Design for Manufacturing (DFM) is considered an important aspect for injection molding. However, one molding technique that seems to be an exception is micro injection molding. The reason for this is simple – research is still being conducted to assess the various capabilities of the micro injection molding process.
Due to this simple yet important point, plastic product manufacturers have to consider a lot of questions when using micro injection molding as the production technique:
- How small should the product be?
- How high will the tolerance levels be?
- Will or should there be undercuts in the product?
- What kind of features should the mold cavity have?
Hence, it is important for plastic product manufacturers to consider certain aspects when designing a micro-injected part.
Appraising the Factors
The following points need to be considered, as they will affect the quality of the micro-injected part:
- Mold Cavity Design: The design of the mold cavity is important, as a large cavity surface can result in the plastic cooling quicker than expected. This can also lead to micro cavities not being filled completely. Furthermore, it can result in thin walls, which will affect the finished product’s performance in an application. Hence, the mold cavity surface should be of an appropriate size to ensure effective creation of a product.
- Inserts: The use of inserts is an important aspect to consider in micro injection molding. The main goal of using inserts is to allow different micro geometries to be tested without disrupting the basic structure of the mold. Using molds with inserts reduces the overall cost of the design process. Using adjustable inserts can also allow for easy testing of prototypes.
- Mold Cavity Pressure: This factor is still being evaluated to see whether it will suit micro injection molding. Checking the mold cavity pressure of micro molds can be a tough task due to its small size. One of the solutions consists of installing a piezoelectric force transducer behind the injection pin. Another solution involves using a miniaturized quartz sensor, which can directly measure the mold cavity’s pressure.
- Demolding: This is a process used to remove a mold from a casting. Demolding is performed either by hand, or by using compressed air. The orientation of the polymer injection process will affect the shrinkage of the plastic. This in turn will affect the demolding process. Two suggestions have been offered to decrease shrinkage:
- Increase the holding pressure.
- Have a longer cooling time while the part is inside the mold cavity.
By nature, micro molding is a tough manufacturing process. An error in the design process can result in the manufacturing of a defective product. Keeping these points in mind will ensure that a micro part will be designed according to the client’s requirements.
