July 14, 2022

Plastic Injection Molding Troubleshooting Guide

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Quick link of the Troubleshooting Guide:

1) Dark brown spots
2) Brittle fracture
3) Bubbles (Or Steelyard balance : stranded gas)
4) Burn marks
5) Plastic injection molding machine of mucosa
6) Grain crack
7) Plastic degradation
8) Injection molded parts deforms
9) Injection molded cloak
10) Injection molded parts does not shrink
11) Surface roughness
12) Silver streak
13) Surface wrinkled skin texture
14) Color distribution
15) Fusion line location decline
16) Insufficient filling
17) Injection molded parts size differences
18) Systolic trace
19) Dirt marks
20) Sprue adhesion
21) Empty hole
22) Curved injection molded parts
23) Spraying trace
24) Surface layer (peeling)

Dark brown spots
Spots and stripes still visible even the molding parts have the correct color.

Troubleshooting Solution Guide
Injection molding machine 1. The last production of degradable plastics materials in the
cylinder, screw, valve adapter maybe curing inside the aggregate hot
runner pipe.
Use cleaning compounds or high molecular weight PMMA material to clean the injection cylinder unit.
2. Plastic material traps in the cylinder device’s dead
area or stagnant area, causing it to stay too long in the high
1. cylinder and screw should be removed and thoroughly clean the surfaces in contact with the polymer melt.
2. Check whether the nozzle is located correctly in injection cylinder.
3. Use open or direct type nozzle to replace opening and closing nozzle.
4. Check the stop valve for cracks, etc. Change a new device if necessary.
3. Plastic enters the mold cavity too fast causing excessive shear polymer. Reduce the injection speed.
4. Melt temperature is too high. 1. Reduce fire zone melt temperature in a feed tank. Check the flow rate if its sufficient for cooling the hopper locking device, adjust the flow rate if necessary.
2. Reduce the cycle time to increase plastic that is passed by the cylinder device.
5. Using the incorrect screw surface speed and back pressure, causing the molten plastic over cut. Use minimum back pressure and the correct use of the screw surface speed
6. Use a correct type of screw design in the process of plastic. Use a lower rate of a extrusion screw.
Mold 1. Grease or oil occur within the mold. Mold and nozzle should be removed and thoroughly cleaned.
2. Gate is too small. Increase the gate size.
3. Wall injection molded too thin, so that plastic flow is not sufficient to pass through, so it causes no degradation. Check the correctness and consistency of wall thickness, if necessary, will be modified.
4. Hot runner mold produces impurities. The hot runner mold aggregates tube completely remove and clean.
Plastic 1. PVC or other heat-sensitive plastic appear impurities. Check the source of impurities, especially with PVC manufacturing and conveying plastic pipe part.
2. Excessive heating of the back using the previous materials. Strict inspection after the separation of impurities in materials.
3. Due to the lack of room cleaning or plastic dry cause plastic blended with burnt particles. Dry cleaning and reuse of some materials.
4. Poor plastic flow characteristics caused by Insufficient lubrication of plastic. Adda certain amount of external lubricant (such asZeng0. 05%to0. 1% zinc stearate).

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