The involvement in a plastic injection molding project will surely enable you to understand that the mold can easily become the most expensive part in a project. Among the multiple factors that affect the cost of a plastic injection molding product, the top three ones are undoubtedly the dimensions and complexity of the part, the quantity of the part, as well as the effort required to build the plastic injection mold.
As we know, the cost of all manufactured products is dependent on that of the raw material and the labor required. Therefore, the cost of a plastic injection molding product is also dependent on the costs of the plastic material and the labor involved throughout the production process. Here, we would like to focus on one of the most influential factors throughout our operation, i.e., the plastic injection mold tooling. Later on, we will have a brief discussion on the vast diversity of plastic material options.
Mold tooling size and design
Among all the items built to produce a plastic product, a plastic injection mold, also referred to as a die or an injection mold tooling, stands out to be the most expensive one that’s built specifically to produce the plastic part via a very simple plastic injection molding process, which works as follows: the molten plastic material is first fed into a mold via the pressured injectors, and then, as the mold cools down, the plastic part is formed before the mold opens in two halves to release the part. A molding cycle consists of the closing, injection, and opening operation of a mold.
But, the devil is in the detail, as the saying goes. In the plastic injection molding process, the complicated and instantaneous motion of numerous moving components are involved, among which, some are designed with micron-level tolerances. Hence, a plastic injection mold plays a key role in this process. Molds are available in a diversity of different dimensions and designs, each of them is built to produce an integral part of a complete product, and each with a cavity (or more cavities to produce more than one parts in a single cycle) that holds the molten plastic. To ensure precision, the cavity needs to be created to extremely tight tolerances.
To build a mold for a particular project, the first thing to do is to work on an engineering table, to define the most effective size and number of mold cavities. In the process of mold making, the main factors include the size and shape of the entire mold. For plastic parts that are large-sized and sophisticated, the cavities need to be intricately machined and polished, though the most commonly seen and less costly ones are those having two halves that simply open and close against each other. However, there are also very complicated molds that are designed with such additional features as the slide, the lifter, and the cam, so as to facilitate the handling of the undercut.
Mold steel material
Next, we have to consider the cost of the mold material. Steel is the most common material for the plastic injection mold, of which the type and grade are of great importance. As there are extremely tight tolerances for the part, all the cavities of a plastic injection mold must be able to last long without any wear, deformation or pits.
Therefore, hardened or pre-hardened steels become the best choices for making molds, so as to minimize mold deformation or wear. There are different reasons for the wear of steels and other metal materials, i.e., heat, friction, thermal change, pressure and fatigue. The number of parts to be produced determines what kind of material you choose for your mold. The greater the number of parts, the higher-grade steel (better quality and therefore more expensive) should be selected. Remember that, the material cost is only one of the factors, while the steel machining and finishing cost is dependent on the characteristics of the material you choose.
Plastic Material types
Throughout the globe, we have countless products that feature plastic parts. Thanks to its benefits of high strength, light weight and infinite design possibilities, plastic is more and more widely used.
Different plastics are regularly used in different industries that impose different requirements for the material. For example, The cost of plastic injection molding material used in different industries also varies a lot. Similar to other goods, when purchased in large quantities, the unit price of the material might drop. Yet, the ingredients of the material can be either simple or complicated, depending on its specific application, because the plastic materials are created to different specific needs, such as precision cutting, as well as resistance to chemicals, electricity, heat and more.
Manufacturer size and expertise
The cost of the tooling used for steel machining also varies greatly. In addition, the plastic parts are greatly varied in size and shape, so a mold manufacturer needs a large number of cutting tools, abrasives and more in storage for finishing the mold. Usually, a mold manufacturer enjoys the expertise necessary for the recommendation and manufacturing of various plastic injection molds. However, you might have to ask a mold company to build a product that they have never built before. This can cause the cost and risk to significantly rise.
Conclusion
As we all aware, the cost of plastic injection molding is composed of a string of items: the resin material, mold tooling, engineering and manufacturing, etc.The cost of plastic injection molding also includes other manufacturing factors, such as maintenance and utilities. So, we need to have a great design first and then optimize it for manufacturability from the beginning, so as to help the customer save time and money throughout the whole process.