Disadvantages of injection molded parts

1 Disadvantage: The so-called disadvantages of injection molded parts refer to the failure of the injection molded parts to meet the original design, use and other quality requirements of the injection molded parts during the injection molding process. The description of shortcomings may include a possible cause.

For example, under-injection, i.e. incomplete injection, may be described as insufficient filling pressure of the mold or insufficient plastic to fill the mold. It is useful to try to describe it in the simplest terms without involving any possible causes. With this method, we will not have any preconceptions when we look for the cause of the shortcoming in the next step.



2 disadvantages: finding the cause can be a long process because he needs to consider the plastic, the injection molding machine, the processing of the mold. The following are suggested guidelines to use.

a). Plastic: Check the grade or type, check for impurities, and verify that it meets the manufacturer's specifications. If this drawback is evident in several batches of plastic from the same manufacturer or the same plastic from another supplier, it means there is no problem with the plastic. Observe the effect of the reused material, paying special attention to its different processing characteristics from the new material of the same type.

b). Injection molding machine: Check all functions of the injection molding machine and consider any factors that may affect pressure, temperature, ratio, and time. If the shortcomings appear intermittently, this usually suggests an error in the operation of the injection molding machine, such as temperature fluctuations caused by a bad thermocouple. If the shortcomings appear in the same location in a single-cavity mold, this suggests the cause of the problem is in the injection cylinder device (e.g., reflux valve) or in the control adjustment of the injection molding machine.

c). Mold: Make sure that the mold is properly installed and at the correct temperature and that all parts are running smoothly. If the shortcomings are always in the same cavity or cavities of a multi-cavity mold, then the shortcomings are usually in the feed system (i.e. the runners or gates of these cavities).

d). Process: Check that the pressure, temperature, and time are set according to the plastic supplier's recommendations. If the shortcomings disappear when the mold is used in another injection molding machine, the shortcomings are most likely due to the consistency of the processing conditions used with those produced on the original machine. If the shortcomings disappear when another person operates the machine, the shortcomings may be due to human error. Check the speed, the management of the injection operation, and the dwell time of opening and closing the safety door.

3 Solve the shortcomings of injection molding parts: The appearance of shortcomings of injection molding parts undoubtedly brings quality hazards to injection molding production, to solve these shortcomings can start from the following aspects.

a). Determine the impact of the shortcomings: If the shortcoming makes the injection molded part unusable or unsellable, this shortcoming must be eliminated. If it is only a weak impact, it may not be necessary to eliminate it.

b). Determine where the responsibility lies: This may only be of academic research interest, but if it reappears to the shortcoming, the operator, the plastic, the injection molding machine, the mold, and the process all need to be reviewed.

c). Take action to avoid shortcomings: Failure to take appropriate action can have a devastating effect on the profitability of the project by producing poorly molded parts and, as a result.

d). Take steps to prevent the recurrence of defects: Record all the conditions that were used to confirm the elimination of defects. Indicate any repairs or changes to the mold or injection molding machine, as well as changes in the type and grade of the plastic and the quality of the work. If recycled material is used, the quality of the ratio used must be indicated.

These steps to cope with shortcomings may seem redundant, but no method of finding shortcomings is perfect unless all methods are taken into account. Although the defective products can be recycled and used, it is not economical to manufacture them.

The most important thing in compiling these strategies is to ensure that the semantics of all terms are clear and understood by all who care. To clearly describe the shortcomings of an injection molded part, all possible causes should be examined. Their effects should also be accounted for, and when the causes are identified, the necessary steps should be taken to reduce and prevent their reoccurrence. There are six strategies.

1. name the drawback: Because there are different names for drawbacks, do not change the name when you decide to use it.

2. Describe the drawback: When describing the drawback, you may include a possible cause. For example: "Insufficient injection", that is, incomplete injection, may be described as "insufficient filling pressure of the mold" or "insufficient plastic to fill the mold" Try to use the simplest words without involving any possible causes to describe it, this is a very useful method. With this method, we won't grab any preconceptions when looking for the cause of the shortcoming in the next step.

Finding the cause of the defect: This can be a long process, as it requires consideration of the plastic, the injection molding machine, and the molding process. Here are the suggested guidelines to use.

a). Plastic: Check the grade or type, check for impurities, and confirm that it meets the manufacturer's specifications. If this drawback is similar on several batches of plastic from the same manufacturer or the same plastic from another supplier, this means there is no problem with the plastic.

b). If the defect is intermittent, this usually suggests an error in the operation of the injection molding machine, such as temperature fluctuations caused by a bad temperature sensing line. If the defect appears in the same position in a single-cavity mold, this suggests that the cause of the problem is in the injection cylinder device or the control adjustment of the injection.

c). Mold: Determine if the mold is properly installed and at the correct temperature and that all parts are running smoothly. If the drawback disappears the drawback always appears in the same or several cavities of a multi-cavity mold, then the drawback usually appears in the feed system, (i.e. the runners or gates serving these cavities).

d). Process: Check that the pressure, temperature, and time are set according to the plastic supplier's recommendations. If the shortcomings disappear when the mold is used in another injection molding machine, the shortcomings are most likely due to problems with the consistency of the processing conditions used and produced on the original machine. If the defect disappears when another person operates the machine, the defect may be due to human error. Check the speed, the management of injection action, and the dwell time of opening and closing the safety door.

4. Determine the impact of the shortcoming. If the shortcoming makes the injection molded part unusable or unsellable, this shortcoming must be eliminated.

5. Determine where the responsibility lies, this may only be an academic research interest, but if the shortcoming reappears, the operator and also the raw material, injection molding machine, mold, and processing process should be reviewed.

6. Take action to avoid the shortcomings. Failure to take appropriate action can produce inferior injection molded parts and the resulting impact on the profitability of the project.

In each example of injection molding shortcomings, the shortcomings of the injection molded parts are usually caused by the following factors: the operation of the injection molding machine, the function of the mold or plastic processing performance, etc., the problem or shortcoming is usually more than one cause. Suggested remedies are provided for each of the following shortcomings under the headings of the injection molding machine, mold, and plastic.