Molding and Custom Tooling Considerations

Posted by linneasimone on December 28th, 2020

The high precision manufacturing process or molding is the most preferred methods of making parts and components. In this process of manufacturing, molten plastic is injected into a carefully designed mold where plastic hardens to form the desired part.

Even before the manufacturing begins, the main concern remains to get a mold that can produce parts with great accuracy. The mold consists of two main parts: the mold core and the mold cavity. A closed mold with these two parts has a void which is called the part cavity and it receives the molten plastic. A mold can have just one cavity (single-cavity mold) or multiple cavities (multi-cavity mold). Based on the number of cavities, molds can be used to produce just one (with single-cavity mold) or multiple identical parts (with multi-cavity) mold during the same run.  

Designing the mold is a crucial step. A mold has several components and designing those components, known as tooling, requires specialize expertise as it is a highly complex process. In order to ensure accuracy in the mold design, a manufacturer must pay attention to custom tooling and molds parts machining.

The process of mold design requires great precision along with the scientific know-how to produce accurate and high-quality parts with perfect dimensions. The success of the design process also depends on the selection of the proper grade of steel so that the components that run together do not wear out prematurely. Proper hardness of steel is also essential to ensure good balance between wear and toughness. The tooling process should also include strategies for the placement of waterlines for maximum cooling and minimum warping. Tooling engineers have to put in a lot of efforts in calculating gate/runner size specifications for proper filling and appropriate cycle times. Additionally, efforts are also required in determining the best shutoff methods for tooling durability.

Runners are the channels through which the molten plastic flows during the injection molding and reaches the mold cavity. Gate at the end of each channels control the direction of the flow. These two systems are quite crucial for successful mold making because these two components assure even distribution of plastic and cooling.

Yet another key consideration in mold designing and tooling is the proper placement of cooling channels in mold walls to circulate water for even cooling. Uneven cooling can result in defects, also known as hot spots.

If molding requires more than one part, then insert molding should be considered. In this process, custom mold inserts should also be given enough attention.

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