Very small, high precision plastic molding goes into micromolding for medical devices, according to Aaron Johnson at Accumold (Ankeny, Iowa)
There are three different things to keep in mind with micromolding to keep in mind:
- Micro means the size of the part. It is the most common definition when dealing with micromolding.
- Micro features relates to tiny parts on a larger part. As a whole, the part can be big, but its components can be smaller, or micro features.
- Micro intolerance is how the parts are measured and how close to the needed measurement the part has to be to be considered a good or usable part. When a part is molded, it has to measure within the needed measurement (the tolerance), which could be as small as a thousandth of an inch. Small parts that are simple to make have tolerances that are not as tight and would be considered regular molding.
Micromolding is made from a variety of commonplace thermoplastic moldable materials that include PEEK, PEI, liquid crystal polymer and nylon. Some micromolding parts can be made of durometer or elastomeric as well. They can also be made of optical-grade and medical-grade materials for medical device parts. The types of materials used allow for the size of molds to be smaller than the size of a dime.
To make a part, there is a runner system that is the vessel for plastic to get from its melting point to the cavity to make the desired shape. The runner can be really long in some cases, and that extra space is needed to get the plastic where it needs to go. The size of the runner system in relation to the size of the part is waste. According to Johnson, you don’t want to make a tiny part and have a lot of waste. True micro molding is efficient in relation to the part size and the runner system.
Some companies have set their largest micromolding to half an inch and some have sizes as small as 800-by-300-by-380 microns. Micromolded parts can also have a part volume of 0.005 cubic inches or less, according to Accumold.
The level of detail and expertise required for building microparts is unique. While the task of making a small part can be daunting, the parts can be simple to make as long as the company is equipped to build high-precision parts. The process of micromolding differs with each company.