Product manufacturers that produce consumer goods featuring plastic parts have two main options when it comes to cost-effective production. They can use either injection molding or blow molding. This article will outline the differences between these two processes and the main advantages of each of them to help manufacturers make informed decisions.

What Is Blow Molding?

Blow molding follows a process similar to that of glass blowing, but it’s used for plastic parts. Plastic bottles, for example, are almost always manufactured using blow molding, as are some forms of plastic packaging. Manufacturers can learn more about their packaging options from

How It’s Done

Manufacturers heat a plastic tube filled with air to create what’s known as a parison. They then clam a mold down to trap the parison, which continues to fill in. This offers plenty of design freedom, but it requires careful attention to factors like wall thinning, air leaks, and streaks. Quality control is an important element of blow molding, so business owners looking for packaging manufacturers capable of using this technique should make sure they are trained to monitor every aspect of the molding process.

Advantages of Blow Molding

This process is perfect for making one-piece hollow plastic objects like bottles. It’s an economical way to create uniform, thin-walled containers for packaging liquids and solids. The one-piece construction means there’s no need to connect individual pieces of plastic, which allows manufacturers to create shapes that can’t be created using injection molding. Machinery costs are also lower than those associated with injection molding, so it’s an economical option for those who need mass-produced plastic containers.

What Is Injection Molding?

Injection molding involves creating a pre-engineered, detailed mold from aluminum or stainless steel, then injecting it with liquid polymers under high pressure and temperatures. It’s typically used for high-volume orders of precision parts.

How It’s Done

Injection molding requires attention to detail during the pre-manufacturing stage. The molds must be properly engineered to ensure precision before they can be filled and cooled to release newly manufactured plastic parts. The reason such attention to detail is required is that injection molds are fabricated in two parts, so they require a perfect match between mold halves. As with blow molding, injecting molding requires careful attention to quality control.

Advantages of Injection Molding

Injection molding is better for large runs of precision parts, especially when they require multiple cavities. It’s a precise and efficient process with low scrap rates but is typically more expensive than blow molding. Injection molding also offers more flexibility. Customers can change the material type or color with ease without substantially increasing their production costs. If uniformity is a priority, injection molding is always the way to go since it’s impossible to get plastic to thin out 100% evenly using blow molding.

The Bottom Line

Both injection molding and blow molding have their place. Those looking for an affordable way to mass-produce plastic bottles and other types of packaging or parts in one piece may want to look into blow molding, especially if they don’t require precision and complete uniformity of thickness. Those who require precision parts with uniform thickness, or want to have plastic parts manufactured to fit perfectly together, should find a company that uses injection molding. It will be more expensive, but the additional investment may be worthwhile, especially for large orders.


By Chakraborty

Dr Chakrabarty is the Chief Innovation Officer of IntuiComp TeraScience. Earlier she was Assistant Professor of Delhi University, a QS ranked university in India. Before that she has held research positions in IIT Mumbai, IIT Chennai and IISc Bangalore. She holds 2 patents and over 20 research publications in her name which are highly cited. Her area of research is in smart technologies, integrated devices and communications. She also has a penchant for blogging and is an editor of Business Fundas.