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The Pros and Cons to Plastic Injection Molding

Plastic Injection Molding is a process that involves forcing molten plastic into a metal mold under great pressure. During the injection process, the plastic flows through a heated barrel and then gets pushed through a nozzle at extremely high temperatures, which causes the plastic to melt.

The melted plastic enters the mold cavity and quickly cools and solidifies once it comes in contact with the metal mold. Then, the excess plastic is removed from the mold and trimmed off to make sure that it matches the design specifications of the product.

However, with all great things, there are some disadvantages or downsides to injection molding. Some cons are that it is costly, time-consuming, and sometimes extremely difficult to remove molded plastic from the metal mold. These problems can lead to molding defects which then have to be repaired or reworked.

In this article, we will touch on both the pros and cons of plastic injection molding. We’ll even discuss some tips for reducing cost and choosing the right process.

The pros of plastic injection molding

It is cost effective, fast, and produces high-quality parts. During the injection molding process, plastic pellets are fed into a large screw-type machine where they are melted down to the point of liquefaction. Once in liquid form, these pellets can be injected under very high pressure directly into the cavity of the metal die or mold.

Once in the die, pressure is applied to the molten plastic stream, which ensures that it fills every cavity of the mold. Parts can be produced quickly and easily. Because only a small volume of material is needed for each part, this process is very cost effective as well.

The flexibility afforded by injection molding can be seen in the diversity of products that this process is used to create. From the soles of shoes, headlights for cars, and even gear shift knobs inside automobiles themselves, plastic components are everywhere because of injection molding. Simply put, there is no other manufacturing process capable of producing such an incredible diversity of parts so quickly and cost-effective.

The cons of plastic injection molding

There are, of course, limitations to injection molding that must be considered by engineers when designing new products. The first drawback is that the process only works with plastics and other polymers, which are sometimes difficult to work with. In addition, injectable materials can be overworked if pressures are not maintained properly throughout the process.

Pressure plays a significant role in the success of plastic injection molding. Too low pressure results in poor part quality, while too much pressure can cause spalling or tearing parts. The process also requires precise design capabilities, which are not required for other manufacturing operations. If not calibrated properly, a series of defects can occur in the final molded parts, leading to unusable components.

Plastic injection molding is an incredibly fast process, but even it requires a wait time for the parts to cool between run times.

Because of the fast cycle times, plastic injection molding is perfect for prototyping and small-batch runs. Other processes might find it too cost prohibitive. However, the process is not as efficient or effective as other forms of production methodologies at higher production rates.

Despite these drawbacks, plastic injection molding remains an efficient method of producing both large and small quantities of complex plastic parts.

How to choose the right manufacturing process for your product

Choosing the right manufacturers is a crucial step in the product development journey. Whether you’re in the prototyping or mass production stage, knowing the right questions to ask can make an enormous difference.

First, you need to ask yourself what are the most important factors for you? Are you looking to produce small runs of custom-made parts at a high level of quality, or do you want to meet higher volumes with lower costs?

You must also consider how much control you have over your product design. If the design is not something that would be easy to manufacture using off-the-shelf parts, then you’ll need to find a manufacturer that is willing and able to work with your design.

Tips for reducing costs and improving efficiency in your manufacturing process

To reduce costs, you are looking for manufacturers that can offer lower unit prices through economies of scale. The more units they produce, the cheaper it will be for you when buying large quantities.

Manufacturers work on turnaround times, so when looking at multiple potentials, suppliers look into how quickly the manufacturer can turn around the order. Again, if your part is simple enough to make quickly, you can afford to work with manufacturers that are slower at completing orders.

When deciding on which supplier to use, it’s important to look into what they need from you in terms of the injection molding process. They will ask for drawings or CAD files of your part. They will need a mold of your part in order to manufacture it.

It is important that you choose the right supplier because there are a lot of factors outside of your control when working with them, such as their speed and ability to meet deadlines.

Managing more than one supplier means hiring multiple employees, which means more overhead costs and less of your money in your pocket. It is more difficult to keep track of suppliers that are located in different areas.

If you need to change suppliers, the process will be much more difficult if they are not near each other. Gauges can take weeks or months to approve blueprints. Communication between suppliers may become difficult due to time zone differences and language barriers. Other technological advances have made communication easier, meaning that companies are less likely to want to use a supplier that is far away.

If a supplier does not provide high-quality products, it can be difficult for a business to stay afloat during the re-tooling process. This also delays projects and wastes resources. Employees will work harder when they have been trained with processes from one company, making them less likely to want to work for other companies that use different processes.

Customized products are more expensive than mass-produced products, which may cause problems with generating consumer interest. Mass-produced items can be made quickly and cheaply. If these products do not last as long or serve their purpose as well as a customized item, the customer will return less often for new purchases.


This is just one process used in manufacturing. Other processes have advantages and disadvantages too, but this process provides some insight into how companies can be creative with their manufacturing techniques to meet consumer demands.

Plastic injection molding has various pros and cons. However, the pros outweigh the cons when it comes to this manufacturing process. Businesses can take advantage of these pros and minimize the damage inflicted by its cons, allowing them to produce products efficiently and effectively.

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