崑山科技大學

機 械 工 程系

Improvement on Injection Molding

Technology

射 出 成 型 模 具 技 術 改 良

Student: Josue David Ayala Guido

Advisor: Shu-Hsing Chen

Department of Mechanical Engineering

Kun Shan University

Tainan, Taiwan, R.O.C.

Hands-On Project Report

June, 2016

 

 

 

1 

  

2  

Table of Content

Abstract 3

1. Introduction of history of injection molding 4

1.1 Introduction of plastics 4

2. What is injection molding? 8

3. Applications of Injection Molds 9

4. Mold and Part Design 13

5. Some typical plastics and their uses for injection molding 19

6. Advantages and disadvantages of Injection molding 21

7. Injection molding design 22

8. PowerMILL Simulations for the cavity and core 34

9. Conclusion 38

10. Glossary of some Plastic Injection Molding Terms 39

11. References 42

  

3  

Improvement on Injection Molding

Technology

Abstract

Since the increasing development of plastic industry is a fact and improvement and creativity

are essential to implement better plastic techniques for making complex shapes, injection

molding is the most popular for producing plastics products. There are many reasons of

which two are listed: high productivity and efficiency to manufacture dozens, hundreds or

thousands of pieces with simplest or the most difficult shapes. The main purposes to write

this paper are to provide basic information, concepts and give some ideas of how important

and at some point necessary comes to use injection molding of thermoplastics. By injection

molding, plastic parts are easy to make with the injection mold, fast to produce in relation of

the complexity in many or couple seconds, have lower price because thermoplastics are

cheaper than metals and other materials, and high performance in engineering and different

utilities. The paper begins with the definition of injection molding and brief history of how it

has become more important while the industry has progressed. Applications of injection

molds, plastics and their uses and examples of polymers best suited for injection molds are

also subtitles of this paper. The description of a two plate molds, the importance of injection

molding, advantages and disadvantages, applications of this technique and drawings of a two

plate mold and glossary of words is the last information in relation with injection molding.

Key words: Plastics, injection molding, molds

  

4  

1. Introduction of History of Injection Molding

How did the world of injection molded parts begin? In 1868, billiard ball maker Phelan and

Collander, John Wesley Hyatt invented a way to make billiard balls by injecting celluloid

into a mold. Hyatt improved the celluloid so that it could be processed into a finished form.

In 1872 John and his brother Isaiah patented the first injection molding machine. This

machine was relatively simple compared to the machines used by today's injection molding

companies. It contained a basic plunger to inject the plastic into a mold through a heated

cylinder. The industry progressed slowly over the years producing injection molded products

such as plastic collar stays, buttons, and hair combs. In the 1940's the concept of injection

molds grew in popularity. This is because World War II created a huge demand for

inexpensive, mass-produced products. In 1946, James Hendry built the first screw injection

molding machine, revolutionizing the plastics industry with an auger design to replace Hyatt's

plunger. The auger is placed inside the cylinder and mixes the injection molded material

before pushing forward and injecting the material into the mold. This allowed colored plastic

or recycled plastic to be added to the virgin material and mixed thoroughly before being

injected. Today screw injection molding machines account for 95% of all injection machines

companies. The industry of injection molds has evolved over the years, from producing

combs and buttons to a diverse array of custom injection molded products for the following

industries: medical, aerospace, consumer, toys, plumbing, packaging, automotive, and

construction.

1.1 Introduction of Plastics

Plastics are made from polymers and are produced in the temperature at which they become

plastic in order to obtain the finished product. Polymer macromolecules are composed of

groups of atoms that are repeated more or less ordered along the chain. Macromolecules of

interest in terms of technology are those whose molecular weight exceeds 10,000. In view of

their technical utilization of plastics are classified considering the thermomechanical behavior,

which takes into account the variation of deformation of a polymer material under constant

load, depending on temperature. Thus there are the following groups of polymers:

thermoplastics, elastomers and duroplast. The explosive development of plastics industry due,

on one hand the emergence of many new polymers with very different characteristics, on the

  

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other hand improve their processing technologies, the rapid expansion resulted in the last 20

years of plastics applications, the emergence of numerous produced from synthetic polymers

or modified natural, artificial metals or other materials shortages, which have invaded the

artificial environment evolving lives, decisively influencing socio-economic development.

