Injection Moulding_TY(1)(1)(1).pdf

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2. Bytheendofthisunit,youwillbeableto;
Describethebasicsofinjectionmoulding.
Listdowntypes&importantpartsofinjection
moldingmachine.
Categorize&explainthefunctionsofeachunit
ofinjectionmoldingmachine.
Describethecompletecycleofinjection
moldingprocess.

3. Identify&explaintheeffectofprocess
parametersonproductquality.
Identify&troubleshootthepossible
defects.
Listdowntheadvantages,disadvantages
andapplicationsofinjectionmolding
machine.

4. Injectingmoltenthermoplasticmaterial
intoaclosedmouldwhichisrelatively
cool.
Heating
Melting
Injection
Cooling
Ejection

5. HandInjectionMouldingM/c
Plunger/RamtypeInjectionMouldingM/c
ReciprocatingScrewTypeInjectionMoulding
M/c

6. 6
2/12/2018
Injection System
Hydraulic System
Mold System
Clamping System
Control System
Components of Molding Machine

10. Hand Injection Moulding Machine
Verticalmachineconsistsofhandle,barrel,
plunger,bandheaters,atorpedo,nozzle&
mould.

11. Plunger Type Injection
Molding Machine
Vertical & Horizontal Plunger Type Injection Molding Machine

13. Injection Unit & Ejection Unit:
Zones:
Feeding zone
Compressing (or transition) zone
Metering zone

14. Feedingthereadytoprocessmaterial
Plasticizationofthematerialby
reciprocatingScrew.
Injectionofthemoltenmaterialtoaclosed
mouldviafeedsystem
CoolingoftheMould&simultaneously
refillingofthematerialforthenextcycle.
Openingofmould&ejectionoftheProduct.
CloseoftheMouldfornextcycle.

15. The mould closes and the screw begins moving forward for
injection.
The cavity fills as the reciprocating screw moves forward,
as a plunger.

16. The cavity is packed as the screw continuously moves
forward.
The cavity cools as the gate freezes off and the screw
begins to retract to plasticize material for the next shot.

17. The mould opensfor part ejection
The mould closes and the next cycle begins

18. Cycle Time in injection moulding

19. Injection Mould

20. Injection Screw
Thescrewhasthreezones.
•FeedZone:Plasticfirstentersthescrewandisconveyedalonga
constantrootdiameter.
•TransitionZone:Plasticsisconveyed,compressedandmeltedalong
arootdiameterthatincreaseswithaconstanttaper.
•MeteringZone:Meltingoftheplasticsiscompletedandthemelt
isconveyedforwardalongaconstantrootdiameterreachinga
temperatureandviscositytoformparts.

21. Root Diameter
Flights
Flight width
Pitch
Flight Length

22. TheL/Dratioistheratioofthe
flightedlength(EffectiveLength)of
thescrewtoitsoutsidediameter.
Mostinjectionscrewsusea20:1L/D
ratio.Butitmayrangefrom18:1to24:1
InthecaseofThermosetitmayrange
from12:1to16:1.

23. Theratioofthefirstflightdepthoffeed
zonetothelastflightdepthofmeterzone,
OR
FirstChannelVolumeoffeedzonetolast
channelvolumeofmeteringzone,
Typicallyrangesfrom1.5:1to4.5:1formost
thermoplasticmaterials.
Mostinjectionscrewsclassifiedasgeneral
purposehaveacompressionratioof2.5:1to
3.0:1.
Thermosetscrewshavea.........ratio.

24. Theinjectionspeedistheforward
speedofthescrewduringits
injectionoperationperunittime.
EffectofInjectionSpeed
…
…
…

25. Thescrewrotationspeed(RPM)istherateat
whichtheplasticizingscrewrotates.
Thefasterthescrewrotationresultthe
following..
Fasterthematerialiscompressedbythe
screwflights
Increasingtheamountofshearheating
Lowresidencetime

26. Polystyrene (PS) **
Polyethylene
Polypropylene (PP)
Acrylonitrilebutadiene styrene (ABS)
Acetal
Acrylic
Polycarbonate (PC)
Polyester
Fluoroplastic
Polyimide
Nylon
Polyphenyleneoxide
Polysulphone
Polyvinyl chloride (PVC)

27. Highproductionrates.
Largevolumeproductionispossible.
Relativelylowlabourcost.
Processishighlysusceptibletoautomation.
Partsrequirelittleornofinishing.
Manydifferentsurfaces,colours,andfinishesare
available.
Aestheticsofproductscanbehighlyoptimized.
Formanyshapes,themosteconomicalwayto
fabricate.
Fabricationofverysmall&intricateshapes
possible.

