With dozens of manufacturers, hybrid materials, additives, and fillers available on the market, there are thousands of material options. This can be overwhelming. However, in reality, there are only a handful of materials that make up the bulk of the market. It’s easier to understand if you start with some core material characteristics.
Plastics (in this context) are nothing more than groups of polymer chains. These are microscopic groups of repeating atoms (think of it like DNA). The composition of these polymer chains varies between different types of plastics. That variation has a significant impact on the properties of the plastic and your part. Two plastics could look the same but exhibit drastic differences in performance.
For the sake of design, we just want to understand the general characteristics of plastics. We will look at the major characteristics of plastics and some design considerations. There are two major categories of plastics; Thermosets and Thermoplastics.
Plastics are the most common materials for producing end-use parts and products, for everything from consumer products to medical devices. Plastics are a versatile category of materials, with thousands of polymer options, each with their own specific mechanical properties.
Plastic manufacturing processes have been developed to cover a wide range of applications and part geometries. For any designer and engineer working in product development, it is critical to be familiar with the manufacturing options available today and the new developments that signal how parts will be made tomorrow.
This guide provides an overview of the most common manufacturing processes for producing plastic parts and guidelines to help you select the best option for your application.
Consider the following factors when selecting a manufacturing process for your product:
Form: Do your parts have complex internal features or tight tolerance requirements? Depending on the geometry of a design, manufacturing options may be limited, or they may require significant design for manufacturing (DFM) optimization to make them economical to produce.
Volume/cost: What’s the total or the annual volume of parts you’re planning to manufacture? Some manufacturing processes have high front costs for tooling and setup, but produce parts that are inexpensive on a per-part basis. In contrast, low volume processes have low startup costs, but due to slower cycle times, less automation, and manual labor, cost per part remains constant or decreases only marginally when volume increases.
Lead time: How quickly do you need parts produced? Some processes create first parts within 24 hours, while tooling and setup for certain high volume production processes takes months.
Material: What stresses and strains will your product need to stand up to? The optimal material for a given application is determined by a number of factors. Cost must be balanced against functional and aesthetic requirements. Consider the ideal characteristics for your specific application and contrast them with the available choices in a given manufacturing processes.
Plastics come in thousands of varieties with different base chemistries, derivatives, and additives that are formulated to cover a wide range of functional and aesthetic properties. To simplify the process of finding the material best suited for a given part or product, let’s look first at the two main categories of plastic: thermoplastics and thermosets.
Thermoplastics are the most commonly used type of plastic. The main feature that sets them apart from thermosets is their ability to go through numerous melt and solidification cycles without significant degradation. Thermoplastics are usually supplied in the form of small pellets or sheets that are heated and formed into the desired shape using various manufacturing processes. The process is completely reversible, as no chemical bonding takes place, which makes recycling or melting and reusing thermoplastics feasible.
Common materials:
In contrast with thermoplastics, thermosetting plastics (also referred to as thermosets) remain in a permanent solid state after curing. Polymers in thermosetting materials cross-link during a curing process that is induced by heat, light, or suitable radiation. This curing process forms an irreversible chemical bond. Thermosetting plastics decompose when heated rather than melting, and will not reform upon cooling. Recycling thermosets or returning the material back into its base ingredients is not possible.
Common materials:
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