Improving Processing of Rubber in Injection, Transfer · PDF fileImproving Processing of Rubber in Injection, Transfer and Compression Molding Process ... Improving Processing of Rubber

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Improving Processing of Rubber in Injection, Improving Processing of Rubber in Injection, Transfer and Compression Molding ProcessTransfer and Compression Molding Process

Acrolab Ltd.Windsor Ontario Canada

[email protected]

Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber

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Introduction

Mold heating time is the biggest contributor to the overall cycle time in almost all rubber molding applications

Many molders fail to claim additional savings that can be achieved through optimized heating process


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Molding Process

Mold heating generally accounts for more than two thirds of total cycle time

Heating51%

Open & Eject6%

Close3% Fill

11%

Pack & Hold29%


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Benefits of Optimum Heating Process

• Temperature Uniformity

• Reduced Residual Part Stress

• Cycle Time Reduction

• Scrap Rate Reduction

• Energy Savings

• Reduced Maintenance


5

Factors Affecting Mold Heating

MOLD

• Material Thermal properties

• Part Geometry

• Thermal breaks between plates or inserts

• Location of Thermocouple

RUBBER PART

• Thermal properties

• Part Thickness

• Geometry


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Thermal Conductivity of Materials

****390 – 15,000ISOBAR

2,600x0.13 – 0.16RUBBER15,600x0.025Air

2,400x0.15 – 0.30Plastics

0.60

20 – 40

105

237

Thermal Conductivity (W/m K) at 20 C

650xWater

13xSteel

3.7xBeryllium Copper

1.6xAluminum

FactorMaterial


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Types of Isobars


STANDARD

HOLLOW

STEPPED

FINNED

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Isobar - Function


HEAT IN

HEAT IN HEAT OUT

HEAT OUT

LIQUID FLOW

METAL WICK

ISOBAR SHELL

VAPOUR FLOW

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Isobar Function and Orientation


HEAT OUT

HEAT IN HEAT INHEAT OUT

VERTICAL HORIZONTAL / INCLINED

HEAT INPUT MUST BE BELOW HEAT OUTPUT

HEAT INPUT AND OUTPUT CAN BE ANYWHERE ALONG THE ISOBAR LENGTH

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Isobars

• Passive Device

• Superthermal Conductors

• Thermal Uniformity of +/- 1 °C

• Orientation Dependent

• Operating Temperature 0 – 280 °C


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Thermal Performance of25mm Diameter x 150mm Long Core


COREWITH ISOBAR

CORESOLID

MOLDED PART

CORE PIN

ISOBAR

HEATEDMOLDPLATE

HEATER

12

25

50

75

100

125

150

175

200

0 5 10 15 20 25 30 35 40

Time (Minutes)

Tem

pera

ture

(C)

With Isobars

Without Isobars



Steady State

Steady State

13Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber


100

125

150

175

200

225

0 2.5 5 7.5 10 12.5 15

Length (Cm)

Tem

pera

ture

(C

)

With Isobars

Without IsobarsCore Top

Core Base

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Examples of Cores with Isobars


ISOBAR CORE PIN

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No Isobars With 4 Isobars

Isobar Design in Heated Cores

Indirect Heating of Isobars


TEMPERATURE UNIFORMITY OF

HEATED CORE

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91.4 mm



ISOBAR

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Isobar Design in Transfer MoldingTree Bar Mold


Core Pin

Tree Bar

Isobar

Heater



ISOBAR

EpoxyPlug


Rubber Molding over Flat Plates

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ISOPLATEN

Bi-Level Matrix of Heaters and Isobars

Acrolab Ltd. – Copyright 2003 – Introduction to Mold Cooling & Heating


STANDARD PLATEN24” x 24” x 3”With 5 heaters

Heaters ONThermocouples


STANDARD PLATEN24” x 24” x 3”With 5 heaters

One Heater disconnected

Heaters ONHeater OFFThermocouples


HEATER TEMPERATURE PROFILE VS LENGTH


ISOPLATEN24” x 24” x 3”With 5 HeatersWith 13 Isobars


ISOPLATEN24” x 24” x 3”With 5 HeatersWith 13 Isobars

One heater disconnected

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Standard Platen Isoplaten

Acrolab Ltd. – Copyright 2003 – Introduction to Mold Cooling & Heating

27Acrolab Ltd. – Copyright 2003 – Introduction to Mold Cooling & Heating

ISOPLATEN

0

20

40

60

80

100

120

140

296

298

300

302

304

306

308

310

312

314

316

Temperature (°F)

Fre

qu

ency

Frequency

ISOPLATEN1 Heater Disconnected

020406080

100120

292

295

298

301

304

307

310

313

316

Temperature (F)

Freq

uenc

y

Frequency

STANDARD PLATEN

010203040506070

290

293

296

299

302

305

308

311

314

317

320

Temperature (F)

Fre

qu

ency

Frequency

STANDARD PLATEN1 Heater Disconnected

0

5

10

15

20

25

259

267

275

283

291

299

307

315

323

331

339

347

355

Temperature (F)

Freq

uenc

yFrequency

Isoplaten vs. Standard Platen


Isoplaten vs Platen Consideration

• Thermal uniformity +/-2 °C vs +/- 15 °C

• Single Zone vs Multiple Zone Control


Mounting Holes

ISOPLATEN

IsobarHeaterThermocouple


T - Slots

ISOPLATEN



Center Hole

ISOPLATEN



Thermocouple

ISOPLATEN

IsobarHeater

Thermoswitch


Rubber Molding of Automotive Gaskets

EXAMPLE#1


Bottom Plate

IsobarHeater


Top Plate – with Isobars in Inserts

IsobarHeater


Rubber Molding of Automotive Gaskets

EXAMPLE#2


Top Cavity Plate

IsobarHeater


Middle Cavity Plate

IsobarHeater


Bottom Cavity Plate

IsobarHeater


Rubber Molding of Automotive SealsExample#3


49 Cavity Injection Mold

Isobar


Rubber Molding ToolExample#4

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Ø25mm X 7.5" LG. ISOBARS- 12 PCS

STANDARD REVERSE

Ø25mm X 6.5" LG. ISOBARS- 15 PCS


Single Cavity Tool


Thermoset Molding of AutomotiveHead Lamp Reflectors


2 Cavity Thermoset Head Lamp Reflector Mold

HeaterIsobarThermocouple


2 Cavity Thermoset Head Lamp Reflector Mold

HeaterIsobar

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Isobar Design in Head Lamp Molds

Isobars shownPrior to Install

Optic Surfaces

Electrical BoxShown with heaterLeads and T/CMold Insulated


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Heat GenerationIn mold Inserts

Cooling Isobars

Heaters

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Heat GenerationIn mold Shoe

HeatingZone

ElectricalBox

50



Heat GenerationIn mold ShoeWith Isobarsin Slides

Slide withIsobars

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Improving Processing of Rubber in Injection, Transfer · PDF fileImproving Processing of Rubber in Injection, Transfer and Compression Molding Process ... Improving Processing of Rubber