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Injection Molding Machine 1

Causes and Remedies 2

Molding Operation 2

Product Design and Mold Design 3

Mold Shrinkage and Dimensional Accuracy 5

Hot Runner Molding 7

Reuse of Iupilon / NOVAREX 8

Annealing Treatment of Iupilon / NOVAREX 8

 At the side where the capacity is small,

plasticizing time and injection time become long,

capacity of the molding machine

That is,

the filling shortage is caused due to the extension of molding cycle and slow filling rate

at the side where the capacity is large,

dwell time of the resin inside the cylinder becomes long,

and the resin thermally decomposes

The capacity range in the figure is indicated rather widely,

but when it is easy to be thermally decomposed with materials containing lots of pigments and additives,

it is better to conduct the molding at shot weight of 70~80% of the injection capacity

using the material (for example,

) for the molding of Iupilon / NOVAREX is good


concerning the molding of glass fiber reinforced grade (Iupilon GS etc

) and optical grade (Iupilon H-400 etc

it is good to consider the following for the barrel material

As for glass fiber reinforced PC,

it is good to use the bimetal (double-structure cylinder covered the inside with another metal and centrifugal casting) to prevent the barrel abrasion

For example,

the H alloy (Hitachi Metals Ltd

N alloy (Japan Steel Works Ltd

K alloy (Kobe Steel Ltd

Figure 1・1-3 indicates the abrasion data when molding glass fiber (30%) PC in case of using the H alloy barrel

The abrasion of the metering section vicinity where the feed section and the backflow prevention ring contact with is improved 1)

In addition,

the bimetal cylinder such as H alloy is also effective in suppressing the generation of the burn of Iupilon / NOVAREX although the burn mark and black specks due to thermal decomposition become problems in the transparent use

“H alloy” catalogue hopper cylinder

nitrided steel cylinder after 6-month use (disposed after measuring)

H-503 cylinder after 1 and a half year use (prolonged use)

type characteri stic alloy system hardness longitudinal heat expansion coefficient (℃)

distance from the cylinder tip (mm)

 The 3-stage type screw of the single flight is usually used

The screw design consists of the basic design based on the premises of smooth conveyance of pellet,

and measurement with a little unevenness

Supply (feed section): Stroke is designed long for conveying and melting the pellet,

and increasing plasticization quantity

Compression (compression section): Return the air and water involved in the feed section to the hopper side and deaerate

In addition,

a sufficiently melting mechanism is required

Because PC is a high viscosity material,

the rapid compression type is unsuitable and moderating compression type with gradually increasing outside diameter is recommended

Measurement (metering section): In order to suppress the measurement unevenness,

the measurement stroke is designed long,

4D ~ 5D or more

The screw design of PC is indicated in Fig


Notes: % in (

) shows an example of total length L

Basic shape of screw stroke

Screw diameter (mm) 30 60 90 120 120

Screw depth Feed section Metering section (mm) (mm) 5.6 1.8 6.6 3.0 9.5 4.0 12.0 4.8 Max. 14.0 Max. 5.6

Compression ratio 2.0:1 2.2:1 2.4:1 2.5:1 Max. 3.0:1

Screw pitch H=1

0D Screw diameter more than 80mm H=0

9D Screw diameter less than 80mm Fig


Design of screw for PC

Newcome:SPE Tech Pap Reg Tech Conf

PIONEER VALLEY SEC (’77 june 8/9) 45 – 78

In the same figure,

L/D is 20,

the ratio of Feed (F) / Compression (C) / Metering (M) is divided into 60/20/20,

pitch H is almost equal to screw diameter D,

The screw that its surface is covered with thick film hard Cr coating is good

When the glass fiber reinforced material is used,

there is a problem of abrasion,

but constantly preparing spare screw and regularly exchanging after recoating are recommended

The screw that processed nitriding treatment is hard to be worn due to its high hardness

On the other hand,

for transparent product and colored product (except the black) avoiding the burn,

because it is easy to cause the burn in PC molding,

it had better use the screw that processed with (Ni+Cr),


TiC treatment at the surface though it is a little expensive


the example which uses dulmage,

pin screw mounted at the screw head with the purpose to improve the melting and mixing and the dispersibility is observed with the precondition of not giving excessive shearing force to PC and the design without PC stagnation

check ring The screw head is equipped with the backflow prevention valve to maintain the effective injection pressure by preventing a part of measured resin from backflow through the ditch of the screw at the time of injection

The structure of this valve is indicated in Fig


It can be understood that it is easy for resin stagnation with this valve structure


the design of the flow path without dead space by taking enough R so as not to provide the corner as much as possible is expected

