There are many benefits of plastic injection molds, but corrosion can still be a potential issue. While there are ways to minimize corrosion, once it becomes a problem you are faced with either replacing the mold or finding out if the corrosion will transfer from the mold to the parts. Replacing plastic injection molds can be a time consuming and costly process. If nothing else, it can put you behind schedule.
If there is little to no risk of transferring corrosion from the mold to the final product, that will give you time to have a new mold made before you will have to retire the current one.
Metal Molds
First, you have to consider the mold’s material. If it is a metal, it is possible to pass the corrosion on to the final product, particularly if the part is made of the same material. It is most likely the contaminant will appear on the surface of the product as that is the part that was directly exposed to the problem. This will at least make it easy to identify if there is a problem.
Plastic Injection Molds
There is a very small risk (largely because it is theoretically possible) that some of the corrosion will pass on, it is very unlikely with plastic injection molds. If the molded product isn’t made from the same materials as the injection mold, the risk is even lower.
Combination Molds
To give your molds the same properties required by metal molds and the low risk of corrosion of plastic, it is possible to overlay some high-temperature plastics (such as nylon) over the metal mold. The plastic layer acts as a protective barrier between the metal and the product, including protecting the final product from any corrosion that occurs on the metal itself. Using higher temperature plastics allows you to continue to meet other specifications during the process, such as minimum temperature or resin requirements.
The plastic also helps to protect the metal mold. The constant exposure to heat and degraded resins encourages corrosion. With the additional plastic barrier, the metal is exposed to fewer of the elements that cause corrosion.
Conclusion
The risk of transferring corrosion from a mold to a final product is greater with some types of molds than others. With caution and planning, you can significantly minimize the chance that the problem will be passed to your final products.
Topics: Injection Mold Design