The Process Behind In-Mold Labeling

In-mold labeling (IML) is a sophisticated manufacturing technique where meticulously cut plastic films, referred to as labels, are seamlessly integrated into the injection mold using a specialized handling unit. These labels are securely affixed in place, often employing a vacuum or a static electricity charge, before being injected with plastic material.

Subsequently, a precise combination of heat and pressure is applied to melt the substrate film, seamlessly merging it with the plastic material within the filling and holding cycles. Notably, this innovative technology is frequently employed alongside stacking molds, boosting production rates while consistently delivering top-notch quality and reproducibility.

Now, if you’re new to in-mold labeling, this article will take you through everything related to this injection-molded labeling approach used in modern manufacturing processes. So keep reading to learn all about it!

Key Stages of the IML Process

The IML process unfolds through three pivotal stages: pre-production, molding and labeling, and post-production. While the labeling during molding stage takes center stage, understanding the nuances of pre-production and post-production is pivotal to ensuring the production of high-quality IML components.

Pre-Production Preparations

Pre-production encompasses the meticulous preparations made by manufacturers and designers before venturing into the injection-molded labeling phase. These preparations play a pivotal role in determining material selection, label alignment, machine setup, and more, all of which significantly impact the final product’s quality.

Here’s a closer look at the pre-production steps:

  • Label Material Selection: Choosing the right label material is paramount for IML. It ensures the label’s resilience throughout the plastic fabrication process and its suitability for the intended environment. Common materials like polypropylene and polyethylene are renowned for their resistance to chemicals, moisture, and UV light. They come in various sizes and thicknesses, catering to diverse label designs. Additional considerations include ink compatibility, appearance, finishes, textures, transparency levels, and adherence to product design. IML materials may also encompass paper coated with adhesive or plastic film, known as In-Mold Paper Labeling (IMPL) or In-Mold Transfer (IMT).
  • In-Mold Label Design: A visually appealing label design tailored to the label’s dimensions is essential. Design considerations extend beyond aesthetics, encompassing factors such as legibility, durability, and compatibility with the chosen IML material and molding process. By harmonizing these elements, you can craft IML designs that enhance your products and reinforce your brand image.
  • Ink Selection: The ink used for label printing must be hard-wearing and capable of withstanding the rigors of the molding process, including heat and pressure. It should also seamlessly interact with the plastic film, preventing issues like smudging or poor adhesion.

Molding and Labeling Process

The heart of the IML process lies in the injection-molded labeling stage, where precision and attention to detail are paramount. This stage unfolds in the following sequence:

  • Label Placement: Once the label’s position is defined, it is meticulously positioned within the mold cavity. Precise alignment is critical to ensure optimal fusion between the label and the injected plastic.
  • Injection/Forming: The next step involves the injection of molten plastic, which can occur through methods such as injection molding, blow molding, or thermoforming. Each method boasts unique requirements, which we’ll explore further in the subsequent section.
  • Cooling: The cooling phase allows the in-mold label to meld seamlessly with the plastic component. As the material cools and solidifies, the finished product is gently ejected, poised for the next steps.

Post-Production Excellence

The post-production phase of IML encompasses a series of meticulous steps geared toward upholding quality, consistency, and adherence to design specifications. This phase involves tasks such as flash removal, final product packaging, and preparation for subsequent assembly processes.

Post-production plays a pivotal role in ensuring that IML components meet essential criteria, including precision, finish, and durability. This may entail rigorous quality control checks, ranging from visual inspections to mechanical testing, all designed to align with specified standards.

The Three Different In-Mold Labeling (IML) Processes

The three different production processes used to perform in-mold labeling are:

#1 – Injection Molding

Injection molding is a popular way to shape materials like thermoplastics (Check thermoplastic manufacturing) and thermosetting polymers. In this process, manufacturers inject heated, liquefied plastic into a mold through a small opening.

As the plastic cools and solidifies within the mold, it takes on the desired shape. During injection molding with in-mold labeling, a preprinted polypropylene label is placed into the mold. This label fuses seamlessly with the thermoplastic during injection, resulting in a fully labeled plastic product.

