上海理工大学材料科学与工程学院塑料成型工艺与模具设计英文课件chapter3

1、3.1 Injection molding process3.2 Compression molding process3.3 Transfer molding process3.4 Extrusion molding processChapter III Forming Process of Plastic MoldingInjection molding, Mainly used for the molding of thermoplastics Principles of Injection MoldingParticles, powdered plasticInjection mach

2、ine barrelMeltinjectionCooling curingPlastic partsClamping deviceInjection deviceright angle connected setDemolding mechanismRodCylinderPrevent reflux valveHeaterScrewfunnelMotor Injection Molding EquipmentClamping unitInjection unit1. Main function of injection molding machineEjectMold clamping act

3、ionholding pressure and feedingInjection Plastic fluid into the cavity under certain pressure and speedMelt plastic to fluid state Injection Molding Equipment2. Classification of injection molding machinePlasticizing: the process that putting the plastic into the barrel heated to flow state and havi

4、ng a good plasticityCan be classified as horizontal, vertical and angle injection molding machine according to their shape Injection molding machine can be classified as: plunger type and screw type injection molding machine according to the plasticizing way3.1.2 Injection Molding Equipment2. Classi

5、fication of injection molding machineHorizontal-typeVertical-typeAngle-type注射成型设备3.1.2 Injection Molding Equipment3.Plunger type injection molding machinenozzleHeaterfunnelPlungerHeating barrelshuntCooling water3.1.2 Injection Molding Equipment Large part of the pressure used in the compaction of so

6、lid plastic and overcome the plastic barrel friction maximum injection volume is limited:The maximum injection volume depends on the plasticizing capacity of the barrel (related to the area with plastic heat) and the piston diameter and stroke the plasticizing uneven:Plastic shuttle heat transfer de

7、pend on the barrel wall and the shunt, the plunger to promote plastic mixing, easy to result in the plasticizing uneven phenomenon3. Plunger type injection molding machine injection pressure loss:Shortcomings of the plunger-type injection machine:3.1.2 Injection Molding Equipment injection speed is

8、uneven:From the plunger into contact with plastic to compaction plastic, injection speed is gradually increased easy to produce a laminar flow phenomenon and the barrel difficult to clean3.plunger type injection molding machineShortcomings of the plunger type injection machine:4 screw injection mold

9、ing machine3.1.2 Injection Molding Equipment4. screw injection molding machineClampingInjectionholding pressurecoolingMold openingejectClampingInjectionScrew rotatingScrew injection machine molding cycleThe advantages of screw injection molding machine:With the rotary motion of the screw, the materi

10、al within the heat evenly plasticizing capacity.3.1.2 Injection Molding Equipment4 screw injection molding machineadvantages of screw injection molding machine:Less dwell time and decomposition reducedLower heat loss, lower injection pressure moldingShort cycle times, high efficiency, production pro

11、cess can be automatedCan form complex shapes require high dimensional accuracy and inserts available3.1.2 Injection Molding EquipmentScrew compared with the rotating action of the piston, resulting in contributing (Ft), allows materials in the spiral groove between the mixing role, increasing the pl

12、asticizing capacity.Screw injection machine and plunger-type injection molding machineplunger - typescrew - type3.1.2 Injection Molding Equipment3.1.3 Injection Molding ProcessInjection processPost-processingPre-processingTesting of raw materials, dyeing and dryMold cleaningInsert preheatingBarrel c

13、lean-upAnnealingHumidity1. Pre-processingTesting of raw materialsDyeing of raw materialRaw material dryingMass VolumeMobilityMoisture and volatile matter contentShrinkageOven dryingInfrared dryingHot-plate dryFrequency drying3.1.3 Injection Molding Process2 injection processTesting of raw materialsP

14、retreatmentClampingInjectionPutting into the funnelPackingDemoldingLoad embedded parts Clean-up barrelClean up mold Coating release agentEmbedded pieces of clean-up, warm-upPre-plasticizingPost-processing of plastic partsCooling3.1.3 Injection Molding Process3 post-treatmentInfrared or circulating h

