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Incomplete filling 1. Characteristics of injection molding defects: The injection molding process is incomplete, as the mold cavity is not filled with plastic or certain details are missing in the molding process. 2. Possible reasons for the problem: (1) Insufficient injection speed. (2) Plastic shortage. (3). No screw shimming was left at the end of the screw’s stroke. (4) Variation in runtime. (5) The temperature of the injection cylinder is too low. (6) Insufficient injection pressure. (7) The nozzle section is sealed. (8) The heater outside the nozzle or feeding cylinder cannot operate. (9) The injection time is too short. (10). The plastic is attached to the throat wall of the hopper. (11). The injection molding machine has too low capacity (i.e., injection weight or plasticizing capacity). (12). The mold temperature is too low. (13). Rust preventive oil that has not been thoroughly cleaned from the mold. (13). The retaining ring is damaged, and there is backflow of molten material. 3. Remedies (1). Increase the injection speed. (2). Check the amount of plastic in the hopper. (3). Check whether the injection stroke is set correctly; make changes if necessary. (4). Check whether the check valve is worn or cracked. (5). Check whether the operation is stable. (6). Increase the glue melting temperature. (7). Increase back pressure. (8). Increase the injection speed. (9). Check the nozzle orifice for any foreign objects or unplasticized plastic. (10). Check the outer layer of all heaters using an ammeter to verify that the energy output is correct. (11). Increase the time for the screw to move forward. (12) Increase the cooling capacity in the throat area of the feed hopper, or reduce the temperature in the rear area of the injection cylinder. (13) Use a larger injection molding machine. (14). Appropriately increase the mold temperature. (15). Clean the rust inhibitor from inside the mold. (16). Inspect or replace the retaining ring. Variations in the dimensions of injection-molded parts 1. Characteristics of defects in injection-molded parts: Changes in weight and dimensions during the injection molding process exceed the manufacturing capabilities of the mold, the injection molding machine, and the plastic material used. 2. Possible reasons for problems: (1) Uneven distribution of plastic in the feeding cylinder. (2) The temperature of the injection cylinder or the range of fluctuations is too large. (3) The injection molding machine has too low capacity. (4) Unstable injection pressure. (5) The screw reset is unstable. (6) Changes in operating time, inconsistent solution viscosity. (7) The injection speed (flow control) is unstable. (8). An unsuitable type of plastic was used for the mold. (9) Consider the effects of mold temperature, injection pressure, speed, time, and holding pressure on the product. 3. Remedial measures (1). Check that there is sufficient cooling water flowing through the hopper throat to maintain the correct temperature. (2). Check for defective or loose thermocouples. (3). Check whether 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 then compare them with the actual injection volume and the amount of plastic injected per hour. (5). Check whether there is a stable amount of molten material available during each operation. (6). Check whether the backflow preventer is leaking; replace it if necessary. (7). Check for incorrect feed settings. (8) Ensure that the screw returns to its position stably after each operation, with a variation of no more than 0.4 mm. (9). Check for inconsistencies in operating time. (10). Use back pressure. (11). Check whether the hydraulic system is operating properly, and whether the oil temperature is too high or too low (25–60°C). (12). Select the appropriate plastic type for the mold (primarily considering shrinkage rate and mechanical strength). (13). Readjust the entire production process. Shrink marks: 1. A characteristic of defects in injection-molded parts; they are usually related to surface marks (see the “Holes” section) and result from the plastic shrinking and separating from the mold surface. 2. Possible reasons for the problem: (1) The melting temperature is either too high or too low. (2) Insufficient plastic in the mold cavity. (3) The surface in contact with the plastic overheats during the cooling phase. (4) The flow path is unreasonable and the gate cross-section is too small. (5) Is the mold temperature suitable for the properties of the plastic? (6) Unreasonable product structure (excessive reinforcement at the edges, excessive thickness, and obvious unevenness in thickness). (7) The cooling effect is poor, causing the product to continue shrinking after demolding. 