ABC of Moulds

8/19/2019 ABC of Moulds

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Sprue Lock Pins

A pin has the edge of which is undercut to pull a part in mold opening and remove a sprue from a

sprue bush.

After mold opening, this pin will function as an ejector pin and ejects the sprue from a aprue bush.

Also it releases gas contained in molten plastic.

Ejector Plate

Also called a push plate. A plate that supports an edge of an ejector pin or a push back pin to eject a

part from a mold.

It is ejected by an ejector device of a molding machine, and returned to the original position when

the edge of a push back pin collides with a cavity plate during mold clamping.


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Stop Pins

A stopper installed to keep an ejector plate horizontal or prevent the ejector plate from retreating

too far and damaging a core adaptor plate.

Ejector Guide Pins / Ejector Guide Bush


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An ejector guide pin is also called a push plate guide pin and functions as a guide for sliding of an

ejector plate.

Because an ejector guide bush slides, a hard material is used.

An ejector guide bush is also called a push plate guide bush. It is a cylindrical

part used to determine the position by matching the ejector guide pin.

Push Rods

A shaft linked to the force (hydraulic or mechanical) of the molding machine in order to get the

ejector plate to work.


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Gas Spring / Gas Spring Holder

A gas spring forcibly pushes back an ejector plate. The strength of the spring is adjusted by

adjusting the filling pressure.

When using a gas spring, make sure to avoid high temperature (heat may expand gas, deteriorating

the original functions of a gas spring).

Calculating Filling PressureTo figure out filling pressure ( P) from early load (Wo):

P = 100 * Wo /C (C : constant)

To figure out corresponding spring constant ( K ) from filling pressure ( P) and gas

spring constant (G):

K =G * P / 100

To figure out force by displacement ( x) from the top D.C. of the piston rod (W ):

W = P (Gx + C )

* See the catalog of each manufacturer for constant (C ) and gas spring constant (G).

A gas spring holder is a block used to fix a gas spring to an ejector plate.

Counter bore process for a bolt installation hole, for it also functions as an push

rod.

Gas Spring / Gas Spring Holder


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A gas spring forcibly pushes back an ejector plate. The strength of the spring is adjusted by

adjusting the filling pressure.

When using a gas spring, make sure to avoid high temperature (heat may expand gas, deteriorating

the original functions of a gas spring).

Calculating Filling Pressure

To figure out filling pressure ( P) from early load (Wo):

P = 100 * Wo /C (C : constant)

To figure out corresponding spring constant ( K ) from filling pressure ( P) and gas

spring constant (G):

K =G * P / 100

To figure out force by displacement ( x) from the top D.C. of the piston rod (W ):

W = P (Gx + C )

* See the catalog of each manufacturer for constant (C ) and gas spring constant (G).

A gas spring holder is a block used to fix a gas spring to an ejector plate.

Counter bore process for a bolt installation hole, for it also functions as an push

rod.


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Runner System

In this chapter, you will learn about the functions, characteristics, and shapes of the sprue, runner,

and gate.

The molten plastic injected from the injector nozzle will go through a sprue (sprue bush), a runner ,

and a gate and fill up in the cavity.

As the temperature of molten plastic is lowered while going through the sprue and runner, the

viscosity will rise; therefore, the viscosity is lowered by shear heat generated when going through

the gate to fill the cavity.

Sprue

A sprue is a channel through which to transfer molten plastic injected from the

nozzle of the injector into the mold. It is a part of sprue bush, which is a separate

part from the mold.

Runner

A runner is a channel that guides molten plastic into the cavity of a mold.

Gate

A gate is an entrance through which molten plastic enters the cavity.

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The sprue, the runner, and the gate will be discarded after a part is complete.

However, the runner and the gate are important items that affect the quality or

the cost of parts.

Gate

The gate is categorized into restrictive gate, which narrows the entrance, and

nonrestrictive gate, which does not narrow the entrance.

The gate has the following functions:

• Restricts the flow and the direction of molten plastic.