In addition,

as for high viscosity material such as PC,

the fatigue failure occurs in the screw of small aperture when receiving the load by repeated rotation,

the use of screw of wide aperture is recommended

Back flow ring type equipped with nail


Design of Shut Off Valve

As for compound reinforced PC such as glass fiber reinforced material etc

the backflow prevention ring sometimes cracks when the load becomes large compared with the non-reinforced material

When molding without being aware of this,

the uneven dimension and the deviation from tolerance in the molding of a precise part occur due to the unstable measurement

It is necessary to note that such a trouble easily occurs in case of overload and insufficient purge


it is necessary to avoid using the needle shut off nozzle and torpedo nozzle due to resin stagnation

The open nozzle is the best for use

The open nozzle is easy to cause drooling,

and it is difficult to prevent them but using a long-extended nozzle and adjusting independently the temperature at two separate places of the tip and the bottom,

the heater with heat capacity can be heated to about 370℃ is used,

and a band heater is usually used

When disassembling to clean the nozzle and cylinder head and when the heater is stuck with drooling resin,

It is necessary to note that it is easy to cause the burn when continuing molding without being aware of heater disconnection

either the hydraulic type or the toggle type is available

Since the average value of the mold internal pressure in the molding of Iupilon / NOVAREX is 350-500kg/cm2,

the clamping force F can be calculated by the following equation




it is necessary to note that when the arrangement of molding is eccentric from the center of mold (center of die plate),

which is higher than the above formula is required

clamping pressure of the molding machine (ton)

projected area of the molded piece Fig

Multistep program control

The improvement of poor appearance of the moldings,

the reduction of size unevenness between the molding shots,

and the measures against sink marks,

warpage and flash can be achieved by controlling the injection rate,

screw rotation speed and back pressure with multistep program control at the time of injection

The effect of multistep program control in PC and its control system are indicated in Fig


The outline is introduced below

Effect Prevention of jetting mark at gate part,

prevention of flow mark of sharp corner,

prevention of core falling and prevention of flash

Holding pressure Screw rotation speed Back pressure

Reduction of molding stress and prevention of sink mark Stability of measurement Stability of measurement

Disturbance Comparison controller Setting value


Controlled object

Control variable

Detecting value Detector


Outline of multistep program control system

〈 Control of the injection rate〉 Since the poor appearance is resulted from the change of rate of the flow front,

the measures can be done by controlling the injection rate

The relationship between the flow rate and the defective phenomena is summarized in Table 1・3-2

It can be understood that the injection rate should be set to an appropriate range because there is a problem even if the flow rate is too fast or too slow

Table 1・3-2 
 Flow rate and defective phenomena Defective phenomena results from too Defective phenomena results from too slow fast flow rate of resin flow rate of resin Flow mark Jetting mark Transcription defect of mold Gas burn surface Sink mark due to trouble of Weld line air purge Short shot 

It is understood that the setting range of the injection rate to have a product of good quality is narrow (shaded part) in case of general molding

injection rate area to obtain good product when setting program of injection rate

area to obtain good product when not setting program of injection rate


gate flow mark transcription defect of mold surface

Defective area of injection rate

〈 Control of the holding pressure〉 The defective phenomena such as sink marks,

warpage and flash are related to the holding pressure

The measure against these phenomena becomes possible by controlling the holding pressure

The relationship between the defective phenomena such as sink marks,

warpage and flash and the holding pressure is summarized in Table 1・3-3

Figure 1・3-3 indicates the pattern of the holding pressure program which was obtained to avoid the defective phenomenon area



Holding pressure and defective phenomena 

Defective phenomena results from too low holding pressure Short shot

Defective phenomena results from too high holding pressure Flash

Sink mark



Crack Mold release defect

Shrinkage strain

Residual stress 

 1・3-3 Holding pressure pattern to avoid defective area 〈 Control of screw back pressure and screw rotation speed〉 The stability of measurement (plasticization) is related to screw back pressure and screw rotation speed

It is possible to improve the accuracy of uneven repeated measurement by controlling these factors

From this figure,

it is thought that the unevenness of the measurement position,

mold release resistance was decreased by the multistep program control

mold release resistance (kgf) no program shot number control

Stabilization by the program control of plasticization process ( Material: S-2000)

Defective Moldings,


Defects to be encountered in molding of Iupilon / NOVAREX are almost similar to those of other plastic materials

The defective causes and remedies of general grade and glass fiber reinforced grade are summarized in Tables 1・4-1 and 1・4-2,

The effect that the mold temperature of glass fiber reinforced grade has on the appearance is indicated in Fig


Table 1・4-3 shows the problems and remedies in an accurate molding

Table 1・4-1 Defective causes and remedies of general grade Defective molding

Silver streaks Moisture in the pellets (uniformly distributed in the direction of injection) Silver streaks (irregularly distributed Overheating of the resin and often shaped like a comet locally)

