Incorrect operating conditions, damaged machines and molds will produce many molding defects. Here are some solutions for your reference. In order to reduce downtime and find out the causes of operation problems as soon as possible, the operator should record all the best injection conditions on the "Injection Conditions Record Form" for reference when solving problems in the future.
(1) The finished product is incomplete.
Fault cause treatment method
If the plastic temperature is too low, increase the temperature of the glue melting cylinder.
The injection pressure is too low to increase.
The injection amount is not enough to increase the injection amount.
The match between sprue sleeve and nozzle is not suitable, so the match is readjusted due to plastic leakage.
The time before injection is too short, so increase the injection time.
Glue injection speed is too slow. Speed up the glue injection.
Improper low pressure adjustment and readjustment.
If the mold temperature is too low, increase the mold temperature.
Due to uneven mold temperature, readjust the mold water pipe.
Appropriate vent holes should be added at the proper position where the die is not well vented.
If the nozzle temperature is not low, increase the nozzle temperature.
After gluing, the overflow position of the mold reopened unevenly.
The runner or overflow is too small. Enlarge the flow passage or overflow.
The lubricant in plastic is not enough to increase the lubricant.
Insufficient back pressure will slightly increase back pressure.
Disassembly, inspection and repair of rubber ring and glue-melting screw wear
If the injection quantity is insufficient, replace the injection molding machine with larger specifications.
If the product is too thin, inject glue with nitrogen.
(2) Shrinkage of products
Fault cause treatment method
Insufficient injection of mold glue
If the amount of melted glue is insufficient, add the amount of melted glue.
Injection pressure is too low or too high.
Back pressure is not high enough. backpressure
Glue injection time is too short and too long.
Glue injection is too slow and glue injection is too fast.
Overflow unbalanced mold overflow is too small or located.
The nozzle hole is too thin, and the plastic solidifies in the runner bushing, which reduces the back pressure effect. The whole mold or replace the nozzle.
Material temperature is too high and material temperature is too low.
Improper mold temperature and proper temperature adjustment
The cooling time is not enough to extend the cooling time.
Excessive glue injection in the pressure accumulation section should be terminated at the front end.
The product itself or its rib column is too thick to review the finished product design.
If the injection volume is too large, replace the diluent injection molding machine.
Disassembly and maintenance of the wear of rubber ring and rubber melting screw
The gate is too small, and the back pressure of plastic solidification increases the gate size.
(3) die sticking of finished products
Fault cause treatment method
The supersaturation of filler will reduce the injection pressure, time, speed and injection quantity.
The injection pressure is too high to reduce.
Too much glue injection reduces the amount of glue injection.
Glue injection time is too long, so reduce the glue injection time.
If the feed temperature is too high, reduce the feed temperature.
Uneven feeding will lead to partial overflow, thus changing the size or position of overflow.
If the mold temperature is too high or too low, adjust the mold temperature and the relative temperature on both sides.
There is a demoulding chamfer in the mold, and the chamfer is removed by trimming the mold.
The surface of the mold is not smooth, and the mold is polished.
The demoulding causes the vacuum mold opening or ejection to slow down, or the mold increases air intake equipment.
Injection molding cycle is too short to strengthen cooling.
Insufficient release agent slightly increases the dosage of release agent.
(4) The runner (nozzle) is stuck on the mold.
Fault cause treatment method
The injection pressure is too high to reduce.
The plastic temperature is too high to reduce the plastic temperature.
The runner is too large to modify the mold.
Runner cooling is not enough to prolong the cooling time or reduce the cooling temperature.
The demoulding angle of runner is not enough. Modify the mold to increase the angle.
If the matching between the runner bushing and the nozzle is incorrect, readjust their matching.
The inner surface of the runner is not only provided with a demoulding chamfer maintenance mold.
Overhaul mold for damaged gate outer hole
Non-runner grab pin plus grab pin.
The supersaturation of filler will reduce the amount, time and speed of glue injection.
Insufficient release agent slightly increases the dosage of release agent.
(5) Hair and glitter
Fault cause treatment method
If the plastic temperature is too high, the plastic temperature will decrease and the mold temperature will also decrease.
Too high injection speed will slow down the injection speed.