Plastics are some of the most important and widely used materials in the industrialized world.

Defined as solid, synthetic, organic polymer materials, plastics are easily formed into almost

any shape desired. They have a wide range of physical properties—strength, rigidity, opacity,

color, toughness, hardness, ductility, heat tolerance, thermal and electrical conductivity, etc.,

and can thus be used in a variety of products and applications. The properties of plastics are

so diverse that they can be and are substituted for metals in which case they are called

“engineered materials” and, when formed into fibers, substitute for natural fibers like silk and

wool, (Figure 2). Plastic products are created by the molding, forming, and shaping of solid

or liquid resins. Two types of resins are used in the manufacture of plastics— thermoplastics

and thermosets. Thermoplastic resins can be heated and formed repeatedly, but thermoset

resins, once heated and formed, cannot be remelted. The process of melting a thermoset resin

irreversibly alters the internal linkages of the polymers, making it difficult to recycle products

made from the thermoset plastic. In contrast, thermoplastics are generally suitable for

recycling. Plastics occupy a very important role although in recent years has reduced oil and

gas extraction, primary sources of raw materials used in manufacturing plastics. The first

industrial plastics were obtained between 1927-1950, so that in the last 70 years over 80% of

surrounding has been replaced by products made of plastic. Cellulose was present on the

Earth when there were trees and plants as the main constituent of plant cell walls. Because of

this there is no specific date for its discovery, appeared before human birth. Recognition of

cellulose as a main constituent of plant cell wall was in 1838 due to findings Anselme Payen

French botanist who first isolated from wood pulp. That was understood structure. Currently

polysaccharide cellulose is the most widespread in nature and is under the guidance of

scientists producing real changes in the processing, use and plant genetics. Although

obtaining cellulose derivatives was attributed to Professor Christian Shonbein Swedish,

English inventor Alexander Parkes and American entrepreneur John Wesley, basically, the

latter is considered the father of the plastics industry. Based on metal injection machine,

patented in 1870 by John Smith and Jesse Locke, Hyatt brothers made and patented in 1872

the first machine injected molding. This was the first and most important step in achieving

development and plastics processing industry. Since then they have taken many steps, big and

small but what is most important is that it has developed plastics processing industry so that

 

 

today 8

materia

plastics

Table 1

80% of prod

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. Evolution

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lastics [3]

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olymeric

 

 

Figuree 2. Parts ussed in machhine manufaacturing

 

7 

 

 

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9 

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(b)

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11 

 

 

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12 

vity.

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4. Mold

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should

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Figure 6

ions of a Tr

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preferred fo

are preferr

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flow

m (0.25 in.)

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of the larges

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the second

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d angle, ap

trance diam

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re the easies

nd runner di

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st to eject f

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should be a

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nd runners

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runner who

alanced flow

s should be

 

13 

y 42mm

bushing

pressure

than the

sprue.

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from the

e 0.6 cm

avoided.

cle times

are still

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ose cross

w during

slightly

 

 

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should b

turn of

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that the

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with TP

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remaine

prevent

or runo

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cold slu

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PU.

lug Wells: D

ed dormant

t this cold m

offs should b

vities. Prope

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F

s should be

oned to rem

Figure 7 sho

per runner s

should be d

ches all of

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design and t

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eral, those c

During inje

in the nozz

material from

be incorpor

erly sized r

e shown in F

Figure 7 Pr

e perpendic

move burrs a

ows a proper

izing, the la

designed to

f the gates

been molded

temperature

molds have

created for P

ection, the in

zle while the

m entering t

rated into th

runner syste

Figure 8.

roper Runne

cular to th

and sharp ed

rly sized run

ayout of the

give balanc

simultaneo

d successfu

e control ha

e usually b

PVC would

nitial surge

e previous s

the cavity an

he runner sy

ems design

er Sizing. [4

e main run

dges, and co

nner system

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ced flow to

ously. TPU

ully in hot ru

ave become

een designe

d offer the b

e of materia

shot was be

nd causing

ystem befor

ned for bala

4]

nner, and th

ontain a cold

m.

