1?Mist stripes
Reason:
Because there are some unmeltable substance layers (possibly water and gas) on the mold surface separated by plastic parts, or the plastic has difficulty in entering, the original mold surface cannot be completely copied.
Improvement method:
A) plastics
Check the MFI value of plastics. Check the formula of plastic. Measure the humidity of plastic.
B) mold
Whether the cooling pipe leaks or not, and the surface of the mold is poorly polished.
C) injection molding machine conditions
Too low mold temperature and too much release agent increase the drying degree of plastic.
2. Glass fiber stripes.
Reason:
Due to the influence of the length of glass fiber, the relationship between the direction and orientation of the melt before flowing, the change of the flow speed and cooling speed, and the poor arrangement of glass and iron, some of which are upright and some are inclined, glass floating surface (uneven distribution of glass fiber) appears, which will not only affect the appearance, but also reduce the engineering structure of injection molded parts.
Improvement method:
A) plastics
Replace the short glass fiber material? Replace glass bead material
B) mold
. Change the value of the entrance.
C) injection molding machine conditions
Improve injection speed and mold temperature.
Increase the melt temperature and prolong the holding time.
Increase holding pressure
Check whether the nozzle temperature is enough.
3. Stomach effect
Reason:
This situation is caused by poor air discharge in the mold, which may be caused by design, material selection or
Due to poor injection molding conditions.
Improvement method:
A) mold
Check whether the exhaust passage is unblocked, increase the exhaust passage and change the inlet position.
B) injection molding machine conditions
Reduce the injection speed and clamping pressure.
Reduce the injection temperature
4. Silver marks
Reason:
This situation is due to a large amount of water vapor in the mold, or a large amount of vaporized water in the hot melt plastic in the injection barrel, or gas/water generated by chemical reaction of additives, which are injected into the cavity together during the injection molding process and radiated under pressure to form a silver line pattern.
Improvement method:
A) plastics
Improper storage of plastics
B) mold
Whether the cooling pipe leaks. Avoid overly sharp designs.
Reduce the carving depth
C) injection molding machine conditions
Increase the drying temperature and time.
Increase the back pressure and reduce the back rope.
Reduce the injection speed.
Check the sealing degree of radiation value. Check/replace additives, such as pigments.
5. Weld marks
Reason:
Injection molding parts encounter poor mold clamping during the inflow, so there will be a bonding line, and another similar situation (MeldLine) will occur during the flow. The original difficulties caused by the two are the same, whether it is poor design of plastic parts or poor injection conditions, the most important thing is that the peak value of confluence flow = or >; Temperature drop 10 degrees.
Improvement method:
A) plastics
. Switch to a higher traffic level.
B) mold
Avoid sudden change of design thickness. The gate should not be set in a thin position. Check whether the exhaust passage is blocked.
Increase the surface treatment of the mold. Sliding door (the purpose is to move the line)
C) injection molding machine conditions
Improve the mold temperature and injection speed.
Improve melting temperature and holding pressure.
6. Water wave effect
Reason:
Due to poor cooling conditions, too low injection speed or too low melt temperature, water ripples will appear in injection parts. In addition, the plastic will cool quickly when it enters, so it cannot move smoothly and press the plastic on the mold wall. However, the plastic enters radially, and the cooled surface forms water ripples/finger patterns.
Improvement method:
A) plastics
. Switch to a higher traffic level.
B) mold
Increase the gate diameter. Increase the diameter of flow passage
C) injection molding machine conditions
Improve plastic speed, warm plastic pressure (first stage), plastic melting temperature and mold temperature.
Note: Use the mold temperature controller, and remember to add mold insulation board.
7. Black spots
Reason:
Black spots appear in injection molded parts, and the overall reason is impurities. The sources of impurities are also very wide, such as injection molding operation control, mold impurities and wear, injection molding machine barrel impurities and wear, raw material pollution/abrasive pollution and so on.
Improvement method:
A) plastics
Check/replace raw materials. Check/replace abrasive materials. Check/replace additives
B) mold
Check/optimize the die runner dead zone. Check the cleanliness of the mold. Replace worn mold parts. Check/clean the hot nozzle system.
C) injection molding machine conditions
Reduce the melt temperature. Adjust the temperature of the hot nozzle.
