injection molding vs blow molding

You are creating a product that will require molded plastic parts. While injection molding and blow molding are two of the most popular methods to create high-quality, affordable plastic parts and products that are cost-effective, they are not the same. Thus, their purposes and requirements are different. What’s the difference?

This quick guide to injection molding and blow mold will save you time when searching for suppliers.

Products of varying types

The most obvious difference between injection molding and blow molding parts is the fact that injection molding produces solid parts while blow molding creates hollow ones.

Injection molding is a viable choice if you need to produce something with a rigid wall. Common examples of injection-molded parts include bottle caps, hair combs and housings for computers or televisions.

Blowing molding is a great option if you require a piece that can hold fluids, be flexible or structural. Bottles are the most popular example of a blow-molded product.

Blow molding is a low-cost method of creating billions of bottles. However, blow molding can be used to create a wide range of industrial parts such as coolers, fuel tanks and stadium seats. Here is a complete list of blow-molded products.

Processes that differ

Injection molding is where melted resin is injected in a hollow mold until it’s completely filled. Injection molding is held together by intense pressure.

This pressure is sufficient to allow for all interior parts to be filled with high-pressure molten plastic resin. The “tonnage” pressure required to keep the mold together determines the size and cost of a product.

A plastic tube can be heated up and filled with hot plastic to form a blow mold. The mold is then placed around the “parison”, trapping the plastic and allowing air to continue filling the parison until it forms the part.

The weight of the “shot” of plastic used in the mold determines the size of the machine and the associated costs.

For similar components dimensions and weights, the unit costs of injection-molded and blow-molded parts are identical.

Different types of mold

For precise control of material flow, injection molds need to have high precision matches between the mold halves. Injection molding is 90% of the work.

The rest of the process should go smoothly once you have created a functional mold that is error-free. An injection mold is generally more expensive than a blow mould because of its precision.

Blow molds allow for more flexibility between the mold halves, as each mold half creates its own wall shape. The mold is only half the battle in blow molding.

You must monitor variables like wall thickness, flash, air leaks, streaks, and flash. Wall thickness variation is one of the most significant factors for product designers. Quality control is also an imperative part. Quality oversight should be handled by a supplier’s quality team.