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1、Page 1 Moldflow Korea Gas Technology Application Examples Gas Assisted Injection Molding 1. Introduction to G.I.M 2. Gas Injection Equipment 3. General Design Concept 4. Basic Concept for TV 5. Customer Success Stories Page 2 Moldflow Korea Gas Technology Application Examples What is Gas Injection M
2、olding ?What is Gas Injection Molding ? A molding process where an inert gas is introduced at pressure into the polymer melt stream, towards or at the end of, polymer injection Page 3 Moldflow Korea Gas Technology Application Examples ? Surface defect ? Gas penetration length ? Structural stability
3、? Processing window ? Polymer residual thickness ? Rib and Channel design ? Polymer Injection location ? Prevent Blow out ? Prevent fingering ? Prevent weld line & trap ? Prevent poor penetration ? Cooling channel ? In economical aspect What is the Design Issue for What is the Design Issue for Gas I
4、njection Molding ?Gas Injection Molding ? Page 4 Moldflow Korea Gas Technology Application Examples Polymer injectionGas injection Gas compressionGas retrieving Gas Injection Molding ProcessGas Injection Molding Process 12 34 Page 5 Moldflow Korea Gas Technology Application Examples Position of flow
5、 front at end of polymer injection Polymer is injected into the cavity. A frozen skin layer forms on contact with the cold mold walls Gas Injection Molding ProcessGas Injection Molding Process First Stage : Polymer Filling Second Stage : Gas Injection Polymer Melt Frozen Layer Hydro-Dynamic Layer Fr
6、ozen Layer Gas Channel Polymer Melt Nitrogen gas is introduced into the polymer melt displacing a proportion of the molten core into the unfilled sections of the mold Page 6 Moldflow Korea Gas Technology Application Examples Position of gas front at end of polymer injection Third Stage : End of Gas
7、Injection Hydro-dynamic Layer Melt Polymer The gas continues to displace polymer melt until the cavity filling process is complete Gas Channel Frozen Layer Fourth Stage : Gas Packing Gas channel In the packing phase, the gas compresses the polymer from within the component, compensating for volumetr
8、ic shrinkage and maintaining the external geometry of the part Solidified (Frozen) polymer Position of Gas flow front at end of gas (packing) stage Page 7 Moldflow Korea Gas Technology Application Examples MF/GAS operationMF/GAS operation Calculates volume of polymer to be driven forward based on ge
9、ometry, frozen layer and capillary number The Capillary number calculation is based on velocity, viscosity and surface tension Capillary Index Ca = V h/ t V : Melt Velocity h : Melt Viscosity t : Surface Tension Page 8 Moldflow Korea Gas Technology Application Examples GAS INJECTION EQUIPMENT Page 9
10、 Moldflow Korea Gas Technology Application Examples Which Gas Methods do exist ? Volumetric Control - Cinpres According to Expansion of Hollow Region, Pressure Inside Decreases But Difficult to Control Muti Profiled Pressure Pattern Pressure Decay Effect is better than that of Pressure Control Metho
11、d Pressure Control - Gain,Battenfeld Be Able to Control Continuous Pressure Easy to Control Multi Profiled Pressure Step Control Method is Similar with Compact Injection Molding Machine But Difficult to get Smooth Pressure Decay Effect Two Way Control - GIL Be Available to Control Two Method by User
12、s Selection Page 10 Moldflow Korea Gas Technology Application Examples Type of Gas Injection Gas Direct into Sprue 1. No Additional Mold Tooling for Gas Flow 2. Not Available for Hot Runner Mold 3. Difficult to Multi Cavity Mold 4. Long Gas Flow Channel Gas Direct into Cavity 1. Gas is delivered Dir
13、ect to Somewhere into Cavity 2. Available for Hot Runner Mold 3. Needs Extra Mold Tooling Costs Page 11 Moldflow Korea Gas Technology Application Examples Nozzle for Gas Direct into Sprue Gas Polymer Polymer Shut-off Switch into Cavity Page 12 Moldflow Korea Gas Technology Application Examples Nozzl
14、e for Gas Direct into Mold Gas Channel Frozen Layer N2Gas Gas is injected at a sealed position directly into thicker section Page 13 Moldflow Korea Gas Technology Application Examples GENERAL DESIGN CONCEPT Page 14 Moldflow Korea Gas Technology Application Examples Designing for GIMDesigning for GIM
15、 Factors that must be considered: Component function Finished part should meet the requirements of the design specification Component geometry Rib structure & layout Determines the polymer “history” prior to injection of gas and the subsequent route taken by the injected gas Page 15 Moldflow Korea G
16、as Technology Application Examples Designing for GIM (Gas Channel)Designing for GIM (Gas Channel) Optimum Design Range (1) b/s = 23 (2) h/b = 1.53 Optimum Design Range (1) a = b = (2.54.0) x s (2) c = (0.51.0) x s (3) d = (5.010.0) x c S= 2.5 3.5 Page 16 Moldflow Korea Gas Technology Application Exa
