School Work

3D Printing

Description
3D printing
Categories
Published
of 12
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Related Documents
Share
Transcript
  INTRODUCTION3D printing was originally developed in 1984 by Ch! #ll and is an additive pro!ess o$ %a ing a three&di%ensional solid ob'e!t $ro% a digital %odel( 3D printingis a!hieved by laying down s!!essive layers o$ %aterial to $or% shapes( There has been re!ently a hge growth in the sales and se o$ 3D printing and the %ar et $or these in!reased by )9* $ro% )+11 to year )+1)( To print, the %a!hine reads thedesign $ro% an (stl $ile and lays down s!!essive layers o$ %aterial to bild a series o$ !ross se!tions( These layers, as de!ided by the C-D %odel, are 'oined or ato%ati!ally $se to !reate the $inal shape( This te!hni.e allows $or the ability to!reate al%ost any shape or geo%etri! $eatre(The printer resoltion /layer thi! nessand 0& resoltion2 are de$ined as either dpi /dots per in!h2 or %i!ro%eters( Typi!allayer thi! ness is arond 1++ %i!ro%eters /%2( #igher end %a!hines however /Ob'et Conne series and 3D 5yste%s6 7roet series2 !an print layers as thin as 1 %(The 0& resoltion o$ 3D printers is arond :+ to 1++ %(-%ong other ses, 3D printing has $ond pro%ise in the bio%edi!al $ield as a %eans to generate tisses!a$$olds ot o$ biodegradable poly%ers as well as potentially tisses by printing !ellsand %atri into a de$ined area(Crrent syntheti! bone gra$ts s$$er $ro% poor handling !hara!teristi!s, brittle%e!hani!al properties, and in!onsistent bioa!tivity( ;y blending a biodegradablea%phiphili! poly%er with hydroyapatite /#-2, the %ain %ineral !o%ponent in bone,we developed an i%proved syntheti! bone gra$t( The poly%er<#- !o%posites were$abri!ated in both )&D and 3&D $or%s by ele!trospinning and 3&D printing( These%aterials ehibited ni.e handling !hara!teristi!s s!h as high tensile elasti!ity/=)++* $ailre strain2 and sel$&sti$$ening properties pon hydration, allowing their $a!ile<stabile $iation arond an open de$e!t or within a !on$ined de$e!t( They are alsosperhydrophili!, enabling the absorption o$ a.eos !ell sspensions and proteintherapeti!s(  Design 7roperties>ow %e!hani!al strength is a %a'or !hallenge in poros s!a$$olds, and is pri%arily !ontrolled by pore vol%e and distribtion( This is also tre $or 3D printed!era%i! s!a$$olds and li%its their se to only non&load bearing and low&load bearingappli!ations( Opti%i?ed post pro!essing approa!hes and !o%positional %odi$i!ations!an i%prove %e!hani!al properties o$ !era%i! s!a$$olds( To investigate the e$$e!t o$  printing orientation and layer thi! ness on the %e!hani!al properties o$ greenspe!i%ens, !o%pression tests were per$or%ed on raw @p 1:+ spe!i%ens(The !o%pression strength, ong6s %odls and toghness o$ the 3D printed porossa%ples were deter%ined and !o%pared with ea!h other to $ind the opti%% printing!onditions( The sa%e test setp and para%eter were sed $or all other sa%ples(Cal!i% 5l$ate s!a$$olds not sb'e!ted to any post hardening de%onstrated lower !o%pressive strength, !o%pressive %odls and !o%pressive toghness than thosereported $or !an!ellos bone( The !o%pressive stress&strain !rves shown in Aigre13/aB!2 are !hara!teri?ed by the initial non&linear toe region $ollowed by the %ainlinear region and then the !on!ave shape till the $ailre point( The $l!tationsobserved in this region !old be attribted to the layer by layer !ollapse o$ the%i!rostr!tre nder !o%pression load( The average vales o$ !o%pressive strength,ong6s %odls and toghness o$ $ive sa%ples were shown in Aigre 14/aB!2(Aigre 13( Co%pressive 5tress&5train Crve $or di$$erent layer thi! ness in 0 /a2, /b2 and @ /!2 dire!tion printing(  Aigre 14( Co%parison o$ !o%pressive strength /a2, ong6s %odls /b2 andtoghness /!2 in sa%ples printed with di$$erent layer thi! ness in varios orientation(-!!ording to the !o%pressive stress&strain !rves in Aigre 13/aB!2, s!a$$oldsnderwent the elasti! displa!e%ent $ollowed by $ailre in strts and %i!ro!ra! sgeneration in the periphery wall o$ the s!a$$olds printed in 0 and  dire!tion throghthe hori?ontal strts( Aailre also o!!rred throgh the verti!al strts in the body o$ sa%ples printed in @ dire!tion( oreover, the lo!ation o$ $ailres is not !on!entratedin the %iddle o$ the s!a$$olds( This indi!ates that internal str!tre has a signi$i!antin$len!e on the %e!hani!al properties o$ 3D7 sa%ples(-s shown in Aigres 14/aB!2, di$$eren!e in printing orientation reslted in varios!o%pressive strengths( The !o%pressive strength