so an impor

all gates, i

U (thermopl

unner syste

the most c

ed originally

best charact

l is general

eing ejected

a visual def

re material

anced flow

he runner j

d slug well

ortant consid

ideally desi

lastic polyu

ems. In man

complex par

ly for plasti

teristics for

lly cool sinc

d from the m

fect, cold slu

is allowed

which inc

 

14 

junction

at every

deration.

igned so

urethane

ny cases,

rt of the

ics other

success

ce it has

mold. To

ug wells

to enter

orporate

 

 

Figu

Gates:

designs

generou

loss. Th

Figure

restricti

the dist

pinpoin

in weig

gates sh

land len

In mult

the app

highly s

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keep sin

toward

conditio

caused

the flow

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ure 8 Runne

TPU comp

s including

us cross-sec

he gates sh

9 illustrate

ion. Tab ga

tortion in th

nt gates and

ght where th

hould alway

ngth is that i

igated cavit

earance and

stressed due

in thick sec

nk marks to

a cavity wa

on called "w

by the rapi

w front com

hould be ta

er Systems w

pounds hav

fan, lab, ed

ctional area

hould be va

es several

ates are stro

he gate area

tunnel gate

he flow len

ys be as sho

it should be

ties, the gat

d performan

e to orienta

ctions of th

o a minimum

all or deflec

worming."

id cooling o

ming from th

aken in des

with Balanc

ve been mo

dge, subma

to allow the

apor-honed

acceptable

ongly recom

that comm

es should be

ngth from th

ort as possib

e no greater

te location a

nce of the m

ation, gates

he part and a

m. When ga

ctor pin to b

Worming i

of the inject

he gate, a we

signing par

ced-Flow Ca

olded satisf

arine and sp

e material t

with all ro

gate desig

mmended fo

monly occur

e restricted t

he gate is l

ble. A good

than one-h

and number

molded part.

should be l

allowing th

ating into a

break up the

is a random

tion melt. If

eld line wil

rts to keep

avity Layou

factorily thr

prue. In gen

o flow freel

ough edges

gns with ro

or the softer

s with very

to very sma

ess than tw

d rule of thu

alf the gate

r of gates ar

. Since gate

located in n

he material t

thick sectio

e melt enter

m pattern of

f the design

l usually re

the numbe

ts and Cold

rough a wi

neral, the g

ly with a mi

s and sharp

ounded corn

r TPU grad

flexible ma

all parts of a

wo inches. T

mb for dete

thickness.

re very impo

e areas are a

noncritical s

to flow to t

on, the flow

ing the cavi

f weld lines

n of the par

sult when th

er of gates

d Slug Wells

ide variety

gates should

inimum of p

p corners re

rners for m

des. They e

materials. Th

a few ounce

The land le

ermining th

ortant in re

almost alwa

sections of t

the thinner

w should be

ity and to p

s opposite

rt requires a

he flow fron

to a mini

 

15 

s. [4]

of gate

d have a

pressure

emoved.

minimum

liminate

he use of

es or less

ngth for

e proper

lation to

ays more

the part.

sections

directed

prevent a

the gate

a split in

nts meet.

mum to

 

 

minimiz

affect p

ze weld line

performance

es. Multiple

e.

e weld lines

Figu

Figure 1

D

A -

B -

C -

D -

s could detr

ure 9 Gate D

10 Mold Ven

Dimensions

0.001 to 0.

0.100 to 0.

- 0.500 typi

0.400 minim

ract from th

Designs. [4]

nting. [4]

s:

002

150

ical

mum

he surface ap

]

ppearance a

 

16 

and may

 

 

Mold S

shrinka

maintai

Where

allowan

annealin

what is

molding

Vents: B

and gre

initial t

12.7 mm

10.The

pump. W

in the c

vents th

mm wid

Shrinkage:

ge value of

ined, it is su

standard or

nce for the p

ng or expos

normally ex

g compound

Because of

eater will al

trials on the

m (.25 in. to

cooling sys

Water is cir

cavity passe

hat are mach

de), See figu

Mold desig

f any therm

uggested tha

r coarse to

particular L

sing parts to

xpected. Th

ds.

the low vis

llow TPU c

e new tool

o .50 in.) w

stem is mad

rculated thr

es through th

hined into t

ure 11.

