Battery-Electric Rail Platforms: Photo-Etched Encoder Discs, EMI Shields and Precision Shims
Alstom announced on September 11, 2026 that it had signed contracts worth about €1.2 billion with TransPennine Express for 29 five-car battery-electric trains, long-term maintenance and charging infrastructure. The trains are planned around Alstom's Adessia Stream platform, with manufacturing expected to begin in Derby in 2028 and deliveries from 2032. Alstom also stated that the program is expected to generate at least £360 million of spending with British suppliers.
Metching has no disclosed relationship with Alstom or TransPennine Express. The contract nevertheless provides a useful sourcing signal because a new rail platform creates engineering demand well beyond batteries. Traction feedback, power electronics, communications, HVAC, braking controls and serviceable assemblies all depend on thin metal parts whose dimensional stability matters over vibration, temperature cycles and long service lives.
Where thin precision metal enters a battery-electric train
Rail equipment combines relatively low production volumes with long qualification cycles and many platform variants. That can make hard tooling inefficient during early development, especially for components that are flat, thin and likely to change before serial production. Photo etching is therefore worth considering for selected parts rather than for large structural hardware.
Traction-motor or auxiliary-motor encoder discs with repeated slots or optical patterns.
EMI/RFI shielding frames and covers around control, communications and power-electronics assemblies.
Grounding spring contacts and finger-stock profiles for enclosure continuity and board-level shielding interfaces.
Precision shims, spacer rings and adjustment plates used to set bearing, sensor, gearbox or electronics assembly positions.
Thin airflow, filter or restriction plates inside selected cooling and HVAC subassemblies when the geometry is suitable.
Encoder discs: geometry matters more than the part name
An encoder disc can look simple until the drawing is reviewed. Slot width, angular pitch, radial runout, concentricity to the mounting bore and finished flatness all influence signal quality. If the disc is very thin, mechanical blanking can introduce burrs or distortion that complicate optical or magnetic sensing.
Photo etching creates the entire two-dimensional pattern without a cutting tool contacting the sheet. It is useful for prototypes and bridge quantities because several slot patterns can be placed on one tooling set. However, the etched edge has a thickness-dependent profile, so the designer still needs a sensible relationship between slot width and material thickness.
EMI shields and grounding contacts in rail electronics
Battery-electric trains add power-conversion electronics while also carrying radios, passenger information, sensing and control networks. Shielding performance is a system property: conductive material, seam design, grounding path, aperture size and enclosure assembly all matter. A chemically etched shield can integrate ventilation holes, access windows, identification marks and bend features in one flat blank before forming.
For spring contacts, flat-profile accuracy is only the first step. Alloy temper, forming radius, plating sequence, working deflection, target force and fatigue life must be defined. A flat blank that matches CAD perfectly can still fail if the formed contact operates outside its elastic range.
RFQ parameters buyers should define
Material grade and temper, such as stainless steel, nickel silver, phosphor bronze or another specified strip alloy.
Thickness and critical slot, aperture, web or spring-beam dimensions.
Flatness, concentricity, angular accuracy and datum strategy for encoder or alignment parts.
Vibration, thermal-cycle, corrosion and environmental requirements relevant to the rail qualification plan.
Plating or surface-treatment specification and which dimensions apply before versus after plating.
Expected annual volume, service-life quantity and whether future geometry variants are likely.
When stamping, laser cutting or machining is better
Photo etching should not be used as a blanket recommendation for rail components. Battery trays, structural brackets, heavy busbars, housings and load-bearing parts belong to forming, fabrication or machining processes. A simple shield produced in stable, very high volume may be cheaper to stamp once tooling is justified. Laser cutting can be practical for thicker low-volume plates where edge heat effects and burr condition are acceptable.
A good sourcing decision considers the full lifecycle. Photo etching can shorten early design cycles and avoid hard tooling, while a later transition to stamping may reduce serial-production cost. Planning that transition at the RFQ stage avoids redesigning the part when volumes increase.
A practical supplier qualification checklist
Ask how the supplier controls material lot traceability and strip temper.
Request inspection methods for angular features, concentricity and flatness rather than only linear dimensions.
For shielding, define the final formed condition and grounding interface—not only the flat pattern.
For spring contacts, include force-versus-travel and cycle-life targets in addition to the flat drawing.
Clarify packaging and handling for thin parts that can be bent or scratched before assembly.
FAQ
Can photo etching make traction-motor encoder discs?
Yes, it can be a strong route for thin prototype, low-volume and complex-pattern discs. Final suitability depends on material, thickness, slot geometry, flatness and sensing method.
Is photo etching suitable for railway EMI shields?
It is useful for thin shields with complex openings, frequent design changes or moderate volumes. Shielding performance must still be verified after forming, assembly and grounding.
Does a rail project always stay with etching for serial production?
No. Mature high-volume parts may move to stamping or another process. Etching can remain valuable for engineering changes, service parts and lower-volume platform variants.
Key takeaways
Battery-electric rail programs create thin-metal opportunities in feedback, electronics shielding and precision assembly rather than only in the battery system.
Encoder discs and shims benefit from low-stress, burr-free flat processing when geometry is still changing.
Process selection should include a planned production transition when volumes and geometry stabilise.
How Metching can support rail component development
Send the flat and formed drawings where applicable, material specification, thickness, critical datums, surface finish or plating, environmental requirements and expected volume. Metching can review the flat geometry for photochemical machining and flag features that may be better handled by stamping, forming or machining.
Related capability: Metching stainless steel etching
Sources
Program announcement: Alstom and TransPennine Express sign €1.2 billion contracts for Britain's first mainline battery-electric trains — September 11, 2026
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