Remedy Dry the pellets thoroughly at 120℃

Do not allow the pellets to cool in the hopper

Perform free injection and observe the state of bubbling of the melt

(i)Overheated spots in the cylinder or nozzle (i)Lower the temperature of the overheated spots (ii)Stagnation of the resin in the cylinder or(ii)Clean the stagnant part or replace the stagnant part with a part free from nozzle stagnation Brown discoloration

(iii)Over heating of the resin or too long dwell(iii)Check the stagnant part and the joining time part of the cylinder and nozzle (iv)Inadequate rotation speed of screws (iv)Set the rotation speed of screw at 45‐ 60rpm

Cloudy black specks and Air trapped in the pellets bubbles

Raise the back pressure in a screw type Molding machine

Local discoloration

Insufficient venting of the mold and heat

Cut a 0.01mm∼0.03mm deep vent in the

Generated by adiabatic compression of the air parting face of the mold Change the position of the gate to obtain a Voids and black specks Adiabatic compression of the air entrapped in uniform flow of the resin in every direction

and silver streaks around the resin in the mold

Correct the eccentricity and non-uniform the voids thickness of the core

Lower the injection rate Stains (i)Contamination by foreign matters or other (i)Pay enough attention to storage of the resin resin

(ii)Contamination by eroded material of the Clean the hopper,

(ii)Inspect the sliding surface of the (iii)Fats or oils in contact with the melt

(iii)Inspect the injection unit and the mold and prevent oil leakage

Defective molding

Dark brown or black specks Peeling of a layer of decomposed resin formed on Clean the internal surface of the cylinder

or particles the internal surface of the cylinder

Keep the temperature of the cylinder at 160‐180℃ when the operation is stopped

Cloudy surface

Due to the use of a mold release agent

Polish the mold

Reduce the amount of a mold release agent

Sink marks on the surface Shrinkage occurring during freezing is not Or bubble inside

(i)Prolong the application of the holding pressure

sufficiently compensated by the holding pressure (ii)Prevent heat loss from the nozzle

(iv)Make the wall of the molded piece as thin as possible

(v)Attach the gate to the part with the largest wall thickness

(vi)Prolong the cooling time when sink marks are formed after release from the mold

(vii)Increase the feed cushion of pellets

Mold flash (i)Insufficient mold clamping force or too high injection pressure

(ii)Wearing off of the mold

(i)Increase the mold clamping force or reduce the injection pressure and holding pressure

Inspect the mold

( i ) Lower the holding pressure

Provide a sufficient draft and polish the mold

(ii)Attach a device to break the vacuum in the (ii)Vacuum created between the mold and the molded mold

Difficult molt release or (i)Larger mold release force required Deformation during molt release

(iii)Mold release force not working on the part (iii)Increase the number of ejector pins

where the molded piece is adhered closely to the mold

Short shot

(iv)Molded piece not sufficiently cooled during

(iv)Lower the mold temperature and speed up cooling

(v)Prolong the cooling time

(i)Too low cylinder temperature,too fast

(i)Raise the cylinder temperature,enlarge the

raise the mold temperature and the freezing of the passageway,too low mold temperature injection rate,and improve the air vent of the mold (ii)Too small wall thickness (ii)Increase the wall thickness

(iii)Irregular filling of cavities

(iii)Change the passageway to obtain simultaneous filling

(i)Too low resin temperature (ii)Low injection rate

(i)Raise the resin temperature,particularly the nozzle temperature (ii)Perform high speed injection

Ripple near edges

Jet flow,

Caused by the cooled resin or the resin cooled by Enlarge the gate

Lower the injection rate

Change colliding with the mold being carried forward the position of the gate

Raise the nozzle


Defective causes and remedies of glass fiber reinforced grade

FLow marks

Weld marks

Ripple near the gate

Inadewuate flow of the melt (i)Rapid change in the cross section of the (i)Desin the molded piece such that the cross molded piece

section changes not stepwise but smoothly

(ii)Inadewuate flow of the resin melt around (ii)Round the sharp corners

Cooling of the resin occuring brfore merging

Raise the resin and mold temperature and perform high speed injection

Enlarge the gate

Cooling of the resin before the holding Enlarge the gate pressure working

Peeling of a surface layer Contamination by foreign matters and other Perform purge sufficiently

(especially when bent) (i)Moisture in the pellets (Defects due to (i)Dry the pellets at 120℃

Perform purge and moisture are often unnoticeable) examine the degree of resin bubbling

Breakage of molded pieces (ii)Raise the nozzle temperature and remove (ii)Too low nozzle temperature

Detach the nozzle from the mold after injection

(iii)Resin cooled between the nozzle and the (iii)Remove such cooled resin every time it sprue bushing

Use a shut off nozzle

(iv)Generation of internal stresses due to low ( iv ) Keep the mold temperature at 70 mold temperature,