Adjust the quantity of remaining materials. Clean the barrel of injection molding machine.
Check the wear of injection molding machine barrel, screw and check valve.
8. Top printing (push-out mark is visible)
Reason:
Ejection and printing of injection molded parts are caused by difficulty in demoulding. There are basically two reasons why demoulding is difficult. One is that the plastic parts are not cured enough when the mold is pushed, and the other is that the mold is not well designed/made.
Improvement method:
A) plastics
Replace additive-grade materials with high demoulding efficiency.
B) mold
Check the alignment/correction rate of cooling pipes, increase cooling pipes, increase the smoothness of the lower mold and increase the inclination of the mold.
Check/add mold exhaust passage.
Optimize the ejection system.
C) injection molding machine conditions
Reduce the holding pressure and holding time.
Optimize the pressure transfer point and reduce the mold temperature.
Optimize the ejection speed.
Increase cooling time
Note: remember to add the corner plate of the mold when using the mold thermostat.
9. Deformation during the period
Demoulding)
Reason:
The deformation of injection molded parts can be caused by several situations, the first one is immediately after demoulding, and the second one is after demoulding for a period of time. The first case is the deformation caused by poor curing conditions/poor mold design, and the other is the deformation caused by poor injection conditions provided during injection molding.
Improvement method:
A) plastics
Replace plastic varieties with higher strength/fiber reinforced materials. Replace additive-grade materials with high demoulding efficiency.
B) mold
Check the smoothness/calibration rate of the cooling pipe. Add cooling pipes. Increase the smoothness of the lower die.
Increase the draft angle of the die, check/increase the exhaust passage of the die, optimize the ejection system and increase the strength of the die.
. Add ribs for molded parts.
Injection molding machine conditions
Reduce the holding pressure and holding time.
Optimize the pressure transfer point and reduce the mold temperature.
Optimize the ejection speed.
Increase cooling time
Note: The other is "deformation caused by excessive shrinkage". It is necessary to increase the warm plastic pressure and injection time.
10. Short file
Reason:
The phenomenon of insufficient filling of injection molding parts may be caused by two environments, one is caused by poor injection operation factors, and the other is caused by poor design of injection molding parts. Most of the defects caused by injection molding factors are due to the influence of temperature drop and excessive pressure drop from gate to filling. The defects caused by poor design of injection molding parts are mostly due to poor/too far gate opening, uneven thickness, too thin overall glue position, special design restrictions, poor exhaust and so on.
Improvement method:
A) plastics
. Switch to a higher traffic level.
B) mold
Optimize the gate opening position, optimize the wall thickness of plastic parts, optimize the special design, and check/increase the mold exhaust passage.
. Add auxiliary sub-processes of molded parts.
C) injection molding machine conditions
Increase injection capacity and improve injection melting temperature.
Increase the plastic pressure/holding pressure to improve the injection speed.
Increase injection time, increase mold temperature, reduce mold locking pressure, and use special injection molding machine.
1 1 ~ cold core
Reason:
The phenomenon of cold material flow mark in injection molding parts is caused by the fact that the molten plastic solidifies slightly in advance when passing through the gate or nozzle, and then enters the cavity with the molten plastic in the later stage. The situation is so serious that the bonding line is not deep.
Improvement method:
A) mold
Add/optimize cold material wells
B) injection molding machine conditions
Improve/optimize nozzle temperature, switch to fine-hole nozzle, reduce reverse cable and use closed nozzle system.
12? Bad entrance point (dull scenic spots nearby
Spure)
Reason:
There is a bad phenomenon at the entrance of injection-molded parts, which is actually a case of high shear stress cracking, which mostly appears on submerged gates and high-viscosity plastic parts. The reason is that when the high-viscosity molten plastic passes through the extremely fine opening, it must pass at high speed and high pressure, so there will be overload cracking defects near the entrance.
Improvement method:
A) plastics
Replace plastics with higher fluidity grade. Use additives to improve fluidity.
B) mold
Increase the diameter of the mold gate and the smoothness of the mold runner gate.
. Change gate position
C) injection molding machine conditions
Reduce the injection speed. Adjust the injection speed by stage optimization (S-F).
Improve the melting temperature of injection molding and the mold temperature.
Use a special injection molding machine.
