What are the advantages of in-mould labelling over post-mould labels?

The label becomes part of the wall: no edges to peel, no adhesive to fail, full-surface photographic print quality, and the decoration step disappears from the supply chain. IML tubs also allow thinner walls because the label adds stiffness.

Does IML slow down the moulding cycle?

Yes, typically by 1-3 seconds, because a robot must place the label before each shot. Against this, the downstream labelling operation, its labour, its scrap and its logistics disappear entirely, which is usually a net win at volume.

What does IML tooling cost compared with standard tooling?

IML tooling typically costs 20-40% more than the equivalent standard mould, because it needs label-holding features, precise electrostatic or vacuum label retention, and integration with the label-placement robot. Budget tooling from €5,000-10,000 upward depending on cavitation.

Which plastics work with in-mould decoration?

PP is the IML packaging standard because labels are usually PP-based and fuse chemically with the tub. For IMD films, PC, ABS, PC/ABS and PMMA bases are common on durable parts, with the film system matched to the substrate by the film supplier.

In-Mould Labelling and In-Mould Decoration (IML / IMD): The Complete Guide

In-mould labelling (IML) and in-mould decoration (IMD) move the printing press into the moulding machine. Instead of moulding a plain part and decorating it afterwards, a printed label or film is placed in the cavity and becomes part of the product during the shot. The result is decoration that cannot peel, scratch off or run out of register. This guide explains how both processes work, what they demand from design and tooling, and how the economics compare with post-mould decoration.

What is the difference between IML and IMD?

IML (in-mould labelling): a pre-printed label, usually PP film of 50-80 µm, is placed against the cavity wall; molten PP flows behind it and fuses with it. The label becomes the outer surface of the part. This is the technology on virtually every premium butter tub, yoghurt pot and paint pail in a European supermarket.
IMD / IMF (in-mould decoration / forming): a printed carrier film, often with textured or hard-coated surfaces, transfers its ink layer onto the part during moulding (or remains as a film). This decorates durable goods: automotive interior trim, appliance fascias, phone housings, control panels with backlit symbols.

The shared principle is identical: print first, mould second, decorate never again.

How does the IML process work step by step?

Labels are printed and die-cut in stacks, typically offset or digital print on PP film
A side-entry or top-entry robot picks a label with a vacuum or electrostatic head
The robot places the label into the open mould, where static charge or vacuum pins it to the cavity
The mould closes and plastic injects behind the label, fusing the surfaces
The finished, fully decorated part ejects; no secondary operation exists

Cycle-time impact is typically 1-3 seconds for label placement, running in parallel with ejection where the machine layout allows.

What does IML demand from part design?

Wall sections: IML labels wrap the outside; coverage should be designed as full panels with defined label edges, typically stopping 0.5-1 mm short of rims and corners
Radii: labels cannot wrap tight corners; keep wrap-around radii above ~2-3 mm or design label breaks
Gate position: the fill front must not wash the label out of position; gates are positioned to flow parallel to the label, never directly at its edge. A mould flow simulation is strongly recommended for any wrap-around label
Ejection: parts shrink onto cores as usual; nothing special except that scuffed labels are scrap, so core surfaces and ejection must be flawless
Venting: trapped air cannot escape through the label; venting at the label's far edge is critical to avoid burns and voids under the film

The standard wall thickness and draft angle rules apply unchanged underneath the label.

What does IMD demand from part design?

IMD adds forming to the equation: the film is often thermoformed into a 3D shape before or during moulding. Design must respect film stretch limits, typically 30-50% elongation before print distortion becomes visible, and register marks must survive forming. Graphics are pre-distorted to compensate. Backlit symbols need controlled ink density; hard-coated films need corner radii above ~1 mm to avoid coating cracks. These constraints are worked out with the film supplier early, not discovered at T1.

What does the tooling look like?

IML moulds differ from standard moulds in four ways: label seating surfaces machined to film precision, electrostatic charging pins or vacuum circuits, runner and gate layouts proven not to disturb the label, and tight integration with the placement robot and its end-of-arm tooling. Expect tooling to cost 20-40% more than the equivalent plain mould. IMD tools add film-feed or carrier systems and often temperature-controlled forming stations.

How do the economics compare with post-mould decoration?

Cost element	IML / IMD	Post-mould (pad print, label, paint)
Tooling	+20-40% on the mould	Standard mould
Label / film	€0.01-0.05 per part (IML)	Label + adhesive + application
Cycle time	+1-3 s	Moulding cycle unchanged
Secondary operation	None	Printing/labelling line, labour, scrap, WIP
Durability	Decoration is the surface; cannot peel	Adhesive and ink systems can fail
Changeover	Swap label stack	Retool print jigs, colour changes

Break-even typically arrives quickly at volumes above a few hundred thousand parts, and IML additionally allows wall thickness reductions of 10-15% on packaging because the label stiffens the wall, which saves material on every shot. For alternatives, see our plastic part decorating guide.

Which materials and films are used?

IML packaging is overwhelmingly PP-on-PP, because the PP label fuses chemically with the PP tub, making the finished article a mono-material package that recycles cleanly, a growing advantage under EU packaging rules. IMD films use PC, ABS, PMMA or PET carriers with ink systems qualified against the substrate resin; film suppliers such as the major IMD specialists qualify specific film-resin pairs, and Nordmould works from those qualified pairs rather than experimenting at the mould.

When is in-mould decoration the right choice?

Choose IML/IMD when volumes are high, decoration covers significant surface area, durability matters, or recyclability arguments favour mono-material construction. Choose post-mould decoration when volumes are low, decoration is small (a logo, a few characters), the design changes frequently, or the part needs coating processes like painting or laser marking that in-mould methods cannot replicate. For premium surface depth effects on technical parts, also consider overmoulding and insert moulding where a decorated skin is combined with structural overmoulding.

Nordmould can review your decorated part and compare in-mould and post-mould routes on total cost before tooling is committed.

Related guides

Planning a decorated part at volume? Ask Nordmould for an IML/IMD feasibility review before you commit to a decoration route.