• Simplifies cutting of a runner and moldings to simplify finishing of parts.

• Quickly cools and solidifies to avoid backflow after molten plastic has filled up in the

cavity.

Restrictive Gate

A restrictive gate has a narrow entrance to the cavity to restrict the amount of molten

plastic in order to improve filling in the cavity.

The restrictive gate has the following characteristics.

o Generates shear heat by going through the narrow gate, raising the temperature of

molten plastic and improving the filling in the cavity.

o Reduces residual stress, and thus reduces part defect such as warp.

o As the cooling solidification time is shortened, molding cycle is also shortened.

o As the gate trace is less, it is possible to complete finishing process in a short time.

The restrictive gate has the following types.

Side Gate Submarine Gate

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(Tunnel Gate)

The most common gate.

Put to the side of parts.

The gate trace will be left.

Often used for the structure with more than

two cavities.

The gate will be automatically cut off during

mold opening.

The position is flexible (front, side, or back

of parts).

The gate needs to be thought about not to beleft inside the cavity.

Pin Point Gate Fan Gate

Suitable for molding multiple parts.

The position is relatively flexible.

The structure is complicated due to three plate

method of die.

Suitable for large and flat plate parts.

Finishing is difficult and cost is high due

to the wide gate.The gate trace will be left.

Film Gate Valve Gate

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Suitable for thin plate parts.

Finishing is difficult and cost is high due

to the wide gate.


The valve of the gate opens the gate according

to injection timing.

Sprue and runner will not be discharged due to

hot runner method.

Put to either the front or the back surface of

parts.

Nonrestrictive Gate

A nonrestrictive gate involves a method in which molten plastic fills up in the cavity

directly from the sprue.

The nonrestrictive gate has the following characteristics.

o Reduces the loss of injecting pressure due to direct cavity filling from the sprue.

o Less molding material because there is no runner .

o The simple mold structure reduce the cost and produces a mold with less trouble.

o It is likely that residual stress is generated and parts have crack .

The nonrestrictive gate has the following type.

Direct Gate

The sprue plays the role as gate.

Put on the front or back side of parts.


Determining Gate Position

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Point 1

Set a gate position where

molten plastic finished filling

up in each cavity

simultaneously. Same asmultiple points gate.

Point 2

Basically set a gate position to

the thickest area of a part. This

can avoid sink marks due to

mold shrinkage .

Point 3

Set a gate position to an

unremarkable area of part or

where finishing process can be

easily done.

Point 4

Avoid injecting from the

direction where the air in the

cavity or the gas generated

from molten plastic is inclined

to accumulate.

Point 5

Fill up molten plastic using thewall surface in order not to

generate jetting.

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Undercut refers to the convex or concave area of part. When removing the part

from the mold, you need some device so that the part of the mold which

contacts to the undercut can be moved to remove the part from the mold since

the part will not be removable directly without the device.

This process is called Undercut process.Undercut process uses different methods depending upon whether the

undercut is outside or inside the part.

Here are some examples of parts with undercut.

Push-pin Grip of a driver Grip of a cup

Now, let's learn about external slide core method, internal slide method, and hydraulic cylinder

method of undercut process.

External Slide Core Method

The external slide core method is usually used for the process of outer undercut.

Working along with the open / close movement of a mold, this method slides the slide core to process the undercut.

The hydraulic cylinder method is also available, which will be explained in detail later

Slide Core Body Unit

The portion where the undercut process is performed linked along with the movement of

mold opening. The amount of movement of the slide core and the angle and the length of

the angular pin are key factors to this unit.

The locking block installed to the cavity plate receives the pressure from the injection

when closing the mold. Upon opening of the mold, the slide core moves backward by theforce from the angular pin and the spring, thus releasing the part.

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As the hole will be misaligned and the angular pin will not be inserted if the slide core

moves too far backward, a core stop block needs to be installed.

This correlation is illustrated below.

(Click each name in the figure to display the

description.)

