Overview

A high precision ring washer photo chemical etching process forms flat annular shims, spacers and adjusting rings out of thin sheet metal instead of blanking them with a die. A photoresist mask is laminated to both faces, exposed through artwork that carries the inner bore, outer diameter, tabs and locating notches, then developed so the unprotected metal is dissolved in a matched etchant. Because removal is chemical, the washers leave the line burr-free, free of roll-over and free of the cold-work hardening that stamping introduces, so flatness and spring temper stay uniform across the whole sheet. Typical stock includes stainless steel 301/304/316L, beryllium copper, phosphor bronze and spring steel from 0.02 mm to 2.0 mm.

For assembly engineers, the value of photo chemical etched ring washers shows up in the stack. Stamped shims drift in thickness as a die wears and bow locally from punching stress, so when several are stacked the gap error accumulates and bearing preload, seal compression or optical spacing goes out of spec. Etched washers are produced at the same rate across a panel, holding thickness to ±0.005 mm and flatness to 0.02 mm per 25 mm, which lets total stack height be calculated directly from nominal values. Changing a part number only means a new film, so prototype runs and mixed-thickness kits stay economical without tooling.

Parameter Window

• Available Materials: stainless steel 301/304/316L, beryllium copper, phosphor bronze, spring steel, nickel alloy
• Material Thickness Range: 0.02–2.0 mm (down to 0.02 mm foil)
• Tolerance: thickness ±0.005 mm, OD/ID ±0.02 mm, flatness ≤0.02 mm per 25 mm
• Minimum Feature: ring web 0.20 mm, tie bridge 0.15 mm, locating notch 0.30 mm
• Surface Options: passivation, electropolish, deburr, nickel plating, PTFE coating, anti-tarnish
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Drawing Review — Check OD, ID, web width and notch geometry, and confirm thickness tolerance, flatness and the stack datum face.
2. Material & Temper Selection — Choose stainless, beryllium copper or phosphor bronze for the required spring and corrosion behavior, and verify incoming gauge.
3. Cleaning & Lamination — Degrease and laminate dry film resist to both faces under controlled heat and pressure so no bubbles sit under narrow webs.
4. UV Exposure — Expose through high-resolution film with inner and outer profiles registered to a shared datum for panel-level concentricity.
5. Development — Wash out unexposed resist to open the ring contour, then inspect bridges for residue or broken lines.
6. Etching — Spray chemistry matched to the alloy; dwell time and conveyor speed control sidewall and thickness removal in this precision etching process.
7. Stripping & Flattening — Strip resist, neutralize, then flatten and stress-relieve to restore flatness before passivation or plating.
8. Inspection & Packaging — Measure thickness, OD/ID and flatness against the approved sample, then interleave or tray-pack by thickness class.

Core Advantages

1. Stable flatness: Chemical removal leaves no stamped roll-over, so thin washers stay flat and seat evenly in a stack.
2. Tight thickness control: Panel-wide processing holds ±0.005 mm, so stacked error does not accumulate.
3. No work hardening: Without cold work, spring washers rebound consistently and preload stays stable over time.
4. Burr-free edges: Clean bore and rim edges do not score seal faces or shed particles into a chamber.
5. Low changeover cost: A new part number needs only a new film, not a die, so mixed small runs stay economical.
6. Predictable stack gap: With thickness and flatness both controlled, multi-shim assemblies hit the target gap on the first build.

Typical Applications

• Bearing preload shims: Graded-thickness rings setting shaft bearing clearance and preload in motors and spindles.
• Valve stack gaskets: Multi-layer hydraulic manifold shims where flatness keeps seal load even.
• Optical spacer rings: Annular spacers controlling lens separation and optical axis parallelism.
• Vacuum chamber shims: Burr-free thin rings that will not shed particles into process chambers.
• Connector grounding washers: Nickel-plated beryllium copper rings combining spring contact with corrosion resistance.
• Gauge calibration sets: Thickness-graded shim packs for feeler gauges and metrology calibration.

Design Notes & Process Considerations

1. Tolerance budgeting: Allocate per-shim tolerance from the assembly chain rather than tightening every ring, which raises lapping and sorting cost.
2. Flatness callout: State flatness per 25 mm and whether it is measured loaded or free to avoid inspection disputes.
3. Web-to-thickness ratio: Keep the narrowest web at least 1.5× stock thickness, or side etching will thin it.
4. Stack datum: Define the locating datum and clamping sequence so stacked rings do not tilt cumulatively.
5. Deburr & cleanliness: Specify burr-free edges and ionic residue limits; vacuum and optical parts need extra cleaning.
6. Complete drawing: Put thickness, flatness and stack gap on the drawing so the first sample matches the assembly.