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What Is In-mold Labeling? Enhancing Product Durability and Branding

injection molding in mold labeling

Published:  May 12, 2023         Reading Time:  About 3 minutes

In-mold labeling (IML) is a common step in plastic molding for industries such as food, automotive, personal care, and beauty, etc., that desires permanent labeling on plastic products. Aside from guaranteeing permanent labeling, the process is also a durable, versatile, less costly, and sustainable labeling solution.

If you work with injection molding or blow molding, you understand the significance of staying updated on the latest techniques. One such technique is IML, which can have a big impact on the look and functionality of your plastic products.

But what exactly is the IML printing process? And how can you know if it’s the right choice for your project? In this article, we’ll provide a comprehensive overview of in-mold labeling, covering everything from its basic properties to advanced considerations. Whether you have extensive experience or are new to plastic molding, this guide will assist you in making well-informed decisions.

What’s In-mold Labeling (IML)?

what is iml printing
what is in-mold labeling printing

IML fuses a pre-printed label with the plastic part by placing it in the mold. Injection in-mold labels are positioned inside the mold and infused with molten plastic during injection molding. After that, the label fuses with the plastic part, and on complete solidification when cooling. This creates a finished product with a permanent, durable, and long-lasting label.

In-mold labeling has a few advantages over other traditional labeling methods. For one, industries such as automotive and home care/laundry make use of it. The big reason is that the formed product has a durable and long-lasting label. Automation in label placement enhances productivity and reduces production costs, offering an additional benefit in the process.

Working Principle of In-mold Labeling

In-mold labeling inserts a label in the mold before injecting molten plastic, creating a durable, visually appealing label integrated with the product. But how can you ensure that your IML process is optimized for maximum efficiency and quality? Next, we’ll break down the key steps of the IML process, from pre-production to post-production.

Key Steps of the IML Process

The IML process consists of pre-production, molding and labeling, and post-production steps. The key step of the process itself is the molding and labeling stage. However, knowledge of the pre-production and post-production steps can help ensure you produce only quality IML parts.

Pre-Production Steps

The pre-production steps comprise the different steps taken by the manufacturers and/or designers before the molding and labeling stage. This is critical to the success of the IML process as it aids in the selection of the right material, label alignment, machine setup, etc., which in turn can influence the finished product’s quality. Pre-production steps comprise the following;

  • Label Material Selection: The right material is crucial for IML to ensure the label can withstand the plastic fabrication process and function well in its environment. Common materials like propylene and polyethylene offer high resistance to chemicals, moisture, and UV light, and come in different thicknesses and sizes to suit various label designs. Other factors to consider include ink acceptability, appearance, finishes, textures, transparency levels, and product design. IML materials can also be paper coated with adhesive or plastic film, known as In-Mold Paper Labeling (IMPL) or In-Mold Transfer (IMT).
  • In Mold Label Design: In-mold label design should be visually appealing and tailored to the size of the label. The design should also consider functional requirements such as legibility and durability, and be compatible with the IML material and molding process. With these factors in mind, you can create IML designs that enhance your products and brand image.
  • Ink Selection: The ink used for printing the label should be durable and able to withstand the heat and pressure of the molding process. The ink should also be compatible with the plastic film without leading to smudging or other adherence issues.  

Molding and Labeling Process

Considered the most important IML process stage, this stage comprises the following steps.

  • Label Placement: After designating the label, place it in the correct location in the mold cavity. Proper alignment is important to aid maximal and correct fusion between the label and the injected plastic.
  • Injection/Forming: After placement, injection of the molten plastic can occur via injection molding, blow molding, or thermoforming. Each method is unique with certain requirements explained in the next section.
  • Cooling: This allows the fusion of the in-mold label with the plastic part. On cooling and solidification, the finished product is ejected.  

Post-Production Steps

The post-production stage of IML involves multiple steps to ensure quality, consistency, and adherence to the specified design. This stage can include removing flashes and other materials, packaging the finished part, and processing it for further assembly.

