What do water bottles, a hoover, your car lights, a toothbrush and your phone case have in common?
They probably all have been produced with the same technique – Injection molding!
A wide variety of industries take advantage of this cost-effective and time-efficient method, such as automotive, consumer goods, education & training, healthcare, housewares, public services & administration and telecommunications. Since injection molding produces high volumes of quality parts quickly (i.e. short cycle times), it’s considered one of the most preferred processes among manufacturers who must produce a large number of complex parts each year.
This article will go over the injection molding process, its advantages and why it is one of the most common mass production processes.
How Does Injection Molding Work?
The injection molding process is a process used to produce parts of nearly every shape and size through the use of a hollow, steel-walled ‘tool’ known as a “mold”. This tool can be thought of as an empty frame into which raw material will be poured and then compressed.
The first step to make an injection molded part is to design the part using: sketches, computer aided design (CAD), or computer aided manufacturing (CAM). Once these files have been created they need to be translated from 2D data into 3D models/designs that CAD/CAM software programs can read. Then this is fed into the molding machine which will create the mold.
This process begins by feeding plastic pellets into a hopper above the machine. These pellets are melted and liquified and forced through a long barrel, or “injector” into a mold. The mold itself must be machined from aluminum or steel and present different sections as determined by the product which is being manufactured. Once inside, the material takes the general shape of whatever cavity exists within the mold.
When the liquid plastic comes in contact with these surfaces it solidifies almost immediately, squeezing out all air bubbles present and creating an even surface finish across its whole structure. All plastic injection molded parts have a surface texture created by the tools that made them. That said, it is possible to get the surface finish and texture you want by changing the surface finish of the mold tools. With some materials such as polyurethane foam, it may help if the liquid is under pressure when injected into the mold to fill every space inside of it uniformly for higher quality products.
In terms of production capabilities, injection molding is easy to understand as an automated manufacturing process.
What Products Can Be Made With Injection Molding?
A wide range of products, such as toys, household items and even medical devices are made using the process of injection molding. The most common components produced on an industrial scale with this method are plastic caps, bottles and containers. Other examples include electronic equipment housings, gear shift knobs or any other product that needs a specific shape for proper function but can be produced in scale.
And anything in between!
Plastic rivets for example which can be found in almost every car are made using injection molding because they require a precise shape to function properly.
All types of packaging like milk cartons or yogurt cups are also molded parts. At first glance, it might not be obvious but all these products have one thing in common: they are all made with the same process.
What Materials Can Be Used?
The reason why injection molding is so popular in the production of consumer goods and other products is that any material that can be shaped into a ‘billet’ or ‘rod’ can be injected.
This includes all thermoplastics, metals, and elastomers (such as rubber). It depends on what the finished product is meant for. However, most of the time plastics are used. It is easy to melt and harden. Plastics are available in a wide range of properties, colors and can be modified to almost any extent.
What Are The Advantages Of This Process?
The high quality and quantity of the products produced by injection molding is what makes this manufacturing process so popular. Other advantages are:
- Fine surface finish and excellent dimensional accuracy, which means that they exhibit very smooth surfaces with little or no flaws such as holes, cracks or uneven seams.
- Precision is why most companies choose this process. The finished product is almost flawless and needs no post-processing afterward.
- Considered a “green” manufacturing process, that is more energy-efficient than other plastic production methods such as extrusion and blow molding.
- Allows for mass production at relatively low costs because it is an automated form of manufacturing. High quantities can be produced very quickly without compromising on the quality of the product.
- Unlimited possibilities of shape and size, which make it possible to create almost any type of product.
- Lighter than the alternative which is important f.e. in the automotive industry.
- The low cost of raw material
With all its benefits – low costs; fast lead times; superior repeatability – industries should not be surprised to see injection molding grow exponentially in the majority of industries.
