(16). Check or replace the stop ring.
Dimensional differences in injection molded parts
1. Characteristics of injection molded part defects
The variation of weight dimensions during the injection molding process exceeds the production capacity of the mold, injection molding machine, and plastic combination.
2. Possible causes of the problem
(1). Uneven plastic input into the injection cylinder.
(2). Temperature or fluctuation range of injection cylinder is too large.
(3). Injection molding machine capacity is too small.
(4). Unstable injection pressure.
(5). Unstable screw reset.
(6). Variation in operating time, inconsistent solution viscosity.
(7). Unstable injection speed (flow control).
(8). Use of plastic varieties that are not suitable for the mold.
(9). Consider the effect of mold temperature, injection pressure, speed, time and holding pressure on the product.
3. Remedies
(1). Check that there is sufficient cooling water flowing through the hopper throat to maintain the correct temperature.
(2). Check for poor quality or loose thermocouples.
(3). Check that the thermocouple used with the temperature controller is of the correct type.
(4). Check the injection volume and plasticizing capacity of the injection molding machine and compare it with the actual injection volume and the amount of plastic injected per hour.
(5). Check that there is a steady flow of molten hot material in every operation.
(6). Check the backflow preventer valve for leakage and replace it if necessary.
(7). Check for incorrect feed settings.
(8). Ensure that the screw's return position is stable,not more than 0.4mm change in each operation.
(9). Check for inconsistencies in operating time.
(10). Use back pressure.
(11). Check for proper hydraulic system operation and high or low oil temperature (25 to 60°C).
(12). Select the right type of plastic for the mold (mainly from shrinkage and mechanical strength considerations).
(13). Re-adjust the whole production process.
Shrink marks
1. Characteristics of injection molded part defects
Usually associated with surface marks, and is formed when the plastic shrinks away from the mold surface.
2. Possible causes of the problem
(1). Melt temperature is either too high or too low.
(2). Insufficient plastic in the mold cavity.
(3). Overheating of the surfaces in contact with the plastic during the cooling phase.
(4). Irrational flow channel, too small gate section.
(5). Whether the mold temperature is compatible with the characteristics of the plastic.
(6). The product structure is not reasonable.
(7). The cooling effect is not good, the product continues to shrink after demolding.
3.Remedy
(1). Adjust the temperature of the injection cylinder.
(2). Adjust the screw speed to get the correct screw surface speed.
(3). Increase injection volume.
(4). Ensure that the correct bedding material is used, increase screw forward time:increase injection pressure:increase injection speed.
(5). Check that the stopcock is correctly installed, as abnormal operation can lead to pressure loss.
(6). Reduce the surface temperature of the mold.
(7). Correct the runner to avoid excessive pressure loss: Enlarge the cross-section according to the actual need.
(8). Control the mold temperature according to the characteristics of the plastic used and the structure of the product.
(9). Improvement of the product structure where possible.
(10). Try to allow sufficient cooling of the product.
