Custom Bicycle Light Prototype Production with CNC Machining

Project Background

As urban traffic congestion increases and environmental awareness grows, cycling has become a preferred mode of transport and recreation for young people. This shift is driving strong demand for bicycles and high-performance accessories such as advanced lighting systems.

To meet this growing market, an innovative company with a skilled R&D team focuses on developing intelligent, lightweight bicycle lighting systems. Their designs emphasize modularity and rapid iteration to suit a range of scenarios, from city commuting to mountain biking, and balance safety, functionality, and aesthetics.

However, meeting the demands for product iteration and high standards in performance and design required a manufacturing partner with both speed and expertise. That’s why they chose WayKen. Leveraging our experience in rapid prototyping and low-volume manufacturing, we provide full support from design validation to functional testing, accelerating time to market.

Key Structural Components of Custom Bicycle Lights

This project involves three critical optical components: the lens, reflector cup, and light guide. Each presents distinct structural features and machining requirements.

1. Lens: High-Precision Optical Surface

The lens is typically made of optical-grade PC or PMMA materials, offering high light transmittance and good impact resistance. Its design can either be machined as a single piece or split into sections.

Machining the lens as a single piece ensures better overall optical performance and structural strength, while split machining is more common during the prototype verification stage. Special attention must be paid to machining accuracy, as even minor defects can affect its optical performance.

2. Reflector Cup: Multi-Curved Surface with Metallization Requirements

The reflector is usually designed with complex, multi-curved surfaces to achieve precise light control and reflection. Its internal surface requires a high-gloss finish to enhance reflection efficiency.

The surface of the reflector often undergoes vacuum aluminum plating to boost reflectivity. This process demands a high level of surface cleanliness and a controlled processing environment after machining. Any mishandling can result in poor coating adhesion or reduced reflectivity.

3. Light Guide: Microstructured Surface for Uniform Light Distribution

Made from high-transparency PMMA (light transmittance >92%), the light guide evenly distributes light from a point source along a linear path using the principle of total internal reflection.

Its surface incorporates micro-scale optical tooth structures, which require high-precision 5-axis CNC machining for accurate reproduction.

During cutting, parameters such as tool speed, feed rate, and cooling must be carefully optimized to prevent surface defects like burn marks, swirl patterns, or scratches—common issues caused by localized heat buildup.

Additionally, different zones of the part may require different surface finishes. For example, one area may need a frosted texture for diffusion, while another must remain polished for clarity. This demands complex toolpath planning and, in some cases, selective manual polishing after machining.

Optimized Manufacturing Strategies for High-Performance Bicycle Lights

Before manufacturing this light prototype, WayKen conducted a comprehensive analysis. To ensure high optical quality and functional integration, we developed custom solutions for each of the core components: the lamp lens, reflector, and light guide.

1. One-Piece Optical-Grade Machining and Finishing for Lens

The lamp lens is made from optical-grade PC material. Its design requires one-piece machining, which means it cannot be split into separate components. Its structure features a ring of sealing grooves and irregular contours, all of which must meet strict optical transmittance requirements. These features demand high machining precision and advanced surface treatment.

Machining Strategy:

• 5-axis CNC machining is used with ball-end mills to accurately form complex curved surfaces.
• The sealing groove is machined using high-precision end mills that match groove dimensions and maintain tight tolerances.
• Cutting parameters are tightly controlled to avoid surface defects such as flow marks or weld lines.

Surface Finishing:

A multi-step polishing process using sandpapers of varying grits removes micro-scratches and machining marks.

This is followed by vapor polishing with a PC-specific solvent to achieve optical-grade transparency.

2. CNC Machining and Vacuum Metallization for Reflector

The reflector features a complex structure with multi-curved and undercut areas, significantly increasing machining difficulty. Additionally, the inner surface must undergo vacuum aluminum plating to achieve a mirror-like finish, placing high demands on surface quality and cleanliness.

The reflector also needs to be precisely assembled with the light guide to ensure optimal optical performance and system consistency.

Machining Strategy:

To overcome the limitations of conventional CNC machining for undercut features, we adopted a modular design. The reflector was split into three separate, machinable components (as shown in yellow and green below). This decomposition allowed us to use standard three-axis CNC machines while ensuring accuracy and surface quality.

PC material was selected for its machinability and cost-efficiency during prototyping, making disassembly practical. In designing the split components, particular attention was paid to the interface with the light guide to ensure accurate assembly and optical alignment.

Finishing Process:

• R0.5 mm tools are used with controlled feed rates to avoid melting or deformation.
• Surfaces are hand-polished to Ra 0.05 μm in preparation for vacuum aluminum plating.
• The final metallized surface achieves a uniform, mirror-like finish.

3. Processing and Polishing Solutions for Light Guide

The light guide includes spherical geometry and micron-scale tooth structures that evenly distribute light via total internal reflection to create a uniform linear lighting effect.

Some zones require a mirror-like SPI-A1 finish, while others need only a matte SPI-C3 level, adding significant complexity to CNC programming and surface finishing.

Machining Strategy:

High-precision 5-axis CNC machining ensures the accuracy of complex spherical shapes and micro-structured surfaces.

Cutting parameters are carefully optimized—feed speed, cutting depth, and spindle speed—to prevent deformation or surface defects like scratches and swirl marks due to heat accumulation.

Surface Finishing:

For SPI-A1 areas, WayKen’s professional manual team uses 1000–2000 grit sandpaper and a 5-step hand polishing process to remove tool marks from PMMA surfaces.

Finally, polishing wax is applied to eliminate fine sanding marks and achieve a mirror-like optical finish.

Feedback

The customer praised WayKen’s work on the bicycle light prototype project, highlighting our professionalism in handling complex structural and optical requirements, as well as efficient project management and communication.

With advanced 5-axis machining capabilities and a skilled engineering team, WayKen specializes in producing high-accuracy optical components and complex geometries. Our end-to-end support helps customers turn challenging designs into high-quality, cost-effective products.