Photo Etched Stainless Steel Rotary Encoder Code Wheels with 0.01mm Slit Windows

Photo Etched Stainless Steel Rotary Encoder Code Wheels

An encoder code wheel turns rotation into a light and dark pattern that the read head converts into counts. It looks like a flat washer with a ring of slots, but what decides whether the encoder behaves is how straight the slot walls are, how evenly the slots are pitched, and whether the wheel stays flat while it spins. This page covers code wheels and encoder discs etched from stainless steel or nickel foil between 0.02 mm and 1.0 mm, made to the customer's own drawing.

What the read head is really measuring

• Slot wall straightness. A tapered or stepped wall changes the amount of light passing through as the wheel turns, and the duty cycle of the A and B channels moves with it.
• Slot width and pitch. Both come from a single piece of artwork, so neighbouring windows keep the same pitch from one production run to the next - no tool wear to compensate for.
• Burrs and bridges. A burr or a partly etched web narrows or closes a window. The etching route creates neither, so there is no deburring step that could bend a thin wheel.
• Flatness and concentricity. A wheel that runs out of plane changes the gap at the read head once per revolution, and that appears in the output as a periodic error rather than as a visible defect.

Mounting and handling features

Hub bores, index notches, mounting holes, lightening cut-outs and arc segments are produced in the same pass as the window pattern, so the windows and the mounting features share one datum instead of being located in two operations.

Why the pattern is made chemically

• No press force on thin foil. 0.05 mm sheet buckles under a press and can pick up shear stress at the window edge; chemistry removes material without touching the part mechanically.
• No heat at the cut. There is no recast layer and no heat affected zone along the slot, so the foil keeps the properties it had when it was supplied.
• Changes are made in artwork. A new resolution, an extra index window or a revised hub is a new phototool, not a new stamping die, which keeps small and mixed batches practical.
• Both faces at once. Etchant is sprayed on the front and back of the foil simultaneously, which keeps the window wall square through the thickness instead of tapering from one side.

Foil grade and thickness

SUS304 covers most encoder work, SUS316 is chosen where humidity, coolant mist or wash-down is part of the machine's life, and nickel is used where the finest slits are needed in the thinnest section. Foil from 0.02 mm to 1.0 mm. The grade and gauge are checked against the drawing before film work starts, because not every combination of material and thickness is available off the shelf.

Specification

Process route

1. Drawing review: slot width, web width and foil thickness are checked against what the etching process can hold.
2. Phototool: the exposure film is generated from the DXF or STEP file that was approved.
3. Resist lamination: cleaned foil is laminated with photosensitive resist on both faces in the cleanroom.
4. Exposure and development: the code pattern is transferred, and the unexposed resist is washed away to leave bare metal only where windows will be etched.
5. Spray etching: etchant is sprayed on both faces, with line settings set per material and thickness.
6. Strip, flatten, measure and pack.

Inspection and records

Parts are measured against the approved drawing, window integrity is checked on samples drawn from each batch, and a first article inspection record can be issued with the shipment when the order asks for it.

What to send with an enquiry

• DXF, STEP or a dimensioned PDF of the wheel, the aperture mask or the code strip
• Foil grade and thickness
• Slot count or PPR, and which tolerance decides whether the part works
• First order quantity, plus the annual volume you expect
• Any flatness, surface finish or marking requirement

Commercial note

Every wheel is made to the customer's drawing, so price, minimum quantity and shipment schedule are settled per project once the drawing, the foil grade and the quantity are agreed. Two wheels of the same outer diameter can differ widely in the etching work they need, so this page describes the process rather than a fixed offer.

Send the drawing in DXF, STEP or PDF format and our engineering team will confirm the etching route and prepare the quotation for your review. Parts are produced in Shenzhen under ISO 9001, ISO 14001 and IATF 16949 certified processes.