15、ot air oven or liquid medium (mineral oil, paraffin) , on a certain temperature for some time, and then slowly cooledPut molded plastic parts into hot water (100 -120 ), isolated from the air, to achieve moisture balance. Humidity slow cooling to room temperature.Annealing:Humidity: Annealing temper

16、ature: above the use temperature of 10 20 20 below the phase transition temperature of 10 20 3.1.3 Injection Molding Process3.1.4 Injection Molding Process parametersTemperaturePressureTime(Molding cycle) long Molding cycle, warpage after ejection, affect dimensional accuracy. 1 Temperature barrel t

17、emperature Nozzle temperature mold temperature high internal stress, easy to cracking, poor surface qualityTemperature too highTemperature too lowSlightly lower than the barrel temperature: to prevent “salivation phenomenon”; not too low.When the scope of Tf (Tm) Td is narrow, the barrel temperature

18、 should take lower valuesBarrel back temperature is the lowest, the front is the highestTf (Tm) Td, to ensure the normal flow of plastic melt, no deterioration or decomposition 3.1.4 Injection Molding Process parameters1.Plastic flowability2. Filling pressure3. Productivity4. Product Internal stress

19、5. Product finishing6. cooling time7. Product density or crystallinity8. Mold shrinkage rate9. Product deflectionUsually, the majority of mechanical strength of molding product increased with the mold temperature, but the elongation and impact strength decreased.Effect of Mold temperature for moldin

20、g partsDetermination of mold temperature(1) mold temperature is usually below Tg or are unlikely to cause the temperature of the workpiece deformation, demolding temperature slightly higher than mold temperature.(2) High viscosity (such as polycarbonate, polysulfone) should choose high mold temperat

21、ure. Low viscosity (such as PE, PA) should choose lower mold temperature(3) consider the mold temperature influence for molecular orientation, crystallization, internal stress and physical properties. Lower Mold temperature: more obvious orientation effects, high internal stress, not easy to crystal

22、lizationHigher mold temperature: easy to crystallization3.1.4 Injection Molding Process parameters2 Pressure plasticization pressureAlso known as back pressure (The pressure exerted on the melt of the head Screw when the screw rotation), can be adjusted by relief valve injection pressureExerted by p

23、lunger or screw head on plastic melt, generally from 40 130MPa, can overcome melt flow resistance and ensure filling rateInjection pressure is determined by: plastic type, type of injection machine, gating system, wall thickness, flow length, etc.3.1.4 Injection Molding Process parameters2 Pressure

24、Packing pressureTo continue exert pressure after the plastic melt filling into the mold cavity. The role is to make the melt curing under pressure, feeding shrinkagegenerally less than or equal to the injection pressureHigh packing pressure is easy to produce flash and internal stress, while low pac

25、king pressure cause inadequate filling3.1.4 Injection Molding Process parameters Completed the time required for injection molding process.3 Molding timeMolding cycle or the total cycleMolding cycleFilling timeInjection timeClosed mold cooling timeOther timesDwell time3.1.4 Injection Molding Process

26、 parametersInjection Molding process windowInjection pressureMaterial temperatureDecompositionChalkingForming difficultflashingBad surfaceShort shot3.2 Compression Molding ProcessCompression moldCompression molding pressCompression molding productsMelt forming3.2.1 Compression Molding PrincipleCompr

27、ession molding1. molding methodAlso known as compression molding or suppress. Mainly used for the molding of thermosetting plastics, thermoplastics can also be used for molding.Powder, granular or fiber materialPlaced in cavity of the molding temperatureClamping pressureForming curing3.2.1 Compressi

28、on Molding Principle2. compression molding characteristicsPlastic added directly into the cavity, the feeding chamber is an extension of the cavity Mold is fully closed when plastic parts are final shape pressure punch directly to the plasticDifficult to obtain accurate dimensional, especially high-

29、precision plastic partsNot suitable for plastic parts with fine, easy-off inserts and more embedded pieces of plastic partsEasy to forming polymer with more fiber filler3.2.1 Compression Molding Principle(5) production cycle is long and inefficient2. compression molding characteristics simple operat

30、ion, and simple mold structureMulti cavitiesLess parts shrinkage, small deformation, to the performance of uniform and high strength.Can suppress the large flat plastic parts or a suppression of multiple plastic partsNo gating system, less material consumption3.2.1 Compression Molding Principle3.2.2