Lower the injection pressure and pressure and holding pressure,

and holding pressure and avoid excessive extremely non-uniform distribution of the pressure after complete filling

Make wall thickness

the wall thickness distribution uniform

(v)Contamination by foreign matters

(v)cylinder and nozzle and cleaning

Defective molding

Defect of surface gloss

(i)Low mold temperature (ii)Low holding pressure

(i)Raise the mold temperature (at 110 ‐120℃ if possible) (ii)Raise the holding pressure

(iii)Perform high speed injection

(i)Provide a proper taper in the range of 1/100‐1/50

(ii)Inadequate position of ejector pins

(ii)Make adequate position of ejector pins

(iii)too high mold temperature

(iii)Lower the mold temperature

(iv)Prolong the cooling time

(v)Too high holding pressure

(v)Lower the holding pressure

Defect of mold release

Local burn

(i)Stagnation of the resin in the molding (i)Examine the molding machine

Dismantle and machine perform cleaning

(ii)Install the vent hole in the mold

(ii)Overheating of the resin due to adiabatic compression of the air in the mold

Hue non-uniform

(i)Specks of the resin and floating of glass (i)Make the molding conditions proper

(ii)Widen the tolerance level of hue

(i)Apply the mold release agent too much

(i)Decrease the applied amount of the mold Defect of strength of the release agent

weld part ( ii ) Inadequate position of the gate and (ii)Change the position of gate and re-examine distribution of the thickness

the distribution of the thickness



Relation between the mold temperature and the appearance of glass fiber reinforced grade Color difference: the color difference with glass reinforced PC (black) was obtained by considering the non-reinforced PC (black) as a controlled material

Defective molding

Deformation under load

Insufficient elastic modulus

Insufficient shape rigidity

Change of dimension Large thermal expansion coefficient

according to environment Anisotropy of thermal expansion conditions coefficient

B Application of low bubble molding

C Rib reinforcement A Combination of reinforced material

A Addition of non-oriented reinforced material

A Combination of reinforced material

Change of dimension by heat

A Combination of reinforced material

Excessive molding strain

Creep deformation

Estimated error of

A Examination of kind and content of reinforced material

C Combination with metal (insert,outsert)

Moisture absorption

Change of dimension over time

Anisotropy of molding shrinkage

C Raise the mold temperature

C Annealing treatment C Uniform distribution of thickness C Molding by low holding pressure and high mold temperature A Combination of reinforced material

B Design creep within the limit

A Use the low warpage grade (in case of reinforced grade)

C Fulfillment of molding shrinkage data Form,

position and size of gate Thickness,

thickness distribution Shape effect(roundness,straightness etc) Error by the mold

Non-uniform dimension of Non-uniform material mold process

A Control the viscosity,

Performance of the mold device

Non-uniform molding conditions Measuring error Durability of the mold


D Improvement of processing accuracy D'Consider the influence of mold structure

Anisotropy of molding shrinkage

Non-uniform pressure in the same cavity

B Improve the performance of injection molding machine,

C Control the holding pressure,

resin temperature and mold temperature

C Control the dimension measurement D'Consider the mold strength D'Mold material A Use the low warpage grade (in case of reinforced grade) A Use the low viscosity material

B Use the injection compression molding machine

C Low holding pressure,high speed filling C Examine the number and position of the gate

Defective molding


Non-uniform cooling

C Examine the distribution of thickness C Balance of the mold temperature D'Examine the mold heating and the cooling ditch

Sink marks

Due to the failure of holding pressure

A Use the low viscosity material

B Use the high pressure molding machine and

the injection compression molding machine

C Examine the position and size of the gate

C Make the wall of the molded piece as thin as possible

C Adjust the resin temperature,

mold temperature and holding pressure etc

Defect of mold release

(prevention of sink marks by bubble generation)

Improper taper

A Use the mold release grade

Adhesion to mold surface

C Increase a sufficient draft,

Use the low bubble grade Sink marks prevention grade C Lower the mold temperature

Imbalance of ejector power C C

low mold temperature Use the spray mold release agent

(pay attention to defects of the appearance,

crack of molded pieces) D'Pay attention to mold polish direction D'State of mold surface (coating,polishing degree) D'System and position of ejector

Defect of gas

Too much gas generation

Consider the pyrolysis,

Surface cloudiness Mold corrosion

Insufficiency of preliminary drying of materials

B Use the vent injection molding machine

Defect of dimension

C Too high molding temperature

Defect of mold release

Too long molding cycle Insufficient gas venting B C C


Cavity vacuuming Lower the injection temperature Install the air vent

Measures regarding the materials Measures regarding the molding machine,

Measures regarding the product design,

Measures regarding the mold design

Molding operation 2・1 Preliminary drying of materials ・Dryer Since Iupilon / NOVAREX have an ester bond in the main chain,

the hydrolysis occurs when heated with the moisture

As a result,

particularly the molecular weight and the impact strength are reduced

the preliminary drying before molding is necessary because the generation of silver streak and void at the appearance occur

