Types of injection molds

There are many different ways to classify the injection molds by multiple different categories based on their features, such as feeding system, mold opening, tool steel, part volume, mold structure and SPI standard. These classifications are not exclusive, but rather every mold will fit a label within each category. For example, you may have a mold that consists of a cold runner system, two plates, and has unscrewing system. Choosing the right mold type for your production is crucial because the type of mold will directly impact product quality and overall costs.

There are multiple different ways to classify a mold based on different attributes of the mold. We will discuss the primary 5 categories:

Plastic Injection Mold Types by Mod Structure

2K Mold

2k mold is designed for 2k molding, which is a process of molding two different plastic materials into one plastic part at one time

Insert Mold

Insert molds are used for Insert molding process in which plastic is injected into a insert mold that contains an pre-placed insert.  Inserts can be made of metals or different types of plastic. 

Over Mold

With an overmold, the production of the substrate parts is a standard injection molding process involving an aluminum mold with no heating or cooling lines running through it.

Unscrewing Mold

Plastic Injection Mold Types by feeding system

Hot Runner Mold

A hot runner system is an assembly of heated components which convey molten plastic from the machine nozzle into the cavities of the mold. Hot Runner molds refer as runnerless molds.
The use of hot runner system can improve overall molding system efficiency by shorting cycle time, balance melt flow, elimination of the runner to save the material and labor cost. It also greatly improve the part quality and consistency, and allows more design flexibility and molding automation.

A hot-to-cold runner system is simply a hot runner system of less nozzles feeding small balanced cold runners. This can reduces the weight of the full cold runner and can provide a more balanced flow of resin to the cavities.

However, not all injection molding applications are suitable for hot runner molding. Some materials are heat sensitive and the time to temperature relationship-especially when the shot size is very small, it can be a problem. Some families of parts, for handling and orientation purpose, may be best kept attached to the runner until they reach another downstream operation. The hot runner is also expensive, if the part volume is low, it is not cost effective to use hot runner.

Cold Runner Mold

A cold runner is simply a channel formed between the two halves of the mold, for the purpose of carrying plastic from the injection molding machine nozzle to the cavities. Cold Runner molds usually consist of two or three plates that are held within the mold base. cold runners were widely used on injection molds.

Two plate injection mold refers to single parting surface mold, the mold with sprue, runners, gate and cavities are all on the same side of the mold, divided by the parting line into moving half and fixed half.

Three plate injection mold are used in multi cavity cold runner mold when a two plate mold design does not permit a suitable gate location.

Leave a Reply

Your email address will not be published. Required fields are marked *