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Technology Data

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KOPA®-PA66

Pre-Drying

KOPA®-PA66 resin is kept at max. 0.2% moisture content in packages. However, it is apt to absorb moisture during processing work. Therefore, processing should be completed in less than two hours after the package is opened. Once moisture is absorbed, the resin must be dried by means of a hot-air dryer or dehumidifying dryer. Normally, the latter is better. Drying normally requires 5 hours at 70~80℃ .

Injection Molding

Selection of Injection Molding Machine
In is preferable to adopt in-line screw and screw-plunger type, as these are advantageous for melting power, temperature adjustment, prevention of material loss, and speedy internal pressure formation.

Pressure
If injection pressure is too low, part structure will be defective, and if too high, the resin layer floats during cooling, or causes deviation in structure or density, and/or easy breakage or damage from stress.

Temperature of Cylinder
Temperature is adjusted in accordance with the structure of parts and specification of injection molding machines. The resin melts at 255℃, and standard grade is maintained at 265~280℃, whereas a 10~20℃ increase in temperature is applied for glass fiber reinforced grade. Resin properties may be degraded if the temperature is too high and/or injection time is too long.

Temperature of Mold
Mold temperature is adjusted between 40℃ and 80℃ depending on the required property of molded parts. Cosmetic and mechanical properties of parts can be improved by increasing mold temperature.

Examples of Injection Molding Condition for Each Grades
GRADE별 성형조건 예
Item Unit KN311
KN333H
R
KN333
HI
KN3322
VO
KN333
G30
KN3321
G15V0
KN333
MS
Cylinder Rear 260 260 260 265 260 255
Temp Middle
Front
Nozzle
270 270 270 285 280 270
280 275 275 290 290 280
270 265 270 280 280 270
Mould Temperature 80 70 80 80 80 80
Injection
Pressure
1st
2nd
㎏/㎠ 900 1000 950 1100 1200 850
㎏/㎠ 450 520 450 420 600 500
Back Pressure Sec 10 10 10 15 15 10
Injection Time Sec 5 5 5 4 4 4
Cooling Time Sec 10 20 14 10 10 8
Delay Time Sec 2 3 2 2 2 3
Screw RPM Sec 100 100 100 110 110 100
Injection Speed 1st step Low Low Low Middle Middle Middle
2nd step Middle Middle Middle high high Middle
3rd step Low Low Middle Middle Middle Low
Trouble shooting Guide for KOPA®-PA66 Resin Molding Problems

To achieve optimum part quality and minimum cycle time, the molder must know how to overcome molding problems.
The follow figure is a guide for troubleshooting and offers solutions for most problems encountered with KOPA®-PA66 resin.

GRADE별 성형조건 예
Item Britt
leness
Short
Shot
Poor
Surface
Stain Flash Void Flow
Mark
Poor Mold
Release
Warpage Burning
Cylinder
Temp
DOWN UP UP DOWN DOWN DOWN UP DOWN DOWN DOWN
Mold
Temp
UP UP UP UP DOWN DOWN UP DOWN
Nozzle
Temp
DOWN UP UP DOWN DOWN UP DOWN DOWN
Injection
Speed
DOWN UP UP DOWN DOWN UP DOWN UP DOWN
Injection
Pressure
UP UP DOWN UP UP DOWN UP DOWN
Holding
Pressure
DOWN UP UP DOWN UP DOWN UP DOWN
Back
Pressure
DOWN UP DOWN DOWN UP DOWN
Cooling
Time
UP UP
Screw
rpm
DOWN DOWN
Nozzle
Diameter
UP UP UP UP UP UP UP
Gas
Vent
O O O O O O O OUP
Gate
Size
UP UP UP UP UP UP
Gate
Position
O O O O
Drying O O O O

Note. UP : Need to Increase    DOWN : Need to Decrese    factors : Study for Effecting Factors

Products and Mold Design

Parts Design
In designing an injection molded part using KOPA®-PA66, thicknesses of 0.75~3mm for glass fiber reinforced grade and 0.5~5mm for non-reinforced grade are standard. If they are too thick, distortion or shrinkage is likely to occur. Therefore, changes should be done on a gradual basis. A rib 0.5 or 0.6 times thicker can prevent shrinkage, though for painting work, a thickness of 0.3 times is advised. The tolerance of injection molding under normal conditions is + 2%, though this figure can be adjusted down to + 0.5~0.1% when mold temperature is well controlled, processing cycles are normal, and no undue impact occurs to the injection molding machine.

Mold Design
Steel is the ideal material for making molds, as KOPA®-PA66 does not corrode metal. But for the flameproof grade, it is desirable to use a base metal with higher chrome content, as the grade can corrode metal. A 0.5~1% of taper is good. For the shrinkage factor, parallel to flow direction, 2.5~3% is the standard for the general grade, 0.5~1% for the glass fiber reinforced grade. The shrinkage factor of molds for any resin vary in accordance with the additive used, process condition, thickness and shape of the part, the position of mold gate, cooling circuit, etc., making it very hard to determine. When processed parts are loosening from stress and finally stabilized, an additional 15~30% shrinkage occurs.