31、 Compression Molding Equipment1. Molding equipment effect2. Types of molding equipmentBy TransmissionMechanical press：Spiral pressHydraulic press：Hydraulic press and hydraulic pressProvide necessary pressureMold top pieceClampingSome cases to pass heat required 3.2.3 Compression Molding ProcessPre-p

32、rocessingMolding processpost-processingPreheat and dryPreloadInserts placedClampingVentingMold cleaningStress RelievingModified polishingSpecial treatmentdemoldingPacking and curingFeedingCompression molding circulation To facilitate operations and improve the quality of plastic parts，first pre-mold

33、ed powder, fibrous plastic powder in the pre-press, pressed into a certain weight, the shape of the same ingot1. Preparation before moldingPreloadPreloading methodAdvantages of using pre-ingotFeeding fast and accurateReduce compression ratio, reducing the size of cavity, less air content for better

34、heat transfer and little bubbles3. 2.3 Compression Molding ProcessComplex production process, not used often1. Preparation before molding advantages of using pre-ingotAvoid feeding process dust emissions and improve working conditionsPreheating temperature can be increased and shorten the preheating

35、 and curing timeease of forming complex or with a small insert plastic parts3.2.3 Compression Molding Process3.2.3 Compression Molding Process1. Preparation before moldingCompression molding powderPreload conditionsThe best particle sizeCompression ratio (plastic / ingot) should be about 3.0Containi

36、ng lubricantsPressure:Pressure range of 40 200MPaTemperature : Room temperature or 50 90 preloadPrinciples:The density of ingot up to 80% of the maximum density of plastic partsDryWarm-upPreparation before moldingPreheat and drypurpose of heating before Plastic molding :Plastic molding before heatin

37、g:High-frequency heatingInfrared preheatingOven preheatingHot plate to preheat.Provide hot plasticRemove moisture and volatile matter3.2.3 Compression Molding Process3. 2.3 Compression Molding Process As the conductive part of the plastic parts or plastic parts and other parts connected to parts.1.

38、Preparation before molding Inserts placedInserts placed requirements in the correct position, smoothInserts-Commonly used insert bushings, screws, nuts, terminal, etc.Large inserts in the mold mounted on the press after the first warm-up2.Molding process Feeding the key of feeding is the feedstock T

39、he quantitative methods: reasonable stacking plastic, Stowage of powder or pellets to be high in the middle surrounded by low, to facilitate gas emissions.Volumetric method: Convenient but not very accurateGravimetric method: Accurate, troublePiece-rate method: Pre-ingot, counting3.2.3 Compression M

40、olding Process2. Molding process(2) Mold punch touches the plastic: slow down the mold speed (venting) Before punch touches the plastic: to speed up the clamping speed (reduce cycle time, avoid plastic premature curing)clamping after Feeding, the clamping time ranging generally from a few seconds to

41、 tens of seconds.The clamping process is divided into two parts:3.2.3 Compression Molding Process Clamping pressure to a certain pressure, immediate relief, punch up slightly, 1-3 times2. Molding process exhaust Exclusion of moisture and volatiles into a gas and chemical reaction by-products, so as

42、not to affect the performance and surface quality of plastic partsgood flowability Plastic use late pressure method, the pause of 15 to 30s from the punch and plastic come into contact with the die completely closed processPlastic parts with a small metal inserts are not using the exhaust operation,

43、 in order to avoid displacement or damageMethods:Objective:3.2.3 Compression Molding Process Cross-linking reaction to the extent required to maintain a certain time, under the molding pressure and temperature. Time from closed pressurized to demolding2. Molding processPacking and curingundercuringo

44、vercuringInadequateOverPressure the length of time is based on the plastic type, preheating of the impact of plastic parts shape and degree of compression.Dwell time:Curing phase of the request:Degree of cure3.2.3 Compression Molding Process2. Molding process(5) demoldingComplex plastic parts under

45、pressure, cooled to a certain temperature after demoldingPlastic parts mold release method:Manually demolding outside of moldautomatically demolding3.2.3 Compression Molding Process3 Molded post-processingCopper shovel or compressed air to clean up, so as not to damage the mold appearance mold clean