The relief distance

and the tilt angle of

the angular pin are as

follows:

S: Undercut amount

S1: Slide stroke

amount

: Tilt angle of slide

core

: Tilt angle of

angular pinS1 = S + 5mm up

= +(2 - 5 )

20

In order to prevent the

slide core and the

loking block from

intervening with each

other in mold opening

and closing, make the

tilt angle of the

angular pin smaller

than that of the

locking block.

Also, a gap of 0.5mm

is added to the hole

for angular pin for

errors occurring at

processing.

Push Back Spring

The mass when the slide core is sliding varies depending on the direction of sliding.

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Suppose you install a 5kg slide core on the side parallel to the ground. How long should

the spring be? The stroke is 20mm.

D: Spring diameter

L: Spring free length (see a catalog by each

manufacturer)

E: Spring close length (see a catalog by each

manufacturer)

F: Stroke

G: Length of shrinkage by slide weight

K : Spring constant (see a catalog by each

manufacturer)

W : Slide weight

If using light load [ K = 0.6kgf / mm] for spring:

Spring constant

( K )

Free length

( L)

Max. deflection ( F

+ G)

Outer diameter

( D)

Usage

count

0.6kg/mm 65mm 32.5mm 16mm 350,000

times

To figure out the slide mass, it is 1.5 times the weight of the slide core:

W =5*1.5=7.5kg

As the length of shrinkage due to the weight of the slide mass is:

G = W/K :

G = 7.5/0.6 = 12.5mm

As the free length of the spring is: L = E + F + G :

L = 32.5 + 20 + 12.5 = 65. Referring to the catalog,

Use the spring with L = 65.

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Answer D = 16 L = 65mm

Core Plate / Cavity Plate

A steel device to mold a molding material into a certain shape. The section that is engaged in

opening / closing movement is called a core plate, and the section that is not is called a cavity plate.

Generally, the front side of a part is a cavity plate and the rear side is a core plate.

The core plate leaves a trace on a part, because it has an ejector pin to push the part.

The cavity plate has a sprue bush, which is the entrance for molten plastic.

Locking Block

A block to push a slide core that is ejected back by injection pressure.

Angle of Angular Pin and Angle of Angled Side of Locking Block

Angle of angular pin:

Angle of side of locking block:

(1) If > :

If the angle of an angular pin is larger than the angled side of a locking pin, the


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tilted sides of a slide core and the locking block may collide with each other,

possibly damaging the mold.

(2) If = :

If the angle of an angular pin and a tilt angle of a locking block are equal, the slide

core cannot be lowered, since it is pushed down by a spring, which puts the

locking block over the slide core for the clearance of the angled hole of the slide

core.

(3) If < :

Since the angled sides of the slide core and the locking block touch each other

only when the mold is completely closed, the movement is smooth.


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From (1), (2), and (3), the angle of the angular pin must be smaller than the angle of the side. The

normal angle of the angular pin is 12 - 25 degree, and the angle of the parting side is basically larger

than the pin angle.

Core Stop Block

A part that determines the position where a slide core retreats when opening the mold.

In addition to the core stop block, a ball plunger, a return spring, or a stop pin can also be used.


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Slide Core

A part that slides inward upon opening and closing of the mold.It works on the undercut process along with mold opening / closing movement to mold the undercut

of a part.

The larger the undercut becomes, the longer an angular pin needs to be and the more the movement

of the slide core will be; therefore it may not be easily used.

The slide core moves to avoid retreating by injection pressure at the locking block when closing the

mold and at the core stop block when opening the mold. In between them, an angular pin controls

the movement of the slide core.


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Core Push Back Spring

A part used to hold down a slide core when a mold is open.

Without this, the slide core may be out of alignment when the mold is open, and also an angular pin

may not go into the angled hole when closing the mold.

It is changed depending on the sliding direction of the slide core, such as up, down, or horizontal.

Undercut

A shape that prevents a part from being removed in the opening direction of a mold after molding.


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If a part has such a shape or a prong , the part cannot be removed in the opening direction.

