Volume II: Fundamentals of Injection Molding Series
`
`... material
`selection and
`product design
`fundamentals
`OOUG~ M. BRYCE
`Society of Manufacturing Engineers <@>
`
`•
`
`•
`
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`

`

`Plastic Injection Molding
`
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`

`Plastic Injection Molding
`
`... material selection
`and product design
`fundamentals
`
`By Douglas M. Bryce
`
`Volume II : Fundamentals of
`Injection Molding series
`
`Published by the
`Society of Manufacturi ng Engineers
`Dearborn , Michigan
`
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`

`

`Copyright © 1997 by Douglas M. Brycc and Socicty of Manufacturing Engineers
`
`9876543
`
`All rights reserved, including those of translation. This book, or parts thereof,
`may not be reproduced in any form or by any means, including photocopying,
`record ing. or microfilming, or by any information storage and retrieval system,
`without permission in writing of the copyright owners.
`
`No liability is assumed by the publisher with respect to the use of information
`contained herein. While every precaution has been taken in the preparation of
`this book, the publis her assumes no responsibility for errors or omissions.
`Publi cation of any data in this book docs not constitute a recommendation or
`endorsement of any patcnt. proprictary right, or product that may be invol ved.
`
`Library of Congress Cat<llog C<lrd Num ber: 97-068807
`International Standard Book Number: 0-87263-488-4
`
`Additional copies may be obtained by contacting:
`
`Society of Manufacturing Engineers
`Customer Service
`One 5MB Drive
`Dearborn, Michigan 48121
`1-800-733-4763
`
`SME staff who participated in producing this book:
`
`Donald A. Peterson, Senior Editor
`Rosemary K. Csizmadia, Production Team Leader
`Dorothy M. Wylo, Production Assistant
`Jennifer L. Courter, Editorial Assistant
`Karen M. Wilhelm, Manager, Reference Publications
`Cover design by Judy D. Munro, Manager, Graphic Services
`
`Printed in the United Stales of America
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`
`
`
`
`Understanding
`The Injection Molding Process
`
`'p
`
`
`
`
`
`EVOLUTION OF THE PROCESS
`
`
`
`
`
`In 1868, a gentleman by the name of John Wesley Hyatt developed a plastic
`material called celluloid and entered it in a contest created by a billiard ball
`manufacturer. The purpose of the contest was to find a substitute for ivory,
`
`I hich was becoming expensive and difficult to obtain. Celluloid was actually
`invented in 1851 by Alexander Parkes, but Hyatt perfected it to where it could
`be processed into a finished form. He used it to replace the billiard ball ivory
`and won the contest’s grand prize of $10,000, a rich sum in those days. Unfor—
`tunately, after the prize was won, some of the celluloid billiard balls exploded
`ion impact during a demonstration (due to the instability and high flammability
`of the material) and further refinement was required to use it in commercial
`
`ventures. Nonetheless, the plastics industry was born, and it would begin to
`flourish when John Wesley Hyatt and his brother Isaiah patented the first injec~
`tion molding machine in 1872. They used this machine to injection mold cellu-
`loid plastic. Over the next 40 to 50 years others began to investigate this new
`
`process and expand its application to manufacturing such items as collar stays,
`_ buttons, and hair combs. By 1920, the injection molding industry was well en-
`“
`trenched, and it has been booming ever since.
`
`During the 1940s the industry exploded with a bang (not because of the
`
`instability of celluloid) as World War 11 created a demand for inexpensive,
`mass—produced products. New materials were invented for the process on a
`regular basis, and technical advances resulted in more and more successful
`
`
`
`applications.
`
`
`
`CHARTING INDUSTRY EVOLUTION
`
`
`From its birth in the late 18003, to recent developments and applications, the
`injection molding industry has grown at a fast and steady rate. It has evolved
`
`from producing combs and buttons to molding products for all production fields,
`
`including automotive, medical, aerospace, and consumer goods, as well as toys,
`plumbing, packaging and construction. Table I-1 lists some of the important dates
`
`in the evolution of the injection molding industry. Am. Honda V. W H - IPR2018-00619
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`
