Injection molding is one of the most reliable ways of making plastic molded parts. But sometimes, the finished product might have a dull luster, contrary to your expectations. Fret not – because it is a pervasive issue and is generally easy to fix.
The luster of the plastic component mostly depends on the raw material and the quality of the mold. The operation of the machine might also be responsible for the dull luster. I’ll explain everything you need to know about this issue and how to solve it in the following section.
Reasons for Dull Luster on Plastic Molded Parts
There are two fundamental reasons why plastic molded parts have a dull luster. One reason is the material used in the manufacturing process, and the other reason is the operational parameters of the injection molding machine.
There are quite a few problems with the material that can cause a dull luster in the plastic molded parts. Poor fluidity of the melted liquid is one of them. The consistency of the melted plastic has a significant impact on the finished product. That’s why good fluidity improves mold design and reduces imperfection. It can also give a glossier sheen to the finished product.
Another cause of dull luster is the excessive ratio of recycled material. A lot of plastic injection molding manufacturers use recycled materials in injection molding. But these materials usually degrade in their quality, so using too much in a batch will visibly affect the plastic molded parts.
Additives are used in injection molding to increase the durability or rigidity of the plastic component. There’s always a golden ratio of additives for any plastic part. Adding too much can increase the rigidity at the cost of brittleness. Mixing the wrong amount of additive can often cause dull luster.
The operation parameters can affect the plastic molded parts just like the base material. Low cooling rates are one of the most common issues contributing to the dull luster of plastic. Uneven cooling across different sections can also cause a drab sheen in certain parts.
High pressure is necessary to ensure an even texture on the plastic molded parts. A slow injection rate from the injection molding machine will cause the plastic to spread badly. That can result in a dull luster in the finished plastic.
The dwell time is how long the melted plastic stays in the pressurized mold before cooling. Every mold design and material requires a different time combination. Setting the time too short may cause a dull luster, amongst other deformities.
Solutions for Dull Luster on Plastic Molded Parts
Now that you already have a clearer idea of what causes the dullness in the plastic molded parts, let’s look at how you can fix it.
1. Raise the Temperature During Molding
If your problem is due to the poor fluidity of the melted liquid, then raising the temperature during the molding process should help. A higher temperature usually results in a more desirable fluidity. Increasing the injection speed and the molding temperature should give you the best result.
2. Clean the Surface of The Mold
Low-quality molds can sometimes cause dullness in the outer layer of the plastic molded parts. However, this could happen even with high-quality molds if the mold is dirty. In that case, thoroughly cleaning the mold or die would solve your issue.
3. Make Sure the Material Is Dry Before Molding
Moisture can cause many imperfections in injection molding. That is why the raw plastic needs to go through a drying process. You are suggested to run your plastic through the dryer before starting the molding process. If all goes according to the plan, you should be able to get rid of your dull luster.
However, some materials do not require active drying, like polyethylene and other non-polar substances that do not mix with water. Almost every other material has some level of polarity, and they all require drying to ensure a glossy luster.
Even though dullness is a common issue with injection molding, experienced plastic injection molding manufacturers can efficiently resolve this issue. They have competent employees and organized facilities where experts handle everything. One such manufacturer would be Abery, and they always provide the best possible plastic molded parts.