Etched encoder discs (also called code wheels) are core sensing parts for optical encoders. They convert rotational angle and speed into digital pulse signals. These thin metal discs are manufactured via photochemical etching, forming highly uniform grating tracks, radial slots or coded apertures. Common types include incremental encoder discs and absolute encoder discs. Typical materials are SUS304 / SUS316 stainless steel, copper and nickel alloy, usually from 0.02 mm to 0.5 mm thickness.

Manufacturing Workflow of Etched Encoder Discs

DFM & Pattern Optimization: Engineers optimize grating layout and compensate for isotropic undercut to guarantee consistent line width and angular accuracy.

Substrate Cleaning: Ultra-thin metal sheets are degreased and ultrasonically cleaned to ensure stable photoresist lamination.

Dry Film Lamination: Photosensitive dry film is bonded on both sides of the metal sheet.

High-precision UV Exposure & Development: The encoder grating pattern is transferred onto photoresist. Unprotected resist is washed away to expose metal areas to be etched.

Dual-sided Chemical Etching: Synchronized spray etching forms the fine grating slots. No mechanical cutting force applied.

Resist Stripping & Surface Passivation: Remove residual photoresist, then apply anti-rust passivation treatment.

Full Inspection: Check dimensional tolerance, flatness, grating uniformity, concentricity and edge quality before delivery.

Core Advantages of Etched Encoder Discs

Burr-free, clean grating edges Molecular-level material removal leaves sharp, smooth slot edges. No micro-burrs or slag, preventing signal jitter during high-speed rotation.

Zero residual stress, no distortion Non-contact chemical processing introduces no work hardening. Ultra-thin discs maintain excellent flatness; grating pitch will not shift after assembly.

High pattern uniformity & micron tolerance Grating lines and apertures keep consistent width across the full circular track. Tolerance can reach ±0.005 mm, supporting high PPR high-resolution encoder designs.

No hard tooling cost Only digital artwork is required. Fast prototyping and low-cost pattern revisions, ideal for R&D validation and small-to-medium batches.

Multi-code-track capability Multiple concentric code tracks can be fabricated on a single disc for absolute encoder requirements.

Stable mechanical performance Metal etched discs feature good temperature resistance and structural rigidity compared with plastic or glass discs, suitable for vibration and harsh industrial environments.

Typical Applications

Industrial automation: Servo motors, stepper motors, CNC machine tools, linear motion modules

Robotics: Collaborative robot joints, robotic arm angle feedback

Automotive: E-drive motors, steering angle sensors, LiDAR motion feedback

Precision instruments: Medical diagnostic equipment, optical measuring devices

Consumer & office equipment: Printers, scanners, speed detection modules

Design Notes

Etching follows isotropic undercut rules, so line width compensation must be added in CAD drawings. Minimum grating width is limited by metal sheet thickness. While etching delivers excellent thin-disc performance, extremely thick substrates or ultra-high aspect ratio structures may require electroforming as an alternative.