28. Rejections&wastagescanbereused.
Sameitemscanbemouldedindifferent
materials,withoutchangingthemachineormould
insomecases.
Closedimensionaltolerancescanbemaintained.
Partscanbemouldedwithmetallicandnon-
metallicinserts.
Partscanbemouldedinacombinationofplastic
andsuchfillersasglass,asbestos,talcand
carbon.

29. Intenseindustrycompetitionoftenresultsinlow
profitmargins.
Mouldcostsarehigh.
Mouldingmachineryandauxiliaryequipmentcosts
arehigh.
Lackofknowledgeaboutthefundamentalsofthe
processcausesproblems.
Lackofknowledgeaboutthelongtermproperties
ofthematerialsmayresultinlong-termfailures.
Wastagesintheformoffeedsystems.

30. Material Flow Pattern

31. Mould
cavity
Fountain
flow
Frozen layers

32. Slow injection speed
Low orientation/Stiff flow
Mould
cavity
Thicker frozen layers

33. Mould
cavity
Fast Injection Speed
High orientation/Easy flow
Thinner frozen layers

34. Toggle System
Atoggleismechanicaldevicetoamplifyforce.
Inamouldingmachine,twobarsjoined,togetherendto
endwithapivot.
Theendofonebarisattachedtoastationaryplaten,
andtheotherendofasecondbarisattachedtothe
movableplaten.
Whenthemouldisopen,thetoggletakestheshapeof
alphabet“V”.
Whenpressureisappliedtothepivot,thetwobars
formastraightlineandclosesthemould.

36. ADVANTAGES
•Low cost and lower input needed to run
•Positive mould clamping
•High tonnages possible
DISADVANTAGES
•Do not read the clamp force.
•Clamping is not so straightway.
•Higher maintenance as lubricant is provided.
TOGGLE TYPE CLAMPING

37. Aclampingunitactuatedbyhydrauliccylinderwith
ram,whichisdirectlyconnectedtothemovingplate
toclosethemould.Therearetwohalvesinhydraulic
cylinder,whichisactuallyinletandoutletofoil.
Whenoilgoestothecylinderwithpressure,pushes
theramtoforwarddirectionbywhichmovingplaten
movesandmouldclosedandwhenoilcomesfromthe
cylindertheramcomebackandmouldisopened.

39. ADVANTAGES
•Clampspeedeasilycontrolledandstoppedatany
point.
•Easyadjustmentofclampingforceandeasymould
setup.
•Lowmaintenanceaspartisselflubricated.
DISADVANTAGES
•Itcostshighandmoreexpensivethantogglesystem.
•Non-positiveclamp.
•Morepronetomaintenance
HYDRAULIC CLAMPING

40. melt temperature
moldtemperature
screw rotation speed
back pressure
injection pressure
injection speed
holding time
cooling time

41. moldopen time
moldopening stroke
ejection system

42. In Mould Insert Moulding
Post Mould Inserting
Drilling
Chrome Plating
Polishing
Assembly
Welding

43. Printing: Process of making a mark or impression onto a
substrate for decorative or informational purposes.
Painting
Metallizing/shielding
Surface treatment
Annealing
Machining

44. Post Mould Inserting
Postmouldinsertingistheprocessbywhicha
metal,orpreformedplastic,insertisincorporated
intoamouldingbymeansofasecondaryprocess
oncethecomponenthasalreadybeenmoulded.

46. Depressioninamouldedpartcaused
byshrinkingorcollapsingofthe
resinduringcooling.

47. Resin feed inadequate
Improper mould design.
Parts cool too rapidly
Rib section in part too
wide.
Temperature of mould
surface opposite rib
too hot.
Entrapped gas.
Nozzle too restrictive,
land length too long.
Pressure too low.
Mould temperature too
low or high
Stock temperature too
high
Gate too small
Improper gate location
Nozzle and metering zone
temperatures too high.
Excessive cooling time in
mould
Unbalanced flow pattern.
Bad check valve.

48. Turbulenceintheresinmeltflowcaused
byundersizedgate,abruptchangein
cavityvolume,ortoohighinjection
pressure.

49. Excessive injection speed.
Melt temperature too high.
Melt temperature too low.
mould Temperature too low.
Nozzle opening too small.
Gate and length too long.
Sprue, runner, and/or gate size too small.
Nozzle heating band malfunction.
Inefficient gate location.

50. Blackmarksorscorchmarksonsurface
mouldedpart;usuallyonthesideofthe
partoppositethegateorinadeepcavity.

51. Excessive Injection speed
Excessive injection
pressure.
Inefficient mould
temperature.
Excessive amount of
volatiles due to improper
Venting.
Improper gate location
Front zone temperature
too high.
Screw speed too high.
Excessive back pressure.
Compression ratio of screw
too high.
Faulty temperature
controllers.
Frictional burring--
gates too small
Dead material hung up
on screw or nozzle.
Melt stock
temperature too high
or too low.
Nozzle diameter too
small
Over-heated heater
band
Incorrect screw rpm.

