16 Dec 2022
an example of a single cavity injection mold

Plastic injection molding is a process in which molten plastic injects into a mold cavity, then it cools down until a solid part forms in the shape of the mold. There are many factors that make that process specific for each part, and one factor to consider is how many cavities a mold uses.

H2: What is a mold cavity?

An injection molding cavity is the space that is hollow in an injection mold in the shape of a plastic product. Designing the mold is one of the first steps to creating an injection molded plastic part. When designing the mold cavity, there are several factors to account for, including knit lines, parting lines and durability. But another very important aspect of cavity molding is deciding how many cavities to include in a single mold.

H3: What is a single cavity mold?

A single cavity mold simply means that for one mold, there is one cavity. When the injection molding machine runs one cycle, one part will be produced. This type of mold is cheapest, easiest to maintain, and is especially necessary for larger parts. However, when producing a high volume of parts, it can become inefficient to use just one injection molding cavity.

an example of a single cavity injection mold

H3: What is a multi cavity mold?

Multi cavity injection molding means that there is more than one cavity in one mold. A thin passage exits the first part to allow for the travel of molten plastic to the next part. Or, there could be multiple entry points to a single mold, leading to different parts. We could build a 2, 3 or 4 cavity injection mold, or even more depending on part size and other restraints. San operator at Rex Plastics removes a part for a multi cavity mold that uses 2 cavities. ome products require multiple different parts, and it could be possible to put two or more separate parts in one mold, making one each and assembling afterwards. Multi cavity injection molding allows for more efficient part production, since there are several parts that are made with each cycle of the machine.

H2: Single cavity vs multi cavity molding

The advantages to multi cavity injection molding may seem clear—more parts per cycle, leading to greater overall efficiency of time and money. This is a good option for customers that need a very high output of parts within a limited time. However, a single cavity mold is less expensive than a multi cavity, for budget-minded smaller operations. A single cavity mold is usually less expensive to maintain, and if there is a problem with one cavity in a multi cavity mold, then the whole mold will be unusable until someone fixes the mold. A multi cavity mold would eventually offset its high startup cost with a more efficient part production, but it might not be the best choice for all customers.

shelves filled with just some of the molds we’ve made for customers at Rex Plastics.

H2: Single and multi cavity injection molding with Rex Plastics

At Rex Plastics, we have been single and multi cavity injection molding for over 50 years. We know how to design the right mold for your part, so reach out to us for a quote today.