Post-production ensures functional IML parts that meet criteria like accuracy, finish, and durability. This may involve quality control checks, such as visual inspections and mechanical testing, to meet specifications.

Types of In-mold Labeling Process

Although injection molding is commonly associated with in-mold labeling, alternative methods can also achieve it. Here, we will talk about the three most common IML forming methods: injection molding, thermoforming, and blow molding.  

Injection Molding

injection molding importance
injection molding importance

In-mold labeling (IML) is commonly associated with injection molding, the recommended process among plastic injection molding suppliers. In injection molding IML, the label is placed in the mold using a polymer carrier and secured with mechanical means or air pressure. The molten plastic is injected into the mold, fusing with the label to create a permanent decoration on the plastic part.

Injection IML comprises different injection molding techniques such as insert molding and over-molding both compatible with in mold labels. It is a cost-effective method that provides manufacturers with long-lasting products and efficiency in production. Common products made using injection IML include ice cream tubs, computer keyboards, smaller plastic paint buckets, and cell phone keypads.

Blow Molding

Blow molding is the second most popular IML process, after injection molding. In this process, a plastic material is heated until it stretches to form a tube, which is then placed in the mold and blown to take the shape of the mold cavity, forming the final product.

Unlike injection molding, the label is fixed in the mold cavity before the plastic tube is placed. As the tube is blown and takes the shape of the mold, the label fuses with the plastic to create a highly durable labeled product.


Thermoforming is the least common IML process, but it’s still an effective technique for creating high-quality, decorated plastic products. This process involves heating sheets of plastic material until they become soft and pliable, and then stretching and placing the sheet on the mold using vacuum suction or mechanical pressing.

Thermoforming occurs in three stages: heating, forming, and trimming. In the heating stage, the thermoplastic material softens, making it easy to shape. During the forming stage, the plastic sheet is stretched and placed on the mold, where it conforms to the shape of the mold using vacuum suction or mechanical pressing. In the trimming stage, excess material is removed from the finished part.

For thermoforming IML, manufacturers insert the label into the mold before the forming stage. During the cooling process, the plastic sheet and the label fuse together, resulting in a fully decorated plastic part or product. Thermoforming IML is commonly used to make rigid plastic products like cups, tubs, trays, lids, and blisters for use in the food, medical, and retail industries.

Importance of In-mold Labeling (IML) in the Industry

In-mold labeling printing is becoming increasingly popular in various industries due to its ability to deliver high-quality, durable, and customizable labels. This labeling process offers numerous benefits, including increased production efficiency and reduced operating costs. Here are some of the key advantages of this labeling technique.

Increased Branding and Customization Options

IML offers increased branding and customization options for manufacturers, thanks to its high-quality color printing and quick design changeovers. With IML, manufacturers can produce labels of exceptional quality that enhance their brand image and appeal to their target audience.

By leveraging IML’s full-color printing capabilities, manufacturers can create labels that are visually striking and help their products stand out on the shelves. This can be particularly important in crowded markets where differentiation is key to success.


In-mold labeling is a cost-effective labeling process that can provide significant benefits for manufacturers, particularly in mass-production scenarios. It is characterized by shorter manufacturing times and a simplified manufacturing process, thanks to the integration of the labeling step into the molding process.

Compared to traditional labeling methods that require an additional step and more resources, IML can help manufacturers reduce production costs by eliminating the need for new labor and consumables. This results in a more streamlined and efficient production process that can save both time and money.

Durability and Longevity of Product

One of the key benefits of IML is that it fuses the label permanently with the plastic part during the molding process, creating a strong bond that enhances the overall durability of the product. This means that the label won’t peel, crack, or fade over time, even when exposed to harsh environments or frequent use.

