《模具设计指南.ppt》由会员分享，可在线阅读，更多相关《模具设计指南.ppt（53页珍藏版）》请在三一办公上搜索。
1、,release 05/1997Design guide,contents,update,EN,GE Plastics,Design guide,release 05/1997,a,1,1,2,3,Design guide 1 ContentsC o n t e n t sGeneral Introduction,Design Development,.9,1.1 Introduction.91.2 Material design factors.91.3 Development steps.91.3.1 End-use requirements.91.3.2 Preliminary desi
2、gn.101.3.3 Material selection.101.3.4 Design modification.101.3.5 CAD/CAE.101.3.5.1 Flow analysis.101.3.5.2 Stress analysis.111.3.6 Prototyping and testing.111.3.7 End-use testing.11,Design for stiffness,.13,2.1 Introduction.132.2 How to determine stiffness.132.2.1 Material.132.2.2 Geometry&loading.
3、142.2.3 Other factors influencing stiffness.142.2.4 Calculating the stiffness.152.2.5 Modal analysis.152.2.6 Safety factors.152.3 Increasing part stiffness.152.3.1 Ribs.152.3.2 V-grooves.152.3.3 Corrugation.162.4 Optimization of stiffness.162.4.1 Optimization for part weight.162.4.1.1 Material Selec
4、tion.162.4.1.2 Geometric considerations.162.4.2 Optimization for stiffness to cost ratio.16,Design for strength,.19,3.1 Introduction.193.2 Material Strength.193.2.1 Ultimate strength.203.2.2 Yield strength.20,Design guide 1 Contents3.2.3 Strain to failure.203.2.4 Proportional limit.203.2.5 Material
5、toughness.203.2.6 Other measures.203.3 Effects of various factors on strenght.203.3.1 Other factors.203.4 Part Strength.213.4.1 Ultimate part strength.213.4.2 Part yield strength.223.4.3 Part toughness.223.5 Improving part strength.223.5.1 Material choice.223.5.2 Geometry optimization.233.6 Design c
6、onsiderations.23,4,Design for behaviour over time,.25,4.1 Introduction.254.2 Static time dependent phenomena.254.2.1 Creep.254.2.1.1 Creep recovery.264.2.1.2 Creep failure modes.264.2.1.3 Apparent modulus.264.2.2 Stress relaxation.274.2.3 Design considerations.284.3 Dynamic time dependent phenomena.
7、284.3.1 Fatigue.284.3.1.1 Fatigue and endurance limits.284.3.1.2 Factors affecting fatigue.294.3.2 Wear resistance.294.3.2.1 Types of wear.294.3.2.2 Factors affecting wear.29,5,Design for impact performance,.31,5.1 Introduction.315.2 Common impact testing methods.315.2.1 Pendulum methods.325.2.2 Fal
8、ling weight methods.325.3 Design considerations.33,6,7,Design guide 1 Contents,Design for appearance,.35,6.1 Introduction.356.1.1 General remarks.356.2 Surface defects.356.2.1 Sink marks.356.2.2 Weld lines.356.2.3 Air traps.356.2.4 Voids.366.2.5 Streaks.366.2.6 Delamination.366.2.7 Jetting.366.2.8 G
9、ate marks.366.2.9 Summary.37,Design for precision,.39,7.1 Introduction.397.1.1 Mould shrinkage.397.1.2 Secondary effects.397.2 Shrinkage phenomena.397.2.1 Cooling.397.2.2 Packing.407.2.3 Orientation.407.3 Materials and shrinkage.407.3.1 Amourphous materials.407.3.2 Crystalline materials.417.3.3 Rein
10、forced materials.417.4 Design related factors.417.4.1 Part wall thickness.417.4.2 Ribs.417.5 Mould related factors.417.5.1 Gate location.417.5.2 Gate type.427.5.3 Gate size.427.6 Processing related factors.427.6.1 Melt temperature.427.6.2 Mould temperature.427.6.3 Injection time.427.6.4 Packing pres
11、sure.427.7 Secondary effects.427.7.1 Thermal expansion.427.7.2 Moisture absorption.42,8,9,10,Design guide 1 Contents7.7.3 Post crystallization.427.7.4 Creep under load.427.8 Simulation techniques.427.9 Summary.43,Design for mouldability,.45,8.1 Introduction.458.2 Material issues.458.2.1 Melt flow le
12、ngth.458.2.1.1 Viscosity.458.2.1.2 Thermal properties.468.2.1.3 Shear properties.468.2.2 Melt temperature.468.3 Shrinkage.468.3.1 General remarks.468.3.2 Warpage.478.4 Cooling time.478.5 Design considerations.488.5.1 General remarks.488.5.2 Nominal wall thickness.488.5.3 Projections.488.5.4 Radii.49
13、8.5.5 Ribs.498.5.6 Support ribs.498.5.7 Bosses.508.5.8 Undercuts.508.5.9 Coring.518.5.10 Draft angles.518.5.11 Textures&lettering.518.5.12 Flow leaders.528.5.13 Moulded-in-stress.528.5.14 Weld lines.528.6 Processing considerations.528.6.1 Venting.528.6.2 Gating.538.7 Ejection.54,Design for recyclabi
14、lityDesign for automation,.55.57,11,Appendix,.59,1Introduction,The intention of this guide is toprovide the design and engineeringcommunities with an insight into theconsiderations necessary whendesigning applications in engineeringthermoplastics.Many of theseconsiderations relate to mouldingcriteri
15、a,so those involved in themanufacturing and processing ofplastics components should alsofind it useful.Typically,design manuals deal with aspecific resin family,presentingproperties,design criteria,assembly andother related information.GE Plasticsproduct line includes crystalline,amorphous,thermopla
16、stic elastomersand glass mat reinforced polymers.Because of this diversity,this brochurewill concentrate on issues common to allinjection mouldable thermoplasticresins.,This design guide differs from most byvirtue of its Designing for concept,helping the reader move quickly to theissue that needs ad
17、dressing.Consequently,discussion of certainaspects can occur in more than onesection,which demonstrates howintegral the process of designing forplastics is.Following the explanatorychapters is a section showing typicalengineering material performancegraphs for a range of GE Plasticsthermoplastic pol