Common examples of products manufactured using injection molding and in-mold labeling include:

  • Butter or ice cream tubs
  • Skincare products packaging
  • Plastic paint buckets
  • Computer keyboards
  • Cell phone keypads

#2 – Blow Molding

Blow molding is the preferred process for creating hollow plastic parts. Manufacturers employ this technique to stretch or extrude heated plastic into a mold’s shape. This process has historical roots in glass blowing, and it remains essential for creating various products, especially those requiring a waterproof label integration in molding.

In blow molding with in-mold labels, the extruded plastic is introduced into a hollow tube, which is then captured in the mold. Air is blown into the tube, causing it to take the mold’s shape. The mold’s inner wall contains a polypropylene sheet with printed or embedded labeling.

As the plastic cools and solidifies, the label becomes an integral part of the product. This method is commonly used for liquid containers, such as those for liquid soaps, shampoos, dishwashing detergents, ketchup, and sauces.

#3 – Thermoforming

Thermoforming differentiates itself from the previous processes by using heated plastic sheets rather than fully melted plastic. Manufacturers rely on heated plastic sheets and a forming tool to shape containers.

 In the case of in-mold labeling, the preprinted labels accompany the plastic sheets during the forming process. The heated sheets are stamped onto a mold, where the printed labels fuse with the plastic.

Thermoforming is frequently employed for producing plastic cups (check the cup overmolding process), including ice cream cups and coffee cups, as well as plastic tubs designed for ice cream packaging.

Elevating Industries Through Precision in CNC machining and injection molding

Advantages of Implementing In Mold Labeling (IML)

Incorporating In-Mold Labeling (IML) into the manufacturing process offers several significant advantages:

  • Cost Efficiency: IML reduces long-term production costs by minimizing waste, labor, and time. The labels are integrated directly into the mold, eliminating the need for separate labeling during the molding process, reducing labor costs, and minimizing material waste.
  • Streamlined Production: With IML, products are 100% finished right after the plastic injection process, eliminating the need for post-labeling procedures. This streamlines production saves time, and reduces the need for additional manpower.
  • High-Quality Graphics: IML allows for exceptionally high-quality graphic resolution. Products that rely on visual appeal at the point of sale benefit greatly from this advantage, ensuring that the packaging stands out and attracts consumers.
  • Integrated Visual Effect: Since the label becomes an integral part of the product during the molding process, the visual effect is seamless and appears as if the product was directly printed, enhancing its overall appearance.
  • Durability: In-mold labels are highly resistant to rubbing and scratching. The labels endure longer due to a protective plastic layer that shields the design. This durability ensures that the product maintains its visual appeal throughout its lifecycle.
  • Temperature Resistance: IML labels are capable of withstanding a wide range of temperatures, including heat, cold, freezing, and microwaving, just like the product itself. This resilience ensures that the label remains intact and legible under various storage and usage conditions.

IML vs. IMF vs.IMR: How Are They Different?

When considering IML, you might often come across the terms IMF (In-Mold Film) and IMR (In-Mold Decorating). To avoid any confusion, it is important to understand what they are and how they are different from IML.

Precisely, in-mold labeling focuses on putting preprinted labels made of strong polypropylene into a mold before plastic is injected. As the plastic takes shape in the mold, it merges with the labels, creating a single product with labels already in place. It’s great for making visually appealing and well-labeled plastic items.

Compared to IML, IMF is also quite similar. However, instead of labels, it uses printed plastic films with designs. These films are carefully put inside the mold and blended with the melted plastic as it shapes into the final product. IMF is known for its ability to create intricate and colorful designs on various plastic items.

In contrast to the two, IMR takes a different approach. It uses a decorated or printed film that’s placed on the mold’s surface. When plastic is injected into the mold, the design of the film transfers onto the plastic product’s surface. IMR is perfect for achieving high-quality and finely detailed graphics on the product’s exterior.

To sum it up, IML focuses on integrating labels, IMF uses printed films inside the mold, and IMR uses decorated films on the mold’s surface. Each method has its unique advantages, so it’s important to choose the right one for specific production needs.


In-mold labeling stands as a cost-effective and efficient method for rapidly manufacturing labeled containers. Its durability, resistance to wear and tear and waterproof nature make it an ideal choice for embedded labeling molded containers.

When seeking in-mold labeling solutions, entrusting your projects to Prototool is the key to unlocking the full potential of this process.

With a wealth of professional experience and cutting-edge approaches, Prototool ensures that your molded-in labeling needs are met with precision and excellence, making

Engineering Excellence in Every Detail

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