In-Mould Decorating (IMD) and In-Mould Labelling (IML)

In-Mould Decorating (IMD) and In-Mould Labelling (IML)

Key Takeaways

• IMD back-moulds a pre-formed, second-surface-printed film, so the graphic sits behind 125–500 µm of polymer.
• IML drops a flat printed label into a packaging mould, held by static charge or vacuum through a 4–8 s cycle.
• Ink washout is the signature IMD defect; gate location and fill speed decide it, not the ink.
• The film-to-resin bond is the weak link. Specify the resin pair, tie layer and adhesion test, not just the artwork.

In-Mould Decorating (IMD) and In-Mould Labelling (IML)

In-mould decorating (IMD) is the process of placing a printed, usually pre-formed, polymer film into an injection mould and moulding resin behind it so that the film and its graphic become the finished surface of the part; in-mould labelling (IML) places a flat printed label into the mould so that it fuses with the moulded part, typically a polypropylene container. Both move decoration into the moulding cycle, which is why they are specified together although their films, resins and economics differ.

IMD is also called film insert moulding (FIM). In-mould electronics (IME) extends it: conductive traces, touch pads and LEDs go onto the film before forming, so the decorated surface is also the circuit.

IMD Versus IML: Where the Line Falls

Film and Label Constructions

An IMD film is a stack, and every layer has a job:

• Carrier film. Polycarbonate at 125–500 µm is the default; PMMA-capped PC coextrusions add weathering for exterior trim; PET suits flat parts; PP film is the IML label standard.
• Hardcoat. A UV- or thermally cured first-surface layer, 3–10 µm, for scratch and chemical resistance; formable grades are fully cured only after forming.
• Graphics. Screen or digitally printed on the second surface, often with a backing colour and a light-blocking layer for backlit designs.
• Adhesive or tie layer. A printed heat-activated binder matched to the back-mould resin; PC on PC can fuse without it, ABS and PMMA usually need it.

Abrasion therefore attacks the hardcoat, not the ink, and the bond that fails in service is almost always film-to-resin, set by resin compatibility and mould temperature.

Process Steps and Key Parameters

The IMD route runs print, dry, die-cut, form, trim, insert, mould. Forming is thermoforming above the film’s glass transition or high-pressure forming (HPF) below it at 100–300 bar, which holds registration and sharp radii better. IML skips forming.

Design Rules for Film, Graphics and Gate

• Draw depth and radii. Keep draw below about 30 mm and corner radii at 2–3 mm for thermoformed film; HPF reaches 0.5–1 mm, but film thins in corners, so keep graphics off them.
• Gate placement. Gate on the back face, never through a printed area, so the flow front crosses the graphic as a sheet, not a jet.
• Registration. Pre-distort the artwork for forming stretch; expect ±0.1–0.3 mm on HPF and ±0.5 mm on thermoforming; locate the blank on formed features, not the graphic.
• Wrinkles and bubbles. Avoid abrupt draw changes, relieve sharp corners, dry the film and vent where film meets resin.

Defects and Troubleshooting

Specifying and Verifying an In-Mould Decorated Part

IMD and IML trade variable data and low tooling cost for durability and volume. Pad printing and hot stamping cost less to tool and suit short runs but leave the ink on the surface; laser marking and inkjet handle the serial numbers a fixed film cannot. Where a graphic must survive years of hand contact and cleaners, in-mould wins; see plastics decorating methods compared.

A specification names the film construction (carrier, thickness, hardcoat, ink, tie layer), the back-mould resin grade, the gate position and the tests the part must pass. Artwork alone is not a specification.

Run adhesion after the exposures, not only on fresh parts, and record which interface failed: ink-to-film, film-to-resin or hardcoat. Methods are detailed in abrasion and chemical resistance testing of decorated plastics.

Related Terms and Reading

• Decorating and finishing services
• Surface energy
• Accelerated aging
• Measuring adhesion and abrasion durability
• Laser marking vs inkjet printing

Applying this in production

The Sabreen Group provides independent engineering support for in-mould decorating and in-mould labelling qualification and troubleshooting. If you are specifying a process, qualifying a material or troubleshooting a production problem, our engineering services team can help. Contact us to discuss your application.

Frequently Asked Questions

What is the difference between in-mould decorating and in-mould labelling?

IMD places a printed, pre-formed film of 125–500 µm into the mould and back-moulds PC, PC/ABS, ABS or PMMA behind it, so the film becomes the part’s outer surface. IML places a flat printed label, usually 50–100 µm polypropylene, into a packaging mould and fills it with the same polymer.

Why does the ink wash out near the gate on an IMD part?

Melt-front shear on the second-surface ink. The usual causes are a gate too close to the graphic, a fill speed set for an undecorated part and melt at the top of its range. Move the gate, slow the fill through the graphic and print a protective binder over the ink.

How is an IML label held in position inside the mould?

A robot places the label on the core or in the cavity, then either an electrostatic charge pins it to the grounded steel or vacuum ports through the mould surface hold it. Static suits fast cycles; vacuum is used where the label must not shift during a long fill.

Which resins can be back-moulded onto an IMD film?

Polycarbonate film bonds directly to PC and PC/ABS, and through a printed tie layer to ABS and PMMA. Polypropylene and polyethylene do not bond to PC film; they pair only with PP or PE labels in IML. Glass-filled grades need an opaque backing print; qualify any pair by cross-hatch after thermal cycling and humidity.

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