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Custom Plastic Molding: Thermoforming vs Injection Molding

December 05, 2020

Custom Plastic Molding Process

Custom plastic molding process is a term we use to describe the process of molding plastic into various shapes according to its need. Plastic, which is also an essential product of modern-day industries, has been in demand for centuries.

It is now almost impossible to name a thing that is not made of plastic or doesn’t comprise of it. From parts of a machine to our daily use items or even faulty human body parts consist of plastic as a significant component.

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The Custom plastic molding process involves shaping a liquid or solid material using a matrix or a mold. We use different polymers of polyethylene or polypropylene (in liquid or powder form) and place it into a mold or a matrix so we can shape the plastic according to the need.

This process involves the application of pressure and heat of various ranges to get the desired result.

Custom plastic molding

Types Of Custom Plastic Molding:

Injection molding and thermoforming are the most common processes of plastic molding. However, there are some more that I have mentioned below:

  • Rotational molding.
  • Injection molding.
  • Blow molding.
  • Extrusion molding.
  • Compression molding.

Injection Molding  Vs. Thermoforming:

Injection molding and thermoforming are the two main processes of the custom plastic molding process. Although these processes don’t differ much, both have unique features and are important for specific functions.

In injection molding, we inject the liquid polymer into the mold under extreme pressure and high temperature. Which then yields plastic parts upon cooling.

On the other hand, thermoforming involves heating up of thermoplastic sheets, which we later form on the mold’s surface.

Let us now look at both the processes individually that’ll make it easier for you to make a better decision when opting for the right process.

Injection Molding Process:

The injection molding process is one of the significant custom plastic molding processes. It involves injecting heated material into the metal molds, which, just like other forms of plastic molding when cooled, reveals a solid plastic piece.

It is widely used in the industry for the manufacture of small products of daily use to large parts of vehicles; all aspects are covered using this technique.

Using this technique we can produce things such as bottle caps, toys, combs, chairs, tables, etc.

Not only this but using this technique we produce most if the mechanical gears.

Types Of Equipment:

This process used for the manufacture of most of the plastic products does not require many types of equipment.

Mould is the main component of the injection molding process, which is not only of main importance but also highly expensive. These molds are made using metals like aluminum and nickel.

Steel molds are usually more expensive, but they generally have a longer lifespan, making them more useful in the industry. On the other hand, aluminum molds are comparatively cost-effective but not so efficient in work.


The injection molding process offers plenty of benefits:

  • Advance tooling:

This process allows the user to produce high-quality products that are finely detailed, unlike other processes. This fine detailing is possible due to the extreme pressure used in this technique.

  • Precision:

It is ideal for repeated use over a period of time. It is particularly for the intricate objects that cannot be manufactured using thermoforming.


Applications that are made by using this process include:


  • Buildings: Door and window locks, handles, tools, etc.
  • Medical industry: X-ray components, machinery, several diagnostic kits, surgical types of equipment.
  • Automotive: gears, blades, panels, etc.

Thermoforming Process:

Thermoforming is one of the two most commonly used processes of custom plastic molding. It is of great importance in the industry due to its innumerable advantages.

In this process, we heat a thermoplastic sheet until it softens and then stretches it over a single sided mold.

The most common types of the thermoforming process include:

  1. Vacuum forming.
  2. Mechanical forming.
  3. Pressure forming.

The vacuum forming process uses heat and pressure to obtain the product upon cooling. We use a vacuum to get the desirable result once we stretch the sheets over the mold. Though the pressure forming process is much alike, it uses greater pressure to get the fine details. So we use it more where extreme precision and detailing requires.

Types Of Equipment:

Here is the list of the types of equipment we require for this process:

  • Pressure or vacuum former
  • Rotatory transformer ( three or four stations)
  • CNC robotic routers
  • Molds (aluminum, male/female, etc.)



This extremely important process of molding plastic offers plenty of advantages. Here is the list of some below:

  • Low-cost tools:

Molds we use in thermoforming are made of low-cost aluminum, unlike injection molding in which we use high-quality steel. since it uses a single-sided mold rather than double sided, it consumes half of the material, which consequently reduces the cost.

  • Increased speed:

We use thermoforming extensively due to its increased speed. It is much faster in product development than the injection molding process. Also, it uses light aluminum rather than heavy steel as the main product of mold, which makes it faster in work.

  • Versatility :

One of the unique features of thermoforming is the incorporation of textures and colors. It allows the users to add various colors to the products allowing durable and vivid coloring. Also, it helps to enhance the appearance of the product by allowing silk screening, coatings, and stencil work, which adds textures to the piece.

  • Adaptability :

Thermoforming allows the users to modify the objects with ease and with minimal cost making it the most preferred process in the industry. This is also due to the single-sided mold rather than the double-sided used in the injection forming process.


Cost-effectiveness, versatility, and adaptability of the thermoforming process make it useful for many applications in the industry:

  • Buildings: panels, tool cases ( interior & exterior).
  • Office: printers, computers, faxes, furniture, panels, etc.
  • Automotive: bumpers, dashboards, seats, etc.
  • Transport: lightweight components, seat components, dashboards, etc.
  • Medical industry: imaging equipment, diagnostic equipment, bed components, panels, etc.
  • Aerospace: gears, window panels, air ducts, etc.

Custom plastic molding


Both custom plastic molding techniques: injection molding process, and thermoforming provide a lot of benefits in the industry. These two processes provide unique effectiveness in crafting plastic parts according to the particular requirement.

The injection molding process is a better option for small intricate products for large industries. Providing fine detailing and aesthetic look to the product. While thermoforming is common for large products but in small industries.

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