gn, part de

moplastic ma

at a prototy

lerances ar

SP TPU com

o a point ove

his data is pr

scosity of th

compounds

have indica

ide by .03 m

de up of pa

ough them

he small eje

the parting

esign and o

aterial. In c

ype tool be m

re all that i

mpounds sh

er temperat

resented in

he melt, norm

s to flash. T

ated necessa

mm (.001 in

assages in th

to remove

ector pin cle

surface (typ

operating c

cases where

made befor

is required,

hould be use

ure will inc

Technical D

mal vent de

Therefore, v

ary location

nch) deep is

he mold tha

heat from t

earances in

pically abou

onditions a

e very close

e building t

the standa

ed. It should

crease the m

Data Sheets

epths of 0.05

vents should

ns. A vent

s usually su

at are conne

the hot plast

the mold, a

ut 0.03 mm

all affect th

e tolerance

the producti

ard mold sh

d be noted t

mold shrinka

s of LSP TP

5 mm (.002

d be cut on

channel 6.4

ufficient, Se

ected to an

tic. The air

and through

m deep and

 

17 

he mold

must be

ion tool.

hrinkage

that post

age from

PU

2 inches)

nly after

4 mm to

e Figure

external

r trapped

h narrow

12 to 25

 

 

Figure 111. Cooling ssystem [4]

 

18 

  

19  

5. Some Typical Plastics and Their Uses for Injection Molding

Thermoplastics

General properties: low melting point, softer, flexible.

Typical uses: bottles, food wrappers, toys, …

Examples:

• Polyethylene: packaging, electrical insulation, milk and water bottles, packaging

film

• Polypropylene: carpet fibers, automotive bumpers, microwave containers, prosthetic

body parts for disabled people

• Polyvinyl chloride (PVC): sheathing for electrical cables, floor and wall coverings,

siding, credit cards, automobile instrument panels

• Polystyrene: disposable spoons, forks etc., also used to make Styrofoam™ (soft

packaging material)

• Acrylics (PMMA: polymethyl methacrylate): paints, fake fur, plexiglass

• Polyamide (nylon): textiles and fabrics, gears, bushing and washers, bearings

• PET (polyethylene terephthalate): bottles for acidic foods like juices, food trays,

mylar tapes

• PTFE (polytetrafluoroethylene): non-stick coating, Gore-Tex™ (raincoats), dental

floss.

The most common methods of processing plastics to manufacture plastic parts are similar to

methods we have learnt for metals and glass. These include Extrusion, Injection molding,

Blow molding, Casting, etc. Among these, perhaps injection molding is the most significant

for local industry – almost all manufacturing companies use parts that are injection molded,

whether they make toys, home-appliances, electronics or electrical parts, watches, computers,

etc.

 

 

Figure

Figure

12. Exampl

13. Injectio

les of Inject

on Molding P

tion Molding

Part design

g Parts [sou

ned in Solidw

urce: www.y

dworks for th

ylmf.com.hk

he previous

k] [6]

two plate m

 

20 

mold.

  

21  

6. Advantages and Disadvantages of Injection Molding

Advantages

‐ Fast production. Plastics part can be produce amazingly fast in a few seconds.

‐ Material and color flexibility. The produced part can easily be change color and

flexibility there is a tool made.

‐ Labor costs low. Once all the parameters are set (amount material for the part,

temperature of the nozzle, clamping cycle, etc.) injection machines can run

automatically, so there is no need of many people for this operations.

‐ Design flexibility. The amount of flexibility of plastic parts can be limitless, the

results of such properties and restricted by the manufacturers.

‐ Low waste. Majority of plastics are recyclable. The wasted material can be grinded

and reused for the same purposed.

Disadvantages

‐ High Initial tooling cost. It is pretty expensive to start producing plastics parts.

Injections molding machines, molds, skills to run it and some other tools are

necessary.

‐ Part design restrictions. To make a very good mold design requires a lot of knowledge

and years of experience, there are many requirements to follow for working with

different size, materials, temperature and related factors.

‐ Accurate cost. Some plastics parts are not able to be produced by simple methods. It

also has relation with cost, and regards with materials to make the molds could be

very expensive. Sometimes mold parts have to be remade.

