Overview

An encoder disc etching service produces code wheels and aperture discs for optical encoders by photochemical machining. Radial slots, absolute-track patterns and index windows are etched straight through metal foil between 0.05 mm and 0.3 mm thick, so each slot is formed by dissolution rather than by punching, laser cutting or mechanical slitting. The result is a disc with vertical slot walls, no burr on either face, and slot position held to ±0.01 mm across the full track.

Edge quality is what matters in this application. An encoder reads light through the slots, so a burr, a tapered wall or a ragged edge scatters the beam and shows up as jitter and duty-cycle error in the output signal. Substrates are usually 301 or 304 stainless, beryllium copper, brass and nickel, often supplied with black oxide or matte black coating to cut internal reflection. Encoder disc etching service therefore appeals to builders of servo motors, rotary stages and motion stages who need a thin, flat, dimensionally repeatable disc without a stamping die.

Parameter Window

• Available Materials: stainless steel 301/304, beryllium copper (BeCu), brass H62, nickel, copper C1100
• Material Thickness Range: 0.05–0.30 mm
• Tolerance: ±0.01 mm on slot position and disc OD, ±0.005 mm on slot width
• Minimum Feature: 0.03 mm slot width, 0.03 mm land between slots at 0.1 mm stock
• Surface Options: black oxide, matte black coating, Ni or Au plating, passivation, adhesive hub mounting
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Pattern Review — Check slot count, duty cycle and track pitch against the optical read head, and confirm that lands stay above the minimum web.
2. Material Selection — Pick foil by stiffness and flatness need: stainless for general use, BeCu where fatigue and spring properties matter.
3. Cleaning & Lamination — Degrease the foil and laminate dry film on both faces in a clean hood, since a single dust particle blocks a 0.05 mm slot.
4. Exposure — Expose both sides through registered films on a vacuum frame so the track pattern is concentric with the disc center within ±0.01 mm.
5. Development — Develop and inspect slot openings under a toolmaker's microscope; measure a sample of slots before the etch to catch drift early.
6. Etching — Through-etch in a spray system with tight temperature control; end point is judged by slot opening and wall verticality, not by time alone.
7. Stripping & Coating — Remove resist, neutralize, then black oxide or matte coat to suppress reflection; coating thickness is kept off the slot walls.
8. Inspection & Packing — Verify slot width, duty cycle, concentricity and flatness, then pack individually between liners to avoid dents and scratches.

Core Advantages

1. Vertical slot walls: Chemical through-etching leaves a near-parallel wall, so the light beam is clipped cleanly and duty cycle stays stable.
2. Burr-free both faces: No punch entry roll-over and no exit burr, which removes a deburring step that would distort a 0.1 mm disc.
3. No stress, no warp: Etching applies no mechanical force, so thin foil stays flat and the disc runs true at high RPM without balance correction.
4. Fine slots at high count: 0.03 mm slots and 0.03 mm lands allow several hundred windows per track on a disc under 30 mm diameter.
5. Pattern change without tooling: Track count, duty cycle and index pattern change with the film, so a new resolution costs a film rather than a die.
6. Thin foil handling: 0.05 mm stainless and BeCu can be processed without the wrinkling and edge cracking that mechanical methods cause.

Typical Applications

• Servo motor encoders: Incremental discs with A/B/Z tracks for commutation and speed feedback in compact servo drives.
• Rotary stages: High-count discs for positioning tables where interpolation error must stay below one arc-second.
• Absolute encoders: Multi-track Gray code discs with fine inner tracks that only chemical etching can resolve.
• Optical choppers: Slotted wheels that modulate a beam at a fixed frequency in analytical instruments.
• Medical and lab instruments: Encoder discs for syringe pumps and analyzers, supplied clean and flat for low-noise readout.
• Industrial valves and actuators: Position feedback discs that survive oil mist and vibration without losing slot geometry.

Design Notes & Process Considerations

1. Slot width against thickness: Keep slot width at 1.0–1.5 × foil thickness; narrower slots etch with visible taper and lose contrast at the read head.
2. Duty cycle: Specify 50/50 where the decoder expects it, and note that etched slots close up by roughly half the etch allowance per side.
3. Land width: Hold lands at 0.03 mm or more at 0.1 mm stock; a land that etches through destroys the track and cannot be reworked.
4. Concentricity datum: Define the center from a hub bore or an etched reference circle, and state the concentricity the read head can tolerate.
5. Optical finish: Matte black or black oxide reduces reflection from the disc face; a bright polished disc raises stray light and hurts signal margin.
6. Handling and flatness: Specify flatness and pack between liners. When specifying an encoder disc etching service, state the measuring method as well, because a 0.1 mm disc deflects under its own weight on a flat plate.