52. Inabilityoftwomeltfrontstoknit
togetherinahomogeneousfashionduring
themouldingprocess,resultinginweak
areasinthepartofvaryingseverity.

53. Material too cold.
Injection speed too slow
Entrapment of air at weld line.
Improper mould design.
Contamination of poorly
dispersed pigments.
Core shifting.
mould temperature to low.
Injection speed too slow.
Melt stock temperature to low.
Injection pressure too low.
Insufficient mould venting
Cylinder temperature too low.
Injection back pressure too
low.
Nozzle diameter too small.
Excessive screw flights in
metering zone.
Improper gate locations and/or
size.
Distance from gate excessive.
Ineffective flow pattern.
mould release agent (brittle
weld lines).
Inadequate flow.

54. An unfilled space of such size that it
scatters radiant energy such as light.

55. Injection pressure too low
Packing time too short
Insufficient feed of material
mould temperature too low.
Injection speed too high
Excessive cushion
At the side of a rib; rib too thick.
Runners or gate too small or badly
positioned.

56. Excessivedimensionalchangeinapart
afterprocessing,ortheexcessive
decreaseindimensioninapartthrough
cooling.

57. Inefficient injection
forward time.
Ram speed too high or too
low.
Injection and holding
pressure too high or low.
Melt temperature
inadequate.
Excessive nozzle and
metering zone
temperatures.
mould temperature too high
(for thick wall sections).
Parts cool unevenly.
Parts underpacked.
Improper gate location.
Gate too restrictive
Unequal temperature
between mould halves.
Non-uniform part
ejection.
Parts mishandled after
ejection.
Unbalanced gates on
multiple gated part.
Too many stresses in
part.

58. Excessplasticaroundtheareaof
themouldpartinglineonamoulded
part.

59. Mould parting surfaces do not seal properly.
Injection pressure too high.
Clamp pressure set too low or projected area or
item too large for clamp pressure of the machine.
Injection temperature too high.
Feed needs adjustment.
Hold time too long.
Inadequate mould supports.
Oversize vents.

60. Defectonthesurfaceofamoulded
partcausedbygasestrappedwithinthe
partduringcuring.

61. Screw rpm too high
Back pressure too low
mould temperature too low.
Gate improperly located
Insufficient venting.
Regrind too coarse

62. Finecracksinpartsurface.May
extendinanetworkoverthe
surfaceorthroughthepart.

63. Insufficient drying of the material.
Contamination.
Injection temperature too high (crazing accompanied
by discoloringor yellowing).
mould surface contaminated
Inadequate injection speed.
Inefficient injection forward time.
Excessive injection pressure.
mould temperature too low.
Gate too large.

64. Short Shots
Check for material inside the barrel
Increase the injection pressure
Increase the barrel temperature
Increase the gate size
Increase the sprueand runner systems
Increase the rate of injection(short weight)
Increase venting
Description
Molding formed incompletely
Causes
Insufficient material
Inadequate flow
Melt cooling too rapidly
Solutions

65. Insufficient feed, cushion.
Inadequate injection pressure.
Inadequate injection speed.
Insufficient booster or injection high-pressure
time.
Inefficient screw delay.
Inadequate injection back pressure.
Melt temperature too low.
Cylinder temperature inadequate.
mould temperature too low.

66. Gates, sprues, and/or runners too small.
Excessive screw flights in metering zone.
Insufficient venting.
Improper gate location.
Melt index of resin too low.
Excessive clearance between non-return valve and
barrel.
Screw bridging.
Injection press of insufficient capacity.

67. Theprocessingandequipmentforinjectionmoldingof
thermosetsdifferssomewhatfromthatofthermoplastics
sincethermosetscannotberemeltedoncetheyarecured;
thustheycannotresideinthebarrelornozzleforlong.
Thermosetsareheatedinthebarreloftheinjection
moldertodecreasetheirviscosity.
Thermosetsaremostoftenloadedwithreinforcementlike
choppedglassandgraphitefibersorfillerstodecrease
cost,thusincreasetheviscosity;withfiberreinforcement
lowscrewpressuresaredesiredtoreducefiberdamage.

68. Unlikeinjectionmoldingofthermoplastics,
injectionpressureisreducedafterthemold
isfilled;aftersomesecondsthepressureis
totallyremovedandanewshotprepared.
Injectionisdoneintoaheatedmoldinorder
toacceleratecrosslinking.
Specialventingscrewsandbarrelsmaybe
usedwiththermosettingandthermoplastic
polymersthatproducevolatileswhencuringor
heating.

70. Explanationofbasics???
workingprincipleandfunctioningof
Injectionmoulding???
SelectionofproperInjectionmoulding
machinesforoptimizingtheprocess???
Identifyandtroubleshoottheproblems???