The moisture content in the pellets should be assumed to be 0

The results of the molding at various moisture content are shown in Table 2・1-1

These results indicate that the degradation of the impact strength in addition to the generation of defective appearance is very large


it is important to use the dried pellets that the moisture content is lower than the above mentioned limit to have a good performance of Iupilon / NOVAREX

Table 2・1-1 
 Effect of the moisture content at the time of injection molding S-2000(Molecular weight 2

5×104) Moisture Molecular Falling ball impact destruction rate(%) Appearance of content weight of Total destruction molded pieces (%) molded pieces Ductile failure Brittle failure rate 0 0 0 Good 0.014 2.5×104 Good 30 0 30 0.047 2.4 Good 50 0 50 0.061 2.4 A few silver 90 0 90 0.067 2.4 streak Silver streak,

The head makes the heavy bob of 10mmR fall from the height of 10 m The drying conditions of Iupilon / NOVAREX are indicated in Table 2・1-2 Table 2・1-2 
 Drying conditions of Iupilon / NOVAREX Drying conditions Notes Temperature Time required Many examples of use

Multi-tray hot air Pay attention to the ambient moisture circulation dryer 120℃ 4‐5hr or more Thickness less than 30mm is preferable

Many examples of use Pay attention to the ambient moisture Hopper dryer 120℃ 3‐4hr or more and short circuit pass When the input is small,

the moisture distribution is bad

It is often used for the molding of Dehumidifying 120℃ 2‐3hr or more optical disk substrate and optical lens Hopper Dryer etc

(Note) Please note that the grade of the polymer

In order to dry the pellets of Iupilon / NOVAREX until the moisture content is lower than the above mentioned limit、 it is necessary to note the kind of the dryer,

its performance and environment ( temperature and moisture)

The dry efficiency is decreased under high temperature,

high humidity and it requires long time until the moisture content is lower than the limit

The dehumidification hopper dryer that is not affected by the environment and the dry efficiency is good


it is necessary to pay attention to the time degradation of the dehumidifier performance and consider the short pass phenomenon of the pellets when determining the drying capacity

capacity 50kg feed 50kg feed (30 mm think pile) set temperature atmosphere

water absorption percentage (%)

water absorption percentage (%)


it is also necessary to consider preventing the moisture re-absorption by shortening the installation of the hopper dryer,

hopper insulation and dwell time of the pellets as much as possible

- 20 °C

It is good to measure the characteristic of the injection molding machine to use in advance

The general molding temperature of Iupilon / NOVAREX is in the range of 260~320°C,

but it is better to set it as low as possible for deep colored products

As for the setting of the cylinder temperature,

it is common to set the temperature gradient such that the hopper side is higher by 10

- 20 °C

When the rotation torque of the screw becomes overload by the high viscosity grade and so on,

the temperature on the hopper side may be set high oppositely

In addition,

the selection of the molding temperature should be made in consideration of the molding cycle time,

namely the dwell time of the resin in the cylinder

The molding machine with the injection capacity by corresponding to the weight of the molded pieces and molding conditions is selected,

and the dwell time is shortened as much as possible to avoid the thermal degradation of the resin

It is necessary to note that the temperature of the nozzle has a slight affect on the cold flow of the molded pieces and the leakage of the resin (drooling)

holding pressure The injection pressure and holding pressure are set as low as possible if the sink marks and voids do not occur in the molded pieces


in case of the resin with high melt viscosity such as Iupilon / NOVAREX,

the inside of the mold can not be filled from the pressure loss with the flow process of the resin if the pressure is not raised to some degree

As soon as the cavity is filled,

the injection pressure is reduced to the level that does not cause sink marks

In addition,

the pressure is raised to reduce the mold shrinkage of the resin,

but from the point of strain and mold release characteristic which remain in the molded pieces,

the pressure should be set as low as possible


since the flow length increases when the injection rate increases,

the fast filling is carried out for thin-walled molded pieces


when the fast filling is carried out,

defects such as flow marks and flash are produced

Since the recent injection molding machine is equipped with the multistep control of the injection rate (program injection),

both the filling and appearance can be controlled by changing the rate according to the shape and gate of molded pieces

The basic rate program is as follows

(a) Make high speed at the passage of the sprue and runner part

(b) Make low speed at the initial filling of the gate part and product part,

and at the time of filling completion

(c) Make low speed when passing over the thin type core and pin part

flow length exclusive of gate (mm)


generation of the resin burning,

bubble and silver streaks resulting from the deaeration insufficiency,

and easy to cause the thermal degradation by adiabatic exothermic heat

The back pressure is about 5

Since the back pressure has an affect on the leakage (drooling) of the resin from the nozzle,

the consideration of setting temperature is also necessary

When the mold temperature is too low,

and in addition to the defective appearance such as flow marks etc

the molding strain is easy to be generated

On the other hand,

when the mold temperature is too high,

the resin is easy to stick to the mold surface and defect of the mold release and deformation of the molded pieces after the mold release easily occur

