Transcript
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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 gate trace will be left.
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.
The gate trace will be left.
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.
PROPERTY-1 (Drying temperature - injection pressure)
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
PROPERTY 2 (Elongation - Specific gravity)
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
PROPERTY 3 (Tensile strength - impact strength)
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.
PROPERTY-1 (Drying temperature - injection pressure)
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
PROPERTY 2 (Elongation - Specific gravity)
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
PROPERTY 3 (Tensile strength - impact strength)
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.
PROPERTY-1 (Drying temperature - injection pressure)
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
PROPERTY 2 (Elongation - Specific gravity)
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
PROPERTY 3 (Tensile strength - impact strength)
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.
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