3. Remedial measures (1). Adjust the temperature of the feeding cylinder. (2). Adjust the screw speed to obtain the correct screw surface speed. (3) Increase the injection volume. (4). Ensure the use of correct padding ； Increase the time for the screw to move forward ； Increase injection pressure ； Increase the injection speed. (5). Check whether the check valve is installed correctly, as abnormal operation can lead to pressure loss. (6). Reduce the surface temperature of the mold. (7). Adjust the flow channel to avoid excessive pressure loss ； Increase the cross-sectional size as appropriate based on actual needs. (8). Appropriately control the mold temperature based on the properties of the plastic used and the product structure. (9). Improve the product structure where possible. (10). Ensure that the product has sufficient cooling. Stain marks and injection marks 1. Characteristics of defects in injection-molded parts are usually related to the gate area: the surface appears dull, and stripes may sometimes be visible as well. 2. Possible reasons for the problem: (1) The melting temperature is too high. (2) The mold filling speed is too fast. (3) The temperature is too high. (4). Related to plastic properties. (5). There is cold material at the nozzle outlet. 3. Remedial measures (1). Reduce the temperature in the first two zones of the feeding cylinder. (2). Reduce the injection speed. (3). Reduce injection pressure. (4). Reduce the mold temperature. (5) Most parts produced using PE exhibit flow marks, and the position of the feed inlet can be adjusted according to the application requirements. (6). Try to avoid the formation of cold material (control the nozzle temperature properly). Mold flow adhesion 1. Characteristics of injection molding defects: The mold flow is trapped by the sprue bushing. 2. Possible reasons for the problem: (1) The injection sleeve is not aligned with the nozzle. (2) Excessive plastic packing inside the injection sleeve. (3) The nozzle temperature is too low. (4) The plastic has not fully solidified inside the injection nozzle, especially in nozzles with a larger diameter. (5) The arc surface of the injection sleeve does not match properly with the arc surface of the nozzle, resulting in a flow channel that resembles a ‘mushroom’. (6). The flow channel does not have sufficient pull-out slope. 3. Remedial measures (1). Realign the nozzle and sprue bushing. (2). Reduce injection pressure. (3). Reduce the time for the screw to move forward. (4) Increase the nozzle temperature or use a separate temperature controller to heat the nozzle. (5). Increase the cooling time, but a better approach is to use a sprue sleeve with a smaller sprue in place of the original one. (6). Adjust the mating surface between the injection port sleeve and the nozzle. (7) Appropriately increase the pull-out slope of the flow channel. Holes 1. Characteristics of defects in injection-molded parts: They can be easily seen in the \"air pockets\" of transparent injection-molded parts, but they can also appear in opaque plastics. This is related to thickness, and it is often caused by the plastic shrinking away from the center of the injection-molded part. 2. Possible reasons for the problem: (1) The mold was not fully filled. (2) Abnormal operation of the stop valve. (3) The plastic is not thoroughly dried. (4) The pre-shaping or injection speed is too fast. (5). Certain special materials are produced using special equipment. 3. Remedial measures (1). Increase the feed rate. (2). Increase the injection pressure. (3). Increase the time for the screw to move forward. (4). Lower the melting temperature. (5) Reduce or increase the injection speed. (For example, an increase of 45% in speed is required for amorphous plastics.) (6). Check whether the check valve is cracked or not functioning. (7). The drying conditions should be adjusted according to the properties of the plastic to ensure it is thoroughly dried. (8) Appropriately reduce the screw speed and increase the back pressure, or reduce the injection speed. Bending of injection-molded parts 1. Characteristics of defects in injection-molded parts: The shape of the injection-molded part is similar to that of the mold cavity, but it is a distorted version of that cavity shape. 2. Possible reasons for the problem: (1) Warping occurs due to excessive internal stress in the injection-molded part. (2). The mold filling speed is slow. (3) Insufficient plastic in the mold cavity. (4) The plastic temperature is too low or inconsistent. (5). The injection-molded parts are too hot when ejected. (6) Insufficient cooling or inconsistent temperatures of the moving and fixed molds. (7) The structure of the injection-molded part is unreasonable (e.g., the reinforcement ribs are concentrated on one side but are far apart from each other). 3. Remedies (1). Reduce injection pressure. (2). Reduce the time for the screw to move forward. (3) Increase cycle time (especially cooling time). Immediately after ejection from the mold (especially for thicker injection-molded parts), they are immersed in warm water (38°C) to allow the parts to cool down slowly. (4). Increase the injection speed. (5). Increase the plastic temperature. (6) Use cooling equipment. (7) Appropriately increase the cooling time or improve the cooling conditions to ensure consistency in the mold temperature of the moving and fixed molds as much as possible. (8). As permitted by the actual circumstances