`1872 John and Isaiah H
`
` 1868 John Wesley Hyatt injection—molds celluloid billiard balls.
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`yatt patent the injection molding machine.
`stics Industry founded.
`
`styrene (still one of the most popular materials).
`nts create huge demand for plastic products.
`1941 Society of Plastics Engineers founded.
`
`1942 Detroit Mold En '
`'
`
`
`1946 James Hendry builds first screw injection molding machine.
`1955 General Electric begins marketing polycarbonate.
`
`1959 DuPont introd
`
`uces acetal homopolymer.
`1969 Plastics land on the moon.
`
`1972 The first parts—removal robo
`t is installed on a molding machine.
`
`1979 Plastic production surpasses
`steel production.
`
`1980 Apple uses acrylonitrile-buta
`diene-styrene (ABS) in the Apple IIe computer.
`
`1982 The JARVIK—7 plastic heart keeps Barney Clark alive.
`
`1985 Japanese firm introduces all—electric molding machine.
`
`
`1988 ReCycling of plastic comes to age.
`1990 Aluminum molds introduce
`(1 for production injection molding.
`
`1994 Cincinnati-Milacron sells fi
`rst all—electric machine in US.
`
`
`
`
`EVOLUTION OF SCREW'CONCEPT
`AND EVALUATION OF PLUNGER
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`
`
`Understanding the Injection Molding Process 3
`
`heat required from the electrical heater bands to soften the plastic to the correct
`injection temperature,
`
`Although the screw machine is the most popular, there is still a place for the
`
`plunger-type machine. A plunger does not rotate; it simply pushes material ahead,
`then retracts for the next cycle. It, too, resides within a heated cylinder. Because
`
`there is no rotating, there is no shearing or mixing action. So, in a plunger ma—
`
`chine the necessary heating action is provided solely by the external heater bands
`because the plunger produces no friction. Also, if two different colored materials
`are placed together in the heated cylinder they are not blended together. The plunger
`simply injects the materials at the same time. If, for instance, the two colors are
`white and black, the resultant molded part will take on a marbled appearance
`with definite swirls of black and white throughout the part. This may be a desired
`finish for particular products, such as lamp bases or furniture, and the use of a
`plunger machine allows that finish to be molded into the product. Use of a screw
`machine would result in a single color (gray) product because the two colors
`would be well mixed prior to injecting.
`The injection molding industry has made a huge impact in its short life. Start—
`ing in the workshop of the two Hyatt brothers, it has become a major focus for
`manufacturing of products from toys to medical devices, and most everything in
`between. The future holds only great promise for more productive, cost—effective
`methods of producing more products using this technology. Improvedmethods,
`materials, processing, and tooling will increase the advantages for product de-
`signers and manufacturers who choose plastic injection molding as their primary
`method of manufacturing.
`
`JtS .
`
`ter.
`
`11 for
`3 and
`
`nto a
`
`njec-
`3ViC€
`1t for
`
`ial is
`Nhen
`This
`1ixed
`CIGW
`
`ents.
`fea—
`:hese
`ause
`pro—
`less
`
`V
`
`
`
`THE PROCESS
`
`_
`,
`Injection molding is a process in which a plastic material is heated until it be,-
`comes soft enough to force into a closed mold, at which point the material cools
`to solidify and form a specific product. The action that takes place is much like
`the filling of a jelly donut. A hypodermic-style cylinder and nozzle inject the
`heated plastic into an opening created in a closed container (mold). The material
`is allowed to harden again, a finished part is ejected, and the cycle is repeated. as
`often as necessary to produce the total number of pieces required.
`Figure 1—1 shows the actual process in simplified form; in actuality, there are
`more than 100 parameters to be controlled during the process to ensure that a
`quality part is produced in the most economical way. These parameters are dis—
`cussed in detail in Volume I of this series, Plastic Injection Molding...man—
`ufacturing process fundamentals, and should be reviewed by those desiring more
`information. We highlight some of the parameters in this chapter to better ac-
`quaint you with the relationship between the process and the need for proper
`material selection.
`‘
`
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`