46、ing plastic to stressCooling in a plastic moldAfter ejection put into a certain temperature, the oil pool or in the oven slowly cooled or annealedLarge, thick-walled partsEasily deformable thin-walled3.2.3 Compression Molding Process3. post processing modified polishing special treatmentSecondary pr

47、ocessing: moisture and decorating (electroplating, spraying)Go to flash, burrs, surface finish3.2.3 Compression Molding ProcessCompression Molding CirculationCheck plastic qualityPreload, preheating dryingweightingmaterialCleaning inserts, insert preheatingCleaning pressure modeCoating off the mold

48、agentembedded partsPlus materialsClamping Heat and pressureExhaustHeating reliefCuring Pressure and temperature packingMold Relief demoldingPlastic pieces of the whole shapeStress handlingPlastic parts sent to the next process3.2.4 Compression Molding Process parametersMolding pressure (molding pres

49、sure)Molding temperature (molding temperature)Molding timeTo produce high-quality plastic parts, in addition to the mold structure, but also the correct choice of Process parameters.1. Molding pressureDefinition: Punch unit projected area of the parting surface pressure of plastic melt and solidific

50、ation while compression of plastic parts. To exert molding pressure for the purpose of:The mold is closed, to prevent flashOvercome the force of the plastic molding process for a variety of top moldThe viscous flow state material is solidified under a certain pressurePlastic filled with cavity3.2.4

51、Compression Molding Process parameters1. molding pressureA - punch contact with the plastic part in the projected area of the parting surface (mm)The formula is:p =The formula:p - molding pressure (MPa)pb - press from cylinder pressure (MPa)D - press the master cylinder piston diameter (m)Molding pr

52、essure and the types of plastics, plastic structure, mold temperature and other factors3.2.4 Compression Molding Process parameters2. Molding temperatureRefers to the compression required for the mold temperature, the quality of the plastic parts, molded inThermosetting plastic mold temperature is h

53、igher than the mold temperatureSlow hardening, long cycle, lack of hardening; plastic matte finish; physical, poor mechanical propertiesMold temperatureToo highResin, the decomposition of organic matter; the outer layer of plastic parts before hardeningHighShort cycle times, increase in productivity

54、Too low3.2.4 Compression Molding Process parameters3 Molding timePlastic in the closed mold curing to harden the required time. With plastic variety, moisture content, plastic parts molding temperature of the shape and size, and compression mold structure, pre-pressure warm-up, molding pressure and

55、other factors.worse performanceMolding timeShortLack of hardening, appearance and mechanical properties, easy to deformToo longUnder the premise of ensuring the quality of the plastic parts should be sought to shorten the molding time3.2.4 Compression Molding Process parameters Transfer Molding Proc

56、ess3.3.1 Transfer molding principleDeveloped in the compression molding of a thermosetting plastic molding method, also known as transfer molding, plastic extrusion molding.Transfer molding3.3.2 Transfer Molding Characteristics1. Before feeding, mold closed4. mold structure is relatively complex, hi

57、gher manufacturing costs, the molding pressure and complicated to operate, feed consumption more than the compression modulus.2. Plastic parts flying side of the thin, accurate size, uniform performance and higher quality.3. Can be molded deep hole complex shape, with a fine or fragile inserts plast

58、ic parts.5. gas is difficult to rule out the exhaust ducts must be set up in the mold.Or compression molding of powder pre-ingotClampingSqueeze plasticCuringMoldOff modeManufactured articlesPre-heatIncrease pressureHeatingPackingPaul temperatureUnloading pressureClear modeAnd compression molding dif

59、ference is:Pressure Note: Clamping feedingCompression: feeding - Clamping3.3.2 Transfer Molding Characteristics3.3.3 Transfer Molding Process parameters and Equipmenttransfer molding Process parametersLess than compression molding method mold temperatureLower 15 30 than Compression molding, usually

60、between130 190 . The feeding chamber and the lower mold temperature is below the temperature of the box molding pressureLoss of pressure by the gating system, to ensure cavity filled with plastic in10 - 30s. packing time(2) molding equipment3.3.4 plastic requirements for transfer moldinga. With good