Overview

Custom code disc etching is a photo chemical etching service that produces optical encoder discs, grating wheels and index plates by chemically machining light-transmitting slots, concentric code tracks and reference marks into thin metal foil rather than stamping or laser-cutting them. A photoresist mask is exposed with high-resolution artwork of the track pattern, developed, and the unprotected metal is dissolved in a controlled etchant, leaving slots with vertical sidewalls, sharp edges and no burrs or heat-affected zone. Substrates are typically stainless steel 304/316L, Invar 36, nickel, phosphor bronze and brass from 0.05 mm to 0.5 mm, with light slots down to 0.03 mm.

For buyers and design engineers, this precision etching process is specified as a full capability, not just a part number. Encoder resolution depends on track pitch and slot duty cycle, and any burr, rounded corner or ragged edge distorts the photodetector waveform, so exposure and etch parameters are locked: line and space tolerance held to ±0.01 mm, track concentricity within 0.01 mm, and sidewall profile set by spray pressure, temperature and conveyor speed. We run the workflow end to end — artwork review, film tooling, first-article samples and volume production — so a revision is a new film rather than a new die, and prototype lots and ten-thousand-piece runs ship against the same approved sample.

Parameter Window

• Available Materials: stainless steel 304/316L, Invar 36, nickel, phosphor bronze, brass
• Material Thickness Range: 0.05–0.5 mm (commonly 0.1–0.3 mm)
• Tolerance: line/space ±0.01 mm, track concentricity ≤0.01 mm, positional ±0.01 mm
• Minimum Feature: light slot 0.03 mm, grating line 0.04 mm, track pitch 0.10 mm
• Surface Options: black oxide matte, anti-reflective finish, nickel plating, gold plating, passivation
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork & DFM Review — Convert tracks, zero reference and index pulse to vector data, and verify pitch, duty cycle and minimum slot.
2. Material Selection — Choose stainless or Invar for thermal expansion and rigidity, and check incoming gauge and flatness.
3. Cleaning & Lamination — Degrease and laminate dry film resist on both faces in a clean area so no dust or bubbles sit over slots.
4. UV Exposure — Expose through high-resolution film with all tracks registered to one center datum for concentricity.
5. Development — Wash out unexposed resist to open the slot pattern, then inspect each track for residue or broken lines.
6. Etching — Spray etchant matched to the alloy; time, temperature and conveyor speed set sidewall verticality and edge acuity in this precision etching process.
7. Stripping & Blackening — Strip resist, neutralize, then apply matte black oxide or plating to cut stray reflection and raise signal contrast.
8. Inspection & Packaging — Measure slot width, pitch and concentricity with vision metrology, then vacuum-seal approved parts between separators.

Core Advantages

1. High resolution: Light slots down to 0.03 mm and fine track pitch raise encoder pulses per revolution.
2. Sharp vertical edges: Chemical removal leaves no heat-affected zone, so photodetector waveforms stay clean and undistorted.
3. No light-blocking burrs: Panel-formed slots carry no burr or roll-over that could occlude the beam or trigger false pulses.
4. Stable concentricity: Tracks share one center datum, so multi-track eccentricity stays minimal across the disc.
5. Economical revisions: A pattern change is a new film, not a die, so mixed small runs stay cost-effective.
6. Repeatable at volume: Locked exposure and etch parameters keep first articles and ten-thousand-piece lots identical.

Typical Applications

• Incremental encoders: Light-transmitting discs with A/B phase tracks and a zero index pulse for motor feedback.
• Absolute encoders: Multi-track Gray-code discs read without cumulative error, formed in a single exposure.
• Servo motor feedback: Rigid stainless discs resisting vibration and oil in industrial servo environments.
• Robot joints: Thin, lightweight discs for angle feedback in collaborative robot joints.
• Precision rotary tables: Large-diameter annular discs controlling indexing and angular repeatability.
• Optical speed sensing: Grating wheels paired with photointerrupters for rpm and length counting.

Design Notes & Process Considerations

1. Slot-to-thickness ratio: Keep the finest slot at least 1.2× stock thickness, or side etching skews light transmission.
2. Duty cycle callout: State light/dark ratio and allowed edge shift so the received waveform stays in spec.
3. Concentric datum: Specify the center datum and mounting holes, and set a concentricity tolerance to avoid stacked track error.
4. Matte & reflection: Call out blackening or matte finish; bare metal reflection adds stray signal at the receiver.
5. Burr-free requirement: Note no burr and no roll-over, since burrs block light and score the mounting face.
6. Complete drawing: Put pitch, slot width and concentricity on the drawing so the first sample qualifies for production.