Hey there! As a supplier of metal insert moulds, I've encountered a fair share of issues in the manufacturing process. One of the most common problems that we often get feedback on is the appearance of burn marks in the products made by our metal insert moulds. In this blog, I'll be sharing what I've learned about the causes of these burn marks and how we can solve them.
What are Burn Marks in Metal Insert Mould Products?
First off, let's talk about what burn marks are. Burn marks in products made by metal insert moulds are dark, discolored areas on the surface of the finished product. They can range from light discoloration to severe charring, and they're not just a cosmetic issue. Burn marks can weaken the product's structure, affect its functionality, and reduce its overall quality.
Causes of Burn Marks
1. High Melt Temperature
One of the primary causes of burn marks is a high melt temperature. When the plastic material is heated to an excessively high temperature, it can start to break down and degrade. This degradation can lead to the formation of burn marks on the product's surface. The high temperature can be due to improper setting of the heating elements in the injection molding machine or a malfunction in the temperature control system.
For example, if we're manufacturing an EV Busbar Connector, the plastic used needs to be heated to a specific temperature range. If the temperature goes beyond this range, the plastic can burn, leaving marks on the connector.
2. High Injection Speed
Another common cause is a high injection speed. When the plastic is injected into the mould at a very high speed, it can cause turbulence and friction. This friction generates heat, which can be enough to burn the plastic. High injection speed can also lead to air traps in the mould, and when these trapped air pockets are compressed, they can cause localised high temperatures, resulting in burn marks.
Let's say we're making a Drone Busbar Connector. If the injection speed is too high, the plastic might not flow smoothly into the mould, causing burn marks on the connector's surface.
3. Poor Venting
Poor venting in the mould is also a major culprit. During the injection molding process, air needs to escape from the mould cavity. If the mould is not properly vented, the air can get trapped, creating high-pressure areas. These high-pressure areas can cause the plastic to burn as it tries to fill the cavity.
For instance, when manufacturing a Pillow Assy, if the venting channels in the mould are blocked or too small, air won't be able to escape, leading to burn marks on the pillow assy.
4. Contaminated Plastic
Contaminated plastic can also cause burn marks. If the plastic material contains impurities or foreign particles, these can act as hot spots during the heating process. The impurities can burn at a lower temperature than the plastic itself, leaving burn marks on the product.
How to Solve the Burn Mark Problem
1. Adjust the Melt Temperature
The first step in solving the burn mark problem is to adjust the melt temperature. We need to make sure that the plastic is heated to the correct temperature range. This can be done by carefully setting the temperature controls on the injection molding machine. Regular calibration of the temperature sensors is also essential to ensure accurate temperature readings.
For example, if we're using a specific type of plastic for an EV busbar connector, we need to refer to the plastic manufacturer's guidelines for the recommended temperature range. By adjusting the melt temperature within this range, we can prevent the plastic from burning.
2. Optimize the Injection Speed
Optimizing the injection speed is another crucial step. We need to find the right balance between a fast enough speed to fill the mould quickly and a slow enough speed to avoid turbulence and friction. This can be achieved through trial and error, where we test different injection speeds and observe the results.
For the drone busbar connector, we can start with a relatively low injection speed and gradually increase it until we find the optimal speed that produces a high-quality product without burn marks.
3. Improve Venting
Improving venting in the mould is also necessary. We can do this by adding more venting channels or increasing the size of the existing ones. The venting channels should be located in areas where air is likely to get trapped, such as the corners and edges of the mould.
When making a pillow assy, we can analyze the mould design and identify the areas where air is not escaping properly. Then, we can modify the mould to improve venting and prevent burn marks.
4. Use Clean Plastic
Using clean plastic is essential to avoid burn marks caused by contamination. We should source our plastic from reliable suppliers and store it in a clean environment. Before using the plastic, we can also perform quality checks to ensure that it is free from impurities.
Preventive Measures
In addition to solving the burn mark problem, we can also take preventive measures to avoid it in the first place. Regular maintenance of the injection molding machine is crucial. This includes cleaning the heating elements, checking the temperature control system, and lubricating the moving parts.
We should also conduct regular inspections of the moulds. Any signs of wear and tear, such as damaged venting channels or rough surfaces, should be addressed immediately. By keeping the moulds in good condition, we can prevent burn marks from occurring.
Conclusion
Burn marks in products made by metal insert moulds can be a frustrating problem, but with the right knowledge and approach, we can solve it. By understanding the causes, such as high melt temperature, high injection speed, poor venting, and contaminated plastic, we can take the necessary steps to prevent and eliminate burn marks.
If you're in the market for high-quality metal insert moulds and want to avoid issues like burn marks, we're here to help. We have a team of experts who can provide you with the best solutions for your manufacturing needs. Whether you're looking for an EV busbar connector, a drone busbar connector, or a pillow assy, we can offer you top-notch metal insert moulds. Contact us for a consultation and let's start a great business relationship!
References
- Plastic Injection Molding Handbook
- Mould Design and Manufacturing Best Practices
