What is the Difference Between Thermoforming and Injection Molding

The key difference between thermoforming and injection molding is that thermoforming involves a flat sheet of plastic heated to a pliable temperature followed by molding into the tool’s shape through suction from a vacuum, whereas injection molding uses plastic pellets that are heated to a liquid state and injected into the mold.

Thermoforming and injection molding are important industrial techniques that are important in manufacturing objects using plastic.

CONTENTS

1. Overview and Key Difference
2. What is Thermoforming  
3. What is Injection Molding
4. Thermoforming vs Injection Molding in Tabular Form
5. Summary – Thermoforming vs Injection Molding 

What is Thermoforming?

Thermoforming is an industrial process in which a plastic sheet is heated to a pliable forming temperature, which allows the plastic to be formed into a specific shape in a mold. It also allows trimming the plastic into a usable product. The plastic sheet or film refers to a thinner gauge and a certain material type that we can heat in an oven to get a high temperature, which allows us to stretch it into a mold. Thereafter, we can cool it into a finished shape. The simple version of this process is named vacuum forming.

In the process of thermoforming, we can use a small tabletop or lab size machine in order to heat small cut sections of plastic sheets. Therefore, we can stretch it over a mold using a vacuum. The thermoforming process is useful for sample and prototype parts.

The thermoforming process is different from processes such as injection molding, blow molding, rational molding, etc. Primarily, this process is useful in the manufacture of disposable cups, containers, lids, trays, blisters, clamshells, etc. when thin-gauge thermoforming is used. Thick-gauge thermoforming is useful in the manufacture of vehicle parts, dash panels, refrigerator liners, utility vehicle beds, and plastic pellets.

Generally, thermoforming companies tend to recycle the scrap and waste plastic by compressing it in a baling machine. Sometimes, this is achieved by feeding the material into a granulator to produce ground flake which is suitable for sale to reprocessing companies or to is re-used in the company.

What is Injection Molding?

Injection molding is an industrial process that is used for producing objects by injecting molten material into a mold. This process uses a host of materials, including metals, glasses, elastomers, confections, and thermoplastic or thermosetting polymers.

This process is mainly useful in creating wire spools, packaging material, bottle caps, automotive parts and components, toys, pocket combs, musical instruments, small tables, storage containers, etc.

Injection molding involves the use of a ram or screw-type plunger in order to force a molten plastic material into a mold cavity. Inside this cavity, the molten plastic solidifies into the desired shape. We can use this process for both thermoplastic and thermosetting polymers. Moreover, this process uses a high pressure injection of the raw material into the mold. The type of mold can be a single cavity or multiple cavities. When there are multiple cavities, each cavity is identical and can form the same parts. Generally, the molds are made from tool steel or stainless steel.

What is the Difference Between Thermoforming and Injection Molding?

Thermoforming and injection molding are important industrial techniques that are important in manufacturing objects using plastic. The key difference between thermoforming and injection molding is that thermoforming involves a flat sheet of plastic heated to a pliable temperature followed by molding into the tool’s shape through suction from a vacuum, whereas injection molding uses plastic pellets that are heated to a liquid state and injected into the mold.

The below infographic presents the differences between thermoforming and injection molding in tabular form for side by side comparison

Summary – Thermoforming vs Injection Molding

Thermoforming and injection molding are important industrial techniques that are important in manufacturing objects using plastic. The key difference between thermoforming and injection molding is that thermoforming involves a flat sheet of plastic heated to a pliable temperature followed by molding into the tool’s shape through suction from a vacuum, whereas injection molding uses plastic pellets that are heated to a liquid state and injected into the mold.

Reference:

1. Rogers, Tony. “Everything You Need to Know about Injection Molding.” Creative Mechanisms.

Image Courtesy:

1. “Thermoforming animation” By LaurensvanLieshout – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Injection molding diagram” By ariel cornejo – Own work (CC BY-SA 4.0) via Commons Wikimedia