The standard mold temperature is 70~120℃

The mold release agents of silicone derivatives are usually used,

but in case of printing and hot stamp,

and cloudiness in the vicinity of the gate just after the application,

it is better to use the paintable type or unused

removing fat and washing in case of inserts (refer to “Iupilon Technology Report”,

PCR304 for detail)

Sharp corners should be avoided in inserts (Fig


shape examples of good fitting without paterns

flat face pattern without arising notches

The thickness of the molded pieces around the insert is necessary to be 0

In addition,

if the insert is a metal in large size,

In case a large number of inserts are to be used,

the dwell time of the resin in the cylinder is prolonged because it takes long time for the mold installation and as a result,

the thermal degradation of the resin may take place

Carrying out the insert after the molding is better

the molding operation is not over when the material feeding is converted into molded pieces,

but it is necessary to check whether the pieces exhibit enough strength in actual use

From this point of view,

it is very important to select proper molding conditions

The evaluation is not easy although molding conditions are modified and selected while judging their performance in actual use

The requested characteristics of the molded pieces are based on the basis of the customer’s specification,

and it is impossible to conduct everything in the molding process

The management is thoroughly executed in the early stage when producing a new molded piece,

and it is necessary to focus on the point and to conduct day-by-day management afterwards

The item that should be managed in the molding process is to prevent the reduction of strength of molded piece due to 1

the degradation and decomposition of the resin,

This is explained as follows

Decomposition of the resin Measurement of the molecular weight is used as a means to examine the degradation and decomposition of Iupilon / NOVAREX

It is necessary to note that the measurement of the molecular weight is difficult in a special grade,

and can not be judged only by it in some cases

Since the measurement of the molecular weight is time consuming,

it is better to conduct it at the stage of selecting the molding conditions at the beginning and to keep the correlation with other simple test method,

and then manage it For example,

it is also good to bend a sprue and a runner and examine the condition of breakage or conduct an impact test sensitive to the reduction in the molecular weight due to the decomposition of the resin (falling ball impact test etc

to add the impact in the molded piece with the hammer)

As for Iupilon / NOVAREX general grade,

it is inspected by using the combined solvent of MIBK (methyl isobutyl ketone) and methanol

This method is suitable for stress detection by the following reasons

(a) In case of crack generation,

a relatively big crack is generated and is easy to determine

(b) The detected stress can be changed by changing the mixed composition

Table 2・4-1 is summarized based on current practical results


because the detection method of residual stress by solvent is a method of large unevenness actually,

the result should be considered as a rough standard and an evaluation standard in correspondence with practical test must be decided

the correspondent mixed composition of the conventional carbon tertrachloride / butanol system was described Table

Mixed composition(volume ratio) MIBK/Methanol



Detected stress MPa (kg/ cm2)


Too severe for checking stress of normal molded piece Suitable for searching molding conditions for stress reduction and annealing conditions

Molded piece is suitable for stress check in a simple substance

Suitable for the check of assembly articles 13 1/3 1/3 and insert articles loaded by joint stress and (25%) (25%) (130) external force

When the crack is generated at this level,

conduct water washing and observe the crack

Interruption of Operation,

and Cleaning by Dismantling 1) Material replacement Polyamide,

should not be replaced directly with Iupilon / NOVAREX and the reverse is also similar

It is because these resin materials decompose when replacing directly to the molding temperature range of Iupilon / NOVAREX,

and also promote the decomposition of Iupilon / NOVAREX

In such a case,

polyethylene and polystyrene must be used between the two


it is necessary to note the case when a transparent resin such as polystyrene is mixed with Iupilon / NOVAREX because the end point of the replacement can not be clearly discernible


to make the replacement of color,

various replacement materials (cylinder washing material) are available in the market

A proper replacement material can be selected according to the molding temperature range of the material before replacement,

the material of the replacement purpose

and Cleaning by Dismantling The resin is gradually decomposed and formed a carbonized layer on the internal surface of the heating cylinder and around the backflow prevention ring of the screw over a long period of operation

This carbonized layer does not peel off during the normal molding operation


when the temperature of the heating cylinder goes down during interruption of the operation,

the carbonized layer peels off due to shrinkage,

contaminates the molded pieces and becomes black specks when the molding operation is resumed


it is better to keep the heating cylinder at 150 ∼180℃ during interruption of the operation for a short time

