Design Enrichment for Plastic Injection Mold using Flow Analysis

Download Full-Text PDF Cite this Publication

Text Only Version

Design Enrichment for Plastic Injection Mold using Flow Analysis

Mr. Amit Pandurang Kharche

Asstt. Professor

Dr. D. Y. Patil School of Engineering Academy, Pune

Abstract – Mold Design and Development is the building block for producing the desired number of units in a given time limit. The simplicity of the mold ensures the quality of the component produced and the direct and indirect costs of development. A systematic technical review of the inputs in the design phase would help the Organization to achieve its goals. The objective of work is to utilize the inputs from Flow Analysis for Designing a Plastic Injection Molded Component. The effort of this work is to ensure a minimum time for development of the mold as well as deliver a best quality product during trial and testing. The result is aimed at reducing time for product development process.

Keywords: Mold Flow Analysis, Injection Molding, Mold Design

INTRODUCTION

The molding may cause defects and its processing offers a challenge during its development phase. The cost of the mold is high and any process that is not optimized renders heavy overheads during its development cycle and production. So designing the mold which ensures best suitability for the features on the component with smooth flow of molten plastic is very important part of development process.

The successful launch of any plastic product depends on knowing the true costs and profitability before the job is started. Injection molding typically involves large volumes of parts. Small cost overheads per part can be compounded to large cost differences over the life span of the part. Major cost components considered here are material, re-grind and machine costs. Scrap, rejections and regrind costs are also accounted in the cost.

Figure.1 Plastic Injection Molding Overview

Figure.2 Schematic Diagram of Plastic Injection Molding

CASE STUDY ON PLASTIC INJECTION MOLDING

The plastic enclosure for an instrument or product is an integral part of its design, playing a key role in its looks, presentation, value and quality perception. Nylon (Poly Amide) plastic enclosures should complement and enhance the product in every possible way.

Plastic enclosures that house a product is its first introduction. That is why it's important to choose an electronic plastic enclosure that projects the right image for both the product and the company it represents. Function, durability, and protection of the electronics housed are also important considerations in the selection of plastic enclosures. Plastic electronic enclosures are attractive, yet rugged. And, they are surprisingly low cost. All of SIMCO's plastic enclosures are made from ABS plastic and are RoHS compliant.

Plastic enclosures for OEM electronics industry include Desktop, Handheld and Utility boxes. For our study the

`case i.e. the enclosure is used for mounting the switches and protecting the internal electronic components and wiring. Besides, generating aesthetic appeal to the overall switch assembly is also an important objective.

Specifications for case study:

Name of the component- Upper Case RH Material PA6 30%GF

O/A size L=80mm x B=55mm x H=40mm O/A- thickness -Min 1 mm

,Max 2 mm Material properties:

(Source professionalplastics.com) Nylon 6 with 30% Glass-Fiber Filled

Table-1 Physical Properties

Physical Properties

Metric

English

Comments

Density

1.17 –

1.62 g/cc

0.0423 –

0.0585 lb/in³

Average = 1.35 g/cc; Grade

Count = 168

Water Absorption

0 – 7.5 %

0 – 7.5 %

Average = 2.9%; Grade

Count = 113

Moisture Absorption at

Equilibrium

0.9 – 2.5 %

0.9 – 2.5 %

Average = 1.9%; Grade

Count = 68

Water Absorption at

Saturation

1.8 – 8.2 %

1.8 – 8.2 %

Average = 6.1%; Grade

Count = 56

Linear Mold Shrinkage

0.0015 –

0.007 cm/c m

0.0015 –

0.007 in/in

Average = 0.0033 cm/cm;

Grade Count = 109

Linear Mold Shrinkage, Transverse

0.007 –

0.017 cm/c m

0.007 –

0.017 in/in

Average =

0.009 cm/cm;

Grade Count = 50

Melt Flow

4 –

145 g/10

min

4 – 145 g/10 min

Average = 50.6 g/10 min; Grade

Count = 14

Table-2 Electrical Properties

Table-3 Mechanical Properties

Hardness,

Rockwell E

55

55

Grade Count = 1

Hardness,

Rockwell M

90 – 100

90 – 100

Average = 95; Grade

Count = 2

Hardness,

Rockwell R

110 – 121

110 – 121

Average = 120; Grade

Count = 28

Tensile Strength,

Ultimate

65 – 195 MPa

9430

28300 psi

Average = 140 MPa;

Grade Count = 130

Tensile Strength,

Yield

95 – 195 MPa

13800

28300 psi

Average = 140 MPa;

