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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
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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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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%
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Types of Isobars
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
STANDARD
HOLLOW
STEPPED
FINNED
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Isobar - Function
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
HEAT IN
HEAT IN HEAT OUT
HEAT OUT
LIQUID FLOW
METAL WICK
ISOBAR SHELL
VAPOUR FLOW
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Isobar Function and Orientation
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Thermal Performance of25mm Diameter x 150mm Long Core
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Thermal Performance of25mm Diameter x 150mm Long Core
Steady State
Steady State
13Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Thermal Performance of25mm Diameter x 150mm Long Core
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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
ISOBAR CORE PIN
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No Isobars With 4 Isobars
Isobar Design in Heated Cores
Indirect Heating of Isobars
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
TEMPERATURE UNIFORMITY OF
HEATED CORE
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91.4 mm
Isobar Design in Heated Cores
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
ISOBAR
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Isobar Design in Transfer MoldingTree Bar Mold
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Core Pin
Tree Bar
Isobar
Heater
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Isobar Design in Heated Cores
ISOBAR
EpoxyPlug
19Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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
21Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
STANDARD PLATEN24” x 24” x 3”With 5 heaters
Heaters ONThermocouples
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STANDARD PLATEN24” x 24” x 3”With 5 heaters
One Heater disconnected
Heaters ONHeater OFFThermocouples
23Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
HEATER TEMPERATURE PROFILE VS LENGTH
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ISOPLATEN24” x 24” x 3”With 5 HeatersWith 13 Isobars
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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
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Isoplaten vs Platen Consideration
• Thermal uniformity +/-2 °C vs +/- 15 °C
• Single Zone vs Multiple Zone Control
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Mounting Holes
ISOPLATEN
IsobarHeaterThermocouple
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T - Slots
ISOPLATEN
IsobarHeaterThermocouple
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Center Hole
ISOPLATEN
IsobarHeaterThermocouple
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Thermocouple
ISOPLATEN
IsobarHeater
Thermoswitch
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Rubber Molding of Automotive Gaskets
EXAMPLE#1
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Bottom Plate
IsobarHeater
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Top Plate – with Isobars in Inserts
IsobarHeater
36Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Rubber Molding of Automotive Gaskets
EXAMPLE#2
37Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Top Cavity Plate
IsobarHeater
38Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Middle Cavity Plate
IsobarHeater
39Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Bottom Cavity Plate
IsobarHeater
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Rubber Molding of Automotive SealsExample#3
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49 Cavity Injection Mold
Isobar
42Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Single Cavity Tool
44Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Thermoset Molding of AutomotiveHead Lamp Reflectors
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2 Cavity Thermoset Head Lamp Reflector Mold
HeaterIsobarThermocouple
46Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Head Lamp Molds
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Heat GenerationIn mold Inserts
Cooling Isobars
Heaters
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Isobar Design in Head Lamp Molds
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Heat GenerationIn mold Shoe
HeatingZone
ElectricalBox
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Isobar Design in Head Lamp Molds
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
Heat GenerationIn mold ShoeWith Isobarsin Slides
Slide withIsobars