Injection molding is a popular manufacturing method for many reasons. It has proven to be especially valuable to those in the consumer product development sector since plastics are a major component of many consumer products and injection molding is one of the best ways to create them. Let’s take a quick look at the three main stages of the injection molding process, then discuss the pros and cons of the process.
Injection Molding Process, Basic Step 1: Product Design
Design is one of the most important aspects of the production process, as it is the earliest opportunity to prevent costly mistakes later. (Of course, it’s also important to first determine whether you have a good idea, but more on that here.) There are many design goals: functionality, aesthetics, manufacturability, fit, etc. Proper design is one that accomplishes the desired goal at a satisfactory level but may require a great deal of creativity to get there. Product design is often done using computer-aided design (CAD) software, such as SolidWorks. Proficiency in CAD software is critical as it enables faster iterations and more accurate prototyping when necessary.
Some specific ways to avoid costly mistakes during product design are to plan for as uniform a wall thickness as possible and to gradually transition from one thickness to another when thickness variations cannot be avoided. It is also important to avoid creating stress in the design, such as corners of 90 degrees or less.
A skilled team of design engineers will be able to brainstorm, design and refine various solutions to meet the unique complexities of a particular project. Creative Mechanisms’ design team combines decades of experience to create elegant solutions to complex problems. Meet some of our team here, here or here, or visit our client testimonials page to see what past and current clients have to say about our product design capabilities. We think you’ll be impressed.
Injection Molding Process, Basic Step 2: Mold Design
After a similar-looking, similar-feeling design has been tested and further production planned, the mold (or dies) needs to be designed for injection mold manufacturing. Molds are usually made from the following types of metals:
Hardened Steel: Usually the most expensive material used for molds, and usually the most durable (this keeps the unit price down). This makes hardened steel a good material choice for products that are going to be produced in the hundreds of thousands.
Pre-Hardened Steel: Does not last as many cycles as hardened steel, and is less expensive to manufacture.
Aluminium: Most commonly used in single cavity “prototype tools” when the number of parts required for testing is relatively small. Once the tool’s injection molded parts have been tested and approved, a multi-cavity steel production tool is produced. Thousands of parts are available from aluminium tooling but are typically used in smaller quantities.
Beryllium Copper Alloy: Typically used in areas of the mold where rapid heat removal or shear heat concentration is required.
Like overall product design, mold design is another opportunity to prevent defects in the injection molding process. We’ve blogged before about the top 10 injection molding pitfalls and avoiding injection molding mistakes, but here are some examples of how poor mold design can be a costly mistake:
Not designed for the proper draft: This refers to the angle at which the finished product is ejected from the mold. An insufficient draft can lead to popping problems, costing a lot of time and money.
Improper Gate Placement or Size: A gate is the opening in the mold through which the thermostat or thermoplastic material is injected. Each leaf mark (scar) can create aesthetic or functional problems if placed incorrectly.
The number of parts (cycles) required and the material from which they are made will help drive decisions about how and what material to use to make the mold.
Injection Molding Process, Basic Step 3: Manufacturing Process
When the product is properly designed, approved and die-cast, it’s time to start the actual manufacturing! Here are the basics of the injection molding process-
A thermostat or thermoplastic material in granular form is fed into the heating barrel through a hopper. The plastic is heated to a predetermined temperature and driven by a large screw through the gate into the mold. Once the mold is filled, the screw will remain in place to apply the proper pressure for a predetermined cooling time. Once this point is reached, the screw is retracted, the mold opens and the part is ejected. The gate will be automatically clipped or manually removed. This cycle will repeat over and over and can be used to create hundreds of thousands of parts in a relatively short amount of time.
Injection molding is a highly efficient and cost-effective manufacturing process that has revolutionized the production of plastic products. With its ability to produce complex geometries and a wide range of sizes and shapes, injection molding has become the go-to method for producing plastic parts in a variety of industries.
Through the injection molding process, manufacturers can achieve high levels of precision, repeatability, and speed, resulting in a faster time-to-market for products. The process also allows for the use of a wide range of materials, including commodity plastics, engineering plastics, and elastomers, giving designers and engineers a wide range of options to choose from.