molding defect(th)

7/25/2019 molding defect(TH)

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91 69 22 - 2552

(Injection Molding)

[13, 14] (Mold design) (Material properties)

Defects of Injection Molded Parts:

Causes and Troubleshooting

1

(Injection temperature) (Injection speed) (Holdingpressure) (Moldtemperature) [5, 6]

:

1


2/14

92 .

-

(Short shots)

1(a)

(Shot size)

1. (Injection temperature)2.

(Mold temperature)

3. (Injection pressure)

4. (Injection speed)

5. (Back pressure)

6. (Non-return valve)

1. / (Runner)2.

(Gate)3.

(Wall thickness)

4. (Venting)

1(a) (b) [5]

(a) (b)


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93 69 22 - 2552

(Sink marks)

(Holding pressure) (Injection phase) (Shrinkage)

(Rib) 1(b)

1.

(Cushion)

2. /

3. -/ / (

)

4. -// ( )

5. (Cooling time)

6.

1.

2.

/

1. (Additives)

Chemical blowing agents (CBA) [11] (

CO2 N2) (Voids) (Core layer)

2. ( CO

2 N

2) (Gas/Water

assisted injection molding) [9, 13]

(Part sticking)

2(a)


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94 .

1. /

/2. -//

3. 4.

(Mold release agents)

1.

(Ejector pins) (Symmetry)

2. (Cavity)

3.

(Multi-cavities)

4. (Stationary plate) (Sprue)

(Sprue puller) (Sprue bushing)

(a) (b)

2(a) (b) [3]


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95 69 22 - 2552

(Flash)

2(b) (Parting line) (Ejectormarks)

1. (Clamping force)2. /

3. -/

4. /-

1.

2. (Venting)

3.

(Weld lines)

1 /

3(a) [12]

3(a) (b)

[7]

(a) (b)


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96 .

(

) [5, 6, 4] 3(b)

1. -/

2. /

3. (Back pressure)

1.

2.

3.

1. Sequential valve gates

[8]

2. Push-pull injectionmolding [12]3. SCORIM (Shear control

orientation injection molding) [10]

(Jetting)

4(a)

//

1. -

2.


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97 69 22 - 2552

(Blister)

(

) 4(b)

1. //

2. (Barrel)

Back pressure /

4(a) (b) [3, 4]

Suck back (

Drooling [16]) // Feedzone /

(a) (b)


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98 .

(Voids/Bubbles)

5 (Blisters)

(Shrinkage) (Core layer) (Sol id if ied

skin layer/Frozen layer) ( ) (Vacuum)

5 [3]

1. (Cushion) /

/

2. -//

3. Back pressure (Meltdensity)

4.

1.

2.

3.


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99 69 22 - 2552

4.

(Silver streaks)

(Moister)

6(a)

1.

2.

3.

4. Suckback

6(a) (b) [3]

(a) (b)

(Burn marks)

8001,000 oC

6(b)


10/14

100 .

1.

2.

/

3. Suckback

1.

2.

(Conta-

mination)

7(a)

(Pigments)

(Purging)

(Burn marks)

1.

(Hopper)

2. (Purging)

3. (Regrind) (Virgin) (Crusher)

4.

/// Polyvinyl Chloride (PVC)

5.


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101 69 22 - 2552

(Blush marks)

7(b)

1.

2. /

Cold slug3.

(Shrinkage)

- (0.1-2.5%) (Semi-crystalline)

(Amorphous)

(Pressure) (Volume) (Temperature) PVT diagram [2]

1.

//

2. -//

3.

/

7 (a) (b) [3]

(a)(b)


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102 .

(Warpage/Distortion)

8(b)

1.

2. //

3. -/ /

8(a) (b)

(a) (b)

1.

(Cooling path)

2.

8(b)3.

4.


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103 69 22 - 2552

Data Handbook, Van NostrandReinhold, New York, 1989.

[7] Faculty of Mechanical and PlasticsEngineering, Chemnitz Universityof Technology, Germany.

[8] I. Khnert, V. Stoll and G. Mennig,The 21st annual meeting of thepolymer processing society (PPS),Leipzig, Germany, 19-23 June2005, ISBN 3-86010-784-4.

[9] J. Avery, Gas-Assisted InjectionMolding: Principle and Applicat-ions, Hanser Publishers, New York,2001.

[10] L. Wang, P.S. Alan and M.J. Bevis,Plastic Rubber and CompositesProcessing and Applications, 1995,

23(3): 139-150.[11] R.A. Malloy, Plastic Part Designfor Injection Molding, HanserPublishers, New York, 1994.

[12] S. Patcharaphun and G. Mennig,Journal of Reinforced Plastics andComposites, 2006, 25(4): 421-435.

[13] T.A. Osswald, Polymer ProcessingFundamentals, Carl Hanser Verlag,Munich 1998.

[14] T.L. Richardson and E. Lokensgard,Industrial Plastics: Theory andApplications, Delmar PublishersInc., New York, 1996.

[1] ARBURG GmbH, A Brief Guideinto Injection Molding, PostfachLossburg, Germany, 1999.

[2] A.W. Birley, B. Haworth andJ. Batchelor, Physics of Plastics:P r oce s s i n g , P r op e r t i e s an d

Materials Engineering, HanserPublishers, New York, 1992.

[3] Bakelite AG / KISTLER, Defects onInjection Molded Parts.

[4] D.M. Bryce, Thermoplastic Trouble-shooting for Injection Molders,Society of Plastic Engineers, 1991.

[5] Donald V. Rosato and DominickV. Rosato, Inject ion MoldingHandbook: The Complete MoldingOperation Technology, Perfor-mance, Economics, Chapman &Hall, New York, 1995.

[6] D.V. Rosato, Plastics Processing


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104

[15] W. Michaeli, A. Brunswick and C.Kujat, Kunststoffe Plast Europe,2000, 90(8): 25-28.

[16] W. Michael i et al . , Trainingin Inject ion Molding, HanserPublishers, Munich 1995.

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