`4 Plastic injection Molding
`
`
`
`Clamp
`mechanism
`
`Mold halves
`
`Heating
`cylinder
`
`unit
`
`Moving platen ,
`
`Stationary platen
`
`Clamp
`unit
`
`injection
`
`'
`
`Figure 7-1. The injection molding process.
`
`Categorizing the Parameters
`
`First, we must be aware that, although there are so many parameters to control,
`they can be detailed within the confines of four major categories. These are tem-
`perature, pressure, time, and distance as depicted in Figure 1—2.
`Note that the circles in the drawing are interconnected and of different sizes.
`The interconnections indicate that each parameter is both affected by and affects
`other parameters. A change in one may have a major effect on another. The differ-'
`ent circle sizes represent the order of importance placed on each set of param—
`eters; temperature and pressure, for instance, normally are more important to the
`process than time and distance. We take a look at each of the four categories in
`terms of what’s incorporated within each.
`
`Temperature
`
`Temperature of the material. The primary temperature of concern is the tem—
`perature to which the plastic material must be heated before it is injected into a
`mold. All materials have a range of temperatures within which they are most
`efficiently injected while still maintaining maximum physical properties. For
`amorphous materials, (those that soften—not melt—when heat is applied) this range
`
`is ra
`
`als (
`
`is at
`cuss
`
`and
`
`Wit]
`
`ther
`
`plas
`tain
`
`call]
`
`be :
`
`and
`
`prir
`tuni
`
`due
`
`as 1:
`
`spe
`
`gue
`
`ting:
`is a.
`
`sur
`
`cyc v
`ete
`
`acc
`
`cre
`
`sto
`
`tha ‘
`
`
`
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`

`Understanding the Injection Molding Process 5
`
`
`
`is rather broad; with crystalline materi—
`als (those that actually melt when heat
`is applied) it is fairly narrow. (We dis—
`cuss the differences between amorphous
`and crystalline materials in Chapter 2).
`With both types of materials, however,
`there is a temperature point at which the
`plastic flows the easiest and still main—
`tains proper physical properties. This is
`called the ideal melting point and must
`be attained through educated guesses
`and trial-and—error. While this may seem
`primitive, it is only required as a fine-
`tuning adjustment once a specific pro—
`duction run is initiated and is finalized
`
`Temperature
`
`Figure 7-2; Categories of parameters.
`
`as part of establishing particular process
`specifications for specific products. The
`guessing process actually begins by set-
`ting the temperature of the heating cylinder such that the material being injected
`is at a temperature recommended for that generic material.
`The plastic temperature is measured as it leaves the heating cylinder to make
`sure it is within the proper range, and then adjusted up or down depending on
`cycle times, required pressures, mold temperature, and a variety of other param-
`eters. These adjustments are made during a pilot run of the process and until
`acceptable parts are produced. When parts meet specifications, a setup sheet is
`created listing the values for all parameters of concern. These values are then
`stored for use when that specific job is to run again. Table 1—2 shows the recom—
`mended melt temperatures for some common materials. These are the temperatures
`that should be referred to when measuring the material as shown in Figure 1-3.
`The softening (or melting) of the plastic is achieved by applying heat to the
`plastic material, causing the individual molecules to go into motion. To a point,
`the more heat that is applied, the faster the molecules move. However, if too
`much heat is applied, the plastic material begins to degrade and break down into
`its main constituents, one of which is carbon.
`The heat is applied by electrical heater bands wrapped around the outside of the
`heating cylinder of the injection molding machine as depicted in Figure 1—4a.
`The heater bands, which resemble hinged bracelets, are assembled such that
`individual groups of three or four control the temperature of a single zone. There
`are three basic temperature zones for the heating cylinder: rear, center, andfront.
`Each zone is monitored by a thermocouple connected to a temperature control—
`ler. The thermocouple determines whether orfi‘lfit IfliEl‘zgoiieleIiit ngfifgcopw
`PET_HONDA_1009—0009
`
`ntrol,
`tem-
`
`.izes.
`
`fects
`
`.ffer—'
`
`ram-
`
`) the
`
`:s in
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`

