What is In Mould Labelling?
In mould labelling (IML) is a manufacturing technique where a pre-printed label is placed directly inside a mould before plastic injection. During the In Mould Labelling injection moulding process, the molten plastic fuses with the label under heat and pressure, making the label a permanent part of the finished component.
Unlike traditional labelling methods, where stickers or graphics are applied after production, in mould labelling integrates decoration directly into the injection moulding cycle. This eliminates post-processing steps, improves durability, and ensures consistent quality across high-volume production.
For OEMs, product designers, and packaging engineers, IML provides a reliable solution for combining branding, functionality, and structural performance in a single automated process.
What is the In Mould Labelling process?
The In Mould Labelling process is integrated into the standard injection moulding cycle. Instead of applying a label after the part is manufactured, the label becomes part of the moulded component itself.
The process typically follows three main stages:
- Label placement
- Injection moulding
- Cooling and ejection
This seamless integration ensures the label bonds permanently to the plastic substrate without adhesives or secondary operations.
Step 1 – Label placement
The process begins with pre-printed in mould label films. These labels are usually made from the same polymer family as the moulded component, commonly polypropylene (PP).
Before the mould closes, the label is positioned inside the mould cavity using:
- Robotic automation systems
- Vacuum pick-and-place units
- Static charge placement
Precision is critical at this stage. Accurate alignment ensures the label sits perfectly within the cavity and avoids defects such as wrinkles or misalignment during injection.
Automation systems are typically integrated into the moulding cell to maintain high repeatability and consistent cycle times.
Step 2 – Injection moulding
Once the label is correctly positioned, the mould closes and molten thermoplastic is injected into the cavity.
During this stage:
- The molten polymer flows behind the label
- Heat and pressure bond the label to the plastic
- The label and substrate fuse together into a single structure
Because the label material is compatible with the base resin, the bond forms without adhesives or additional finishing steps.
This integration is what differentiates IML in mould labelling from traditional decoration techniques.
Step 3 – Cooling and ejection
After injection, the plastic cools inside the mould until the component solidifies.
When the mould opens:
- The finished part is ejected
- The label is already permanently bonded to the surface
- No additional decoration or labelling process is required
The result is a fully finished component leaving the mould ready for use or packaging.
In Mould Labelling injection moulding vs Traditional labelling
Traditional labelling methods typically involve applying a printed sticker or sleeve after the part has been produced. This requires additional production steps, equipment, and handling.
In contrast, in mould labelling integrates the decoration directly into the moulding cycle.
Key differences include:
| Feature | In Mould Labelling | Traditional Labelling |
|---|---|---|
| Application stage | During moulding | After production |
| Adhesives required | No | Yes |
| Durability | Very high | Moderate |
| Production steps | Single integrated process | Multiple steps |
| Automation compatibility | High | Often manual or semi-automated |
Because the label becomes part of the plastic component, IML offers greater durability, improved efficiency, and better consistency in high-volume manufacturing.
Key benefits of In Mould Labelling
The advantages of in mould labelling make it particularly attractive for OEMs producing high-volume plastic components or packaging.
Superior durability
IML labels are fused directly to the plastic surface, which provides excellent resistance to:
- Scratches
- Moisture
- Chemicals
- UV exposure
This makes the technology suitable for demanding environments such as food packaging, consumer goods, and industrial applications.
Design flexibility
IML enables advanced visual and tactile design options, including:
- 360-degree decoration
- Metallic or matte finishes
- High-resolution graphics
- Textured surfaces
This allows brands to achieve premium visual effects while maintaining production efficiency.
Cost efficiency at scale
Although the initial tooling investment may be higher, IML eliminates secondary labelling operations. This leads to:
- Reduced labour requirements
- Faster production cycles
- Lower total manufacturing costs at scale
For high-volume production, the process becomes extremely efficient.
Sustainability
One of the key sustainability advantages of in mould labelling IML is mono-material compatibility.
Because the label and base material are often the same polymer type, the final product:
- Is easier to recycle
- Requires fewer additional materials
- Generates less manufacturing waste
This supports circular economy initiatives across the industry.
