▁use . ▁Much ▁of ▁this ▁work ▁has ▁been ▁driven ▁by ▁and ▁target ed ▁at ▁DI Y / M aker / enth us iast / ear ly ▁ad opter ▁communities , ▁with ▁additional ▁t ies ▁to ▁the ▁academic ▁and ▁ha cker ▁communities . ▁ ▁Rep R ap ▁Project ▁is ▁one ▁of ▁the ▁longest ▁running ▁projects ▁in ▁the ▁desktop ▁category . ▁The ▁Rep R ap ▁project ▁a ims ▁to ▁produce ▁a ▁free ▁and ▁open ▁source ▁hardware ▁( F OS H ) ▁ 3 D ▁printer , ▁whose ▁full ▁specific ations ▁are ▁released ▁under ▁the ▁GNU ▁General ▁Public ▁License , ▁which ▁is ▁capable ▁of ▁rep lic ating ▁itself ▁by ▁printing ▁many ▁of ▁its ▁own ▁( pl astic ) ▁parts ▁to ▁create ▁more ▁machines . ▁Rep R aps ▁have ▁already ▁been ▁shown ▁to ▁be ▁able ▁to ▁print ▁circuit ▁bo ards ▁and ▁metal ▁parts . ▁The ▁most ▁popular ▁ 3 D ▁printer ▁in ▁the ▁world ▁is ▁the ▁Pr usa ▁i 3 , ▁a ▁Rep R ap ▁printer . ▁ ▁Because ▁of ▁the ▁F OS H ▁a ims ▁of ▁Rep R ap , ▁many ▁related ▁projects ▁have ▁used ▁their ▁design ▁for ▁insp iration , ▁creating ▁an ▁e cos ystem ▁of ▁related ▁or ▁derivative ▁ 3 D ▁printer s , ▁most ▁of ▁which ▁are ▁also ▁open - source ▁designs . ▁The ▁avail ability ▁of ▁these ▁open - source ▁designs ▁means ▁that ▁variants ▁of ▁ 3 D ▁printer s ▁are ▁easy ▁to ▁invent . ▁The ▁quality ▁and ▁complexity ▁of ▁printer ▁designs , ▁however , ▁as ▁well ▁as ▁the ▁quality ▁of ▁k