o$ sa%ples printed in @ dire!tionwas $ond to be very low $or the printed poros sa%ples that is !riti!al $or thedepowdering and handling steps 3+E( 5!a$$olds printed in 0 and  dire!tion withlayer thi! ness o$ +(1 %% had the less !o%pressive strength, however, in!reasinglayer thi! ness $ro% +(+8F: %% to +(11): and +(1): %% had a %ore positive e$$e!ton the %e!hani!al properties o$ the s!a$$old(-s shown in Aigre 14/a2 and 14/!2, althogh the sa%ples with layer thi! ness o$ +(+8F: %% printed in @ dire!tion have the least !o%pressive strength bt ehibit %oretoghness !o%pared to sa%ples with +(1 %% layer thi! ness(-s shown in Aigres 14/a2 and 14/!2, s!a$$olds with layer thi! ness o$ +(1 %%de%onstrated low !o%pressive strength, ong6s %odls and toghness in both 0and  printing orientations( ;y in!reasing the layer thi! ness to +(11): and +(1):%%, the !o%pressive strength in!reased, and the plasti! region was etended,sggesting higher toghness in three orientation o$ 0,  and @( Conversely, thes!a$$olds printed with +(1 %% layer thi! ness de%onstrated a lower level o$ plasti!de$or%ation and generally $ailed shortly a$ter rea!hing the pea load that is %oreevident in @ printing orientation, /Aigre 13/!22( -s it !an be seen, the greatesti%prove%ent in !o%pressive strength and toghness were all obtained when s!a$$oldswere printed with +(11): %% layer thi! ness in 0 printing dire!tion(  It see%s that an in!rease o$ layer thi! ness and de!rease o$ shear $or!es reslt in better powder spreading, stability and ni$or%ity whi!h i%prove the strength(#owever, when layer thi! ness de!reases, the n%ber o$ layers is in!reased( This %ayreslts in higher integrity that in trn will in!rease the strength o$ the spe!i%ens too)3E( It is also worthy to note that, as shown in Aigre 14/a2, nder the sa%e binder satration, with a de!rease o$ layer thi! ness $ro% +(1 to +(+8F: %%, the !o%pressivestrength wold so%ehow in!rease( In s!h !ase, as layer thi! ness de!reases, thesprayed binder wold penetrate better in verti!al and lateral dire!tions over thesr$a!e reslting in less e%pty spa!es between powder parti!les and in!reasing thestrength o$ the spe!i%en( Generally, binder spreading in verti!al dire!tion is %orethan that in lateral dire!tion( 5o, the verti!al dire!tion will be satrated with the binder  be$ore the lateral binder spreading is !o%plete( #owever, it see%s that when thesele!ted layer thi! ness is less than a !ertain threshold, the binder wold !o%pletely penetrate verti!ally and the powder gets satrated, while this is not the !ase in lateraldire!tion( 5o, in!o%plete spreading o$ the binder laterally wold de!rease the sa%pleintegrity and strength( Arther%ore, with a de!rease o$ layer thi! ness $ro% +(1): and+(11): to +(1 %%, the binder penetrates $aster to the botto% o$ the layer( #owever, the previos printed layer prevents the binder $ro% $rther spreading whi!h reslts innonni$or%ity in the inter$a!e layers( There$ore $inding the opti%% layer thi! nessis !riti!al $or printing s!h poros s!a$$olds(The %e!hani!al behavior depends on the orientation o$ the powder spreading and binder 'etting( Aor s!a$$olds printed in  dire!tion the !o%pressive load was applied parallel to the !onstitent layers and the dire!tion o$ binder 'etting( Hhile $or thosesa%ples printed in 0 orientation, the !o%pressive load was applied parallel to the!onstitent layers bt perpendi!lar to the dire!tion o$ binder 'etting( Aor sa%ples printed in @ orientation, the !o%pressive load was applied perpendi!lar to both, the!onstitent layer and the binder 'etting(5!a$$olds printed in 0 orientation present higher !o%pressive strength and %odls in!o%parison with the s!a$$olds printed in  and @ dire!tions( These reslts sggest thatthe printing orientation and layer thi! ness have a great in$len!e on the %e!hani!al properties o$ 3D7 parts( #owever, these reslts are in !ontrast to the stdy reslt o$ (Castilho et al(-!!ording to Aigre 14/a2, the wea est average !o%pressive strength was shown bythe sa%ples printed in @ dire!tion( -lso, %ore average strength was observed insa%ples printed in 0 dire!tion and this set also showed the lowest standard deviation(The sa%ples printed in  dire!tion have the %ean !o%pressive strength( -lthogh,this set showed the highest standard deviation re$erring to the signi$i!ant diversitya%ong strength vales(It shold be noted that de to the low strength o$ sa%ples printed in @ dire!tion, they bro e in the depowdering step(
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks