Injection molding methods design optimization simulation of plastic toy building block by mold flow analysis

Injection Molding Methods Design, Optimization, Simulation of Plastic Toy Building Block by Mold Flow

Analysis, Manmit Salunke, Rushikesh Kate, Vishwas Lomate, Gajanan Sopal, Journal Impact Factor (2015):

8.8293 Calculated by GISI (www.jifactor.Com)

www.iaeme.com/ijmet.asp 33 [email protected]

1,2,3Assistant Professor, Department of Mechanical Engineering, J.S.P.M.’S B.I.T,

Barshi, Solapur, Maharashtra, India

4Associate Professor, Department of Mechanical Engineering, J.S.P.M.’S B.I.T,

Barshi, Solapur, Maharashtra, India

ABSTRACT

Mold flow simulation helps designers to see how their designs will be resulted after injection

molding process without needing to do the Injection Molding process. The use of simulation

programs saves time and reduces the costs of the Molding system design. Injection molding design

simulation holds an important role in analyzing the outcome of the design. In this paper plastic toy

building block part is analyzed and studied to solve the problems frequent rejections due to as

shrinkage, weld lines, air traps, and sink marks. All the designs were simulated with Autodesk Mold

flow Adviser. Autodesk Simulation Mold flow effectively eliminates the use of trial and error

method by validating and optimizing the design of plastic before production. This not only improves

the quality but also help us to guide about the selection of machines and the production planning.

Keywords: Injection moulding, Mould design, Mold flow simulation, Optimization Plastic Injection

mould, Mould Flow Plastic Advisor (MPA)

1. INTRODUCTION

Injection Moulding is one of the common methods to do the mass-production of plastic

product. Thermoplastics are science's gift to the toy industry. They can be melted at fairly low

temperatures, molded in colors with fine detail, and stand up well to play wear because of their

resilience.. Injection moulding is the most commonly used manufacturing process for the fabrication

of plastic parts. A wide variety of products are manufactured using injection moulding, which vary

greatly in their size, complexity, and application. Injection Molding is the way most of our plastic

toys are created. The material is injected under pressure into a two-part mold. The material is

allowed to cool, the mold is opened, and the solid product inside is ejected into a collection hopper.

Common problems associated with injection molding are numerous.

INJECTION MOLDING METHODS DESIGN, OPTIMIZATION,

SIMULATION OF PLASTIC TOY BUILDING BLOCK BY MOLD

FLOW ANALYSIS

Manmit Salunke1, Rushikesh Kate

2, Vishwas Lomate

3, Gajanan Sopal

4

Volume 6, Issue 6, June (2015), pp. 33-42

Article ID: 30120150606004

International Journal of Mechanical Engineering and Technology

© IAEME: http://www.iaeme.com/IJMET.asp

ISSN 0976 – 6340 (Print)

ISSN 0976 – 6359 (Online)

IJMET

© I A E M E





2. COMPUTER AIDED SIMULATION

Nowadays, Computer Aided Design is not limited to sketching and drafting, but also helps to

create analysable models as needed for computer based process simulation. Moldflow software, used

solution for Digital Prototyping, provides injection molding simulation tools for use on digital

prototypes. Providing in-depth validation and optimization of plastic parts and associated injection

molds, Moldflow software helps study the injection molding processes in use today. The Autodesk

Simulation Moldflow results help to identify the main problem areas before the part is manufactured

that are particularly difficult to predict with traditional methods. In conventional optimization

process includes actual shop floor trials in which pattern, feeder size, shape and location cores,

mould layout, gating etc are required to be changed in each iteration which is associated with

machining cost, tooling cost, modification cost, melting cost, fettling and transportation cost as well

as energy, materials, time are wasted in each trial until and unless the required results are obtained.

Analysis is essential for designing and mould making through simulation step-up and result

interpretation to show how changes to wall thickness, gate location, material and geometry affects

manufacturability and also experiments with “what-if” scenarios before finalizing a design. Injection

Moulding simulation software into the mould design process in order to analyze the product, foresee

the possible defects, and optimize the design to achieve the maximum outcome of the products with

minimum cycle time in each production cycle.

3. PROBLEM DEFINITION

Here a plastic toy building block of 60 mm leangth, 34 mm width and 1 mm thick is

analysed by taking different cases of Model and optimize runner. gating, sprue systems Determine

potential part defects, such as weld lines, air traps, and sink marks, and then rework designs to avoid

these problems. Create feed systems based on inputs for layout, size, and type of components, such

as sprue, runners, and gates.

4. OBJECTIVES OF THE WORK

1. To analyze the behaviour of Thermoplastic material during the production cycle from the

filling phase until the ejection phase.

2. To foresee the possible problem for a product design; and therefore able to op-timize the

design in the mould design process.

3. To achieve the minimum production cycle time

4. To construct a rapid prototyping of the mould cavity design into a standard mould plate.

5.1 Model details

A 3d model of part toy is created in solid Edge software

Fig. 1.1 a) 2D dimension of part Fig. Fig. 1.1 b) Actual toy building block





Fig.1.1c) Old design (2mm thikness at middle cavity) Fig. 1.1 d) new design (1mmuniform thikness)

Fig.1) 3D cad model of toy part

Fig. 2 Mechanical Properties of ABS material

5.2 Process settings

Melt temperature: 230.0 (C) Mold temperature: 50.0 (C)

Injection locations: 4 Max. machine injection pressure: 180.000 (MPa)

5.3Mold Data Mold material Tool Steel P-20

Mold dimensions X: 300.00 (mm) Y: 150.00 (mm) Z: 50.02(mm)

Mold plate dimensions A plate: 25.02 (mm) B plate: 25.00 (mm)

5.4Material Data

Family abbreviation-LDPE Family abbreviation-ABS Familyname -

Acrylonitrile

Familyname-polyethylenes (PE) copolymers (abs, Trade name -(10% Rubber)

Mold Temperature Range 20-70 °C 25-80°C

Melt Temperature 220°C 230°C

Ejection Temperature 80°C 88 °C

Maximum Shear Stress 0.11 MPa 0.28 MPa

Maximum Shear Rate 400001/s 12000 1/s

Modulus Of Elasticity 124 MPa 3500 MPa

Poison Ratio 0.41 0.36

Shear Modulus 43.97 MPa 1287 MPa

Melt Density 0.73537 g/cm3 0.94933 g/cm

3

Specific Heat 4230 J/Kg-C 2400 J/Kg-C

Heating/Cooling Rate -0.3333c/s -0.3333c/s





5.5 Coolant information

Cooling circuit 1 Cooling circuit 2

Inlet coordinate : -320.00, -165.00, 42.00 -320.00, -165.00, -30.00

Temperature 25.0°C 25.0°C

Hose, Diameter 10.00 mm Hose, Diameter 10.00 mm

Channel, Circular, Diameter (10.00 mm

Flow rate 10.0000 (lit/min) 10.0000 (lit/min)

5.6 Quality prediction for LDPE and ABS materials

Fig.3 a) single Part LDPE Fig.3 b) single Part ABS

Fill analysis for single part toy shows part have good quality when ABS material preffered.

5.7 Optimum molding conditions for ABS material

FIG.4 Optimum processing conditions

Parameter Optimum Value (ABS ) Default Value (ABS )

Mold surface temperature 58 °C 50.0 (C)

Melt temperature 230°C 230.0 (C)

Injection time 5.2 s 6.08





5.8Feed system cases details

CASE I CASE II CASEIII CASE IV

Sprue

dimensions

Cold, Circular Tapered,

Start Diameter (2.00 mm),

End Diameter (4.00 mm)




Cold, Circular

Tapered, Start

Diameter (5.00

mm), End Diameter

(4.00 mm)

Cold, Circular

Tapered, Start

Diameter (10.00 mm),

End Diameter (8.00

mm)

Runner

dimensions

Cold, Circular, Diameter

(3.00 mm)

Cold, Rectangular, Width

(3.00 mm), Thickness

(2.00 mm)

Cold, Circular,

Diameter (3.00

mm)

Cold, Circular,

Diameter (15.00 mm)

Gate

dimensions




Cold, Rectangular, Width

(2.00 mm), Thickness

(2.00 mm)

Cold, Circular

Tapered, Start

Diameter (3.00

mm), End Diameter

(1.00 mm)

Cold, Circular

Tapered, Start

Diameter (3.00 mm),

End Diameter (1.00

mm)

6. SIMULATION RESULT

6. A Gate Location Analysis

Optimum gate locations may need to be examining by running the filling analysis on

different best gate locations. Figure shows the result of gate location. Blue area represents the best

gate locations for the part.

Fig. 6A) best gate location

6. B Fill Time Analysis result

The Fill time result shows the position of the flow front at regular intervals as the cavity fills.

At the start of injection, the result is dark blue, and the last places to fill are red. If the part is a short

shot, the section which did not fill has no colour. Fill time is the time taken to fill up the part inside

the cavity; it is also to show how the plastic material flows to fill the cavity.

Fig.A caseI Fig.B caseII Fig.C caseIII Fig.D caseIV

Fig .6B) Fill Time Analysis result





6. C Confidance of fill analysis result


Fig . 6C) Confidance of Fill Time Analysis result

6. D Quality prediction analysis result


Fig .6D) Quality prediction analysis result

6. E Injection Pressure.


Fig . 6E )Injection Pressure result

6. F RESSURE DROP


Fig. 6F) pressure drop result





6 .G TEMPERATURE AT FLOW FRONT


Fig. 6G) temperature at flow front result

6 .H. Time To reach ejection Temperature


Fig.6H) Time to reach ejection Temperature result

6 .I. AIR TRAP Analysis result


Fig. 6 .I) air trap analysis result

6 .J) weld lines analysis result


fig. 6J) weld lines analysis result





6 .L) cooling quality analysis result


Fig.6 L) cooling quality analysis result

6. M). Wrap Analysis Result


Fig. 6M) Wrap analysis result

7. RESULTS AND DISCUSSION

CASE I CASE II CASEIII CASE IV

Fill tab

Actual filling time 0.72 (s) 0.70 (s) 0.73 (s) 2.22 (s)

Actual Injection pressure 89.170 (MPa) 93.556 (MPa) 80.323 (MPa) 42.029 (MPa)

Clamp force area 71.6304 (cm^2) 69.9443 (cm^2) 71.6304 (cm^2) 105.3522 (cm^2)

Max. clamp force during filling 25.270 (tonne) 22.052 (tonne) 23.043 (tonne) 22.615 (tonne)

Velocity/pressure switch-over at %

volume 97.80 (%) 98.09 (%) 97.85 (%) 97.65 (%)

Velocity/pressure switch-over at time 0.69 (s) 0.68 (s) 0.69 (s) 2.12 (s)

Estimated cycle time 13.06 (s) 13.07 (s) 13.11 (s) 35s

Total part weight at the end of filling 20.594 (g) 20.568 (g) 20.611 (g) 21.208 (g)

Shot volume 23.1581 (cm^3) 22.8886 (cm^3) 23.3743 (cm^3) 72.2383 (cm^3)

Cavity volume 20.8127 (cm^3) 20.8127 (cm^3) 20.8127 (cm^3) 20.8127 (cm^3)

Runner system volume 2.3454 (cm^3) 2.0759 (cm^3) 2.5615 (cm^3) 51.4256 (cm^3)

Pack tab

Maximum clamp force during cycle 25.270 (tonne) 30.742 (tonne) 30.539 (tonne) 27.198 (tonne)

Max. wall shear stress 0.421 0.431 (MPa) 0.480 (MPa) 0.550 (MPa)

Total part weight 20.629 (g) 21.024 (g) 21.143 (g) 21.208 (g)

Cycle time 15.01 15.68 (s) 15.69 (s) 35.00 (s)





Cooling Quality

Maximum and minimum temperature

variance 5.1 C & -1.2 C

7.8 (C) (C) & -

7.4 C

5.1 (C) & -2.5

(C) 7.3 (C) & -9.5 C

Maximum and minimum cooling time

variance

0.49 (s) & -

0.57 (s)

1.47 (s) & -1.19

(s)

0.49 (s) & -0.57

(s)

1.65 (s) &-1.25

(s)

Cool tab

Maximum temperature, part 49.2 (C) 49.4 c 49.3 (C) 53.5 c

Minimum temperature, part 32.6 (C) 32.5 c 32.6 (C) 34.7 c

Average temperature, part 41.1 (C) 40.9 c 41.1 (C) 45.2 c

Mold exterior temperature 27.4 (C) 27.3 c 27.4 (C) 28.6 (C)

The comparison of initial and modified designs on various parameters

1) Considering initial design for plasic toy, 2mm thikness at moddle cavity, simulation result

showing cooling time of part not uniform and have very high value .Fill analysis shows poor

quality for part. So model is redesigned for unform wall thiknes 1mm .Then simulation result

shows better quality of part.

2) After fill analysis shows part have lower quality for LDPE material and high quality for ABS

material .Different four cases of runner sprue and gate system are analyzed by using ABS

material for plasic toy.

3) In case IV have large filling time and more runner system volume so wastage of material is

high. Case II have lower filling time but more shrinkage.

4) Case I have lower cycle time, high confidence of fill, high quality. So have good optimum

design solution for defect free part.

8. CONCLUSION

The filling time and the cooling time of a four cavity design does not increase to four

times longer than having a single cavity. So the cycle time for four cavities design is the most

optimum and efficient to be used in the production process. The analysis work shows the parameters

such as sink marks, fill time, weld line, air traps etc. that will affects the quality of the finished

product. Plastic Flow Simulation Simulate the flow of melted plastic to help optimize part and mold

designs, reduce potential part defects, and improve the molding process and decrease the cycle time

and to improve the Quality of the Product.

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