The differences between injection molding and blow molding

When manufacturing a product that requires molding plastic parts, you have several processes to choose from, depending on the application and the type of part you want to produce. Injection molding and blow molding are two popular methods for producing high-quality, cost-effective plastic parts.

But before you start researching different manufacturers and formats, it’s a good idea to learn about the differences between the two processes. In this article, we will help you better understand the differences and distinctions between these two processes:

What is the process of blow molding?

The blow molding process is designed to produce high-volume, one-piece hollow objects. If you need to make a lot of bottles, this process is for you. Blow molding creates very uniform, thin-walled containers. And it can do so very economically.

Advantages of blow molding or blow molding:

The cost of blow molding is lower than plastic injection.

The cost of blow molding machines and devices is usually lower.

One-piece manufacturing so there is no need to join different parts of the part, which can produce shapes that injection molding cannot.

In the blow molding process, a plastic tube is heated and filled with air until it essentially becomes a balloon of hot plastic called a parison. A mold is then closed around it and encloses the plastic. While the air continues to fill the parison in the shape of your mold. The size of the machine and the costs related to the production of the blow molding product are based on the weight of the plastic shot used in the mold.

Plastic blow molds have more design freedom between mold halves because each mold half creates its own wall shape. In the blow molding process, mold formation is important, but there are also variables such as wall thinning, air leakage, flash, and streaks that must be monitored. For example, changing wall thickness is often an essential factor for product designers to consider. Quality control is an important part of the process. And it’s important to look for a supplier who is qualified and trained to measure, monitor and improve every aspect of the product.

What products can be made with plastic injection and blow molding machines?

Examples of parts and products created using blow molding or blow molding include: water bottles, shampoo and other small bottles, auto parts, stadium seating and seating, watering cans, coolers, or any other hollow part.

What is the process of injection molding?

Plastic injection or injection molding requires a lot of basic engineering to develop precise tools or molds. Molds, made of stainless steel or aluminum, are injected with liquid polymers at high temperatures and under extreme pressure. The molds are then cooled to release the complete plastic parts.

Plastic injection molding is used to produce a wide range of widely used products, including common plastic items such as bottle caps as well as remote control housings, baskets, chairs, syringes, disposable containers, and more. It is also commonly used to make larger items such as car body panels.

Advantages of injection molding:

Precise and highly engineered tools with multi-cavity (cavity) mold options.

Accurate and efficient processing for large volumes of small parts

Flexibility in the possibility of changing the type of material or color used

Efficient use of materials and low waste rate

Plastic injection molding is ideal for high-volume orders and mass production projects that require thousands or even millions of identical parts. Injection molds must have high precision between the mold halves, so the material flow is perfectly controlled. With injection molding, mold creation is the key to making a complete and accurate part. Once the production mold is finalized and the machine is ready, production begins.

The initial setup is thoroughly checked for any component defects. If no defects are found, full production can begin. Depending on the part and agreement with the molder, quality checks can be done regularly. Experts check for firmness, color accuracy and any common defects such as flash or warping. The precision of plastic injection molding usually makes it more expensive than blow molding.