When the operation is stopped for a long time,

it is good to replace Iupilon / NOVAREX with other resins of lower molding temperature range and lower the temperature

Polyethylene and polystyrene are good as replacing resins

Since the carbonized layer on the internal surface of the heating cylinder and around the backflow prevention ring of the screw gradually becomes thick and begins to contaminate the molded pieces when the decomposition progresses,

the heating cylinder and the screw should be dismantled and cleaned regularly


since the contamination of foreign matters,

black specks are not good for transparent molded pieces,

it is necessary to dismantle and clean once every several months

When various resins are molded with the same molding machine,

it is necessary to dismantle and clean the cylinder and the screw regularly

The dismantling procedure is done by replacing with polyethylene and polystyrene after the resin in the cylinder is emptied as much as possible

After dismantling,

remove the remaining melted resin quickly,

and then remove the carbonized layer with the spatula and brush made of cupper or burn with the burner

If Iupilon / NOVAREX remains and it is impossible to take it out,

an effective method is to wash with a solvent such as methylene chloride etc

In this case,

pay attention to the work environment (ventilation,

Product design and Mold design 3・1 Product design When using Iupilon / NOVAREX,

the contents shown in Table 3・1-1 are considered as problems in practical use

As shown in Table 3・1-2,

it is necessary to investigate and examine sufficiently so as not to cause these problems

In addition,

the calculating formula shown in Table 3・1-3 is useful for the standard of lightening,

decision of the product thickness,

and the selection of molding machine,

Table 3・1-1 Defective phenomena observed in PC molded piece Classification Contents Crack and deterioration of impact strength due to degradation at the time of molding Breaking due to excessive load stress Strength

Deterioration of strength due to concentration of stress Crack of insert and screw tightening part Solvent crack due to oil,

Deterioration due to hot water and alkali

Defect of dimensional due to error of estimation of mold shrinkage factor

Dimension Deformation due to excessive stress and warpage at the time of molding

Deformation due to creep deformation and thermal expansion

Silver streaks,sink marks,flow marks,specks,weld line,hue non-uniform, Appearance Uneven brightness of embossing,uneven brightness of weld part,

floating of glass fiber Table 3・1-2
 Classificatio n General

Items Reason of PC molding,commercialization schedule,weight and material,

Required Lifetime,

electrical property performance Temperature,

kind of contacted substance Use (PVC,

environment Tightening Inserting,

existence of embossing,existence of coating

Table 3・ 1‐ 3



Items W:weight of PC product,

W0: weight of metal product

Weight (in case of constant shape)

ρ2/ρ1 * t2/t1 * Wo

ρ1t1:density and thickness of metal,

ρ2t2:density and thickness of PC t:thickness of PC,

E1:bending elastic modulus of PC,

E2:bending elastic modulus of metal Thickness and Flow Length

Required mold clamping force of molding machine

Capacity of molding machine



P:mold clamping force s:projected area Q:Capacity(g) w:Weight of molding piece(g)

in order to maximize the good performance of Iupilon / NOVAREX,

it is necessary to pay sufficient attention to the shape design

The key points are as follows: (1) The thickness is uniform and no sudden change of the thickness

As for the main items,

the standard and cautions in the molding are described in order as follows

The relationship between the thickness and the flow length for Iupilon / NOVAREX is shown in Fig


In case where the thickness is extremely thin,

and impact strength deterioration occur (thickness 4 ∼ 5 mm or more)

In addition,

the sudden change of the thickness obstructs the flow of resin causes flow marks,

Examples of the design to have the uniform thickness are shown in Fig


flow length exclusive of gate (mm)

I: Region where ordinary molding is possible II: Region where high temperature and pressure are required thickness (mm)

Distribution of the thickness

Since an excessive stress occurs at the corner of the molded piece due to the concentration of stress,

be sure to provide R at the corner

The relationship between the notch R and the impact value for Iupilon / NOVAREX is shown in Fig


The brittle fracture is shown when the notch R is below 0

The relationship between the corner R and the stress concentration factor is shown in Fig


When the corner R is small,

the stress concentration factor becomes large,

residue stress becomes large and defects such as flow marks easily occur

On the other hand,


the ratio of the corner R and the thickness (R/T,

Thickness 1/8 inch,

corner radius R pressure concentration coefficient

ductile failure Izod impact value (J/m) Fig

0mm Fig

 impact value for / NOVAREX 3) WeldIupilon line In addition to the deterioration of strength,

various defective phenomena at the weld part are observed as shown in Table 3・1-4

The reinforcement measures at the weld part such as the gate type,



Defective phenomena observed at the weld part

Practical failure Deterioration of tensile Deterioration elongation and impact of strength strength Generation of Generate in the vicinity crack of insert,

screw boss Defect of Irregular color,

Notes Mainly observed in glass fiber reinforced grade,

Mainly observed in deep colored-substance

appearance brightness of embossing Defect of dimension

Sink marks,

and polymer alloy grade Many defects in glass fiber reinforced grade

Take the gate in the direction where the deposited area of the weld becomes large 

