When it comes to injection molding, resin and material selection would perhaps be one of the most crucial steps of them all. The molding process itself may be seamless. But without the right material to use in the process, the end product would still be less than suitable.
The problem is, there are a huge number of resin grades to choose from. Pick the wrong kind among these choices, and the results can easily turn into your worst nightmare.
What are the things that you have to consider to make sure you make the right choice?
These are the most important factors you have to think about when going through resin selection:
- Melt flow
- Fillers like minerals and glass and how they affect performance
- Surface requirements
- Tensile strength, elongation and modulus
- Price, availability, moldability and colorability
- Regulations to comply with (ISO, FDA, RoHS, etc.)
- Global compliance requirements (EU, NAFTA, etc.)
Remember that the price you are projecting for the part you are making would depend on the resin’s cost.
This is one of the biggest considerations that you would have to make especially if you are in no position to tweak the price of the part that easily.
Some resins are also harder to work with, so it is imperative that you check how long the entire cycle takes. The cycle time will dictate how well the resin will be processed – take too long or too short a time, and the end product will be inferior in quality.
Each kind of resin has different properties that can be detrimental to some parts, but advantageous to others. It is because of this fact that you have to balance the material well.
Check on all the required specifications beforehand and make sure you come up with the right mix that will give the most optimum results. Some cases may call for a single resin type, while others may call for more. Know your own parts well to make sure you get exactly what you need.
Do not rely solely on computer modeling.
One crucial mistake that a lot of people make is relying on CAE or CAD to make the decisions for them.
These programs do not drive material selection, they only assume that the resin you pick is sufficient for your needs. At the end of the day, it would still be your choices that would decide whether the materials would work or not.