 

 

7. Injec

The fol

complet

Fi

ction Moldi

llowing dra

te design.

igure 14. Se

ing Design

awings are p

ection view o

part of the

of cooling s

two plate m

system for th

mold. Thes

(a

(b)

he cavity (a)

se provide m

a)

a) wireframe

more detail

e and (b) so

 

22 

ls of the

olid

 

 

Fig

Mass pr

Output

Density

Mass =

Volume

Surface

Materia

Materia

ABS

gure 15. Pro

roperties of

coordinate

y = 0.00 gra

3.50 grams

e = 3496.23

e area = 449

al used for t

al type

operties of th

f guitar pick

System: --

ams per cubi

s

3 cubic milli

90.11 square

the part desi

he plastic p

cavit

k

default --

ic millimete

imeters

e millimeter

igned: Acry

Principal

Good

rigidity,

part: sprue,

ties, all toge

er

rs

rylonitrile bu

l properties

impact,

heat stabil

runner, gat

ether.

utadiene sty

strength,

lity, high

tes, vents, sl

yrene (ABS

Common u

Housings

electronic

lug, parts of

S)Properties

uses

for app

and c

 

23 

f the

of ABS:

pliances,

omputer

  

24  

gloss and resistance to aging. equipment. Automotive grills

instrument clusters and body

panels.

Properties Chart for Injection Molding Grade Plastics

Acrony

m

Molecula

r Type

Solid

densit

y

(g/cm3

)

Melt

densit

y

(g/cm3

)

Shrinkag

e (%)

Drying

require

s

(hours

@ ºC)

Melt.

Temp

. (ºC)

Mold

Temp

. (ºC)

No

flow

temp

.

(ºC)

Typica

l ink.

Press.

(Mpa)

ABS Amorphu

s

1 - 1.2 0.9 0.5 - 0.6 2-3 @

88-77

195 -

240

38 -

93

135 -

150

120 -

140

ABS E-module

Material Tensile Modulus

(Young's Modulus, Modulus

of Elasticity)

- E –

(106 psi) (109 N/m2, GPa)

Ultimate Tensile Strength

- Su -

(106 N/m2, MPa

ABS plastics ----- 1.4-3.1 40

Reasons to work with ABS:

ABS's light weight and ability to be injection molded and extruded make it useful in

manufacturing products.

The most important mechanical properties of ABS are impact resistance and

toughness. A variety of modifications can be made to improve impact resistance,

toughness, and heat resistance.

  

25  

Shot and part weight

Shot weight Definition

The shot weight is defined as the mass of plastic delivered in one complete filling of the mold,

including the molded parts, sprue, runners, and flash.

Shot weight equation

ShotWeight = Filling System + Part n

Runners

Gates

Sprue

Cold Well

Shot weight= (g/cm3) + (g x 1)

= g = oz

Total Shot weight= oz

Calculating part weight

Mass = grams

Volume = mm3 = cm3

Density= g/cm3 (ABS)

Total part weight (single): oz (~g)

m= cm3 x g/cm3 = g x 1oz / g ≅ oz ≅ oz

  

26  

Material required and Cavity number

Material: Acrylonitrile butadiene styrene (ABS)

2880 Cycles per day

117.304g per cycle

Acrylonitrile butadiene styrene Cost

Core and Cavity Size

V= (476 x 264 x 69.94) mm = 8,788,940.16 mm3 = 8,788.94cm3

S420J2 ≅ 380 TWD/kg

ρsteel = 7.85 g/cm3

Core and Cavity Cost

Qty = 2,880 cycles x 117.304 g/ cycle ≅ 337.835 kg 350 kg

$31 USD /kg⇒29.795 TWD/kg x 350 kg = 10,428.25 TWD ≅ 10,500 TWD 

1 Cav x 2 cycles/min = 2pcs/min

2pcs/min x 60 = 120pcs/hr

12pcs/hr x 24 = 2880pcs/day

2880pcs/day x 30 days = 86,400pcs/month

ρsteel x Vworkpiece x 1kg/1000g x S55C TWD/kg

  