13. Injection
Reason:
The poor injection marks (snake lines) of injection molded parts are due to insufficient plasticization of plastics by injection molding machines, or when the plastics are not completely melted, they enter the cavity together with the molten plastics in the back section through the gate.
Improvement method:
A) mold
Increase the appropriate mold gate diameter and change the gate position.
Add obstacles in front of the gate
B) injection molding machine conditions
Reduce the injection speed. Adjust the injection speed by stage optimization (s-F).
Check/raise the injection melting temperature
Raise the mold temperature. Increase back pressure.
Use a special injection molding machine.
14. Surface spalling
Layer)
Reason:
The bad phenomenon of surface delamination of injection molded parts is due to the incomplete fusion of plastic formula after injection molding, or the rejection and splitting of plastic formula (including additives) after molding.
Improvement method:
A) plastics
Check/replace the plastic mixing formula. Check/replace the mixed formula of plastic additives.
B) injection molding machine conditions
Check the drying conditions of plastics, check/optimize the screw speed, check the plasticization degree of plastics, and reduce the injection speed.
Reduce the melt temperature and increase the mold temperature.
15. Entrained air
Reason:
The bad phenomenon of floating bubbles in injection-molded parts is due to the fact that the injection-molded parts are mixed with a large amount of air during the melting process, or a large amount of air is pumped in when the cable-reversing function is used excessively, and injected into the mold cavity during the injection molding process, and the plastic formula is transparent, so it is easier to see this phenomenon.
Improvement method:
A) plastics
Check whether the plastic particles are too large.
B) injection molding machine conditions
Reduce cable reversal function and increase back pressure.
Reduce the speed of the screw. Check whether the melting system is operating normally.
16. Charred stripes
Reason:
There are many reasons for the bad phenomenon of overheating and discoloration of injection molded parts. If the polymer is overheated, the molecular chain will split, and it will be thermally degraded or burned. At this time, visible overheating discoloration will occur. Sometimes I only see some yellow changes.
It also shows that slight thermal degradation has occurred, which is not only caused by the combustion of the polymer, but also caused by the sleeve agent in the polymer. When dealing with combustion defects, we must know where they appear. If the melt does not change color during cleaning, it means that the melt will burn after leaving the nozzle. We should check the main diameter, runner, inlet water level and mold design.
Or calibration, injection, speed, pressure, etc. If coffee stripes or color changes are found in the cleaning process, it is proved that the degradation occurred in the barrel and burner. If you see coffee stripes and silver stripes at the same time, you should wonder if there is something wrong with the water. If the position is fixed and the configuration of finished parts is the same, the combustion starts from the end of the inspection valve or burner. If the color change is dispersed, degradation will occur in the barrel and screw (on the inlet side).
Improvement method:
A) plastics
Check and replace the mixed formula of plastic additives. Reduce the proportion of abrasive materials.
B) mold
Optimize the sharp angle of plastic parts, increase the diameter of runner/gate, optimize the wall thickness of plastic parts, and check the exhaust passage.
Check the hot runner system.
C) injection molding machine conditions
Lower goochen, lower injection melting temperature, lower screw speed and lower back pressure.
Gradually optimize the injection speed (S-F). Check whether the melting system is operating normally.
Reduce the total period
Check the cleanliness of the drying system. Check whether the injection molding system is normal.
Use compatible injection molding machines.
17. Stress crack
Reason:
The reason for the bad phenomenon of cracks in injection-molded parts is that the plastic of injection-molded parts is subjected to excessive shear stress during the plastic molding process. When aging occurs, the cracking process begins and the plastic is destroyed by shear stress during the plastic molding process. It refers to the injection behavior that the plastic is forced into the cavity with great pressure under the condition of insufficient heating and poor flow, and the parts are excessively elongated. When aging comes, it is easy to break and produce turtle cracks, which is more easy to see in transparent plastic parts.
Improvement method:
A) mold
Increase the diameter of runner/gap and optimize the wall thickness of molded parts.
B) injection molding machine conditions
Optimize the injection pressure in stages. Delayed conversion of holding pressure.
Reduce the holding pressure and injection speed.
Increase the plastic temperature (amorphous material), increase the mold temperature (amorphous material) and increase the cooling time (amorphous material).
Reduce injection temperature (crystalline material), mold temperature (crystalline material) and cooling time (crystalline material)
Use compatible injection molding machines.