`Table 1-2. Suggested Melt Temperatures for Various Plastics
`
`Material
`
`Temperature, °F (°C)
`
`...................................... 400 (204)
`Acetal (copolymer)
`Acetal (homopolymer) ............................................................... 425 (218)
`Acrylic ........................................................................................ 425 (218)
`Acrylic (modified) ..................................................................... 500 (260)
`ABS (medium——impact) .............................................................. 400 (204)
`ABS (high--impact and/or flame retardant) ............................... 420 (216)
`Cellulose acetate .........................................................‘............... 385 (196)
`Cellulose acetate butyrate .......................................................... 350 (177)
`Cellulose acetate propionate ...................................................... 350 ( 177)
`Ethylene vinyl acetate ................................................................ 350 (177)
`Liquid crystal polymer .............................................................. 500 (260)
`Nylon (Type 6) ........................................................................... 500 (260)
`Nylon (Type 6/6) ........................................................................ 525 (274)
`Polyallomer ................................................................................ 485 (252)
`Polyamide—imide ........................................................................ 650 (343)
`Polyarylate ................................................................................. 700 (371)
`Polybutylene
`............. 475 (246)
`Polycarbonate ............................................................................ 550 (288)
`Polyetheretherketone (PEEK) ................................................... 720 (382)
`Polyetherimide ............................................................\............... 700 (371)
`Polyethylene (low—density) ........................................................ 325 (163)
`Polyethylene (high—density) ...................................................... 400(204)
`Polymethylpentene .................................................................... 275 (135)
`Polyphenylene oxide .................................................................. 385 (196)
`Polyphenylene sulfide ................................................................ 575 (302)
`Polypropylene ...........................................................,................. 350 ( 177)
`Polystyrene (general purpose) ................................................... 350 ( 177)
`Polystyrene (medium-impact) ................................................... 380 (193)
`Polystyrene (high—impact) ......................................................... 390 (199)
`Polysulfone ................................................................................ 700 (371)
`PVC (rigid) ................................................................................ 350 (177)
`PVC (flexible) ............................................................................ 325 ( 163)
`Styrene acrylonitrile (SAN) ...................................................... 400 (204)
`Styrene butadiene ....................................................................... 360 (182)
`Tetrafluorethylene ...................................................................... 600 (316)
`Thermoplastic polyester (PBT) ................................................. 425 (218)
`Thermoplastic polyester (PET) ................................................. 450 (232)
`Urethane elastomer .................................................................... 425 (218)
`
`
`
`
`
`
`
`
`
`F.
`
`Fic
`
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`

`
`
`Understanding the Iniection Molding Process 7
`
`
`
`
`
`Hand—held
`
`Molten
`
`plastic
`
`Figure 1-3. Measuring plastic temperature.
`
`pyrometer
`Heater band halves
`
`assembty
`
`Heater bands
`
`Screw or ram
`
`Nozzle
`
`tip
`
`Figure I-4a. The heating cylinder.
`
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`

`U rlubllL‘ IIIIBCIIUH IV\OIOlng
`
`temperature and, if more heat is required, signals the controller to supply more
`electricity to the heater bands in that temperature zone.
`In addition, the machine nozzle (which is mounted at the front of the heating
`cylinder) incorporates at least one heater and is considered an additional zone
`called the nozzle heater zone. This is depicted in Figure l—4b.
`
`Nozzle bands
`
`Nozzle assembly
`
`Nozzle
`
`tip
`
`Figure 7-41). Nozzle heater zone.
`
`Heat is also generated in the heating cylinder by the compressive force of the
`feed screw turning in the cylinder, Figure 1—5.
`This screw augers fresh material into the heating cylinder from the hopper.
`The turning action squeezes the plastic, thus creating friction, which in turn
`creates heat. The amount of friction is controlled by a variety of elements such
`as the rotation speed of the screw, and the distance between the outside diam—
`eter of the flights and the body diameter of the screw, which changes along the
`length of the screw.
`
`Temperature of the mold. Another important temperature is that of the mold.
`A mold is used for containing the injected plastic in a specific shape while the
`plastic cools to a solid. After solidifying, the plastic product is ejected from the
`mold and a new cycle is begun.
`The rate at which the plastic cools is an important factor in determining the
`strength of the plastic material’s physical properties, especially with crystalline
`
`
`
`nH”fiH.HfifiH—Q
`
`E'T‘CLO‘T'JC"
`
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`