The injection pressure is too high to reduce.
Too full filler will reduce injection time, speed and dosage.
Mould for repairing poor clamping line or mating surface
The clamping pressure is not enough to increase the clamping pressure or replace the high-mold injection molding machine.
(6) The treatment method of the failure cause of finished product rupture during mold opening or ejection.
The supersaturation of filler will reduce the pressure, time, speed and quantity of glue injection.
If the mold temperature is too low, increase the mold temperature.
Part of the demoulding angle is not enough to repair the mold.
Maintenance mold with demoulding chamfer
The finished product cannot be balanced and separated from the maintenance mold when demoulding.
Repair the mold with insufficient thimble or improper position.
Local vacuum occurs during demoulding, so the mold can be slowly ejected and air inlet equipment is added.
Insufficient release agent slightly increases the dosage of release agent.
Poor mold design and excessive finished product stress can improve the finished product design.
Improper time or position of the side slider when repairing the mold
(7) Bonding line
Fault cause treatment method
Poor plastic melting will increase plastic temperature, back pressure and screw speed.
If the mold temperature is too low, increase the mold temperature.
If the nozzle temperature is too low, please increase the nozzle temperature.
The glue injection speed is too slow, so increase the glue injection speed.
The injection pressure is too low to increase.
The plastic is unclean or infiltrated with other materials. Check the plastic.
If there is too much demoulding oil, use less molding oil or try not to use it.
If the runner and overflow are too large or too small, please adjust the mold.
The glue joint is too far away from the main channel. Adjust the mold.
The air in the mold can't be exhausted, so it is not enough to add vent holes or check whether the original vent holes are blocked.
The amount of melted glue is insufficient, so a larger injection molding machine is used.
Not using or reducing too much release agent.
(8) Flow pattern
Fault cause treatment method
Poor plastic melting will increase plastic temperature, back pressure and screw speed.
If the mold temperature is too low, increase the mold temperature.
Improper cooling of the mold, readjust the mold water pipe.
If the injection speed is too fast or too slow, please adjust the appropriate injection speed.
If the injection pressure is too high or too low, adjust the appropriate injection pressure.
The plastic is unclean or infiltrated with other materials. Check the plastic.
The overflow amount is too small, which leads to the shooting mode and the overflow amount increases.
The difference in section thickness of finished products is too great, which changes the design or overflow position of finished products.
(9) The surface of the finished product is dull
Fault cause treatment method
If the mold temperature is too low, increase the mold temperature.
Insufficient plastic dosage will increase injection pressure, speed, time and dosage.
There is too much demoulding oil in the mold cavity to clean it.
Improper drying treatment of plastics and improvement of drying treatment
Wipe the inner surface of the mold with water to check whether there is water leakage.
Polis die with unsmooth inner surface of die
(10) Silver stripes and bubbles
Fault cause treatment method
Water-containing plastics are thoroughly dried to increase back pressure.
If the plastic temperature is too high or the plastic stays in the barrel for too long, reduce the plastic temperature, replace the injection molding machine with a small injection quantity, and reduce the temperature of the nozzle and the front section.
Other additives in plastics, such as lubricants and dyes, will be decomposed to reduce their usage, or replaced by substitutes with higher high temperature resistance.
Other additives in plastics are mixed unevenly and incompletely.
The glue injection speed is not fast enough, which slows down the glue injection speed.
The injection pressure is too high to reduce.
The melting speed is too low to improve the melting speed.
If the mold temperature is too low, increase the mold speed.
The thickness of plastic particles is not uniform. Use uniform granular raw materials.
Air is trapped in the glue melting cylinder to reduce the temperature in the back section of the glue melting cylinder, increase the back pressure and reduce the length of the compression section.
The size and position of overflow, the average mold temperature and the average thickness of finished products are not properly adjusted during the process of plastic in the mold.
(1 1) finished product deformation
Fault cause treatment method
When the top of the finished product is not cooled, the mold temperature decreases, the cooling time is prolonged, and the plastic temperature decreases.
If the plastic temperature is too low, raise the plastic temperature and raise the mold temperature.
The temperature of the mold with asymmetric shape and finished product thickness is controlled in different areas. After demoulding, it is fixed with a setting frame to change the molding design.
