In-Mould
Decoration (IMD)

Case Study

Engineering Innovation in IMD

Our dedication to pushing the limits of IMD has led to groundbreaking collaborative efforts with customers and suppliers, delivering solutions previously considered impossible, including challenges involving geometric ratios.

Rosti China successfully implemented a new in-mould decoration (IMD) manufacturing cell for a long-standing customer, introducing an enhanced level of cosmetic design beyond what conventional painting or plating processes can offer. Traditionally suitable for flat geometries, IMD posed unique challenges for the complex 3D components in focus, with an impressive stretch ratio exceeding 45%.

Our approach involved rigorous risk assessment and potential failure mode analysis, treating the initiative as a distinct technical development project separate from the mainstream new product introduction programs. We navigated challenges related to stretch ratio, resin, and part flow length.

Critical factors included:

• Stretch ratio: The significant increase in part profile compared to the flat foil.
• Resin: The optimal condition involves slow and cool entry to minimise ink defects at the gate location.
• Flow length: The optimal ratio of the component wall section against the length from gate to end of fill should be as short as possible to maintain a uniform temperature and pressure gradient.
• Solutions were achieved by harnessing the collective expertise of our partners, including resin, equipment, and decoration foil suppliers. We leveraged digital simulation and analysis to tackle critical-to-quality items, optimising the development cycle to ensure cost- effectiveness and speed to market.

Stretch ratio complexities were addressed by analysing high and low stretch areas in our part’s three-dimensional curves. Resin, a high-temperature engineering polymer (Polybutylene terephthalate (PBT) + glass fibre content), was optimised through Rosti’s advanced injection mould flow simulation ability. The thin wall geometry and resin combination resulted in high injection temperatures and pressures, which were mitigated by Rosti’s digital analysis experience.

Following extensive digital development and scenario analysis, Rosti confidently transitioned to physical tooling and development. From launching steel tooling to having proof of concept and a production part process approved took less than three months. This remarkable timeline was possible due to a deep understanding of process difficulties, robust simulation models, and commitment to innovation, aptly illustrating Rosti’s ‘concept to reality’ philosophy.