`
`
`Understanding the Iniection Molding Process 9
`
`,pply more
`
`he heating
`ional zone
`
`
`
`rce of the
`
`3 hopper.
`h in turn
`
`:nts such
`
`de diam—
`
`Llong the
`
`he mold.
`
`vhile the
`
`from the
`
`ning the
`
`ystalline
`
`
`
`
`
`Fresh material is brought
`forward to front of barrel
`
`
`
`
`
`
`Material pellets
`feeding from hopper
`
`
`fl0 AER-.uga...mi
`
`
`
`
`
`Material is compressed by the
`flights, resulting in heat from
`the shearing action
`
`Screw rotation causes
`
`material to auger forward
`along the screw flights
`
`
`
`Figure 7-5. Cylinder section showing screw action.
`
`plastics. This is because when the material is first heated, the molecules are dis-
`connected from each other and allowed to move about freely. As the material
`cools, these molecules must attach themselves to each other again to regain their
`maximum strength. If they are cooled down too quickly they stop moving before
`they are fully connected and the result is a product with less than optimum physi—
`cal strength. So it is important to cool the plastic at a rate slow enough to allow
`the material to reach proper physical strength, but fast enough to minimize cycle
`time (and total cost). Table 1—3 lists recommended mold temperatures for some
`common plastics.
`_
`Normally, controlling the temperature of the mold is accomplished by running
`water through specially designed channels machined into the mold. These chan—
`nels usually consist of a series of holes drilled through specific plates that make
`up the mold. These holes are connected, by high—temperature hose, to a tempera—
`ture control unit that supplies the appropriate amount and flow of hot or cold
`water to maintain a selected temperature (see Figure 1—6).
`When hotter temperatures are required, such as at start—up time, the tempera—
`ture controller cycles the water through a heating device until the proper tem—
`perature is reached. When cooler temperatures are required, the unit dumps the
`Circulating water to drain and refills itself with water from the input source. In
`this manner the unit is capable of maintaining the temperature of the water circu—
`lating through the mold to within 2 or 3° F (1.1 or 1.70 C).
`Temperature of the oil. Most molding machines are driven béigha/draulic
`Systems, although all—electric models are avAalllalifgthlYeig Egg/"SEE
`$6998?
`
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`

`

`10 Plastic Injection Molding
`
`
`Table I-3. Suggested Mold Temperatures for Various Plastics
`
`
`Material
`
`Temperature, °F (°C)
`
`Acetal (copolymer) ....................................................................... 200 (93)
`Acetal (homopolymer) ................................................................. 210 (99)
`Acrylic .......................................................................................... 180 (82)
`Acrylic (modified) ........................................................................ 200 (93)
`ABS (medium—impact) ................................................................. 180 (82)
`ABS (high-impact and/or flame retardant) ................................... 185 (85)
`Cellulose acetate ........................................................................... 150 (66)
`Cellulose acetate butyrate ............................................................. 120 (49)
`Cellulose acetate propionate ......................................................... 120 (49)
`Liquid crystal polymer .................; ............................................. 225 (107)
`Nylon (Type 6) ...............~.............................................................. 200 (93)
`Nylon (Type 6/6)
`............................................................ 175 (79)
`Polyallomer ......................................................................LI............ 200 (93)
`Polyamide-imide ........................................................................ 400 (204)
`Polyarylate .................................................................................. 275 (135)
`Polybutylene ................................................................................. 200 (93)
`Polycarbonate ..........'................................................................... 220 (104)
`Polyetheretherketone (PEEK) .................................................... 380 (193)
`Polyetherimide ........................................................................... 225 (107)
`Polyethylene (low—density) ........................................................... 80 (27)
`Polyethylene (high—density) ......................................................... 110 (43)
`Polymethylpentene ....................................................................... 100 (38)
`Polyphenylene oxide .................................................................... 140 (60)
`Polyphenylene sulfide ................................................................ 250 (121)
`Polypropylene ............................................................................... 120 (49)
`Polystyrene (general purpose) ...................................................... 140 (60)
`Polystyrene (medium—impact) ...................................................... 160 (71)
`Polystyrene (high—impact) ............................................................ 180 (82)
`Polysulfone ................................................................................. 250 (121-)
`PVC (rigid) ................................................................................... 140 (60)
`PVC (flexible) ..............................................................................
`80 (27)
`Styrene acrylonitrile (SAN) .......................................................... 100 (38)
`Styrene butadiene ......................................................................... 100 (3 8)
`Tetrafluorethylene ........................................................................ 180 (82)
`Thermoplastic polyester (PBT) .................................................... 180 (82)
`Thermoplastic polyester (PET) .................................................... 210 (99)
`
`
`
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`

