Injection Molding Troubleshooting
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Injection Molding Troubleshooting

When dealing with injection molding issues, the speed and effectiveness of your solutions are often related to the issue’s severity and other possible causes. Although there are many common mistakes in the way troubleshooting works, there are also some key ideas that can help improve your chances of success. In this section, we’ll also look at some common injection mold issues that can be solved using the checklist method.
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Plastic Injection Molding Troubleshooting Tips


When dealing with injection molding issues, the speed and effectiveness of your solutions are often related to the issue’s severity and other possible causes. Although there are many common mistakes in the way troubleshooting works, there are also some key ideas that can help improve your chances of success. In this section, we’ll also look at some common injection mold issues that can be solved using the checklist method.


Advanced Troubleshooting Techniques

Understanding the concepts below can help improve the efficiency of your Injection Molding Troubleshooting. It can also help minimize the time needed to fix issues and improve the accuracy of your work.


Before tackling a particular issue, it's important to thoroughly examine the entire process and the part. This step will help identify the cause of the issue and determine if there are other possible causes. Having more problems can help identify issues that are causing problems in the process. It can also help you eliminate those that are already causing issues.


Creating and reviewing documentation is an important step in any process. It can help avoid many issues before they even occur. This should be done incrementally to provide the most information possible for the future. Conversely, documentation should always be consulted when starting a new process.


Aside from the usual hardware inputs, it is also important to include machine outputs as well. This ensures that all necessary details are documented correctly. This helps you to visualize the various steps in the process and how they affect the end product.  Outputs that especially merit documentation are second-stage packing time, screw recovery time, cooling time and finished part weight.


When trying to identify possible sources of problems, consider the effects of different processes on the same issue. Also, consider the effects of certain steps on others. Although it may seem simple, a good rule of thumb is to remember that nothing happens in a vacuum. Generally, changing one aspect of the process can affect many other aspects. It is in this area that fine-tuning and documenting become especially important.


Troubleshooting Common Injection Molding Issues

In this article, we'll discuss some common injection molding issues that can be easily identified and corrected. Most of the time, these fixes will help identify and fix various issues that occur when using a machine.


Short Molding

Short molding is a common issue that occurs when a mold cavity does not get filled before an ejection or cooling process. This issue can usually be caused by either an issue with the mold or a lack of pressure.

(1) not enough material was present for injection into the mold.

(2) the material solidified (either completely or at a gate) too quickly to allow the cavity to fill completely.

To remedy short molding, look into:

● Faster injection speed

● A larger capacity machine

● Higher injection pressure

● Higher mold and/or material temperature (to slow down cooling)


Sink and Void Issues

Voids and sinks are areas where the molded material shrunk and cooled unevenly relative to its surrounding material. They can also form an internal void or a gap in a part. For sink and void issues, the issue may be helped by:

● Increasing cooling time

● Increasing injection pressure

● Increasing hold time

● For design issues, introducing ribs instead of thick sections may also help for more uniform cooling。


Delamination

Delamination is when the plastic resin did not bond or set properly, and the surface areas were peeled in layers. It presents a major threat to the integrity of the part and can be discarded almost immediately. Delamination is a type of decay that usually occurs due to materials or mold that have been contaminated.

Solutions to delamination can include:

● Drying the material

● Raising the material or mold temperature

● Purging and cleaning mold and tool


Flashing

Flash is a process when excess material is present in a part. It is not considered a cause for part rejection but it can create additional production costs and slow down the process. Excess material can be reused, but only at a certain degree, which means that flash will increase their costs.  Flashing typically occurs due to misaligned mold halves, or due to the mold opening under pressure. To remedy flashing, try:

● Increasing clamping pressure

● Re-aligning, flattening and/or cleaning mold faces

● Increasing fill time (thus, decreasing the fill rate)


Weak Weld Line Connections

Weld lines are weak signals that indicate that a material did not properly bond to a given mold. These lines can also prevent a material from flowing smoothly across a mold. Poor weld lines can also occur as a result of contaminants in the mat. Potential remedies for weak weld lines are:

● Purging and cleaning mold and tool

● Decreasing mold lubricant

● Increasing material and/or mold temperature

● Further homogenizing any pigments used in the material through greater dispersion

● Aligning weld lines with vents

● Increasing injection speed


At TEAM MFG, we take the time to thoroughly inspect and resolve any issues that may occur during the molding process. For more information about our molding services, contact us at enquiry@teamrapidtooling.com today.


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