Design of plastic parts

Design of plastic parts made by injection molding technology can be very challenging. Unlike 3d printed parts and machined parts, injection molded parts, in addition to their basic function, should also meet various technological requirements in order to be able to produce them at all. The main challenge is to understand how the injection mold is designed, made and what manufacturing methods are available.

DFM (Design for Manufacturability) is an approach to product design that aims to optimize the design for efficient and cost-effective manufacturing. When it comes to plastic part and product design there are elements of plastic part design that will influence mold design and there are elements of mold design that will influence part design. Through an iterative process in collaboration with the client, we come to a production design together.

• Material selection: The choice of plastic material is important to achieve the desired properties and functionality for the part. Important factors are strength, durability, stiffness, flexibility, chemical resistance, UV stability, and cost.
• Part geometry: The shape and size of the part must be designed with consideration for the intended function and manufacturing process. This includes features such as wall thickness, ribbing, bosses, fillets, chamfers, and undercuts.
• Expected mold life: The expected mold life for a plastic injection molding tool varies depending on several factors such as the material being used, the design of the part, and the complexity of the mold. However, with proper maintenance and care, a high-quality mold made from high-grade materials can last for tens of thousands to hundreds of thousands of cycles.

The injection molding process involves several steps, including:

• Draft angles: Draft angles are critical for ease of ejection from the mold during the manufacturing process. This angle is also dependent on surface type. Typically, a draft angle of at least 1-2 degrees is required to facilitate ejection.
• Gate location and type: The gate is the point of entry for molten plastic into the mold, and its location can affect the part's strength, aesthetics, and manufacturing efficiency. There are several type of cold and hot gates that can be used.
• Ejection: The ejector system on an injection mold is a crucial component that facilitates the ejection of the finished plastic part from the mold after it has been cooled and solidified. Two basic types of ejection are with pins or with slading plate.