`
`
`
`
`
`
`l
`l
`Understanding the Injection Molding Process
`
`
`
`
`Mold "A" half
`
`
`
`Mold "B" holt
`
`
`
`energy for, among other things, tum—
`ing the screw, opening and closing the
`clamp (even in toggle machines), and
`
`actuating ejector systems. During these
`operations, and even when the machine
`
`is running at idle, the temperature of the
`system’s hydraulic fluid rises. This tem-
`
`perature rise results from friction created
`
`by the oil flowing through the machine
`
`and by the compressive force of the oil
`
`when used to provide pressure.
`
`Oil temperature must be controlled
`
`to allow it to function properly. If the
`oil is too cool it will be thick and not
`
`flow easily, which may cause valves to
`
`operate sluggishly or not at all. If the
`
`oil is too hot it will degrade into a thin
`
`liquid filled with chunks of additive
`materials that broke down because of
`
`the heat. These clog passageways and
`
`Drilled and tapped holes
`
`Pipe fittings are mounted
`in the topped holes
`
`. Hoses connect
`
`
`go through mold plates
`
`
`
`the pipe fittings
`
` Pressure
`
`
`
`
`_
`Figure 7-6. Controlling temperature of
`mOId-
`..
`
`interrupt operation of the hydraulic
`mechanisms.
`The temperature of the oil is con~
`trolled by a heat exchanger. This unit
`circulates the oil over copper (or other
`, highly—conductive metal) tubing that weaves back and forth inside the unit. The
`
`tubing is connected to a water inlet and the temperature of the oil is monitored.
`When the oil is cold, the heat exchanger does not circulate the water in the tubes.
`
`The water absorbs heat from the oil as the oil warms up while flowing through
`the hydraulic system. When the oil becomes too hot, the heat exchanger opens
`the water inlet valve to allow water to circulate'through the copper tubing. The
`Circulating water draws heat from the oil until the oil temperature drops to the
`proper level. The system then cycles the water off until needed again. In this
`Way, the heat exchanger can maintain the proper oil temperature at approxi—
`mately 120° F, :5" F (49° C, :2.7° C).
`
`Pressure is required for a variety of reasons in the injection molding process. We
`Will focus on injection pressure, holding pressure, and clamping pressure. Pres—
`sure, for these processes, is provided by the hydraulic oil system within the mold—
`ing machine and a series of control valves, regulators, and directional valves. The
`system normally provides a primary “line” pressuAerpW pszfiQfishg/mgfljoejg
`
`PET_HONDA_l 009—00 1 5
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1009-0015
`
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`