Therefore, the undercut part needs to be removed by a mechanical method before removing the part

from the mold. This process is called the undercut process.


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Property of Plastics

This chapter explains the properties of plastics and the characteristics of typical material in mold

processing.

Property of PlasticsPlastic properties are classified by 5 criteria.

The properties mentioned here could be references for plastic selection. However, these

properties are subject to change due to temperature or humidity changes. Therefore, it is

necessary to account for changes in environmental conditions on selection of plastics.

Mechanical properties

Mechanical properties refer to displacement or breakage of plastic due to some

mechanical change such as applying some load.

Mechanical properties are dependent on the temperature, force (load), and the

duration of time the load is applied. It may also be affected by ultra-violet

radiation when used outside.

Thermal properties

Thermal properties include heat resistance or combustibility.

Thermoplastic has a larger coefficient of thermal expansion or combustibility and

a smaller thermal conductivity or specific heat than other material such as metals.

Chemical properties

Chemical resistance, environmental stress crack resistance , or resistance to

environmental change are referred as chemical properties.

When a plastic contacts chemicals, there is some kind of change. After having a

plastic in contacted with chemicals under no stress for about a week, changes in

appearance, weight and size of the plastic are examined. Such changes are

referred to as chemical properties.

Electric properties Electric properties are also referred to as electromagnetic properties. Electric

properties include insulation, conductivity and electro-static charges.

Due to their good insulation property, plastics are often used in electric fields.

However, plastics do have a defect; they are easily electrified.

Physical properties

Specific gravity, index of refraction and moisture absorption are called physical

properties.

The specific gravity of the plastic is small, and it varies depending on the

character of high polymer , or thermal and mechanical treatment of the plastic.

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Characteristics of Molding MaterialHere, characteristics, application, cautions, molding condition and physical properties of

typical molding material (thermosetting plastic has only physical properties.) are described.

Molding material often changes into different states due to many factors. General features,

applications, caution and molding conditions are presented as follows:

Polyamide (Nylon) (PA)

Characteristics

Excellent in impact resistance and chemical resistance as well as in electric property and

low temperature

Higher fusing point, good thermal resistance.

Due to its self-lubricant character, it is often used for bearings of mechanical parts.

Use

Often used for moving parts of machines (bearing, gear, cam) or bolt.

Caution

Because of its water-absorption character, dimension accuracy may be affected and the

material quality may change. So, it needs to be dry enough before molding.

Low dissolving (melting) viscosity- watery texture may cause development of flashs.

Molding condition

Resin temperature is generally set high.

Control the mold temperatures for uniform cooling.

PROPERTY-1 (Drying temperature - injection pressure)

ResinGra

de

Fill

ers

Abbrevi

ation #

Drying

temperat

ure

[ ]

Drying

time

[hours]

Cylinder

temperature

[ ]

Mold

temper

ature

[ ]

Injection

pressure

[kgf/ ]

Nyl

on

6

- PA6 80 8 - 15 220 - 300 20 - 90800 -

1500Polya

mide

(Nylon)

Nyl

on

6-6

- PA66 80 8 - 15 250 - 350 20 - 901000 -

1500

PROPERTY 2 (Elongation - Specific gravity)

ResinGra

de

Fill

ers

Abbrevi

ation #

Elongati

on[%]

Moldin

g

shrinka

ge[%]

Consecutiv

e

heat

resistance[

]

Therm

al

deflect

ion

temp.

Specific

gravity

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[ ]

Nyl

on

6

- PA6 25 - 320 0.5 - 1.5 82 - 121 60 - 701.12 -

1.14Polya

mide(Nylo

n) Nyl

on

6-6

- PA66 60 - 320 0.8 - 2.0 82 - 12166 -

105

1.13 -

1.15

PROPERTY 3 (Tensile strength - impact strength)

ResinGra

de

Fill

ers

Abbrevi

ation #

Tensile

strength

[kgf/]

Compre

ssive

strength

[kgf/

]

Bending

strength

[kgf/ ]

Impact

strengt

h

[kgf/

]

Nyl

on

6

- PA6490 -

850914 560 - 1250

1.0 -

20.0Polya

mide

(Nylo

n) Nyl

on

6-6

- PA66630 -

8501050 430 - 1200

1.0 -

5.4

Polypropylene (PP)

Polypropylene (PP)

Lightest specific gravity among all plastics generally used

Excellent liquidity

Applied for various gates such as pinpoint gate , direct gate , special gate, etc.