Automation compatibility
IML is highly compatible with automated manufacturing systems. Robotic label placement ensures:
- Consistent positioning
- Reduced human error
- Highly repeatable production
For global manufacturers, this level of automation supports scalable production across multiple facilities.
What materials are used in In Mould Labelling?
Material compatibility is critical for successful in mould labelling injection moulding.
The most common combination includes:
- Polypropylene (PP) for both the label film and the base resin
- Thin label films typically ranging from 50–100 microns
Matching materials ensures that the label and component bond effectively during moulding.
For this reason, early design-for-manufacturing (DFM) collaboration between designers, material specialists, and moulding engineers is essential.
Factors considered during development include:
- Adhesion characteristics
- Material shrinkage
- Melt flow behaviour
- Label thickness
In Mould Labelling in blow moulding vs injection moulding
Although IML is most commonly associated with injection moulding, it can also be used in blow moulding processes.
Injection Moulding
Injection moulding offers:
- Greater dimensional precision
- Complex geometries
- Structural components with integrated decoration
This makes it ideal for technical parts, lids, containers, and branded consumer products.
Blow Moulding
In blow moulding, IML is often used for:
- Bottles
- Containers
- Thin-walled packaging
However, blow moulding generally offers less geometric complexity and lower precision compared to injection moulding.
As a result, in mould labelling injection moulding remains the preferred solution for high-precision applications.
Design Considerations for In Mould Labelling
Successful IML implementation requires careful engineering during the product development phase.
Key considerations include:
Label thickness
The label must be thin enough to conform to the mould surface while maintaining structural integrity.
Gate location
Proper gate placement ensures the plastic flow does not distort or displace the label.
Flow patterns
Resin flow must distribute evenly behind the label to prevent wrinkles or air pockets.
Venting
Adequate venting allows trapped air to escape during injection.
Surface finish
The mould surface must support proper label adhesion and visual quality.
Early supplier involvement is essential to optimise these factors and reduce development risks.
When should you choose In Mould Labelling?
IML is particularly beneficial for products that require durable branding combined with high-volume manufacturing efficiency.
Typical use cases include:
- Consumer packaging containers and lids
- Household product packaging
- Food containers
- Automotive interior components
- Medical and pharmaceutical packaging
In general, in mould labelling is ideal when production volumes are high and product appearance is critical.
Partnering with an experienced IML manufacturer
Implementing in mould labelling in injection moulding requires expertise in tooling design, materials engineering, and automated production systems.
Experienced manufacturing partners support OEMs through:
- Design-for-manufacturing optimisation
- Material selection
- Tool design and validation
- Process automation
- Global production scaling
From concept development to full-scale manufacturing, this collaborative approach ensures consistent quality, reduced risk, and faster time to market.
FAQs
What is in mould labelling?
In mould labelling is a manufacturing process where a pre-printed label is placed inside a mould before plastic injection. During moulding, the molten plastic bonds with the label, making it a permanent part of the finished component.
What is the process of IML labelling?
The in mould labelling process typically involves three steps:
- Cooling and ejecting the finished part with the label permanently fused to the surface
- Placing a pre-printed label inside the mould
- Injecting molten plastic during injection moulding
Is in mould labelling sustainable?
Yes. Many IML applications use mono-material polymer systems, meaning the label and component are made from compatible plastics such as polypropylene. This simplifies recycling and reduces waste.
Is IML suitable for complex injection moulding parts?
Yes. With proper mould design and material selection, in mould labelling injection moulding can be applied to complex geometries while maintaining high cosmetic quality.
What is the difference between IML and IMD?
IML (In Mould Labelling) uses a pre-printed label film embedded into the plastic component, while IMD (In Mould Decoration) typically uses decorative films or foils that transfer graphics or coatings during moulding.
What products use IML?
IML is widely used for:
- Medical packaging
- Food containers and lids
- Consumer product packaging
- Household containers
- Automotive interior components
Discuss your In Mould Labelling project
If you’re evaluating In Mould Labelling for your next plastic component, early engineering collaboration can significantly improve performance, cost efficiency and scalability.
Discuss your In Mould Labelling project with our team and partner with Rosti, your global plastic injection moulding leader to explore how IML can support your product design and production goals.
Or learn more about the fundamentals of manufacturing in our Plastic Injection Moulding Guide.
