What Is Plastic Injection Molding? | Aberdeen Technologies
It's no secret that the business world can be brutal: You have to be fast, you have to be efficient, and you have to be able to keep up with the competition.
As a result, many companies find themselves at a standstill. They know they need to grow, but they don't know-how.
Plastic injection molding (also called insert molding) is one of the most transformative manufacturing processes available today, and it's capable of empowering businesses as wide-ranging as automotive companies and toymakers to increase their output by leaps and bounds.
But what exactly is plastic injection molding?
Understanding Injection Molding
It's no secret that manufacturing businesses have been struggling to keep up in a competitive market. Industries are getting more and more specialized, and manufacturers are having a tough time finding ways to streamline production and increase their output.
That's why more and more manufacturers are turning to injection molding—a transformative process that makes even the most complex products an easy part of your production line.
Injection molding is a game-changing process in which melted plastic is injected under high pressure into metal molds, where it cools and hardens into a final product.
The process is remarkably versatile: with injection molding, companies can create a variety of products from small parts like bottle caps and combs to large products such as industrial containers and automotive parts. It's also capable of creating intricate shapes with fine details—a feat that would be difficult to accomplish using traditional casting or forging techniques.
Injection molding also allows for high levels of automation, which means fewer errors and more consistency between parts. In addition, because the process involves minimal waste—most of the plastic ends up in the finished product—it's highly cost-effective and environmentally friendly.
All of these unparalleled capabilities have made injection molding one of the most widely used manufacturing processes in the world today. Further boasting an ability that even 3D printing can't match—the capacity to produce identical parts at high volumes—injection molding has become an essential tool for companies across a wide range of industries.
What Is Plastic Injection Molding
Plastic injection molding is a process that's been around for a long time, and it's constantly evolving.
The technology was invented in 1872 by John Wesley Hyatt, who wanted to create a substitute for ivory billiard balls, which were increasingly difficult to procure. The first machine was built, and the first plastic billiard balls were made using celluloid.
Since then, plastic injection molding has become one of the most common technologies used in manufacturing industries worldwide. It's used to create products ranging from car parts to medical supplies, toys, packaging goods, and more. This process is cost-effective and allows for high-volume production at a low cost per part.
And here's the best part: plastic injection molding is fully compatible with sustainable processes! Recycled plastics are often used in the production of new products via plastic injection molding. This means that not only can you produce high volumes of highly durable products at low costs when you use plastic injection molding—you can also do so without wasting resources or contributing to pollution or oceanic microplastic buildup.
How a Plastic Injection Molding Machine Works
Transformative in its ability to create complex shapes out of plastic, injection molding has become a manufacturing mainstay. The technology is used in everything from making medical instruments to building Lego bricks. But the science and engineering behind it are often misunderstood. For example, most people don't realize that the process is more art than science.
So how does it work?
A typical injection molding machine works by heating plastic resin pellets until they are molten (about 400-700 degrees F), then pushing the hot material into a cylinder where it is injected through a nozzle into a closed mold under pressure. The mold is made up of two halves; one half is fixed, and the other half is attached to a movable platen. After the melted plastic cools inside the mold for the amount of time specified by the designer, the mold opens, and an arm unloads the molded part.
Injection speed refers to how fast plastic is injected into the mold cavity during cavity fill time. Cycle time refers to how long it takes to close the mold, inject the material and open the mold; cycle time includes clamp time and cooling time.
When designing for injection molding, there are several general rules that apply:
Wall thickness should be uniform throughout the part design. This will provide uniform cooling rates in all parts of the part during solidification and prevent sink marks from developing. A good rule of thumb for wall thickness is 0.063" (1.6 mm) or greater. Wall thickness should not be less than 95% of the shot size of the injection molding machine being used, or else material starvation can occur as the front edge of the cavity fills.
Draft angles are required on all mold surfaces so that when the mold is separated, the part will be easily ejected from the mold. This angle should be a minimum of 1/8˚ to 1/4˚ per side. A steeper draft angle may be required for large parts or parts with deep draws.
Radii are needed at all corners and transitions to provide stress relief and eliminate sharp corners that may lead to cracking or deformation during molding. The minimum radii for injection molding are 0.01" (0.25mm) for most resins and 0.03" (0.76mm) for resins containing high levels of glass fiber reinforcement.
Undercuts are areas in parts that prevent a part from being ejected from a mold without damaging the part or breaking the tooling. Undercut features must either be eliminated from your design, or they must be designed into the mold so that you can remove these features when opening the mold after cavity fill time.
Pros & Cons of Plastic Injection Molding
Advantages of Plastic Injection Molding
Injection molding is a vital tool for the manufacturing industry, particularly in the auto industry. This process, along with blow molding, is a great way to produce hollow plastic parts that can be used for virtually anything. Most parts on your car have been injection molded.
There are several advantages to plastic injection molding:
1) Impeccable Precision
Injection molding creates very precise parts. The machine itself is an automated process that can create high-quality components with impeccable precision. The machine starts by heating up plastic resin pellets until they reach the point of liquefaction. The melted plastic is then injected into a metal mold under pressure, which allows it to assume the desired shape. When the material cools and hardens, it takes on the desired shape with incredible accuracy.
2) Wide Array of Materials
One of the biggest benefits of injection molding is that it can work with a wide array of materials, including metals, glass, and ceramics. Depending on the part requirements, different materials may need to be used for various features. For example, if there is a feature on a part that requires high strength or wear resistance, a metal may be used for that feature, and an engineering resin may be used for the rest of the part. The ability to combine materials into a single part allows for greater design flexibility and reduced costs compared to alternative processes that require assemblies of multiple parts.
3) Short Lead Times
With shorter lead times than other plastic fabrication processes, injection molding can be used to rapidly create thousands of identical products in less time than it takes to make one prototype. With rapid prototyping, manufacturers can quickly test a product or part design before committing to production tooling. For example, if you need 100 pieces and have time to wait for the entire order to be completed, this method is ideal for you as it will save you both time and money.
4) Lower Cost
Injection molding also offers lower costs than other manufacturing processes. It's one of the most efficient processes out there, as it doesn't require a lot of energy or materials to create products as blow molding does. Additionally, the process creates relatively little waste compared to other methods of production.
5) Complex Details
Most injection molding can produce very complex shapes and geometries. Apart from intricate details, it is not a problem for our suppliers. This is a major advantage of plastic injection molding over other manufacturing methods: we can easily create parts with features that would be impossible to make by hand. We can add threads, undercuts, hinges, living hinges, snap fits, and more!
Cons of Plastic Injection Molding
1) High Initial Cost
The initial cost to design and manufacture a plastic injection mold is very high. The cost of the mold depends on the part's size, complexity, and the number of cavities required. The tooling cost is made up of several factors such as the size and thickness of mold, number of cavities, design, materials, etc.
When a new mold needs to be designed from scratch, it will take a longer time to finish as compared with modifying an existing mold. Hence, new molds come at a high price due to the increased time spent on designing and producing them.
2) Takes Longer to Get Started
Crafting molds for plastic injection molding is not a quick process. The molds are not just made in minutes; it takes days and sometimes weeks or months to make the right tools that will be used in the production process. This is why some companies may be hesitant to use plastic injection molding as a first option because they often need large numbers of small parts, and they need it really fast.
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