I believe that many people have encountered many problems in the injection molding process, such as dissatisfaction, flashing, surface depression, dimensional changes and other defects. These defects may be caused by mold design, precision of the injection molding machine, etc., or may be caused by the operator not having proper process conditions. The factors are complex and varied, but they affect each other. Let's take a look at the 18 problems encountered in plastic processing:
Bubble
â—† Possible reasons related to process and equipment
1. The cylinder temperature is too high
2. Injection pressure and back pressure are too low.
3. Insufficient pressure (time)
4. The rate of fire is too high
5. Insufficient filling material
6. Poor temperature setting in each zone of the material pipe
â—† Possible reasons related to the mold
1. The wall thickness (relief) is too high
2. Poor gate or runner
3. Poor gate type or position selection
4. The gate solidifies too early
5. The tendons are too thick
6. The mold temperature is too low
7. Poor exhaust
â—† Possible reasons related to materials
1. Material fluidity and shrinkage are not required
2. Excessive amount of return material
3. The raw materials are not fully dried
2. Weld seam
â—† Possible reasons related to process and equipment
1. The injection pressure (speed) is too low or too high
2. The back pressure setting is not suitable
3. The temperature of the tube is too low
â—† Possible reasons related to the mold
1. The mold temperature is too low
2. The gate or runner is too small
3. Poor exhaust
4. The runner is too long
â—† Possible reasons related to materials
1. Poor liquidity
2. Too much lubricant
3. The presence of foreign matter in the material
3. Spray marks
â—† Possible reasons related to process and equipment
1. The rate of fire is too fast
2. The melt temperature is too high or too low
3. The nozzle diameter is too small
The tube temperature is too high or too low
â—† Possible reasons related to the mold
1. improper gate type or location
2. improper gate shape
3. The mold temperature is too low
4. The gate solidifies too early
â—† Possible reasons related to materials
Improper material flow
4. Size difference
â—† Possible reasons related to process and equipment
1. The feed is unstable.
2. The screw speed is unstable.
3. The temperature is out of control and the back pressure is unstable.
4. The screw reset is unstable and there is more than 0.4mm change.
5. The molding cycle is unstable.
â—† Possible reasons related to the mold
1. Insufficient strength and rigidity of the mold.
2. The use of a poor multi-cavity form.
3. The setting of the ejection system, the pouring system, and the cooling system is unreasonable.
â—† Possible reasons related to materials
1. The material is poorly dried and the particles are not uniform.
2. The shrinkage rate of raw materials is too large.
3. Material viscosity has batch differences
5. Whitening
â—† Possible reasons related to process and equipment
1. Filling too fast
2. The melt temperature is improper
3. The injection pressure is too high
4. The nozzle diameter is too small
5. The nozzle temperature is too low
â—† Possible reasons related to the mold
1. improper gate type or location
2. The gate diameter is too small
3. The mold temperature is too low
4. Insufficient cold wells
5. Uneven thickness at the bend
6. The top force is uneven or too large
â—† Possible reasons related to materials
1. Material stress relaxation is poor
2. Low yield strength of the material
6. Silver pattern
â—† Possible reasons related to process and equipment
1. The cylinder temperature is too high
2. The screw speed is too fast
3. The nozzle is too small, too hot or blocked
4. The amount of shot glue exceeds 80% of the machine capacity
5. There is gas or water vapor in the melt
6. Clearing is not complete
â—† Possible reasons related to the mold
1. The gate is too small
2. Gate or runner obstruction
3. The mold surface has micro cracks
â—† Possible reasons related to materials
1. The material is not fully dried
2. Material contains foreign matter
3. High temperature decomposition of materials
7. Surface peeling
â—† Possible reasons related to process and equipment
1. The cylinder temperature is too low
2. The injection speed is too slow.
3. Insufficient pressure (time)
â—† Possible reasons related to the mold
1. The mold temperature is too low
2. Gate or runner bend
3. improper gate type selection
4. Too much release agent
â—† Possible reasons related to materials
1. Poor material drying
2. Return too much
3. Incompatible additives
8. Black bars
â—† Possible reasons related to process and equipment
1. The rate of fire is too fast
2. The melt temperature is too high
3. The injection pressure is too high
4. The nozzle diameter is too small
5. The nozzle temperature is too high
6. High temperature of the tube
7. The molding cycle is too long
8. Carbide in the tube
â—† Possible reasons related to the mold
1. improper gate type or location
2. The gate diameter is too small
â—† Possible reasons related to materials
1. The material has insufficient high temperature stability
2. Material contains foreign matter
9. Color difference
â—†Material problems
1. Poor thermal stability of selected colorants or other additives
2. The selected colorant reacts with the resin or added additives
3. The rheological properties of the raw materials are too low
â—†Processing problems
1. The baking time is too long or the baking temperature is too high
2. Injection temperature or pressure is too high
3. The residence time is too long, causing discoloration
4. The injection molding machine is not clean and contaminated.
â—†The surrounding environment and other influencing factors