Reinforce the rib in the vicinity of the generated hole of the weld line

Select the position of gate as the weld line does not generate in the vicinity of the insert metal fitting 
 Gate A (good) Weld line does not generate

Gate B (bad) Weld line generates


 4) Shape of Rib It is good to think that the design of a rib is almost the same as other plastic materials


the measure to prevent the generation of sink marks on the rib opposite side,

and the notch effect at the corner part etc

The design standard of a rib is shown in Fig


Do not forget to provide R above 0



Design of a rib

the standard of a taper is in the range of 1/100~1/50 (0

An example of the molded piece with a deep rib is shown in Fig



Example of taper

but when pulling out an undercut by force with a normal mold,

it is difficult to take a deep undercut because of the high mechanical strength and elasticity modulus of Iupilon / NOVAREX

The mold release possible undercut △R in case of a cylindrical piece as shown in Fig

 1 + ( r i / r 0 ) 2
 where L= __________ 1 ‐ ( r i/ r 0) 2 Sprue

Molded piece Undercut Core

Stripper plate


Peripheral undercut △R on the cylindrical piece


draft angle D=3d (d<5mm) D=2d (d>10mm)

it results in the weakening of mechanical strength

Refer to Fig

A≧2D B≧D

the load is generated only in an instant at the time of assembly,

Take a proper R


Snap fit


it is good to add α to the above

Mold Design Since the productivity and quality of the molded piece are greatly influenced by the mold design,

the mold design is extremely important issue

The basic concept of the mold design is as follows

(1) The filling of the resin can be easily done,

(3) Pay attention to the control of the mold temperature

(reduction of non-uniform dimension including the shape,

appearance of the product and stabilization of quality) Each item of the mold design is explained in order as follows

the sprue should be shaped as thin and short as possible

The points which should be noted are the mold release characteristic and air bubble of the base

As for the mold release,

the draft should be 3-5 0 as shown in Fig

3・2‐ 1

As for the air bubble of the base,

it is important to design the diameter of the base to the suitable thickness

When the air bubble occurs at the base in the direct sprue,

it results in the cutting of the sprue,

defect of the product at the time of mold releasing

The diameter for not causing the air bubble at the base is as follows: The diameter of the sprue base ≦(2.5‐3.0) thickness of the base


The pressure loss of the sprue part can be calculated by the following equation

It is preferable to reduce the pressure loss as much as possible

: a v e r a g e diameter of the sprue

: diameter of the sprue tip : d'i a m e t e r of the sprue base

hemi circular and trapezoidal cross section shapes of the runner as shown in Fig

Concerning the thickness of the runner,

it should be decided in consideration of the pressure loss for the lower limit and the economic efficiency for the upper limit

The following empirical relationship between the length and thickness of the runner is the common practice

In the case of a multi-cavity mold,

it is preferable to balance the runner length to each cavity,

and all the cavities should be filled simultaneously as shown in Fig

when it is difficult to balance the runner length,

it is preferable to balance the gate for simultaneous filling as shown in Fig

3・ 2-5

The pressure loss of the runner part can be calculated by the following equation

It is preferable to reduce the pressure loss as much as possible

S:cross section area of the runner part l:circumferential length cut of the runner part

lγ : runner length dγ : hydraulic depth of the runner part

submarine gate and tab gate can be applicable to the g a t e s'h a p e s'

T h e s'i d'e g a t e a n d'p i n p o i n t g a t e a r e c'o m m o n l'y u s'e d'a s't h e g a t e s'h a p e s'o f Iupilon / NOVAREX molded piece

When the thickness of the side gate is thin,

defective appearance such as unfilling,

F r o m t h e m a r k e t r e s'u l't s',

i t i s'o f t e n d'e s'i g n e d't h e g a t e t h i c'k n e s's e q u i v a l'e n t t o 50 ‐ 70% of that of the molded piece thickness

The gate width is 1

The pressure loss of the rectangular cross section at the gate can be calculated by the following equation

△ p : pressure loss at the gate u: viscosity q: volum e flow of the resin W : g a t e width h : g a t e thickness L': g a t e land

As for the pin gate shape,

it is important to determine the most suitable diameter of the gate by considering from the viewpoint of crack and deformation of the product at the time of cutting and gate breakage for the maximum dimension,

while taking defective problems such as jetting and unfilling for the minimum dimension into consideration

T h e t y p i c'a l'p i n p o i n t g a t e s'h a p e i s's h o w n i n F i g


the average value of the pin gate diameter ranges from 1

Thin-walled small articles


Shape and dimension of pinpoint gate

Gate diameter(mm)