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Pro/ENGINEER Mold Design Reference Guide Look for the Authentic CADD Centre Hologram! Pro IE NG I N E E R' W I L D F I R E CONTENTS Introduction to Basic Mold Basic about Mold Applications Molding Process Mold t'f?tC: - - :::··································· Methods of actuation Reference Model creation Creating Rib Features Creating Draft Features Design Model Analysis Modifying the Default Pull Direction Analyzing Model Accuracy Creating the Reference Model Redefining the Reference Model Analyzing Mold Cavity Layout 1() 16 21 21 22 22 22 23 27 27 29 30 35 Analyzing Draft Hinges and Pull Direction Mold Model Parting surface Side Core Et Side Cavity Feed system Multy cavity mold Family Mold Single Cavity mold Parts of mold Draft Molding Machine Ejection Plastic materials Shrinkage Mold manufacturing processes Machining 35 37 41 48 54 56 59 62 67 72 CADD CENTRE · - Preparing Mold Mode l s Pro IE NG I N E E R' t I L D F I R E 91 ······································· - ····· S hrinkage . -····················· 91 102 Workp iece Recl assify ing Mol d Model C omp onents _ 110 Mol dVol ume C re ation 113 C reating S liders 117 Re fe re nce Part: C utout : 129 Lifter Mol dVolumes 132 S ke tching Inse rt Mol dVol ume s � 142 Parting Line andParting S urfaceC reation 148 Creating Mold 217 Spl itting the Workp ei ce 218 Spl itting MoldVol umes 221 Blanking and Unbl anking Mol d Ite ms 231 Analy zing SplitCl assification 236 Mol d C omp one nt Extraction 241 Mold Features C reation 246 Waterl ine C ircuits 246 C re ating Sp rues and Runners 258 Ejector Pin Cl earance Hol e s 266 Fil l ing andOp ening theMold 279 Op ening the Mol d 281 DraftC hecking a MoldOpe ning S tep 288 Inte rfe re nce C hecking a Mol dOp ening S te p 292 Vie wing Mol d Information 295 Project ···············································-······-··-·-····································· ······································ cAnn· CENTRE 321 Basic about Mold Mold manufacturing processes Machining Plastic materials Molding Machine Molding Process Mold types Parts of mold Single Cavity mold Multi cavity mold Family Mold Side Core a Side Cavity Methods of actuation Feed system Shrinkage Ejection Draft Parting surface ProlE N G I NEER W I L D F l l? l' - · 1.lntroduction to Basic Mold Basic about Mold Mol ding(BritishEngl ish: moulding) is a manufac turingp roc ess forp roduc ingp arts from both thermop lastic and thermosetting pl astic material s Molding is the p roc ess of manufac turing by shap ing pl iable raw material using a rigid frame or model c alle d a p attern Amold is a holl owe d-out bl oc k that is fille d with a l iquidl ikepl astic , glass, metal, orc eramic raw material s The liquid harde ns or sets inside the mol d, adop ting its shap e A mol d is the opp osite of a c ast The manufac ture r who makes the molds is c all ed the mol dmake r A rel ease age nt is typ ci ally use d to make removal of the hardened/set substanc e from the mol d easier Fig 1.1 : Mold Component History In 1868 John We sley Hy att devel op ed a pl astic mate rial he named Celluloid whic h had be en inve nted in 1851 by Ale xande r Parks Hy att imp roved it so that itc oul d be p roc essed into finished form In 1872 John, with his brother Isaiah, p atented the first injec tion mol ding mac hine This mac hine was relatively simp le c omp ared to the mac hine s we use today It basic ally worke d l ike a l arge hyp odermic needle injec ting pl astic through a heated cyl inde r into a mold The industry p rogre ssed sl owly over the y ears p roduc ing p roduc ts suc h as c oll ar stay s, buttons, and hairc ombs until it expl odedin the 1940s bec ause WorldWar c reated a huge de mand for inexp ensive, mass-p roduc ed p roduc ts The industry has evol ved ove r the years from p roduc ing c ombs and buttons to p roduc ing a vast array of p roduc ts for many industries incl uding automotive , medic al , aerosp ac e, c onsume r, toy s, p lumbing, p ac kaging, andc onstruc tion CADD CENTRE Pro IE NGIN EER l D F R E Applications Injection molding is used to create many things such as mil k cartons, containers, bottl e cap s, automotive dashboards, p ocket combs, and most other p l astic p roducts avail abl e today Injection mol ding is the most common method of p art manufacturing It is ideal for p roducing high volumes of the same object S ome advantages of injection mol ding are high p roduction rates, high tol erances are rep eatable, wide range of material s can be used, l ow labour cost, minimal scrap l osses, and l ittl e need to finish p arts after mol ding S ome disadvantages of this p rocess are exp ensive equip ment investment, running costs may be high, and p arts must be designed with mol ding consideration Fig 1.2: Application Mold manufacturing processes Mold is the common terms used to describe the tool ing used to p roduce pl astic p arts in mol ding Traditionally , mol ds have been exp ensive to manufacture They were usually only used in mass p roduction where thousands of p arts were being p roduced Molds are typ ically constructed from hardened steel , p re­ hardened steel , al uminium, and/or beryl lium-copper all oy The