Improving Processing of Rubber in Injection,
Transfer and Compression Molding Process
Acrolab Ltd.
Windsor Ontario Canada
519-944-6900
[email protected]
www.acrolab.com
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
Open &
Eject
6%
Heating
51%
Close
3%
Fill
11%
Pack & Hold
29%
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
Material
Thermal Conductivity (W/m K) at 20 C
Factor
390 – 15,000
****
Aluminum
237
1.6x
Beryllium Copper
105
3.7x
20 – 40
13x
0.60
650x
0.15 – 0.30
2,400x
0.13 – 0.16
2,600x
0.025
15,600x
ISOBAR
Steel
Water
Plastics
RUBBER
Air
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Types of Isobars
STANDARD
FINNED
STEPPED
HOLLOW
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar - Function
HEAT IN
HEAT OUT
METAL WICK
LIQUID FLOW
VAPOUR FLOW
ISOBAR SHELL
HEAT IN
HEAT OUT
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Function and Orientation
VERTICAL
HORIZONTAL / INCLINED
HEAT OUT
HEAT IN
HEAT INPUT MUST BE BELOW HEAT
OUTPUT
HEAT OUT
HEAT IN
HEAT INPUT AND OUTPUT CAN BE
ANYWHERE ALONG THE ISOBAR LENGTH
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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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 of
25mm Diameter x 150mm Long Core
CORE
WITH ISOBAR
CORE
SOLID
MOLDED PART
CORE PIN
ISOBAR
HEATED
MOLD
PLATE
HEATER
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Thermal Performance of
25mm Diameter x 150mm Long Core
200
Temperature (C)
175
150
Steady State
With Isobars
125
Without Isobars
100
75
Steady State
50
25
0
5
10
15
20
25
30
35
40
Time (Minutes)
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Thermal Performance of
25mm Diameter x 150mm Long Core
225
Core Base
Temperature (C)
200
175
With Isobars
Core Top
Without Isobars
150
125
100
0
2.5
5
7.5
10
12.5
15
Length (Cm)
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Examples of Cores with Isobars
ISOBAR
CORE PIN
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Heated Cores
TEMPERATURE UNIFORMITY OF
HEATED CORE
No Isobars
With 4 Isobars
Indirect Heating of Isobars
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Heated Cores
ISOBAR
91.4 mm
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Transfer Molding
Tree Bar Mold
Core Pin
Isobar
Heater
Tree Bar
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Heated Cores
Epoxy
Plug
ISOBAR
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Rubber Molding over Flat Plates
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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ISOPLATEN
Bi-Level Matrix of Heaters and Isobars
Acrolab Ltd. – Copyright 2003 – Introduction to Mold Cooling & Heating
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STANDARD PLATEN
24” x 24” x 3”
With 5 heaters
Heaters ON
Thermocouples
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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STANDARD PLATEN
24” x 24” x 3”
With 5 heaters
One Heater
disconnected
Heaters ON
Heater OFF
Thermocouples
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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HEATER TEMPERATURE PROFILE VS LENGTH
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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ISOPLATEN
24” x 24” x 3”
With 5 Heaters
With 13 Isobars
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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ISOPLATEN
24” x 24” x 3”
With 5 Heaters
With 13 Isobars
One heater
disconnected
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Standard Platen
Isoplaten
Acrolab Ltd. – Copyright 2003 – Introduction to Mold Cooling & Heating
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Isoplaten vs. Standard Platen
ISOPLATEN
ISOPLATEN
1 Heater Disconnected
140
Temperature (°F)
316
313
Temperature (F)
STANDARD PLATEN
STANDARD PLATEN
1 Heater Disconnected
70
60
50
40
30
20
10
0
Frequency
Frequency
25
20
15
Frequency
10
5
Temperature (F)
355
347
339
331
323
315
307
299
291
283
275
267
259
320
317
314
311
308
305
302
299
296
293
0
290
Frequency
310
292
316
314
312
310
308
306
304
302
300
298
296
0
307
20
Frequency
304
40
301
Frequency
60
298
80
120
100
80
60
40
20
0
295
100
Frequency
Frequency
120
Temperature (F)
Acrolab Ltd. – Copyright 2003 – Introduction to Mold Cooling & Heating
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Isoplaten vs Platen Consideration
• Thermal uniformity +/-2 °C
vs
+/- 15 °C
• Single Zone vs Multiple Zone Control
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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ISOPLATEN
Mounting Holes
Isobar
Heater
Thermocouple
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ISOPLATEN
T - Slots
Isobar
Heater
Thermocouple
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ISOPLATEN
Center Hole
Isobar
Heater
Thermocouple
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ISOPLATEN
Thermocouple
Thermoswitch
Isobar
Heater
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Rubber Molding of Automotive Gaskets
EXAMPLE#1
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Bottom Plate
Isobar
Heater
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Top Plate – with Isobars in Inserts
Isobar
Heater
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Rubber Molding of Automotive Gaskets
EXAMPLE#2
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Top Cavity Plate
Isobar
Heater
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Middle Cavity Plate
Isobar
Heater
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Bottom Cavity Plate
Isobar
Heater
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Rubber Molding of Automotive Seals
Example#3
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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49 Cavity Injection Mold
Isobar
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Rubber Molding Tool
Example#4
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Single Cavity Tool
Ø25mm X 7.5" LG. ISOBARS- 12 PCS
Ø25mm X 6.5" LG. ISOBARS- 15 PCS
STANDARD
REVERSE
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Thermoset Molding of Automotive
Head Lamp Reflectors
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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2 Cavity Thermoset Head Lamp Reflector Mold
Heater
Isobar
Thermocouple
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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2 Cavity Thermoset Head Lamp Reflector Mold
Heater
Isobar
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Head Lamp Molds
Isobars shown
Prior to Install
Optic Surfaces
Electrical Box
Shown with heater
Leads and T/C
Mold Insulated
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Head Lamp Molds
Cooling
Isobars
Heaters
Heat Generation
In mold Inserts
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Head Lamp Molds
Heating
Zone
Electrical
Box
Heat Generation
In mold Shoe
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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Isobar Design in Head Lamp Molds
Heat Generation
In mold Shoe
With Isobars
in Slides
Slide with
Isobars
Acrolab Ltd. – Copyright 2003 – Improving Processing of Rubber
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