Overview

Mass production stainless steel etching for encoders is a photo chemical etching route that turns thin 304 and 316L stainless steel sheet into rotary and linear encoder discs, gratings and code wheels in one chemical step instead of by stamping or laser cutting. Dry-film resist is laminated to both faces, the slit and code-track artwork is exposed through high-resolution film, and the unprotected metal is dissolved in a ferric-chloride etchant, so hundreds of radial slits, reference marks, index windows and mounting holes all form together in the same bath. Because material removal is chemical and stress-free, the disc leaves the line flat, burr-free and free of work hardening, which keeps the slit edges sharp and the light-passing geometry stable in high-resolution optical encoders.

For sourcing and design engineers, the precision etching process solves three recurring limits of conventional methods on stainless steel: stamping dies that wear quickly on abrasive 304/316L and are expensive to revise for a new line count, laser cutting that leaves heat tint, dross and a recast layer that scatters light at the slit walls, and mechanical machining that struggles to hold flatness across a large, thin code wheel. Since the geometry lives in the film, a new line-count or code-track variant is only a new artwork, and every disc across a panel etches at the same rate, so slit width, pitch and angular position stay consistent from the first article to volume runs. This is why the approach fits encoder programs that need repeatable optical contrast and tight angular error over long production batches rather than one-off prototypes.

Parameter Window

• Available Materials: 304, 316L, 301 and 430 stainless steel, cold-rolled and bright-annealed sheet
• Material Thickness Range: 0.05–1.0 mm for code discs and grating scales
• Tolerance: ±0.02 mm on slit width, ±0.03 mm on cumulative pitch and code-track position
• Minimum Feature: 0.05 mm radial slit, 0.08 mm connecting bridge and 0.10 mm index window at 0.10 mm stock
• Surface Options: passivation, electropolishing, black oxide, PVD anti-reflection coating, anti-fingerprint film
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork Review — Convert customer Gerber or DXF files to vector slit patterns, verify the line count, pitch and bridge width against stock thickness, and lock the index-window position.
2. Material Prep — Select 304 or 316L by corrosion and strength needs, shear flat-annealed sheet to panel size, and inspect both faces for scratches and roll marks.
3. Cleaning & Lamination — Degrease and micro-etch the surface, then hot-roll dry film onto both faces with pressure matched to film thickness so no bubbles sit under fine slits.
4. UV Exposure — Expose both sides through high-resolution film with front-to-back registration so radial slits and mounting holes stay concentric to the hub.
5. Development — Wash away unexposed resist to open the metal to be removed, and inspect every slit under magnification for residual resist before etching.
6. Etching — Spray ferric chloride matched to the stainless grade; time, temperature and conveyor speed govern the precision etching process, sidewall straightness and slit width across the panel.
7. Stripping & Finishing — Remove resist and neutralize, then passivate or electropolish and apply black-oxide or anti-reflection coating to raise optical contrast.
8. Inspection & Packaging — Verify slit width, cumulative pitch, flatness and coating on an optical comparator, then interleave discs with clean liners and record first-article measurements.

Core Advantages

1. Stress-free, burr-free edges: Chemical removal introduces no mechanical force or heat-affected zone, so thin code wheels stay flat and slit walls scatter no stray light.
2. Sharp optical contrast: Uniform slit geometry and optional black-oxide or PVD coatings give clean light-to-dark transitions that improve signal quality in photoelectric read heads.
3. No hard tooling for line-count changes: A new line count or code-track layout is just a new film, so variant runs and volume changeovers avoid stamping-die cost and lead time.
4. Panel-level angular consistency: Every disc on a sheet etches at the same rate, so pitch, slit width and index position match across a batch, stabilizing angular error.
5. Corrosion and wear resistance intact: The 304/316L passive layer is preserved, and no work hardening is added, so discs survive humid, oily or washdown encoder housings.
6. Half-etched features in one pass: Local thinned hubs, alignment notches and bend reliefs form during the same etch, removing secondary machining on the disc.

Typical Applications

• Rotary encoder code wheels: 304/316L discs with radial slit tracks and index windows for incremental motor feedback.
• Absolute encoder code discs: Multi-track grey-code patterns etched with concentric bit rings for position sensing without a home routine.
• Linear grating scales: Long stainless strips with uniform slit pitch used in CNC axes and coordinate measuring machines.
• Servo motor feedback discs: Thin, flat code wheels bonded to motor shafts where low inertia and stable contrast matter.
• Robotic joint encoders: Compact, corrosion-resistant gratings that hold accuracy inside greased, sealed actuator housings.
• Metrology and inspection reticles: Reference grids and calibration slits used as optical standards in alignment instruments.

Design Notes & Process Considerations

1. Slit width versus thickness: Keep the narrowest slit at least half the stock thickness, or undercut will round the slit walls and blur the optical edge.
2. Pitch and angular error callout: State cumulative pitch tolerance and allowable angular error over the full circle, since these drive encoder resolution directly.
3. Flatness for the read head: Specify flatness per 100 mm and allow a leveling step, because disc warp changes the air gap to the photodetector.
4. Coating for contrast: Choose black oxide, PVD or electropolishing by the read-head wavelength, and state reflectivity so the light-to-dark ratio stays consistent.
5. Corrosion grade selection: Use 316L for washdown, saline or chemical exposure and 304 for dry industrial housings, and note the passive-layer requirement.
6. Complete artwork data: Put grade, temper, thickness, line count, pitch, index position and coating on the print together; giving all seven items at once cuts back-and-forth confirmation.