Grade Count = 31

Elongation at

Break

2 – 10 %

2 – 10 %

Average = 4.5%; Grade

Count = 154

Elongation at

Yield

2 – 6 %

2 – 6 %

Average = 3.7%; Grade

Count = 18

Tensile Modulus

3.2 – 11.17 GPa

464 – 1620 ksi

Average = 7.5 GPa;

Grade Count = 105

Flexural Modulus

2.8 – 9.7 GPa

406 – 1410 ksi

Average = 7.2 GPa;

Grade Count = 95

Flexural Yield

Strength

110 – 310 MPa

16000

45000 psi

Average = 220 MPa;

Grade Count = 96

Compressive

Yield Strength

16 – 152 MPa

2320

22000 psi

Average = 100 MPa;

Grade Count=6

Poisson's Ratio

0.35

0.35

Grade Count = 15

Shear Strength

59 – 85 MPa

8560

12300 psi

Average = 72 MPa;

Grade Count = 2

Izod Impact,

Notched

0.6 – 2.4 J/cm

1.12 – 4.5

lb/in

ft-

Average = 1.3 J/cm;

Grade Count = 80

Izod Impact,

Unnotched

6.4 – 11.7 J/cm

12 – 21.9

lb/in

ft-

Average = 9.4 J/cm;

Grade Count = 7

Izod Impact,

Notched Lo Temp

0.5 – 1.37 J/cm

0.937

2.57 ft-lb/in

Average = 0.916 J/cm; Grade Count = 25

Charpy Impact,

Unnotched

4 – 11 J/cm²

19 – 52.4

lb/in²

ft-

Average = 8.6 J/cm²;

Grade Count = 19

Charpy Impact,

Notched Low Temp

0.56 – 1.5 J/cm²

2.67 – 7.14 ft-

lb/in²

Average = 0.987 J/cm²; Grade Count = 18

Charpy Impact, Unnotched Low

Temp

3.5 – 9 J/cm²

16.7 – 42.8 ft-

lb/in²

Average = 7 J/cm²; Grade Count = 11

Charpy Impact,

Notched

0.55 – 3.5 J/cm²

2.62 – 16.7 ft-

lb/in²

Average = 1.6 J/cm²;

Grade Count = 28

Coefficient of

Friction

0.16

0.16

Grade Count=1

Coefficient of

Friction, Static

0.25

0.25

Grade Count=1

Tensile Creep

Modulus, 1 hour

2400

7000 MPa

348000 –

1.02e+006 psi

Average = 4700 MPa;

Grade Count = 16

Tensile Creep

Modulus, 1000

hours

2000

5000 MPa

290000

725000 psi

Average = 3600 MPa; Grade Count = 16

Taber Abrasion,

mg/1000 Cycles

15

15

Grade Count = 1

Mechanical Properties

Electrical Properties

Electrical Resistivity

430000 –

1e+015 ohm-

cm

430000 –

1e+015 ohm-cm

Average = 5E+14 ohm-cm; Grade

Count = 89

Surface Resistance

55000 –

1e+016 ohm

55000 –

1e+016 ohm

Average = 2E+14 ohm; Grade Count =

72

Dielectric

Constant

3.2 – 10

3.2 – 10

Average = 4.6;

Grade Count = 73

Dielectric Constant, Low

Frequency

2.6 – 15

2.6 – 15

Average = 7.4; Grade Count = 52

Dielectric Strength

16 –

41 kV/mm

406 – 1040 kV/in

Average = 34.6 kV/mm; Grade

Count = 69

Dissipation

Factor

0.005 – 0.36

0.005 – 0.36

Average = 0.065;

Grade Count = 68

Dissipation Factor, Low

Frequency

0.0035 – 3.4

0.0035 – 3.4

Average = 0.16; Grade Count = 59

Arc Resistance

60 – 136 sec

60 – 136 sec

Average = 96.3 sec;

Grade Count=26

Comparative

Tracking Index

400 – 600 V

400 – 600 V

Average = 540 V;

Grade Count=44

Hot Wire

Ignition, HWI

7 – 120 sec

7 – 120 sec

Average = 55.4 sec;

Grade Count = 14

High Amp Arc

Ignition, HAI

60 – 120 arcs

60 – 120 arcs

Average = 110 arcs;

Grade Count = 14

High Voltage Arc-Tracking

Rate, HVTR

0 –

10 mm/min

0 – 0.394 in/min

Average = 8.6 mm/min; Grade

Count = 14

Graph: Effect of addition of GF material over properties of virgin nylon (Tensile Modulus)