No need to dry as it has little water absorption

Molding shrinkage rate changes according to mold temperature

Use

Often used for extra large molding parts or extremely thin partsDue to its excellent fatigue resistance, it is often used for hinges that are subject to repeated

bending

Caution

Due to its large shrinkage rate, it may experience deformation if the cooling of the mold is

not sufficient.

Temperature adjustment must be performed for molding that requires precise dimension.

When using the mold that may cause sink marks or holes, injection pressure should be set

relatively higher.

Molding condition

Molding temperature is usually 40 - 60

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Injection pressure standard is 800 - 1200kgf/ ; however, the highest pressure free of

flash is appropriate.

The temperature range appropriate for molding is 200 - 300 , and it is better to set up

within the higher range.


ResinGra

de

Fill

ers

Abbrevi

ation #

Drying

tempera

ture

[ ]

Drying

time

[hours]

Cylinder

temperatur

e

[ ]

Mold

temper

ature

[ ]

Injection

pressure

[kgf/

]

Gen

eral- PP - - 180 - 300 20 - 90

600 -

1410

Polypro

pylene

(PP)-

Gla

ss

fib

er

40

%

PP - - 200 - 300 20 - 90703 -

1410


ResinGra

de

Fill

ers

Abbrevi

ation #

Elongati

on[%]

Moldin

g

shrinka

ge[%]

Consecutiv

eheat

resistance[

]

Therm

al

defor

mation

temp.

[ ]

Specific

gravity

Gen

eral- PP

100 -

800

1.0 -

2.588 - 115

103 -

130

0.90 -

0.91

Polypro

pylene

(PP)-

Gla

ss

fib

er

40

%

PP 2.0 - 4.00.2 -

1.8121 - 138

110 -

161

1.22 -

1.23


ResinGra

de

Fill

ers

Abbrevi

ation #

Tensile

strength

[kgf/

]

Compr

essive

strengt

h

Bending

strength

[kgf/ ]

Impact

strengt

h

[kgf/

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[kgf/

]

]

Gen

eral

- PP210 -

400

260 -

562

352 - 4921.5 -

110

Polypro

pylene

(PP)-

Gla

ss

fib

er

40

%

PP560 -

1000

387 -

492492 - 1000 6 - 11

Polyethylene (PE)

Characteristics

There are two types of polyethylene: low density polyethylene and high-density

polyethylene.

Low-density polyethylene is softer than high-density polyethylene. It is excellent for

molding.

High-density polyethylene has excellent stiffness and impact resistance.

Excellent chemical resistance

No need to dry because it does not absorb water

Use

Low-density polyethylene is used for products requiring softness and flexibility. It is oftenused for complex-shaped plastic or packing material.

Low-density polyethylene is also used to improve flow of molding materials.

High-density polyethylene is used for cylindrical containers, or for large plastic products

such as containers.

Caution

Higher mold temperature results in the following: molding cycle becomes longer, impact

strength is reduced, molding shrinkage becomes higher, and specific gravity increases.

Lower mold temperature causes the surface of the plastic to peel off or deform.

Molding condition

Higher mold temperature will improve brilliance and appearance of the part.

Higher injection pressure will result in uniform temperature of the molten plastic inside the

mold. It also enhances the density and strength of the plastic.

It is advised to apply low holding pressure after filling the molten plastic.


