Makrolon® polycarbonate drives innovation in thick light bar

General Motors Company (GM) wanted to achieve a unique, crystal-like effect for the light bar component of its 2019 Sierra 1500 LD Truck headlamp. GM teamed up with Valeo Lighting Systems and Covestro to bring this design to life, using a tailor-made color and highly transparent polycarbonate from Covestro.
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Create a light bar with a sculptured crystalline appearance

GM, Valeo and Covestro collaborated to create an advanced light bar design for the headlamp, which features a larger and brighter daytime running lamp for improved visibility in clear or inclement weather. In addition to improved safety, the thick light bar also allowed GM to create a unique brand differentiation for the vehicle. Nonstandard, multi-shot thick molding, tooling and processing were instrumental for achieving the light bar’s unique styling and functionality.


Achieve unique crystalline aesthetics with minimal shrink and warpage

The team aimed to design a light bar that looks like crystals, with low yellowness after a long cycle time. With the part’s large, complex shape, the tooling needed a modified surface and special ejection design to properly eject the thick light bar. Since there was a risk of high stress in the part, dimensional accuracy and warpage were also areas of concern.


Makrolon® LED2245 illuminates the road ahead

To meet color and optical clarity requirements, Makrolon® LED2245 polycarbonate from Covestro was manufactured using a different process than standard polycarbonate. As a result, this grade offers high optical clarity in extremely thick cross-sections and provides crystal color development to reduce the yellowness that often occurs in traditional, unlit thick polycarbonate parts. Additionally, Valeo used a proprietary molding process for a low-stress part with high clarity and minimal shrink and warpage.

Automotive lighting plays a dual role, contributing to a vehicle’s safety and its distinctive styling. This light bar illustrates how using Covestro materials can create new opportunities to enhance both of these important aspects.

Michael George

Polycarbonates Market Manager, Lighting                                                                                                                                                                            Covestro

Why Makrolon® LED2245 polycarbonate was the right solution for the light bar

  • Good optical quality Offers high optical clarity in extremely thick cross-sections.
  • Unique aesthetics Custom color development enables crystal-like appearance and effects.
  • Dimensional accuracy Maintains the desired size with minimal shrink and warpage.
  • Replicated micro-optics Enables replication of micro-optic surfaces.

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