PRODUCTS ACETAL What is Polyacetal? Nomenclature Grade Product Certification Molding Guide Bad Molding CAE NYLON 6 Processing Guide Data Sheet NYLON 66 Processing Guide Data Sheet PBT Processing Guide Data Sheet TPE Processing Guide Data Sheet PET Data Sheet ABOUT US	NYLON 66 (KOPA66) Injection Molding of KOPA66 1. Pre-Drying NYLON66 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. 2. Injection Molding 2-1 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. 2-2 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. 2-3 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. 2-4 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. 2-5 Examples of Injection Molding Condition for Each Grades Item Unit KN3311 KN333H R KN333 HI KN3322 V0 KN333 G30 KN3321 G15V0 KN333 MS Cylinder Rear 260 260 260 265 260 255 Temp Middle Front Nozzle 270 280 270 270 275 265 270 275 270 285 290 280 280 285 275 270 280 270 Mold Temp 80 70 80 80 80 80 Injection Pressure 1st 2nd Kg/㎠ 900 450 1000 520 950 450 1100 520 1200 600 850 500 Back Pressure Kg/㎠ 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 Rpm 100 100 100 110 110 100 Injection Speed 1st 2nd 3rd Low Middle Low Low Middle Low Low Middle Middle Middle High Middle Middle High Middle Middle Middle Low 2-6 Trouble shooting Guide for KOPA66 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 KOPA66 resin. Britt leness Short Shot Poor Surface Stain Flash Void Flow Mark Poor Mold Release Warpage Burning Cylinder Temp ↓ ↑ ↑ ↓ ↓ ↓ ↑ ↓ ↓ ↓ Mold Temp ↑ ↑ ↑ ↑ ↓ ↓ ↑ ↓ ↓ Nozzle Temp ↓ ↑ ↑ ↓ ↓ ↑ ↓ ↓ Injection Speed ↓ ↑ ↑ ↓ ↓ ↑ ↓ ↑ ↓ Injection Pressure ↑ ↑ ↓ ↑ ↑ ↓ ↑ ↓ Holding Pressure ↓ ↑ ↑ ↓ ↑ ↓ ↑ ↓ Back Pressure ↓ ↑ ↓ ↓ ↑ ↓ Cooling Time ↑ ↑ Screw rpm ↓ ↓ Nozzle Diameter ↑ ↑ ↑ ↑ ↑ ↑ ↑ Gas Vent O o o o o o o o↑ Gate Size ↑ ↑ ↑ ↑ ↑ ↑ Gate Position o o o o Drying O o o o Note. ↑: Need to Increase ↓: Need to Decrease O: Study for Effecting Factors 2-7 Recycling Unsatisfactory resins, sprue and runner can be re-input and reused up to a 20% mix ratio, unless degradation of the resin is undetected during the injection molding process. Injection molding can be repeated up to 4 times with no indication of degradation, if appropriate conditions are maintained. Glass fiber reinforced grade can be also recycled and reused, but the possibility of mechanical property degradation must be recognized, since glass fibers will break. 3. Products and Mold Design 3-1 Parts Design In designing an injection molded part using KOPA66, 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. 3-2 Mold Design Steel is the ideal material for making molds, as nylon 66 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.
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