choice of material to build a mol d from is, p rimarily one of economics, steel mol ds generally cost more to construct, but their longer l ifesp an will offset the higher initial cost over a higher number of p arts made before wearing out Pre-hardened steel mol ds are l ess wear resistant and are used for lower vol ume requirements or l arger comp onents The mol ds can be manufactured by either CNC machining or by using El ectrical Discharge Machining p rocesses · Machining Mol ds are built through two main methods: Standard machining and EDM S tandard Machining, in its conventional form, has historically been the method of buil ding injection molds With technol ogical devel op ment, CNC machining became the p redominant means of making more compl ex mol ds with more accurate mol d details in l ess time than traditional methods CADD CENTRE ProlEN G I NEER W I L D F I R E The elect ricaldischarge machining(EDM) or sp ark erosionp roc ess has bec ome widety used·n fT'Ol1J croking As well as all owingt he format ion of shap es which are diffic ult t o mac hine, thep rocess alto'IS pre-r.aroe_reo mol ds to be shap ed so t hat no heat t reat ment is required C hanges t o a hardened mol d by convo n!iona drill ing and mil l ing normally require anneal ing t o soft en t he st eel , foll owed by heat t reatmentto haroen it again EDM is a simpl e p rocess in whic h a shap ed el ect rode, usually made of copper or grap hit e, isvery slowly lowered ont ot he mol d surface (over a p eriod of many hours), whic h is immersed in p araffin oil A volt age appl ied bet ween t ool and mol d causes sp ark erosion of t he mol d surface in t he inverse shap e of t he el ec trode Fig 1.3: Machining processes Plastic materials Pl ast ic is sy nt het ic p oly mer of high mol ecul ar weight It is comp osed of organic chemical unit s Poly mer is a single l arge mol ecul e It is formed as a result of t he union of t wo or more mol ec ules of simpl er substance Plast ic are normal ly cl assified int o2 c at egories: Plastics Thermosetting Thermoplastics Fig 1.4: Type of Plastics CADD CENTRE 11 Pro IE NG I N EE R' - '" L D F I R E Thermoplastic A thermoplastic is a polymer that turns to a liquid when heated and freezes to a very glassy state when, cooled sufficiently Thermoplastics are elastic and flexible "thermoplastic materials can be remelted without ' undergoing any appreciable chemical change and you reuse" Thermoplastics materials are as follow: • Polypropylene (PP), Ex: Automobile components etc • Polystyrene (PS), Ex: Toys, Paper weight etc • Polycarbonate (PC), Ex: Helmets etc • Polyamide (PA) Ex: Ropes, gears etc Properties The following are the properties of thermoplastic : • Possesses high glass sparkle • Transparence • High mechanical crack resistance • Soft and flexible Thermosetting Relating to a compound that's softens when initially heated, but hardens permanently once it has cooled Thermosetting materials are made of long-chain polymers that cross-link with each other after they have been heated, rendering the substance permanently hard Thermosetting materials can not be remelted and you can not reuse Thermosetting materials are as follow: • Polyurethane • Alkyds, Ex: Pressure vessels, jigs & fixtures etc • Polyesters, Ex: Automobile parts etc • Epoxies, Ex: Switches, Connectors etc Properties The following are the properties of thermosetting plastic: • High Thermal stability • High dimensional stability • High rigidity and hard ness • Light weight cAnn· CENTRE ProlENGI N E E R W I l ') F I l'I E Molding Machine TheMold designer should know the typ es of molding mac hine are avail able with his c ustomer as this will infl uenc e his mold design You must al so know the c ap abil ities of the mac hines and whether the mac hine c an be expl oited bey ond the ratedc ap ac ities if the need areas fig 1.5: Molding M/C A modern injec tion mol ding mac hine c onsists of foll owing basic part: Feed Nozzle Barrel heater Screw drive arrangement Screw tip Checkvalue Screw fig 1.6: Mold M/C Injection system Hopper A feed hopper is for hol ding and feeding the pl astic material in to barrel Barrel Barrel is acyl indric al shel l or tube In diameter of the barrel guides the extrude sc rew Heaters are cl amp ed on external diameter CADD CENTRE Pro I E NG I N E L D F I E R' R E Extrude screw The screw of an i njection m o l d i n g mac h i n e is d ivided i nto th ree sections or zones • The feed section • The com pression secti o n • The m eteri n g secti o n T h e feed section tra nsports the p lastic m ateri a l from the h o p pe r t o heated portion o f the barrel The p l astic g n u l e is com p ressed to a homogeneous melt in the com p ress i on section:" The fi n a l m ixi n g a n d heating of the material i nto a h o m og e n eous m e l t is ca rried o u t in the m eteri ng zone The d rive fo r the rotation of screw d u r i n g feed cyc l e is obta i n ed from a hyd u l ic m otor or a va ria b l e speed el ectric m otor Fig 7: Extrude Screw Nozzle The Nozz l e i s co n n ected to the end of th e ba rrel Th rou g h the nozzle the softened material passed i nto the mould Genera l p u rpose or sta n d a rd nozzles a re made F i g : Nozzle CAD De CENTRE