1. Raw materials or products should not be stored in direct sunlight.
2. The difference in the type of color difference meter or the accuracy of its color measurement is not enough
3. The effect of product temperature when measuring color difference
10. Insufficient filling
â—† Possible reasons related to process and equipment
1. Insufficient amount of melt glue
2. The barrel temperature is too low
3. Bad back pressure setting
4. Insufficient injection pressure (speed)
5. Injection time is too short
6. Check valve clearance is large
7. The nozzle is blocked
â—† Possible reasons related to the mold
1. The mold temperature is too low
2. improper gate type or location selection
3. Die exhaustion
4. The flow path (gate) of the mold is too small
5. Uneven distribution of mold cavity
â—† Possible reasons related to materials
1. The material itself has poor fluidity
2. Poor material drying
11. Warpage
â—† Possible reasons related to process and equipment
1. Improper pressure or time
2. The melt glue is too long in the material tube
3. Improper molding cycle
4. The barrel temperature is too low
5. Low nozzle temperature
6. Keep pressure and time improper.
â—† Possible reasons related to the mold
1. The mold temperature is too high or too low
2. The gate or sprue is too small
3. improper gate type or location
4. Uneven temperature
5. The ejector area is too small or unevenly distributed
6. Wall thickness deviation is too large
â—† Possible reasons related to materials
Improper mobility
2. Material longitudinal and lateral shrinkage deviations are large
12. Charred
â—† Possible reasons related to process and equipment
1. The rate of fire (shooting pressure) is too high
2. The melt temperature is too high
3. Back pressure is too high
4. The nozzle diameter is too small
5. The nozzle temperature is too high
6. High temperature of the tube
7. Screw speed is too fast
â—† Possible reasons related to the mold
1. improper gate type or location
2. The gate diameter is too small
3. Die exhaust is not good
â—† Possible reasons related to materials
1. The material is not heat resistant enough
2. Too many secondary materials
3. The material is not stable enough at high temperature
13. Poor gloss
â—† Possible reasons related to process and equipment
1. The barrel temperature is too low
2. Insufficient pressure
3. The nozzle temperature is low
4. The melt glue is too long in the material tube
5. Improper molding cycle
â—† Possible reasons related to the mold
1. The mold finish is poor.
2. The gate or runner is too small
3. improper gate type or location
4. Exhaust gas
5. There are foreign objects on the surface of the mold.
â—† Possible reasons related to materials
1. The material is not fully dried
2. Improper flow performance
3 material itself is poor gloss
14. Flash
â—† Possible reasons related to process and equipment
1. The injection pressure (speed) is too high
2. The glue stays in the tube for too long
3. The molding cycle is too long
4. Insufficient clamping force
5. The material temperature is too high
â—† Possible reasons related to the mold
1. Poor contact on the mold surface
2. The mold strength is not enough
3. Poor exhaust
4. The runner is too long
5. The size of the mold parts is not precise
â—† Possible reasons related to materials
1. The liquidity is too good
2. Too much lubricant
15. Sag
â—† Possible reasons related to process and equipment
1. The temperature of the barrel or mold is too high
2. Injection pressure, speed, back pressure is too low, injection time is too short
3. Insufficient pressure (time)
4. The cooling time setting is poor
5. Bad check valve
â—† Possible reasons related to the mold
1. The gate or runner is too small
2. Poor gate location or type selection
3. The gate solidifies too early
4. The tendons are too thick
5. Flow imbalance
â—† Possible reasons related to materials
1. Material fluidity and shrinkage are not required
2. The amount of return material is too large
16 flow marks
â—† Possible reasons related to process and equipment
1. The cylinder temperature is too low
2. Injection pressure is too low
3. Insufficient pressure (time)
4. Improper cycle time
5. The glue stays in the material tube for too long
â—† Possible reasons related to the mold
1. The mold temperature is too low
2. The gate or runner is too small
3. Poor exhaust
â—† Possible reasons related to materials
1. Material fluidity is not required
2. Improper lubricant
3. Too much volatiles
17. Crack
â—† Possible reasons related to process and equipment
1. Overfilling, holding pressure, making residual stress too large
2. The pressure holding time is too long
3. The mold temperature is too low
â—† Possible reasons related to the mold
1. The draft is not enough
2. Poor ejection
3. Excessive release agent
â—† Possible reasons related to materials
Poor drying
2. Too many secondary materials
3. High temperature decomposition of materials
18. Black spots
â—†The cause of bad black spots
1. The injection molding machine is not clean.
2. Injection molding machine temperature setting is too high
3. Injection molding machine nozzle structure is not reasonable
4. The residence time is too long, it is easy to burn, and black spots are generated.
5. The cleaning inside the drying barrel is not clean.
6. Drying bucket blowing (suction) air device, filter pollution
7. The cleaning in the storage tank is not clean.
8. Handling, unpacking, and feeding process are not properly managed, and it is easy to bring impurities such as dust into the surrounding environment.
9. The black spots of the product itself are bad, and should be promptly feedback for investigation.
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