Overview

A custom copper code wheel is the patterned disc or strip at the heart of an optical encoder, produced by photochemical machining from thin copper foil. Etching opens the radial slots, index marks and reference tracks that a photodetector reads, so slot position, slot-to-slot uniformity and concentricity directly set angular accuracy. Because the pattern is dissolved rather than punched, the wheel leaves the line flat, burr-free and free of the tooling marks that would scatter light. Copper C11000 and C10200 are typically supplied from 0.10 mm to 0.80 mm with slot tolerance of ±0.02 mm.

Encoder builders specify a custom copper code wheel when resolution and signal contrast have to hold over a wide speed and temperature range. Copper takes a uniform blackened or anti-reflective finish that improves the light/dark ratio at the sensor, and its conductivity lets the same part serve as a ground or shielding layer. Since every track layout is a phototool rather than a die, a custom copper code wheel moves from prototype to volume without tooling charges and supports frequent changes to line count or index geometry.

Parameter Window

• Available Materials: copper C11000/C10200, oxygen-free copper, brass, 304 stainless, nickel
• Material Thickness Range: 0.10–0.80 mm (common 0.15, 0.20, 0.30, 0.50 mm)
• Tolerance: ±0.02 mm on slot width, ±0.02 mm on slot position, ±0.05 mm on outer diameter
• Minimum Feature: 0.10 mm slot, 0.10 mm web, 1000+ slots per revolution on common diameters
• Surface Options: blackened, anti-reflective coating, Ni/Au plating, passivated, hub-bonded or bare
• Compliance: ISO 9001 process control, RoHS/REACH material traceability

Manufacturing Process / Workflow (8 Steps)

1. Artwork Review — Confirm line count, slot pitch, index track and concentricity against the encoder specification.
2. Material Selection — Choose C11000 or C10200 foil by thickness and flatness, and inspect the coil for dents.
3. Cleaning & Lamination — Degrease and laminate dry film on both faces, keeping the resist thin over fine slots.
4. UV Exposure — Expose through a high-resolution radial film registered to the centre hole for true concentricity.
5. Development — Wash out unexposed resist and microscope-check that every slot and index mark opens cleanly.
6. Etching — Spray-etch with copper-matched chemistry, controlling time and speed for straight slot sidewalls.
7. Stripping & Finishing — Strip resist, neutralize, then blacken or plate for contrast and bond the wheel to a hub if needed.
8. Inspection & Packaging — Measure slot width, pitch and concentricity, verify flatness, then pack with a first-article report.

Core Advantages

1. Accurate slot position: Radial artwork referenced to the centre hole keeps cumulative pitch error low across a full revolution.
2. Clean optical edges: Burr-free slots reduce light scatter, so the detector sees a sharper light/dark transition.
3. Uniform contrast: Blackened or anti-reflective copper gives a consistent signal amplitude over the whole track.
4. Flat and stable: Stress-free etched discs stay planar at speed, limiting runout that would modulate the signal.
5. Tool-free line counts: Changing slot count or adding an index track is a film change, not a new die.
6. Material flexibility: A custom copper code wheel can be made in copper, brass or stainless and plated for wear or contrast.

Typical Applications

• Rotary encoders: Incremental discs that report shaft angle and speed to motor controllers and PLCs.
• Servo motor feedback: High-line-count wheels that close the loop on position and velocity.
• Linear scales: Etched strips read by an optical head for stage and axis position in machine tools.
• Robotics joints: Compact code wheels that give repeatable arm angle feedback in a small envelope.
• CNC and metrology: Precision discs used in coordinate measurement and rotary tables.
• Optical sensors: Reference tracks and index marks for homing and direction sensing.

Design Notes & Process Considerations

1. Slot-to-web ratio: Keep slot width near the web width (typically 0.10 mm each) so the track etches evenly and reads symmetrically.
2. Concentricity callout: Relate the track to the centre hole and state total runout, since eccentricity dominates angular error.
3. Surface finish: Specify blackening or anti-reflective coating and target contrast, because raw copper reflects too much light.
4. Flatness at speed: Call out flatness per 100 mm and balance requirements for high-RPM wheels.
5. Hub bonding: Define hub material, adhesive and datum if the wheel is bonded rather than clamped.
6. Inspection criteria: Agree slot width, pitch and sampling plan; documenting these on the drawing cuts review cycles.