Troubleshooting for silver streaks

Transcription

1 Troubleshooting for silver streaks Types of Silver Streaks Potential Causes Near gates Small gates Check the size of runner and gate Judgment based on experience Fluidity improvement test Shape of gate hinders or CAE analysis resin flow. Flow-hindered areas Die structure hinders Study injection shapes Happens after passing through Regular (Boss, ribs, areas where resin flow. flow-hindered areas the thickness is changed and weld area) Poor heat stability of Check for the discoloration near Check the resin temperathre raw materials silver streaks Other specific areas areas in trouble are Check for passage through Check the die temperature Increase the die temperature through control excessively cool. cooling lines (Improper cooling line) of coolant inflow Occur irregularly in Moisture contents in Purge, and check for discoloration, Blowholes and discoloration occur during purging Test after drying diverse locations raw materials and gas (moisture and deterioration) (Discoloration,deterioration, blowholes,gas and moisture)change operating conditions Check the method of drying raw materials. (Temperature, measurement andback pressure) Irregular Thermal degradation of raw Check the pellet state. Size, uniformity, pinholes Replace with good materials and check. materials after air mixture (size of pinhole and amount of lubricant) at the entrance area. Check back pressure, and Measure back pressure Adjust back pressure before test hopper bridging. Measurement state (Visual ) Test with another injector

2 Troubleshooting for Pin Holes Types of Pin Holes Potential Causes Primary check Judgments solutions Mixed with foreign materials. Check for mixing of contaminated Check pinholes. Use new materials only and raw materials and recycled resins compare. pinholes Poor colorant distribution non-molten resin particles Check the product states. Small pin holes on products Compare with products from good raw materials. Check the films of raw materials and injection products

3 Troubleshooting for Flow Marks Types of Flow Marks Potential Causes Primary check Judgments Flow marks caused by gas Heat stability of resin Check resins. Accompanied by discoloration and Check discoloration and poor gloss excessive gas during purging Change conditions (RPM 60-80) Poor injection conditions back pressure over 10KG, Insufficient measurement Check the injection pressure lower speed, of injector condition. higher die temperature (adjustment of the resin temperature) Unbalanced die structure Check die structures CAE analysis Reduce flow resistance and Check gate locations (Check flow, temperature, improve fluidity Poor condition of cooling Compare sizes pressure, and distribution of resin.) Set injection conditions tube Irregular product thickness Inconsistent die temperature

4 Troubleshooting for Weld Lines Types of Weld Lines Potential Causes Primary check Judgments Thin lines appear on the surface where separated resins merge (They always occur where the resins meet) Die structure Die temperature 1. Check the flow and structure of resins Product design Cylinder temperature 2. Gate (shape, location, quantity) Enlarge the sizes of runner and gate injection condition Injection pressure 3. CAE analysis Increase the injection pressure and speed. Injection speed (Resin flow distribution analysis) Raise the resin temperature Replace with grades having good fluidity

5 Troubleshooting for Short Shots Types of Short Shots Potential Causes Primary Check Judgments Insufficient fluidity of raw materials Compare with physical properties of good raw Check physical properties. Inject with good raw materials Low resin temperature materials. Measure resin temperature. (Test results) and compare. Specific locations defective products and poor structure of die Measure product thickness. Check irregular product Adjust injection conditions low die temperature Check die temperature. thickness. (Increase injection pressure, Poor flow path and gas ventilation Flow distance between gates CAE analysis temperature and speed of the cylinder Check the gate locations and state of flow path. (Resin flow distribution analysis ) and dwelling, and check the operation state.) Burrs and short shots occur simutaneously Insufficient injector capacity Insufficient injector capacity (Oz, Ton) Check product weight and Inject with injector that has (Poor measurement, insufficient injection capacity. high injection capacity and clamping force) clamping force. Check the retainer plate balance. Check the flatness of retainer plate. Inject with another injector and compare. Insufficient resin fluidity Check product sizes and resin fluidity. Check short shots Compare with other grades. Poor product structure the thickness of product is too thin. Set proper conditions.