17、mples Designing for GIM (Gas Channel)Designing for GIM (Gas Channel) Optimum Design Range (1) 1/b = 1.5 2 (2) h2= max. S/2 Gas penetrates Surface (1) Remedy-1 (2) Remedy-1 Gas penetrates surface Formation of initial crack in case of insufficient melt If the gas channel is too small compared with flo
18、w length, fingering can be increased Page 17 Moldflow Korea Gas Technology Application Examples Designing for GIM (Nozzle position)Designing for GIM (Nozzle position) Gas Injected Point No gas penetration area (1) Gas must be located far from branched(2) It is not easy to control the thickness near
19、the gas injection position Risk of Warpage Gas Injected Point Thickness reduction area Risk of sink-marks (3) Gates must be located far from each other Bad Good Page 18 Moldflow Korea Gas Technology Application Examples Designing for GIM (Edge Shape)Designing for GIM (Edge Shape) Bad Design * Sharp
20、edge must be removed Thick Area Thin Area Good Design 1. No Sharp edge 2. Round diameter for round edge must be greater than 1 Page 19 Moldflow Korea Gas Technology Application Examples Mo l d i n gC o n d i t i o nP e n e t r a t i o nT h i c k G a sP r e s s u r e P o l y m e rT e mp . D e l a yT
21、i m e G a sD u r a t o i n T i me . . S h o r tS h o t . . Penetration Length due to Penetration Length due to Molding ConditionMolding Condition Page 20 Moldflow Korea Gas Technology Application Examples Shape Fact or0. 931. 0451. 2771. 2798 Penet r at i on Bl ow Rat i o Penetration Length due to P
22、enetration Length due to the shape factor of gas channelthe shape factor of gas channel Page 21 Moldflow Korea Gas Technology Application Examples G A S R E SIN G A S R E SIN G A SR E SIN G A S R E SIN To design channels be crossed to the flow direction and channels be closed to the polymer injectio
23、n gate may lead to fingering If channel layout is fixed, we have applied to high pressure to avoid fingering Gas Fingering Gas Fingering Page 22 Moldflow Korea Gas Technology Application Examples To prevent blow-out, Polymer Short Shot and wall thickness control Blow out Decreasing shot size and Inc
24、reasing gas channel thickness may lead to Gas Blow Out Increase the polymer shot size and decrease the gas pressure make the gas pene- tration length shorten Gas Blow Out Gas Blow Out Page 23 Moldflow Korea Gas Technology Application Examples BASIC CONCEPT FOR TELEVISION Page 24 Moldflow Korea Gas T
25、echnology Application Examples (1)Angle Gate (2) Curved Tunnel Gate (3) Tunnel Gate Gate Design for TV Gas Mold Part Runner Gas Penetration Part Runner Gas Penetration Part Runner Gas Penetration Page 25 Moldflow Korea Gas Technology Application Examples 1. Gas channel size is 2.5 times for base thi
26、ckness 2. Sink-mark can be easily occurred, if gas channel is bigger 3. Fingering can be easily occurred, if gas channel is smaller . 4. It is better to locate Layout on corner. 5. Gas channel must be designed to achieve flow balancing. 6. Gas channel size must be determined by CAE result. 7. End of
27、 gas channel must be tapered for 2030mm 8. Thick rib can be easily acting as gas channel. Check-List for Design of Gas Channel on TV (1) Page 26 Moldflow Korea Gas Technology Application Examples 9. If the thickness is greater than 4mm, this area acts as flow leader and gas channel. 10. Thickness Fr
28、action is proper if it be in 3040% range Polymer Melt Fountain Region Gas Frozen Layer of Polymer Mold wall (cold) Mold wall (cold) a b Thickness Fraction as Skin Material = a/b Check-List for Design of Gas Channel on TV (2) Page 27 Moldflow Korea Gas Technology Application Examples 1. Injection tim
29、e is set in the range of 3.0 5.0 sec 2. Injection velocity must be kept constant. 3. Temperature of coolant can be increased due to sink-mark, flow pattern ( about 45-60 degC) 4. Melt temperature must be less than 245degC for HIPS. 5. Melt front temperature should be no more 20C below the melt tempe
30、rature ( T melt 20 Modified : 60 sec ) 2. Reduce thickness ( 2.7 mm - 2.5 mm ) 3. Improve operation efficiency for assembly Model : Daewoo TV 25G1 25” TV Back Cover Page 42 Moldflow Korea Gas Technology Application Examples Customer Quote : Moldflow is the best tool to optimize gas channel at the in
31、itial stage. If it can be applied to this kind of project and succeed, you can reduce development time and mold trial number. Chang Kyun,Lee Production Engineering Center, Samsung Electronics EffectsEffects 1. Fix Warpage Problem 2. Fix Sink-Mark Problem 3. Reduce Development Time 4. Reduce Cooling Time 5. Optimized Gas Channel 6. Optimized Part Thickness 7. Can Material Save (ABS-PP) Vacuum Cleaner Housing Gas Vent Mark No Weld line Gas Vent Core
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