Plastic thermoforming uses either male molds or female molds. With male molds, the thermoplastic sheet is placed over the mold. With female molds, the thermoplastic sheet is placed inside of the mold. Male molds are used when the inside dimensions of the plastic part are a priority. Female molds are used when the part’s outer dimensions are more important than its inner dimensions.
Let’s take a closer look at both types of molds so that you can determine the best type of tooling for your thermoformed parts.
Male Molds for Plastic Thermoforming
Male molds are usually less expensive than female molds. Generally, parts formed over a male mold will retain the color and texture of the extruded sheet. Because the plastic sheet shrinks as it cools during the molding process, the thermoformed part adheres to the mold surfaces. To release the part, draft is required.
Draft is the angle the mold wall makes with the vertical. Typically, male molds require greater draft angles than female molds. (With female molds, deep parts and molded-in textures also require additional draft.) With male molds, draft is also used so that plastic parts that are designed to fully nest will release from each other without sticking or jamming.
Female Molds for Plastic Thermoforming
Female molds are usually more expensive than male molds, but a female mold can produce highly detailed parts. With female molds, the mold surface usually produces the exterior surface of the finished parts. This supports the creation of sharp corners and molded-in features such as logos, ribbing, and recesses for name plates. Depending on the part, the inside corners of a female mold may be relatively tight.
Choose Plastic Thermoforming from Gregstrom
Do you have questions about male and female molds, or the various types of plastic thermoforming services that are available? For over 70 years, Gregstrom Corporation has been the plastics manufacturing company that manufacturers trust. For more information, contact us.