Resin GradeFill

ers

Abbrevi

ation #

Drying

tempera

ture

[ ]

Drying

time

[hours]

Cylinder

temperatur

e

[ ]

Mold

temper

ature

[ ]

Injection

pressure

[kgf/

]

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Low

density- LDPE - - 150 - 270 20 - 60

500 -

2110

Interm

ediatedensity

- MDPE - - 200 - 300 10 - 60

562 -

2110

Polyet

hylene

(PE)

High

density- HDPE - - 200 - 300 10 - 80

600 -

1410


Resin Grade

Fill

ers

Abbrevi

ation #

Elongat

ion[%]

Moldin

g

shrinka

ge[%]

Consecuti

ve

heatresistance[

]

Therm

al

defor

mation

temp.

[ ]

Specific

gravity

Low

density- LDPE 90 - 800

1.5 -

5.080 - 100

37.6 -

49.2

0.91 -

0.925

Interm

ediate

density

- MDPE 50 - 6001.5 -

5.048.7 - 121

48.7 -

73.7

0.926 -

0.940

Polyet

hylene

(PE)

High

density- HDPE 20 - 130

2.0 -

6.078 - 124

59.8 -

88

0.941 -

0.965


Resin GradeFill

ers

Abbrevi

ation #

Tensile

strength

[kgf/

]

Compr

essive

strengt

h

[kgf/

]

Bending

strength

[kgf/ ]

Impact

strengt

h

[kgf/

]

Low

density- LDPE 42 - 161 - -

hard to

break

Interm

ediate

density

- MDPE 84 - 246 - 337 - 4922.7 -

87

Polyet

hylene

(PE)

High

density

- HDPE218 -

387

190 -

253

-2.7 -

87


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Acrylonitrile butadienstylene(ABS)

Characteristics

Elastic and unbreakable

Since it is Non-crystalline plastic , it has poor climate resistance

Easy to maintain dimension accuracy, well-balanced material

Relatively easy to perform secondary processing (mechanical treatment or galvanized

treatment, solvent sealing, etc.)

Use

Often used for home electric appliances or interior parts

Caution

Due to its moisture-absorption characteristics, drying is critical before molding. Otherwise,

bubbles or cracks may appear on surface.

Thin plastic shapes, where it is hard to fill in the molten plastic, should be avoided.

Molding condition

Maintain the mold temperature relatively high, around 60 - 80 to stabilize the

temperature

Set injection pressure high as Acrylonitrile butadienstyrene has poor flow.


ResinGrad

e

Fill

ers

Abbrevi

ation #

Drying

tempera

ture

[ ]

Drying

time

[hours]

Cylinder

temperatur

e

[ ]

Mold

tempe

rature

[ ]

Injection

pressure

[kgf/

]

High

stiffn

ess

- ABS 70 - 80 2 180 - 26040 -

80

560 -

1760

Heat

resist

ance

- ABS 70 - 80 2 250 - 30040 -

80

560 -

1760Acryloni

trile

butadien

stylene

-

Gla

ss

fib

er

20

% -

40

%

ABS 70 - 80 2 200 - 26040 -

80

1050 -

2810


ResinGrad

e

Fill

ers

Abbrevi

ation #

Elongat

ion[%]

Moldin

g

Consecuti

ve

Therm

al

Specific

gravity

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shrinka

ge[%]

heat

resistance[

]

deflect

ion

temp.

[ ]

High

stiffn

ess

- ABS3.0 -

20.0

0.2 -

0.960 - 93

82 -

108

1.02 -

1.07

Heat

resist

ance

- ABS5.0 -

25.0

0.2 -

0.988 - 165

93 -

122

1.05 -

1.08Acryloni

trile

butadien

stylene

-

Gla

ss

fib

er

20

% -

40

%

ABS 2.5 - 3.00.1 -

0.293 - 110

93 -

118

1.22 -

1.36


ResinGrad

e

Fill

ers

Abbrevi

ation #

Tensile

strength

[kgf/

]

Compr

essive

strengt

h

[kgf/

]

Bending

strength

[kgf/ ]

Impac

t

strengt

h

[kgf/

]

