A mold base, also known as a plastic injection mold, is a set of equipment that is in charge of conducting the plastic injection process. A standard form of mold base contains not only the base, but also other parts that coordinate with each other, in order to achieve the molding process of plastic products. The mold bases are usually made of metals, which provide rigid and stable support under high temperature and pressure.
As mentioned above, the mold base primarily serves for plastic injection molding, a molding process for producing plastic products. Unlike the general machining techniques that involve cutting in the procedures, plastic injection molding is a totally different concept.
First, the materials being machined are different. The former deals with metal workpieces, and the latter is used for plastic materials. Second, the working principles are different as well. Metal machining requires a high speed spindle that advances the workpieces or cutting tools to remove chips, the unwanted materials, from the workpiece. In contrast, plastic molding doesn’t apply a spindle and cutting tools to divide one work into several pieces. Instead, it changes the shape of plastic materials by means of temperature and pressure differentiation.
A milling machine or lathe provides a working environment for general cutting processes, and a mold base is where plastic injection molding is conducted. The mold base consists of several plates piled up as an assembly, and the assembly provides the base for performing the process. We will discuss the design, application, and benefits of using these tools in the following sections.
Mold bases differ in the number of plates and the structure of base depending on the requirements of applications. The standard design consists of clamping plates, main plates, guide pins and bushes, ejector plates, and a runner plate. Only when the components coordinate with each other will the mold plate perform its functions and complete the molding process.
● Clamping plates
Clamping plates are distributed into the upper and lower plates. The two plates offer support as they deliver a compressive pressure for the internal components of the mold base.
Similar to clamping plates, the main plates also include the upper and lower plates. Each of the main plates contains a cavity that makes a space for injecting the plastic materials. As the two plates are compressed together, the two halves of cavities form a complete shape of the plastic product.
● Guide pins and bushes
Guide pins and bushes are used to guide the plates as they are assembled together. In other words, these parts ensure the right positions of the plates during operation. Some mold bases are equipped with guide pins only, but the bushes act as the sleeves of pins in the larger ones.
● Runner plate
The runner plate is a movable plate, which is responsible for the injecting procedure. The nozzles of the runner plate deliver molten plastic materials, and allow the molten plastic to solidify in the cavities. After that, the formed plastic mold is ejected through the ejector plates in the final procedure.
● Ejector plates
Ejector plates are at the bottom of the base. One is for performing the ejecting function, and the other is for supporting purposes. After the injection procedure, the plastic materials transform from molten to solid state. Then the ejector plates help remove the plastic mold out of the mold base, and complete the final procedure of plastic injection molding.
Considering the manufacturing process of plastic injection molding, the employment of mold bases is when the intricate structure is not the main factor in determining the product quality. Unlike the precision machining process, which aims for precision and efficiency at the same time, plastic injection molding focuses more on the efficiency of the works. To make the balance between efficiency and product quality, a mold base would be the preferable tool for production. Mold bases are available for manufacturing products made of plastic materials. With the different sizes and constructions, the applications range from small toy blocks to large components in mechanisms.
So, why is mold base sometimes preferred over other machine tools? Since mold base encompasses both efficiency and productivity during the manufacturing process, it is a perfect tool for large volume of production. On the one hand, the plastic injection molding process is fast. On the other hand, the up-front cost for investing in the mold base is less expensive than a milling machine, for example. Although precision is hard to achieve in each production, the efficiency and productivity outperform the drawbacks using a mold base may have.
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