18. dent marks
Reason:
There are many reasons for the poor appearance of shrinkage marks of injection molded parts, such as improper selection of plastic characteristics, poor design of plastic parts and poor injection conditions. After analyzing the causes and sources of the above shrinkage marks, the following points are summarized: plastic curing is too slow, effective heat preservation time is insufficient, effective heat preservation time is too low, and heat preservation transmissibility is poor.
Improvement method:
A) plastics
Check the particle condition of plastic, replace the material with low shrinkage grade and add foaming agent.
B) mold
Check the exhaust line of the mold, check the main flow diameter of the mold and the size of the door, and improve the wall thickness of the mold.
Improve the ratio of die wall thickness to rib position thickness, and increase die cooling pipe.
C) injection molding machine conditions
Increase storage capacity. Check the spiral check valve of injection molding machine
. Extend the cooling time. Check/remove accumulated materials at the entrance.
Optimized retention time (+). Optimized retention pressure (+)
Change the mold temperature (-). Change the material temperature (-)
Change injection rate (-), optimize holding time (+), optimize holding pressure (+), and change mold temperature (+).
Change the material temperature (+) and optimize the injection rate (+)
Does the shrinkage mark appear near the gate or in the thick wall position?
} Shrinkage marks are not near the gate or in thin-walled positions?
19. Vacuum bubble
Reason:
The bad phenomenon of vacuum bubbles in injection molded parts is mainly caused by the fact that the plastic of injection molded parts can not be filled with enough density during injection molding. The reasons why plastic parts can't be filled with sufficient density are mostly related to the type of plastic (crystalline/amorphous), premature stop of runner gate from entering plastic or poor design of plastic parts.
Improvement method:
A) plastics
Check the type of plastic (crystalline/amorphous). Replace plastic (PP) with low bubble content.
B) mold
Check, increase the exhaust passage of the mold and shorten the main diameter and flow passage of the mold.
Increase the gate size and reduce the die wall thickness.
Optimize the phase difference ratio between die wall thicknesses.
C) injection molding machine conditions
Increase the total production capacity of Wang Su, optimize the injection margin (Goochen), optimize the injection pressure in stages, and increase the holding pressure.
Improve the injection speed and injection temperature.
Increase the mold temperature and increase the injection time.
Increase cooling time
20. Cloak (Fiash)
Reason:
The poor appearance of injection-molded cloak is mainly caused by too much plastic filling during injection molding. Most of the reasons for the over-filling of plastic parts are related to the grade (MFI) of plastic parts, poor design of plastic parts, mold damage or type of injection molding machine, and the efficiency and adjustment of injection molding machine.
Improvement method:
A) plastics
. Replace materials with lower flow grade.
B) mold
Check the mold for damage. Optimize the phase difference ratio between die wall thicknesses.
. Change gate position
Check/strengthen the mold structure and strength.
C) injection molding machine conditions
Optimize the injection pressure in stages and reduce the injection pressure.
Optimize the position of packing pressure switch to reduce packing pressure.
Reduce the injection speed and holding time.
Reduce the injection temperature, reduce the mold temperature and increase the clamping pressure.
. Replace the model with strong clamping force.
2 1. scratch
Reason:
The bad phenomenon of scratches on injection-molded parts is mainly caused by excessive friction between injection-molded parts and the wall and corners of the mold when demoulding after injection. The reasons for the excessive friction of plastic parts are mostly related to the insufficient demoulding inclination of plastic parts, insufficient structural strength of molds, mold damage, or the efficiency of injection molding machines and the adjustment of injection parameters.
Improvement method:
A) plastics
Replace additive-grade materials with high demoulding efficiency.
B) mold
Check the damage of the clamping line of the upper die to increase the smoothness of the upper die.
Increase the draft angle of the die.
Check/strengthen the structure and strength of the mold. Check/increase the exhaust passage of the upper die. Check the smoothness/calibration rate of the cooling pipe.
Increase the cooling pipe of the upper die.
C) injection molding machine conditions
Optimize the position of packing pressure switch to reduce packing pressure.
Reduce the injection speed and holding time.
Lower the injection temperature, lower the mold temperature and lower the mold opening speed.
The above information was collected by Shanghai Kuixing Injection Processing Factory.