18、ymers.Supplementary publications coveringassembly techniques,polymerprocessing considerations and overviewsof specific resins in the GE Plasticsproduct lines are available on request.In addition,monographs discussingdetailed design studies are releasedperiodically,covering these issues ingreater dep
19、th than is possible in thisgeneralized guide.,3,1.2,1.3,9,1Design development,1.1,Introduction,Throughout the process of productdesign,both functional and materialaspects must be considered.Functionaldesign factors relate to production andassembly.Material design factorsconcern the performance of a
20、materialin service.This performance,whichincludes strengths,weaknesses andlimitations,is investigated to provide the,Specific information needed to establishend-use requirements includes:(a)Anticipated structural requirementsLOADSThese dictate the stresses a materialwill be subjected to,and they def
21、inecomponent deflections.,weighed against the financial aspectsof the product.This exercise is oftencalled Product Risk Analysis.Additional details are not given heresince each company applies its ownmeasures.General Electric Plastics is preparedto provide assistance in this matter,starting point of
22、 the design process.,RATE OF LOADING,and,if required,contact should bemade with the nearest GE Plastics,Material design factorsConsiderable information is needed bythe design engineer to develop aproduct design from the initial concept.This can be a smooth process if carefulattention is given to eac
23、h step involved.The designer must know the end-useperformance requirements of theproposed application.To determinewhether a material can meet theserequirements,the designer must be ableto rely on information provided by theraw material supplier,indicating theenvironmental and physical capabilitiesof
24、 the material.Development steps1.3.1 Establish end-use requirementsThe development of any componentstarts with careful consideration ofanticipated end-use requirements.In general,the lower strengthproperties of polymers compared withmetals and woods require that productsbe designed to utilize a larg
25、erpercentage of their available strength.,A thermoplastic may demonstratedifferent behaviour with changes inloading rate.Therefore,in additionto its magnitude,the rate at whichloading is applied should beinvestigated.DURATION OF LOADINGInitial negligible deflectionsresulting from a small load maybec
26、ome unacceptably large if theload is maintained.IMPACT FORCESBecause the application of highloads for short periods of time mayresult in premature failure,thenature of impact forces to which thecomponent will be subjected shouldbe determined.VIBRATIONThis induces stress and deflectionchanges.Though
27、these may besmall,component failure may occurthrough constant repetition.FORESEEABLE MISUSEThough structural requirements mayhave been satisfied,and anappropriate design proposed,failurecan still occur as a result of misuse.To establish the anticipated risklevel,therefore,a risk assessment ofthe pro
28、duct in use should be made.The relevance tree method is idealfor this purpose,providing data tofacilitate assessment of foreseeablemisuse.The results should then be,sales office.(b)Anticipated environmentsTEMPERATURE EXTREMESAll materials possess a workingtemperature range.Outside thisrange the comp
29、onent cannotproperly perform its intendedfunction.In addition,the propertiesof the material may vary considerablywithin working limits.As all thermoplastics are subject toattack by certain chemical agents,the service environment of theproposed component must beestablished.Outdoor exposure for prolon
30、gedperiods may result in materialdegradation.(c)Assembly and secondary operationsUsually a plastic component is notused in isolation but is just one of anumber of components making upthe end-product.The techniqueused for assembly,such asmechanical fastening,welding andadhesive bonding,needs to becon
31、sidered at the initial design stageto optimize the component for easeof assembly,(and ease of handling inthe case of automated assembly),orease of disassembly for maintenanceand recycling.,10,Design guide 1 Design Development,Secondary operations,such as,1.3.2 Establish a preliminary design,1.3.4 Mo
32、dify the design,painting,printing and hot stamping,also have to be given earlyconsideration in order to design thebest surface profile.This meansavoiding for example sink marks andsharp changes in shape to achieve ahigh quality smooth surface.,A preliminary concept sketch of theproposed component ca
33、n help thedesigner to determine which aspects areinflexible,and which can be modified toachieve required performance.The preliminary sketch,therefore,should include both fixed and variable,If this is necessary,four areas inparticular should be considered:(a)The specific property balance of theselect