27  

Cost equation =

ABS material

Core and cavity plates

Injection machine selection

W= 4.3oz x 1.20 = 5.2 oz

Table 2

Injection machine specifications

JM12MKIII-C

Injection Unit Optional Standard

Shot weight (PS)

oz 16 12

gm 454 341

Injection Pressure kgf/cm2 1130 1504

Screw Stroke mm 180

Screw Speed Range RPM 164

Plasticizing Capacity kg/hr 163 109

Hopper Capacity litre 45

Screw L/D Ratio mm/mm 16 18.6

Injection Rate gm/sec 171.7 129

Cost = 7.85 g/cm3 x 8,788.94cm3 x 1kg/1000g x 800 TWD/kg = 55,194.54 TWD ≅ 55,200 TWD 

  

28  

Clamping Unit

Mould Clamping Force Mp 160

Opening Stroke mm 305

Space Between Tie Bar (H x V) mm 392x304

Mould Thickness (Min-Max) mm 150-380

Maximum Daylight mm 685

Hydraulic Ejector Force Mp 4.4

Hydraulic Ejector Stroke mm 100

Power/Heating Unit

Pump Motor KW [Hp] 18.75[25]

Heating Capacity KW 13.3

System Pressure kgf/cm2 145

Others

Dry Cycle Time sec 2.8

Floor Space (L x W x H) m x m x m 3.9 x 1.2 x 1.7

Oil Tank Capacity litre 150

Machine Weight (Dry) ton 3.4

 

 

Figurres 16. Ejecct pins in thee cavity (a a

(a)

(b)

and b)

(a)

 

29 

 

 

Figures 17. Compleete mold in wireframe (

(b)

(a and b)

(a)

 

30 

 

 

Figures 1

18. Wireframme and solid

d section viiews of the c

(b)

(

complete mo

(c)

old (a,b,c)

 

31 

 

 

(a)

(b)

 

32 

 

 

Figuures 19. Secction views oof the mold with the plaastic part (aa,b,c)

 

33 

(c)

 

 

8. Powe

Rough M

erMILL Si

Machining

imulations

[1]

for the Cavvity and Coore

 

34 

 

 

 

35 

 

 

Finishin

ng [1]

 

36 

 

 

 

37 

  

38  

9. Conclusion

Plastics are commonly used for many products, electronics, in cars, food utensils, toys etc.

The plastic materials are made from polymers and are produced in the temperature at which

they become plastic in order to obtain the finished product. The most common technology of

plastic parts is injection.

The main factors or disadvantages that affect injection molding were listed as follow: High

initial tooling cost, part design restrictions and accurate cost. The main process factors are as

follow: temperature, injection pressure, injection time, cooling time, melting temperature,

mold temperature, filling time etc.

Accordingly from the previous information the results presented refer to: The advantages of

injection molding are fast production, material and color flexibility, design flexibility and low

waste. To make a very good and accurate mold is necessary it has all basic elements to work

properly: sprue, gates, runners and vents, ejection pins, cooling system.

Other part of the paper refers in detail about the injected part, properties of injection molding,

drawings of the mold and simulation of the core and cavity using PowerMILL program.

  

39  

10. Glossary of Some Plastic Injection Molding Terms

ANSI: Abbreviation for American National Standards Institute

Aspect Ratio: Ratio of total flow length to average wall thickness.

Back Pressure: The resistance of the molten plastic material to forward flow. In molding,

back pressure increases the temperature of the melt, and contributes to better mixing of colors

and homogeneity of the material. However, as back pressure increases, so does cycle time.

Backflow: molten resin flows back out of the mold, returning to the runners.

Backing Plate: A plate used as a support for the mold cavity block, guide pins, bushings, etc.

Balanced Runner: A runner system designed to place all cavities at the same distance from

the sprue.

Blow Molding: Method of fabrication in which a warm plastic hollow tube is placed between

the two halves of a mold cavity and forced to assume the shape of that mold cavity by use of

internal pressure. This process forms hollow articles such as bottles, tanks, etc.

Boss: A raised feature of a molded part designed to add strength, facilitate alignment during

assembly or for attachment to another part.

Brighteners: Are used to add smoother or brighter coatings or finishes.

Burned: Showing evidence of excessive heating during processing or use of a plastic, as

evidenced by blistering, discoloration, distortion or destruction of the surface.