High

stiffn

ess

- ABS400 -

610

127 -

879773 - 1000

6 -

33.7

Acryloni

trile

butadien

stylene

Heat

resist

ance

- ABS400 -

560

506 -

702703 - 1050

10.9 -

35.4


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-

Gla

ss

fib

er

20% -

40

%

ABS570 -

740

600 -

1550

1120 -

1900

5.4 -

13.1

Polycarbonate (PC)

Characteristics

High melting point, high melting (fusing) viscosity

Relatively small molding shrinkage rate (0.5 - 0.8%), and not affected by the position of

the gates Does not soften below 150

Excellent impact strength

Use

Used for the parts requiring strength or parts subjected to dynamic and severe loads

Caution

This plastic needs drying before molding due to its water absorption characteristics;

otherwise, appearance or quality may be affected.

High mold temperature causes longer molding cycle

Low mold temperature may cause deformation of the part

If injection pressure is too high, the part may deform internally and be easily broken.

Molding condition

Mold temperature is appropriate between 85 - 110

Higher temperature will lead to better flow and glossy appearance(brilliance). It also

reduces deformation of the product

Injection pressure should be set high

Molding temperature should be between 260 - 300

PROPERTY 1 (Drying temperature - injection pressure)

ResinGrad

e

Fille

rs

Abbreviat

ion #

Drying

tempera

ture

[ ]

Drying

time

[hours]

Cylinde

r

tempera

ture

[ ]

Mold

tempera

ture

[ ]

Injection

pressu

re

[kgf/

]

Polycarb

onate

Gene

ral- PC 120 24

250 -

38080 - 120

700 -

1500

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-

Gla

ss

fibe

r

less

tha

n

10

%

PC 120 24 270 -380

80 - 120 700 -1410

(PC)

-

Glas

s

fiber

10%

PC 120 24270 -

38080 - 120

1050 -

2810

PROPERTY 2 (Elongation


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Boss

The boss shape used to install a screw to parts.

e.g. for a joint of a plastics model

Cavity

The gap generated where a part is molded in the mold.

It sometimes refers to the concave part of the mold and usually is processed on the cavity plate.

Clamping Force / Closing Force

Clamping force is put on a mold to keep the mold closed against the pressure of the injected molten


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The reaction in which more than two molecules of one chemical material are combined to be made

into a new chemical material with several fold molecules.

In other words, more than two materials are combined and react to make a material of properties

different from those of the original.

Clamps / Spacer

The setup tools used to install cavity adaptor plate and core adaptor plate to the movable / fixed

plates of the molding machine.

The spacer functions as a bottom plate for setting a clamp, and the clamp holds down the cavity

adaptor plate and the core adaptor plate with a bolt.

Crack

A breaking on parts caused by inner stress, external shock, or environmental impact.


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Degassing

Degassing is the process to release the water and air contained in a molding material, the gas

generated during molding, and the air existing in the mold before molding.

Molding large or thick parts without degassing may cause swelling or bubbles on the surface,

aggravating the appearance.

Degassing is usually done by making a ditch on the mold or using a hole on the ejector pin.

In the figure below, the land is used to do degassing and air venting.

Draft Angle

The gradient made on the cavity or the core to make removal of parts from the mold smoother.

Draft angle normally requires 1 - 2 degrees, but it depends on the material and molding shape, or


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whether a texture process (the process to make the surface a little rough) is done.

In injection molding, because molten plastics will shrink after molding, make as small a draft angle

as possible on the cavity side, and a large angle on the core (insert) side.

Because crystalline plastics has high mold shrinkage, it shrinks into the inside

of the mold on the cavity side, which makes removal smooth, whereas it

adheres to the mold on the core (insert) side, which makes removal difficult.

Therefore, to make a draft angle, you will need to take the adhesion to the core

(insert) side in consideration.

On the other hand, amorphous plastics has low mold shrinkage and hardly

shrinks to the inside. Therefore, a draft angle on the cavity side is made as large

as the one on the core (insert) side.

ABC of Moulds

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