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e recent y d scussed howregujar modelers coulduse the revo ut onarytechno ogy of 3D printingto produce custom parts

for scale mode s camera dTones and0ther model fg applicat ons. 3D printings ndeed a game changer but there arest I compofents that, owing to strengthor to erance requ rements, need to be'nacl l.d o r. o'ai r r L^ o olremetals. [,4achin ng prec si0n componentss a cha eng ng art form, and tools

w th the necessary precls 0n can costthousands of dollars Fortunate y,lustas 3D pr nting al ows us to bypass theexpense and comp exlty of hav ng p asticparts nject on molded, custom CNC

machin ng makes it pract cai to pr0ducep-.. ..or -reL.l o"r-. to,oLl . a

spec fications.

78 N4odelAirplaneNews.com

HLH Is managed lry JafiL.sMurphy, who rElo<ated lo

Chlna h 2008. Ihe comparyhas morc than 2O0 emplo!'ees and

provlde5 a wlde rdn8e of ma(hhlng andrapld-prototyplng processes.

WHAT IS CNC MACHINING?CNC (Computer Numerical Control)machiningtakes in a family ofprocessesthat use computer controlto operatemilling machines, lathes, and otherequipment. Instead of manually runningthe machine making toolchanges, andrepositioning workpieces, operatorsgenerate "toolpaths" on a desktopcomputer, effectively telling the machinenot only what shape to cut but also whatcutters to use and how quickly to operatethe CNC machine then cuts the partswith little operator involvementi somemachines can change cutters or evenloadfresh workpieces automatically. Once thetool pathis generated, the machine canproduce anynumber of copies

With the growlng influence of rapidprototyping in the industrial world,there are a growing number of suppliersar ound rhe world who use CNC machin.r g

and otherprocesses to quickly andefficiently produce one-off or smallbatch prototypes. I recently started usingone of these suppliers HLHPrototypes(hlhprototypes com), to produce customcomponents formy scale helicoptermechanics. The process is easier and moreaffordable than you might expect:My

custom gearboxparts were less than 5100,andl could order smallbatches for lessthanSS0per set

OVERVIEW OF }ILH PROTOTYPESHLH Prototypes is a rapid-prototypingsupplier in Shenzhen Chjna.It provides a

broad array of manufacturing processes

jncluding CNC machining 3D printing,inlection molding andvacuum casting. lhecompany was founded in 2001 and now has

more than 200 employees lhey currentlyoperate more than 40 CNCmachines,along wir h 3D printer s. va.uum castingmachines, andinjectionmolders.HLHismanaged by lames MurPhY, a natlve of

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Larg€ CNC machlnes can handle a wld€ range ol workplec€s and materlals. When machlnlng metal, a <onstanttlood of cuttlngfluld/coolant ls pumped over the workplece to rcduce cutterwearandlmProvesurfacefinlsh.

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NOVEMBER 2015 79

CNC Machined Parts

the United Kingdom who moved to Chinain 2008. the compary has a strong onlinepresence, and it typically turns aroundquote requests overnight.

GETTI G STARTED'lhe first step, of course, is to draw yourcomponents in 3D CAD (Computer-AidedDesign). Rhino is my personal favodte 3Ddesign application, but therc are manyother options, including open-source ardweb-based products.

[,fy prcject was to build a 42-degree tailrotor gearbox for a scale Huey helicopter.Because I was using parts from AlignT-Rex 600 tail units, the flrst step was tocarcfully measurc the stock side platesand draw them in the CAD environment.'fhis 2D computer model was thenmirrored at a 42-degree angle to get thebasic layout for my new side plates, the 2Ddesign was converted to a 3D solid, and Iwas ready to email my design for quoting.

Because HLH'S business modelemphasizes speed, its pdce quote includesthe cost for international FedEx shipping.If you can wait a tew days Ior your parts,you can save a Iittle on shipping costs, theterms are 50% down, with the balancedue on completion, and HLH commonlycompletes small prctotypes in one to twoweeks.

Based on calEfrrl measu*ments otthe stock Allgn tall udt, I dr€fl rry42-degEe slde lram.s uslng Rhlno,tnylavo te 30 dGslgn proararl- I thenemall€d the 3D model to HLH. Hcesare typlcaly quoted ovemlghL Mycustom aearbox parts rrere less thanS1O0. and I could oder small betch.sIor less rhan S50 per set.

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My completed slde fr.mes errlt edvla FedExFn lo daysaftcr ordfflrE. Ihe rdls€d bosses aEundthe saew holes dlo/ morE poslB,€ allgment.nd wouH bc lmpracdcalwlthout C C technoloBr.the ball beadng! were r p€rfcct press-fit.

80 ModelAkplaneNews.com

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Above and below: Cl{C maclinlng rEkcs lt posslbh to Droduecomplex parts wlth mlnlmal dlEct labor. HLH can Erydy .trynumber of parts, lrom slryle unlt! to thousands. You <an s€ehundreds of product ex.mples ln HLH'S Fllckr album.

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RESULTSMy sales representative kept me posted onmy order statusand provided tracking info when my parts shipped.Ihadmypartsin handjust 10 days after placing my order, whichis impressive. Sohow did theylook? Thephotos speakforthemselves. l was pleased that all tool marks had been buffedout, and the dimensional accuracy simply could not havebeen any better.'lhe assembled gearboxruns silky smoothand Iooks as good as any commercialproduct. I can foreseeusing HLH's services for allsorts of future projects, such asretractable landing gear, scale rotorheads, and custom gears.lhe possibilities are neariy endless. +

82 ModelAjrplaneNews.rcm

',: !r Here are lust a few of HLH'S fle€t ot machtnes. fte company

op€rates more than 40 CNC machlnes ln a range ofstz€s tn addttonto 30 prlntlng, Inlecdofl moldlng, vict um castlnt, and lr,ke EDM(electrlcaldlscharge machlnlng).

.,;,I After CNC machlnlng ls complet€d, parts go to post-6nlshln& wheE remalnlng tool marks are buftud our.HLH canalso pmvlde hlgh-gradepollshedfnlshes.palndry, oranodlzlngat an addltlonal cost.

-l: ir,: r. Ihe ass€mbled 42-d€gr€e gearborIooks as good as any commerclal product.Gearlash ls permanently set andrequlres no adjustment. lvlth CNCmachlnl.rg, lt's posslble for retularmodeleE to d€slgn and producepre€lslon custom ass€mblles

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