Injection Mold & Molding Terminology for Plastic Components

Injection molding technology continues evolving with the market and with the advances in science. Injection molding is the process used in producing plastic components for a variety of industries.

When plastic resin materials are heated the resin will flow, and can then be injected into a mold. An injection mold consists of two halves referred to as the “A” side and the “B” side. The “A” side is where the molten plastic enters the mold - and the “B” side contains the ejector system which removes the parts.

Injection Molding Includes Many Terms and Components

Injection molds are required to have many components in order to make high-quality plastic parts. Below is some of the terminology used to describe the components and processes that are required when producing injection molded parts:

• Sprue – this connects the nozzle of the injection molding machine to the main runner or cavity
• Runner – this component conveys the melted plastic from the sprue to the gate and into the part
• Gates – these are the openings that allow the molten plastic to be injected into the cavities of the mold
• Cold Runner – this design involves the plastic entering into the “sprue” and then traveling through the “runner” where it then enters the part cavities through the various “gates.”
• Hot Runner – this design is an assembly of heated components used to inject molten plastic into the cavities of the mold.  Hot Runners usually make a mold more expensive to manufacture but allow savings by reducing plastic waste and reducing the cycle time.

When observing an injection molding product, you will often see a line running between different sides of the finished plastic part. Here are some descriptions of why parts have a specific appearance:

• The Parting Line – this occurs anywhere there are any two pieces of a mold that meet.

There are also several configurations of injection molds. These configurations are described as follows:

• The Two Plate Mold – consists of one parting line where the mold splits into two halves.  The sprue, runners, gates, and cavities are all on the same side of the mold.
• The Three Plate Mold – has a runner plate in between a moving half and a fixed half.  These molds will have two parting lines and are used because of their flexibility in gating locations.
• An Unscrewing Mold – is what is used when there is a requirement for male or female threads on a plastic component
• The Action Mold – these consist of a mechanical cam action incorporated in their design when a hole, slot, undercut or thread is needed that is not perpendicular to the parting line.
• The MUD Unit – these are standard frameworks for tool sets, which allow for custom machined tooling inserts to be made for specific components.

Large Injection Molding Runs Cost Less 

Plastic injection molding offers many industries a huge number of benefits.  In large runs, molding is much cheaper than when machining the parts individually. The overall manufacturing speed is much faster with this approach as well. This is one of the many reasons there are so many different types of injection molding processes. Some of these include:  

Insert Molding – This is the process of putting a metal insert into a mold and then molding plastic around the insert.  Since multiple parts are manufactured together - this eliminates the need for a secondary assembly operation.

Over Molding – This is the process of over molding, and the production of an injection molded part that seamlessly combines a rigid plastic with a rubber-like elastomer.

Family Molding – This is a process that utilizes a mold that contains various shapes of cavities to mold all the plastic components for one completed part.  Family molds are used when the different plastic components are made from the same material.

Clean Room Molding – This is the process used primarily for medical components. It is the injection molding process that is performed in a clean room environment to protect the parts from any contaminants. 

When considering having plastic parts custom designed and molded - Crescent Industries is the ideal partner for your plastic component or device.

Crescent Industries is your single-source solution for your device by providing mold building, design, engineering, injection molding as well as clean room injection molding, and any secondary operations that may be required to complete your project.  

Contact Crescent Industries today for any of your injection molding needs.