. One is 2200C/10kg for injection modeling status, which is a general criterion of flow belongings. Another status 2700C/2.16kg, which is a particular status for FDM status ( in Zhang ‘s study ) , need to be evaluated. Because the working ambiance of FDM is complicated, the push force of bulge can non be changeless due to the different velocity of bulge. To imitate the environment of FDM, the push force must be understood. The information of MFI will hold the value of mention.
In this undertaking, the difference of MFI between virgin ABS and reused ABS will be evaluated. In theory, for the thermic plastic, repeated warming and chilling rhythm does non alter the size of the plastic molecular ironss, so MFI should non be changed [ 18 ] . However, storage conditions of reused stuffs are normally hapless, normally placed at random, the belongingss of stuff are largely metamorphous.
Harmonizing to Zhang ‘s study, sample drying should be mentioned due to the absorbent of polymer. This component will greatly impact the truth. The specimens including ABS and nylon were put into oven for 2hours at 900C for ABS ( 1200C for Personal computer ) [ 13 ] and maintain dry status to forestall farther H2O absorbing. The other factor impacting preciseness is cleaning. Die diameter affect the velocity of thaw flow. It is easy to hold the deposition in the inner wall. The trial consequence reduces due to the increasing of opposition of thaw flow. So the cleansing is really of import component to the accurate.
2.4.2 Capillary Rheometry Equipment
Capillary rheometer is another manner to mensurate the viscousness of the stuffs. The polymer is put into a trial tubing with a known diameter, and there are several horizontal Markss scribed on it. When put some force per unit area to the polymer, a vacuity is used to acquire the flow polymer, and the clip required is measured for the thaw from one grade to another. Elliott [ 19 ] explains this device besides can prove the denseness and surface tenseness.
2.4.3 Fourier-Transform Infrared Mass spectrometers
FTIR trial designed in this undertaking is to demo the different molecules in the test stuffs other than ABS P400. FTIR trial is to measure what is the material composing of the FDM ABS and after FDM treating stuff, and to happen out whether after FDM processing stuffs become pervert.
Fourier-transform infrared ( FTIR ) is based on the interferogram, which is the thought of the intervention of radiation [ 20 ] . A individual is produced by the alteration of way length between the two beams ; the changeable of distance and frequence are exchangeable by the mathematical of Fourier-transformation [ 20 ] . The most common interferometer used is a Michelson interferometer. There are two perpendicularly mirrors which are bisected by a semi-reflecting movie ( Fig 2 ) .
Fig 9 Schematic of a Michelson interferometer [ 20 ]
The two beams defected from theses mirrors return to the beam splitter where they recombine and interfere. The traveling mirror supplies an optical way difference, which controls the transmittal and contemplation.
2.4.4 Glue Gun
Harmonizing to Zhang ‘s study, nylon strimmer line has been produced with the same diameter as benchmark P400 ABS. However, it was found that the strimmer line was unable to squeeze out from the FDM tip as demand. When the temperature gets to 295 oC, which is the highest temperature restriction for liquefying the FDM machine, a little sum of stuff was extruded [ 21 ] . In this undertaking, glue gun can be used to replace the tip to acquire higher temperature. The gun uses a heat component to uninterrupted heat the plastic gum, the temperature of which can make around 380 grades [ 21 ] .
2.5 mechanical remainder
2.5.1 Tensile Trial
The designing of tensile trial aimed to measure the mechanical belongings among all alternate stuff.
The specimen was studied by tensile trial utilizing a Lloyd LR50KPlus stuffs proving machine ( Fareham, UK ) . For each selected edifice stuff, the testing samples were produced on three forms of raster orientation, which built up in X, Y, and Z axis severally. All tensile trial samples were made with ISO 527-2-5A criterion with a dumbbell form.
Harmonizing to Zhang ‘s study, benchmark P400 ABS sample was trial, the consequence shows in Fig 10.
Fig 10 Tensile trial consequence from three-direction-built P400 ABS samples