Plastic Injection molds

Sometimes, manufacturing one plastic product a million times isn’t what you’re looking for. You may be looking for a very specific design for each of your plastic products. The good news is that there are many different types of injection molds designed to fit your needs! More complex plastic products are formed using more complex injection molds. Here are just a few examples of different kinds of injection molds.  

The Three-Plate Injection Mold

While two-plate injection molds are the most widely used for injection molding, there are advantages to using a three-plate mold. In a two-plate design, a gate connects to the side of a cavity image, rather than the base. This causes the molten plastic to flow into the side, around the base, and into the other side. This could potentially disrupt the flow of the molten plastic and make the plastic product uneven. In a three-plate design, a gate connects to the base of the cavity image, rather than the side. This causes the molten plastic to flow into the base and around to both sides at the same time. Which means that the molten plastic distributes evenly into the cavity image. In a two-plate design, the clamping unit slides the ejector mold (B Plate) away from the injection mold (A Plate) in order to open the mold. As it opens, the ejector pins push the plastic product off of the mold. Since there is only one opening in between the two plates, the sprue and runners are still attached to the plastic product. In a three plate design, the clamping unit pulls all three plates apart, creating two openings. This disconnects the sprue and runners from the plastic product and ejects them separately. In that way, the waste material does not need to be removed manually.  


Some injection molds can form multiple layers around one plastic product by reinserting previously molded plastic products back into the injection mold. This is called overmolding. Overmolding requires specialized injection molds that have two or more injection units, but there is a much smaller margin of error compared to regular injection molds. At first, the basic plastic product is molded with a base color material. There are spaces in the basic plastic product, leaving room for more plastic. Then, a different color material is used and injected into the open spaces. Through this process, a multi-layered plastic product is produced. Examples include car parts such as tires and keys.  

Family Molds

Some injection molds have multiple cavity images that produce different plastic products at the same time. This is called a family mold. In other words, these injection molds can produce many different plastic products in one injection molding process. Examples include model kits for airplanes and cars. Rather than producing one airplane or car part at a time, whole kits can be produced at the same time by one injection mold. Which type of injection mold fits your need? Here at Murray Plastics, we love to work side-by-side with our clients, providing down-to-earth service that can only come from a founder-led United States manufacturer. We pride ourselves in being able to design the perfect mold for your plastic product needs. Speak with one of our expert designers to determine the right mold for your project today.