incremental metal encoder disc
Metal encoder disc (metal code wheel) is the core optical‑sensing component for rotary encoders. Compared with fragile glass discs and low‑strength plastic films, metal encoder discs deliver outstanding mechanical strength, vibration resistance and temperature stability, widely adopted in industrial automation, robotic joints, servo motors and automotive sensors. Metal encoder discs can be classified by coding principle, optical working mode and manufacturing technology.
1. Classification by Coding Principle
Incremental Metal Encoder Disc
Incremental metal encoder disc features evenly spaced radial grating slots. It outputs pulse signals corresponding to rotation angles. Most designs include one index Z‑mark slot for one‑per‑revolution reference position signal. ‑ Features: Track rotation speed and relative displacement; simple pattern structure, lower manufacturing cost. ‑ Limitation: Loses position data after power‑off, requires homing operation on system restart. ‑ Typical uses: Servo motors, stepper motors, speed‑detection modules, general‑purpose automation equipment.
Absolute Metal Encoder Disc
Absolute metal encoder disc is built with multiple concentric code tracks. Each angular position corresponds to a unique digital code, usually Gray code to avoid reading error during position transition. Real‑angle position can be read directly without homing, even after power loss. ‑ Features: Power‑off position memory, high‑safety positioning output; multi‑track complex pattern. ‑ Limitation: Higher technical requirements for pattern precision and coaxiality. ‑ Typical uses: Robotic joint encoders, CNC machine tools, aerospace positioning systems, high‑end automotive motion sensors.
2. Classification by Optical Working Mode
Transmissive Metal Encoder Disc
Transmissive type relies on light passing through precisely etched slots. Light source and photodetector are mounted on opposite sides of the metal disc. Open slots allow light through while solid metal blocks light. ‑ Features: Mature processing by chemical etching; stable signal contrast; good consistency for mass production. ‑ Common material: 304 / 316 stainless steel foil, typical thickness 0.03‑0.15 mm. ‑ Applications: General‑purpose industrial optical encoders.
Reflective Metal Encoder Disc
Reflective metal encoder disc works by light reflection. Some areas of the disc are highly reflective, while other areas absorb light. Light source and sensor are installed on the same side. ‑ Features: Compact assembly structure; no light‑through aperture required on housing. High‑precision reflective discs are often produced by electroforming process. ‑ Applications: Miniature encoders, compact servo units, limited‑space embedded sensor modules.
3. Classification by Manufacturing Process
Chemically‑Etched Metal Encoder Disc
Manufactured by photochemical etching on thin metal foil. Non‑contact cold processing, burr‑free, stress‑free grating structures. Good for both incremental and simple‑track absolute discs. Cost‑effective for prototype and mass‑volume orders.
Laser‑Cut Metal Encoder Disc
Laser cutting forms grating slots by thermal ablation. Suitable for larger‑size discs and low‑resolution requirements. Thermal‑affected zone may occur on fine narrow slots, limiting ultra‑high‑resolution scenarios.
Electroformed Metal Encoder Disc
Electroforming is an additive manufacturing method. High‑precision nickel‑alloy code wheels with steep‑side grating profiles. Achieves ultra‑narrow line width, excellent surface reflectivity, widely used for high‑end reflective absolute encoder discs.
Common Base Materials for Metal Encoder Disc
‑ Stainless steel (304 / 316): Most popular, good corrosion resistance, cost‑balanced for transmissive etched discs. ‑ Nickel‑based alloy: High hardness, excellent surface reflectivity, mainly for electroformed reflective code wheels. ‑ Spring steel: For special applications requiring higher mechanical toughness.
How to Select Suitable Metal Encoder Disc Type
‑ For speed measurement & relative rotation feedback: choose incremental metal encoder disc. ‑ For position retention after power‑off: select absolute metal encoder disc. ‑ Standard encoder layout with separate light‑source and receiver space: transmissive etched metal disc is preferred. ‑ Compact‑size enclosed sensor structure: consider reflective electroformed metal code wheel. ‑ High‑vibration, wide‑temperature industrial environment: prioritize metal disc over glass or plastic film.
If you require custom metal encoder discs, provide your drawings, resolution requirement and working‑condition parameters for technical evaluation and quotation.