Too much filler will reduce the pressure, speed, time and dosage of glue injection.
The uneven feeding of several overflow channels changed the overflow channels.
Ejection system for improving imbalance of thimble system
Due to uneven mold temperature, please adjust the mold temperature.
The plastic near the overflow is too loose or too tight, which will increase or decrease the injection time.
Poor pressure holding will increase the pressure holding time.
(12) There are pores in the finished product.
Fault cause treatment method
The amount of filler is not enough to prevent the finished product from shrinking excessively.
The section, rib or column of the finished product is too thick to change the design or overflow position of the finished product.
The injection pressure is too low to increase.
Insufficient glue injection amount and time increase glue injection amount and time.
Runner overflow is too small. Enlarge the flow passage and overflow.
The glue injection speed is too fast, so slow down the glue injection speed.
Plastics-Plastic containing moisture is thoroughly dried.
The temperature of plastic is very high, and decomposition will reduce the temperature of plastic.
Due to uneven mold temperature, please adjust the mold temperature.
If the cooling time is too long, reduce the cooling time in the mold and use water bath for cooling.
Excessive cooling of the water bath will reduce the water bath time or increase the water bath temperature.
Back pressure is not enough to increase back pressure.
Improper temperature of the glue melting cylinder will reduce the temperature of the nozzle and the front section and increase the temperature of the rear section.
The shrinkage rate of plastic is too great. Use other plastics with less shrinkage.
(13) black stripes
Fault cause treatment method
Plastic overheating
If the plastic temperature is too high, reduce the plastic temperature.
Too fast melting speed will slow down the injection speed.
Overhaul machine for abnormal friction caused by eccentricity between screw and glue melting cylinder.
If the nozzle hole is too small or the temperature is too high, readjust the aperture or temperature.
If the injection volume is too large, replace the smaller injection molding machine.
There is a * angle in the glue melting cylinder, which makes the plastic overheat. Check the contact surface between the nozzle and the glue melting cylinder for cracks or corrosion.
(14) black spot
Fault cause treatment method
The overheated part of the plastic adheres to the inner wall of the glue melting cylinder and is completely blown out. Remove the glue melting cylinder and clean it, reduce the plastic temperature, shorten the heating time and strengthen the plastic drying treatment.
Plastic is mixed with sundries, paper scraps, etc. Check the plastic and shoot it completely in the air.
When injected into the mold, the focus will reduce the pressure and speed of injection, reduce the temperature of plastic, strengthen the vent hole of the mold, close the molding service as appropriate, and change the overflow position.
There is a * angle in the glue melting cylinder, which makes the plastic overheat. Check the contact surface between the nozzle and the glue melting cylinder for cracks or corrosion.
(15) unstable period
Most of the forming shortcomings listed above are related to the stability of the cycle. Proper plasticization of plastics in the furnace or temperature control of molds is the result of heat transfer balance. That is to say, in the whole injection cycle, the plastic in the glue melting cylinder receives the friction heat generated by the rotation of the screw and the heat generated by the electric heating coil. Heat energy is injected into the mold with the plastic, and the heat energy of the mold comes from the constant device of the plastic and the mold, which is lost when the finished product is demoulded, lost in the air or taken away by cooling water. Therefore, if we want to keep the temperature of the glue melting cylinder or mold constant, we must keep the balance of heat transfer in and out. To maintain the balance of heat transfer, it is necessary to maintain a certain stable injection cycle. If the injection cycle time is shorter and shorter, the heat energy in the glue melting cylinder is not enough to melt the plastic, and the heat energy in the mold is more than enough, so the temperature of the mold will continue to rise. On the contrary, it has the opposite result. Therefore, in any injection operation, especially manual operation, it is necessary to control the stable cycle time and try to avoid different speeds. If other conditions remain unchanged, then:
The acceleration of the cycle will cause: insufficient injection, shrinkage and deformation of the finished product, and mold sticking.
The delay of the cycle will cause flash, burr, mold and finished product deformation, plastic overheating and even burning, and the coke left in the mold may cause mold damage. Overheated plastic in the furnace may corrode the furnace, and black spots and black lines may appear in the finished product.