Because the label is an integral part of the plastic part, it also enhances the product’s overall structural integrity, making it more resistant to impact damage and wear and tear. This can be particularly important in industries like automotive, where products must withstand harsh environments and frequent use.

Efficiency and Time-Saving

It integrates the labeling process directly into the molding process, creating a streamlined and efficient production process. This eliminates the need for an additional labeling step, which can save time and reduce the risk of errors or defects in the labeling process. 

Moreover, IML offers automation capabilities, enabling manufacturers to produce labeled products with consistently high quality, increased speed, and reduced manual labor. This can reduce production costs and increase output, making IML a cost-effective labeling solution for manufacturers in various industries. 

Versatility and Adaptability

The versatility and adaptability of in-mold labeling allow for its use in various applications and adaptation to different materials, designs, shapes, and sizes. This process offers extensive customization options, including full-color, high-resolution graphics, and designs tailored to specific branding and marketing requirements.

It Prevents Counterfeit Products

Counterfeit products are a significant problem in many industries, as they can damage a company’s reputation and result in significant financial losses. However, by using IML to label products, manufacturers can create a more secure labeling solution that is difficult to replicate.

IML labels consist of durable materials that are challenging to duplicate or copy, and they fuse permanently with the product during the molding process. This makes it difficult for counterfeiters to remove or replicate the label without damaging the product or making it obvious that it is not authentic.

Furthermore, IML labels offer the flexibility to incorporate security features like holograms or QR codes, enabling product authenticity verification. These security features can be difficult for counterfeiters to replicate, further enhancing the security of the product.

image 144

We’re Here to Meet Your In-mold Labeling Needs

RapidDirect experienced team specializes in delivering high-quality plastic parts with exceptional in-mold labeling. With our state-of-the-art facilities and advanced technologies, we ensure precise label placement and flawless fusion for a stunning end result.

Don’t settle for ordinary labels – unlock the potential of in-mold labeling with RapidDirect. Contact us today to discuss your project!

Disadvantages of In-mold Labeling

There are also some disadvantages of this technique you should consider.

Compatibility of Label and Product Materials

IML labels are typically made from materials that are specifically designed to work with the plastic material used in the molding process. While these materials are highly durable and can create a strong bond with the product, they may not be compatible with all types of plastic materials.

If the label material and product material are not compatible, it can result in issues such as delamination, peeling, or other defects that can compromise the quality and durability of the product. In some cases, manufacturers may need to use a different label material or adjust the molding process to ensure compatibility, which can add time and cost to the production process.

Furthermore, the thickness of the label material can also affect the compatibility of the label and product materials. If the label material is too thick, it may not bond properly with the product material, leading to defects or issues with the final product.

Need for Specialized Equipment and Expertise

IML necessitates specialized equipment to handle and accurately position the labels in the mold during the injection molding process. Precise alignment and secure placement of the label are ensured through dedicated machinery designed for in-mold labeling.

In addition to specialized equipment, IML also requires specialized expertise. The process is complex and requires a deep understanding of injection molding and label placement. Operators should undergo training to handle the equipment, ensuring proper positioning and fusion of the labels to the product.

The need for specialized equipment and expertise can make in-mold labeling more expensive than other labeling methods. It also means that not all manufacturers have the capability to use IML, limiting its availability as an option for some products.

Potential for Label Defects and Misalignment

Incorrect label alignment or label defects can cause misalignment or inadequate adhesion, resulting in labeling defects like wrinkles or bubbles that affect the product’s appearance and function.

Issues during the process, such as uneven cooling or product warping, can cause label defects. These defects result in additional costs for manufacturers, as they may need to scrap or rework defective products.

Misalignment of labels can also be a problem, particularly if the product requires precise positioning of the label for branding or functional purposes. Misaligned labels can impact the product’s appearance. And make it more difficult to read important information or use the product effectively.

Application of In-mold Labeling Products

IML has diverse and numerous applications in several industries due to its efficiency, cost-effectiveness, and customizability. Below are the common applications of IML in several industries.   

