WEBASTO smart fortwo panoramic roof with Makrolon® AG2677: “Sustainability by resin quality”
Webasto has been molding and hardcoating the 1,2 sqm panoramic roof for the second and third generation of the smart fortwo since 2007.
Webasto molds the part from transparent polycarbonate Makrolon® AG2677 in the first component and black PC/ABS Bayblend® T95 MF in the second component. After molding, the part undergoes a two-layer hardcoating process for surface protection.
Webasto is committed to reducing production scrap rates in order to save valuable resources and energy — while also reducing costs.
Tailoring and optimizing the polycarbonate used in this application meant intensive development work for Covestro, which helped Webasto to significantly reduce injection molding scrap.
Panoramic roofs are large, transparent parts with very high requirements for surface quality and optical properties, like the absence of impurities.
For the hardcoating step to achieve high yield rates, the molding process must deliver parts of constantly high quality.
Unfortunately, some defects can only be found after the energy-intensive hardcoating process, unintentionally wasting resources.
In fact, finding flaws/imperfections in single parts means scrapping 9 kg of PC (transparent component) plus 0,8 kg of PC/ABS (black frame).
This translates into every scrapped part wasting more than the 30 kg of CO2 equivalent for the resin alone, which is in addition to the financial loss Webasto incurs for every rejected part.
“We are happy that for years we’ve been able to provide Webasto, the pioneer in large panoramic roofs, with Makrolon® AG polycarbonate. It’s impressive how they are mastering the challenges of producing large and precise polycarbonate parts with such high quality.”
Over the years, through multiple optimizations of Webasto’s part production process, the company has reduced its scrap rate percentage by double digits. Covestro, which in parallel optimized the resin to improve the polycarbonate grade from standard to a grade tailored for transparent optical exterior applications, played a critical role.
The outcome of these optimizations is Makrolon® AG polycarbonate which is being manufactured on dedicated optical production lines using advanced melt filtration. A special compounding process leads to excellent surface qualities whereas tailored raw material and additive packages ensure good lot-to-lot consistency and high suitability for coated applications.
The development of Makrolon® AG therefore also underlines Covestro's many years of expertise in exterior parts made of polycarbonate. A number of innovative and patented solutions for demanding applications bear witness to this.
“Approximately 15% of our scrap reduction has been achieved through optimized Makrolon® AG polycarbonate from Covestro as it significantly increased yield rates in our molding and coating process.”
Key Benefits
- Produced only on dedicated lines: Makrolon® AG is produced on lines that are specialized for optical polycarbonate production
- High purity: Makrolon® AG has a high purity through advanced melt filtration
- Excellent surface quality: Makrolon® AG offers excellent surface qualities due to a special compounding process
- Tailored raw materials: Makrolon® AG uses raw materials and additives tailored for use in high-quality exterior applications
- Selected light fast colorants: Makrolon® AG only contains colorants proven to be light fast in weathered exterior applications