`
`
`12 Plastic Injection Molding
`
`
`which is then adjusted up or down by the control components of the system to
`provide whatever pressure is needed for a particular application. For instance, the
`injection pressure can be adjusted from approximately 500 psi (35.2 kg/sz) for
`fast—flowing plastic, up to 20,000 psi (1406.1 kg/cmz) for highly viscous materials.
`The specific requirements for the various pressure applications follow.
`Injection pressure. Injection pressure is the primary pressure used for the
`injection molding process. It can be defined as the amount of pressure required to
`produce the initial filling of the mold cavity image. (The cavity image is the
`opening in the mold that will be filled with plastic to form the product being
`molded.) Note that we use the phrase initial filling. Initial filling represents ap—
`proximately 95% of the total filling of the cavity image.
`The amount of pressure required will range from very low (500 psi [35.2 kg/
`cm2]) to very high (20,000 psi [1,406.1 kg/cm2]). What determines how much
`pressure is used is the viscosity and flow rate of the plastic being injected. Of the
`more than 20,000 plastic materials available today, most will fall within a pres-
`sure range requirement of approximately 5000 to 15,000 psi (351.5 to 1054.6 kg/
`cmZ). And most of these will have a flow index rating of between 5 and 20.
`The flow index rating (properly re-
`ferred to as the melt index) is a value
`designating the amount of material in
`grams that flows over a 10—minute pe—
`riod from a specially designed rheom—
`eter. This is an official ASTM standard,
`number D—1238, and is depicted in Fig-
`ure 1—7.
`’
`
`cylinder .
`
`The melt index (MI) test is a good
`reference test to determine the relative
`thickness (viscosity) of a plastic mate-
`rial, and thereby its relative ease of flow
`during the injection process. An MI of
`around 5 indicates a very viscous ma—
`terial and requires molding pressures
`that are very high. On the other hand,
`materials with an MI of 20 are easy to
`mold and require low pressures. The
`materials data sheet supplied by the
`manufacturer indicates the melt index
`
`<————
`
`Heated
`
`range for a specific material.
`Of importance here is that the melt
`index also indicates the properties of
`the plastic material being tested.
`Table I-4 shows some of these indi-
`cations.
`Am. I’Ilflldfvlfl/ Me/IP'RdéiélWQier.
`
`PET_HONDA_1009—0016
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`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1009-0016
`
`

`

`The Language of Plastics 2
`
`DEFINITIONS RELATlNG TO MATE RIALS
`
`In this chapter we prov ide definitions fo r Ihe various terms Ihul arc uniq ue to
`plastic materials. These descriptions arc important because they help in the dcc i(cid:173)
`sion-nUlking process for selecting the proper material o r family of mllleri<l!s 10
`provide the required properties for a specific product and process. We start with
`the most pervlIsive term. plastic.
`
`The Delinition of IJlastic
`
`A simplistic definition of plastic (us used to dcsnibe molding materials) might be:
`Any complex, organic, l)oiymcril.ed compmllld capable of beillg
`~'IU/ped or/ormed.
`Generally speaking, the terms "plastic" and "polymer" aTC used interchange(cid:173)
`ably. although strictly speilk ing a polymer is a plastic, but a plastic does not have
`to be a polymer. Plastics can be in the form of liq uids or solids or something
`between the two.
`Plastics are created by refini ng common petroleum products, crude oil and
`natural gas bei ng the main building blocks. Figure 2- 1 is a diagram of how these
`blocks are utilized in making some of the more com mon plastic materials avail(cid:173)
`able today. Experimental work is currently underway to create plastic materials
`from sources other than petroleum, with limited Sllccess recorded in creating pri(cid:173)
`mary materials from stich products as vegetable oils and coat.
`
`Pol ymerization
`
`When we discllSs plostics we arc usually re ferri ng to compou nds that have bcen
`created by way of a process called polymeriwtioll, defincd as:
`A reaction caused by combilling mOl/omer wili! (I catalyst, /lllder pres(cid:173)
`sure, and wili! hear.
`A monolller is a single unit. In the polymerization process we combine many
`single units of plastic into many combined units o f plastic, known as polymer.f.
`Therefore, the process used to produce these polymers is called polymerization .
`The polymers arc what we use for moldi ng. Polymers arc formed by combin ing a
`series of monomers. We will take 11 look at how this is accomplished.
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1009-0017
`
`

`

`38 Plo~tic Iniection Molding
`
`Figure 2-'. Building blocks (or common plastic materiols are derived (rom petroleum
`
`Am. Honda v. IV II - IPR2018-00619
`PET_HONDA_1009-0018
`
`

`

`The language 01 Plm!ic5 39
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