IML in Food and Beverage Packaging

In-mold labeling practically applies to the food and beverage packaging industry, labeling containers such as bottles, cups, and lids with high-quality, photorealistic graphics. The process provides durable labels that are resistant to fading and peeling, making them suitable for use in different conditions.

IML in Medical and Healthcare Products

The in-mold labeling process is applicable in making medical devices and products such as inhalers, syringes, and vials. The process fulfills industry requirements for sterility and tamper-evidence while offering benefits like durability and permanence. Details on such products include dosage instructions, expiration dates, calibration, etc.  

IML in Automotive and Industrial Parts

IML labels are also applicable in the automotive and industrial parts for making products such as dashboard components and exterior trims. It is popular for its cost-effectiveness and durability, enabling manufacturers to customize parts with essential information and branding labels.

IML in Consumer Goods

IML is widely used in the consumer goods industry, particularly in food packaging, cosmetics, household products, and personal care products. It provides a durable and visually appealing labeling option that can withstand exposure to different environmental factors without losing its adhesion or visual appeal. The labels provide branding, ingredient information, and usage instructions, making them easier for consumers to identify and use.

Bonus Knowledge: Comparison of In-mold Labeling with Other Labeling Methods

The IML process has its advantages and disadvantages that aid its application in several industries. However, it is essential to make a thorough comparison before selecting this method over other labeling techniques. This section does a short comparison of common labeling methods with IML.

Pressure Sensitive Labels

Pressure-sensitive labeling is a common labeling option that involves applying the label directly on the product surface. Unlike IML labels, molded directly into the product, PSL has lesser durability and is more susceptible to wear and tear, moisture, and temperature changes.  Furthermore, there is higher customization in IML than in PSL.

IML labels are costlier than PSL labels due to complex production processes, expertise requirements, specialized equipment, and molds, increasing production costs. As a result, IML is suitable for high-quality, customizable, and durable labeling, while PSL offers a more cost-effective solution

Shrink Sleeve Labels

Shrink sleeve labeling involves printing the label onto a film, applying it to the product surface, and shrinking it with heat. Unlike IML’s flat appearance, shrink sleeve labels has a 360-degree, seamless, and highly attractive finish. However, even though both are customizable, IML has higher durability and customizability.

Shrink sleeve labels are ideal for low-volume production but add an extra step, increasing manufacturing time, and can be challenging to recycle due to multiple materials. 

Wet Glue Labels

Wet glue labeling involves adding the label to the product surface with the aid of an adhesive. Both support high-quality graphics and can allow for maximum branding opportunities. However, IML is more durable. Wet glue labels are susceptible to peeling and fading over time in humid or temperate environments.

Heat Transfer Labels

Heat transfer labeling involves printing the label onto a transfer paper and applying it using heat or pressure on the product surface. This gives a high-quality, vibrant finish, clear, and sharp label. Although both are durable, heat transfer labels are susceptible to fading and discoloration. Furthermore, they can be difficult to recycle due to the use of multiple layers of materials, including plastic and adhesives.  

Direct Print Labels

Direct print labels revolutionize the labeling process by allowing printing directly onto the product surface. This cutting-edge approach offers unparalleled flexibility in design, customization, and color options, and ensures exceptional graphics quality. They are durable but can fade or undergo discoloration. Furthermore, they are more sustainable than IML labels as they use less material and do not require an additional step.  


IML printing is a labeling process common to different industries that desire permanent, durable, versatile, and sustainable labeling solutions. There are several types and requirements. This article discussed the labeling process so you can know whether to consider it for your project.

Are you looking for an in-mold labeling service? At Rapid Direct, we offer plastic manufacturing services that can incorporate in-mold labeling. Our online quotation platform provides instant quotations with an automated DFM report after you upload your CAD file and choose your material and quantities. You can also manage and track your order. If you have any questions, feel free to contact our specialists.

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