Etched Encoder Discs: The Slot Pattern Lives in the Artwork

An encoder disc has one job: put the same slot in the same place, every revolution, for years. Stamping gets there with a precision die that wears. Laser cutting gets there with taper and dross on the slot walls. Etching photographs your CAD file into the metal — so disc one and disc ten thousand carry the identical pattern.

Encoder discs are where Metching started in electronics etching. We're a Dongguan plant producing etched components since 2005, specialising in parts for the electronics and semiconductor industries: encoder discs, lead frames, EMI/RFI shielding and chip cooling plates. For discs and code wheels we etch your slot pattern into metal from 0.05 to 2.5 mm thick — stainless steel most often, plus titanium, copper, brass and nickel. No hard tooling. No burr on the slot edges.

The working specs

• Materials: stainless steel (304, 316L) is the default; titanium, copper, brass and nickel also etched

• Thickness: 0.05–2.5 mm

• Finest slots: a through-slot needs to be at least roughly the material thickness (≈0.8–1.2×) — a 0.1 mm disc supports slots around 0.1 mm

• Pattern: slots, index marks and centre bore etched in one pass from one artwork, so everything sits relative to the pattern by design

• Edges: burr-free — no raised edge to scatter the optical beam or foul the sensor gap

• Tolerance: Tolerances are evaluated based on material thickness, drawings and processing requirements. Metching does not apply a single fixed tolerance to every project.

• Diameter: up to Ø600 mm maximum; large, thin discs run in smaller formats to stay flat

Why the pattern belongs in the artwork

Accuracy that lives in a die degrades with the die. Accuracy that lives in a photograph doesn't. Slot position on an etched disc is set when the artwork is made, and it stays there for the whole production run — that's the property encoder designers are actually buying.

The edges matter just as much. A burr standing proud of a slot edge scatters light, and at speed it shows up as miscounts. Etched slots are clean through the full thickness, and nothing sticks up off the disc surface.

Thin discs stay true, too. Low-inertia discs for fast servos run 0.05–0.2 mm stock. Etching adds no mechanical stress and no heat, so the disc comes off the sheet flat instead of dished, and it runs true inside a narrow sensor gap.

Odd patterns cost nothing extra. An unusual slot count, a dual-track layout, an index slot in a non-standard place — all artwork. Prototypes for a new encoder ship without a tooling invoice; samples typically go out in 3–5 days.

Honest limits

Ultra-high-resolution optical encoders belong on glass discs, which resolve finer lines than any metal process. If your slot count demands lines finer than the stock thickness allows, we'll tell you at quotation rather than ship discs that read badly. And we don't etch aluminium discs.

Questions we get

What's the finest slot you can etch?

Start from the thickness rule: about the material thickness, no finer. Choose the disc thickness to suit the encoder gap first, then check the slot count against it — or send us both numbers and we'll check them for you.

Which thickness should I choose?

Discs of 0.05–0.2 mm minimise inertia and suit compact optical encoders; thicker discs hold up better at larger diameters and in harsher environments. In practice the sensor gap and the finest slot width decide it — the sensor gap sets the ceiling, the slot rule sets the floor. If the two fight each other on your drawing, that's a conversation worth having before samples, not after.

Can you match a disc we already use?

Yes, from a drawing, a CAD file or a measured sample. Slot count, track layout, index position and bore — a routine job when an encoder OEM discontinues a disc and the original disappears from the catalogue.

Is the bore etched in the same step?

Yes. Bore, keyways, mounting holes and slots come from the same artwork in a single pass. No second machining setup, no datum shift between the bore and the pattern.

CTA: Send the drawing — or the PPR target and diameter — to info@metching.com or call +1 (630) 474-4019 — Metching, Dongguan · since 2005 · metching.com