Casting: The process of forming solid or hollow articles from fluid plastic mixtures or resins

by pouring or injecting the fluid into a mold or against a substrate with little or no pressure,

followed by solidification and removal of the formed object.

Cavity: A depression, or a set of matching depressions, in a plastics-forming mold which

forms the outer surfaces of the molded articles.

Clamp: The part of an injection molding machine incorporating the platens that provides the

force necessary to hold the mold closed during injection of the molten resin and open the

mold to eject the molded part.

  

40  

Clamping Area: The largest rated molding area an injection press can hold closed under full

molding pressure.

Clamping Force: The force applied to the mold to keep it closed, in opposition to the fluid

pressure of the compressed molding material within the mold cavity and the runner system.

Clamping Plate: A plate fitted to a mold and used to fasten the mold to a platen. Clamping

Pressure: The pressure applied to the mold to keep it closed during the molding cycle.

Clarifiers: Additive used in resins to improve transparency or translucency.

Closed-loop Control: System for monitoring and automatically adjusting injection molding

process conditions such as temperature, pressure and time. The automatic changes keep part

production within preset tolerances.

Coefficient of Thermal Expansion (CTE): The change in length of a material for a unit

change in temperature, per unit of length.

Co-Injection: Simultaneous or near simultaneous injection of multiple materials.

Cold Flow Lines: Imperfections within the part wall due to thickening or solidification of

resin prior to full cavity fill.

Cold Molding: The process of compression molding involving shaping an unheated

compound in a mold under pressure then heating the article to cure it.

Cooling Channels: Channels located within the body of a mold through which a cooling

medium is circulated to control the mold surface temperature.

Cycle Time: The time required by an injection molding system to mold a part and return to its

original position/state.

Degradation: A deleterious change in the chemical structure, physical properties or

appearance of a plastic caused by exposure to heat, light, oxygen, weathering or other

external influence.

Elasticity: The ability of a material to quickly recover its original dimensions after removal of

a load that has caused deformation.

  

41  

Extrusion: The process of forming continuous shapes by forcing a molten plastic material

through a die.

Injection Blow Molding: Blow molding process by which the plastic parison to be blown is

formed by injection molding.

Injection Molding Pressure: The pressure applied to the cross-sectional area of the molding

cylinder.

Injection Molding: The method of forming objects from granular or powdered plastics, most

often of the thermoplastic type, in which the materials is fed from a hopper to a heated

chamber in which it is softened, after which a ram or screw forces the material into a mold.

Pressure is maintained until the mass has hardened sufficiently for removal from the mold.

Injection Pressure: The pressure on the face of the injection screw or ram when injecting

material into the mold, usually expressed in PSI.

Moving Platen: The platen of an injection molding machine that is moved by a hydraulic ram

or mechanical toggle.

Multi-Cavity Mold: A mold having two or more impressions for forming finished items in

one machine cycle. Multidirectional flow: flow direction changes during filling resulting in

orientation in different directions which can cause flow marks, stresses and warping. Multiple

cavity mold: produces more than one identical part with each cycle. Multi-Shot Molding: The

injection of two-or-three materials, in sequence, into a single mold during a single molding

cycle. The injection molding machine is equipped with two-or-three plasticators. (See also

co-injection)

  

42  

11. References

[1] Wangsonhao,wuyesiung,2015, Basic and Practices on Five-axis CNC Milling

[2] Bryce, Douglas M.-Plastic Injection Molding, Volume IV - Manufacturing Startup and

Management-Society of Manufacturing Engineers (SME) (1999)

[3] Ciprian Ciofu, Daniel Teodor Mindru, International Journal of Modern Manufacturing

TechnologiesISSN 2067–3604, Vol. V, No. 1 / 2013

[4] https://www.lubrizol.com/.../Processing-Guides/Injection-Molding...

[5] William C. Eisenhauer, 1964, INJECTION MOLDING OF PLASTICS PRODUCTS

A Manufacturing Possibility in Carroll County, Georgia

[6] https://www.ielm.ust.hk/dfaculty/ajay/courses/ieem215/lecs/6_plastics.pdf

[7] https://www.xcentricmold.com/aboutinjectionmolding.php