Table-4 Processing Properties

Processing

Temperature

235 – 282 °C

455 – 540 °F

Average = 270°C; Grade Count =

59

Rear Barrel

Temperature

227 – 260 °C

441 – 500 °F

Average = 240°C; Grade Count =

8

Middle Barrel

Temperature

235 – 260 °C

455 – 500 °F

Average = 250°C; Grade Count = 8

Front Barrel

Temperature

235 – 271 °C

455 – 520 °F

Average = 260°C; Grade Count =

8

Nozzle

Temperature

235 – 271 °C

455 – 520 °F

Average = 260°C; Grade Count =

6

Mold

Temperature

52 – 115 °C

126 – 239 °F

Average = 91°C; Grade Count =

35

Drying

Temperature

77 – 85 °C

171 – 185 °F

Average = 84°C; Grade Count =

44

Processing Properties

FLOW SIMULATON:

The `flow analysis of the component would provide useful inputs for anticipating the performance of component during its processing phase. It is generally not feasible to generate a soft mold for experimentation because of high cost involved. Variations over the mold design will be done by varying the parameters like type of gate, gating system location, venting location and location of runners and risers for producing the defect free component. These parameters will be changed at least in three levels and appropriate experimentation method will be followed.

Figure 3 Rib: Deflection, all efffects: Deflection

Figure 4 Rib: Deflection, differential shrinkage: Deflection

Figure 5 Deflection, corner effect: Deflection

From the simulation and analysis, mold flow software provides sufficient information regarding its filling time, injection pressure and pressure drop. With these results, users can avoid the defect of the plastic in actual injection such as sink mark, hesitation, air traps, and over packing. The analysis will also help the mould designer to design a perfect mold with minimum modifications and which will also reduce the mold setup time. With this analysis and simulation, it will help to reduce time and cost.

MOLD DESIGN

Figure 6. Schematic Design for Core for Case Study

Figure 7. Schematic Design for Cavity for the Case Study

Figure 8. Schematic Drawing of Mold Part

CONCLUSION

The Design of the Mold and the processing parameters has an influence over the quality of the component produced. Defects can be minimized through improved design of the mold with the study of simulation of flow through the mold. The material, size, intricacy (complexity) and the rate of production required should be studied for evolving the right Mold design for the given component. From the analysis simulation, Mold flow provides sufficient information results such as fill time, injection pressure and pressure drop. With this result, users can avoid the defect of the plastic in actual injection such as sink mark, hesitation, air traps, and Over packing. The analysis will also help the mould designer to design a perfect mould with minimum modifications and it will also reduce the mould setup time. With this analysis and simulation it will help to reduce time and cost.

The analysis done for the component Upper Case RH

shows good concurrence of the data obtained

by use of `Mold Flow vis-à– vis the physical experimentation (trials) done for the component. The inputs received from the software like the prominence of defects and/ or the recommended values for pr ocessing parameters has helped the Desgn phase of the Mold as also its development. For proving the component, the analysis has helped to reduce the number of trials (from about 15nos earlier to about 8nos now) normally required for such components.

REFERENCES

  1. Zhou Chun-ying, Wang Li-tao, Injection Mold Design based on Plastic Advisor Analysis Software in Pro/E, IEEE 2011 [ 205-208 ].

  2. B. Bona, L. Giacomello, C. Greco, A. Malandra,Position Control of a Plastic Injection Moulding via Feedback Linearization Machine Arizona December 1992 [ 2591-2593]

  3. E ONeill, C. Wilson and D. Brown, The benefits of solid modeling in the plastics injection molding industry, IEEE April 1997 [ 99-107 ]

  4. Fauzun, M. Hamdi, A.E. Tontowi, T. Ariga, Formulation of the size and position of spiral cooling channel in plastic injection mold based on fluent simulation results. IEEE 2008.

  5. M. Dastagiri , M. Prasad and M Annamacahrya , Application of Axiomatic Design in injection molding process, IEEE 2010 [ 222-228 ].

  6. Chi-Huang Lu and Ching-Chih Tsai,Multivariable Self- Tuning Temperature Control for Plastic Injection Molding Process, [ 702-709 ].

  7. C.G. Li, Yuguang Wu,Evolutionary optimization of plastic injection mould cooling system layout design, IEEE 2010 [ 693-696]

  8. Schmidt J . Use CAE in the design of plastics components [J ]

.Kunststoffe-German Plastics ,1988 ,78(2) :3-8.

Leave a Reply

Your email address will not be published. Required fields are marked *