34、ed grade,(e.g.tensile strength,impact resistance),(d)Cost limitsThe following should be established:,dimensions.1.3.3 Select the materialA GE Plastics material should be,(b)Processing limitations,(e.g.wallthickness vs flow lengths)(c)Assembly methods,(e.g.snap-fits,adhesives),Component cost resultin
35、g in,selected that will satisfy initially defined,profitable sales Annual volume Economic processing method(s)with estimated cycle time(s)Tooling cost(s)for selectedprocessing method(s)The expected service life ofthe component(e)Regulations/standards complianceCheck which standards orregulations app
36、ly or can be appliedin the market place to thecomponent,product or appliance,for example:,end-use requirements.The comparativeproperty data sheet should be the firstdocument which is consulted.Initialselection may subsequently be refinedby reviewing the time,temperature andenvironment-dependent prop
37、ertiesrelevant to the particular application.Supplementary data,such as abrasionresistance or ductility,may be neededto confirm the selection.Material properties can be divided intotwo main categories.(a)Mechanical properties usedessentially for component design,(d)Cost of modification and its impac
38、ton component and/or project bud-get,(refer to s F I G U R E 1).Strength of materials formulae shouldbe used in conjunction with materialproperty data to calculate necessarydimensions such as wall thickness.(Refer to Chapter 3 Design forstrength).Design calculations of arepetitive or iterative natur
39、e,however,may warrant a computer-aidedapproach.1.3.5 CAD/CAE,STANDARDS,calculations:,Two particularly relevant computer-aided systems are Flow Analysis of an,IEC/CEE International ElectricalCommittee/Commit EuropandElectricitISO/CEN International StandardsOrganization/Commit Europande NormalisationD
40、IN Deutsche Industrie frNormungenBSI British Standards InstituteNF Normes FrancaisASTM American Society for Testingof MaterialsREGULATIONSUL Underwriters LaboratoriesCSA Canadian Standards AssociationCEE Publications of the Commit,Elastic limitTensile strengthModulus vs temperaturePoissons ratioAppa
41、rent(creep)modulusFatigue limitCoefficient(s)of thermalexpansionCoefficient of frictionThermal conductivityDensityMould shrinkage(b)Other relevant properties:HardnessImpact strengthChemical resistanceWeathering resistanceAbrasion resistanceDuctilityFlammabilityHeat deflection temperatureElectrical p
42、roperties,injection moulding,and Stress Analysisof a final component.Both generallyuse the Finite Element Method.Thisapproach considers the geometry andphysical properties of the component asa continuum of small manageable parts,or finite elements.Each element of thestructure is individually investi
43、gated inrelation to its neighbouring elements,the total structure,and the physicalconstraints on the system.A largenumber of simultaneous equationsresult,the solution of which isparticularly suited to the repetitivecapabilities of a computer.1.3.5.1 Flow analysisBecause the performance of aninjectio
44、n moulded component is largelydependent on the moulding process,consideration of the service conditionsof the component in isolation isinsufficient to ensure a successful,Europan dElectricit,To design a plastic component,product.Simple shapes should not givematerial flow problems to the,Factory and
45、building codes.,information concerning anycombination of material propertiesmay be required.If the data areunavailable,or assistance is neededin interpretation,contact should bemade with the nearest GE Plasticssales office.,experienced tool-maker and moulder.However,larger components ofcomplex geome
46、try often presentdifficulties,for example positioning andnumber of gates,runner dimensionsand location of weld lines.,testing.,cycling,itions,s,11,Design guide 1 Design Development1.3.6 Prototyping and testing,In the flow analysis process,a computer,Product performance tests can be,model of the comp
47、onent is produced,and initial gating positions selected.The predicted manner in which thematerial will fill the cavity is thenpresented graphically and numerically.Isochronous temperatures andpressures throughout the system arecalculated,in addition to weld linelocations and undesirable conditionssu
48、ch as overpacking.Moulding variablesand/or gating positions are subsequent-ly changed,if necessary,in order toachieve an optimum flow pattern.By means of this iterative approach,At this point in the procedure,a prototype should be constructed.The prototype and its testing can helpthe designer by:Est
49、ablishing confidence in the designby confirming that component require-ments do not exceed design limits.Developing preliminary productperformance information.Identifying potential problem areasin performance,manufacturing orassembly.Allowing pre-launch assessment andfeedback from consumer trials.,c
50、onducted on functional prototypes orproduction parts.Since functionalprototypes may be produced using non-production tooling or part modelling,caution must be exercised duringtesting and interpreting the results.The prototype may not behave inexactly the same manner as aproduction component.The init
