Case study & manufacturing insights of medical infusion pump keypad & payment terminal keypad
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- Suey
- Issue Time
- Jan 14,2026
Summary
Two production keypads, two different failure pressures: a medical infusion pump keypad that must be silent, wipeable and unambiguous under a nurse's thumb, and an outdoor payment terminal keypad that must survive UV, heat and vandalism. This case breakdown follows the decisions that mattered in each - compound, dome geometry, sealing, legend method and validation - and what a custom programme has to supply to reach them.
Case breakdown
A medical infusion pump keypad and an outdoor payment terminal keypad look like the same component and are not. One is judged on silence, wipeability and the certainty of a press by a gloved nurse; the other on UV stability, temperature range and resistance to a key being struck with a coin. The materials overlap; the tolerances and the validation do not.
- Silent operation is a geometry and compound problem: a shorter dome travel and a softer compound remove the snap that makes noise, at the cost of tactile clarity.
- Payment terminals fail on the legend and the seal long before the silicone body fails.
- Both programmes are decided by validation criteria written before the tool is cut, not after the first samples arrive.
Why the medical infusion pump keypad sets the hardest brief
An infusion pump is operated at night, in a ward, by a nurse who may be wearing gloves and who cannot afford an ambiguous press. The keypad has to be quiet enough not to disturb a patient, tactile enough to confirm a dose entry, and flat enough to wipe down between patients. Those three requirements pull against each other, and the resolution is in the dome, not in the datasheet.
A standard dome with a pronounced snap is loud in a quiet room: the buckling event radiates through the housing. Reducing dome height and softening the compound quietens it, but the key then feels vague. The workable compromise is a shallower dome with a controlled wall thickness and a raised ring around the key top, which restores a sense of location without reintroducing the noise.
Chemical resistance and the silent key, resolved together
Wipe-down chemistry drives the compound, and the compound drives the feel. A 50 Shore A addition-cured silicone with a full post-cure handles alcohol and quaternary ammonium wipes and holds its rebound; a softer 40 Shore A compound is quieter but takes compression set faster under a held key. Choosing between them is a clinical decision as much as an engineering one, and it belongs in the design review.
The legend follows the same logic. Printed characters on a pump are wiped dozens of times a day, so a two-part ink with a proper cure, or a moulded character, is the durable route. On a black keypad, a moulded character with a light pigment fill reads clearly under ward lighting and cannot be wiped away; on a light keypad, laser etching gives contrast without an ink film.
- Compound — addition-cured, 50 Shore A, fully post-cured for wipe resistance and rebound.
- Dome — shallow travel with a raised locating ring, to keep feedback without the noise.
- Legend — moulded or laser-etched where the keypad is cleaned many times a day.
- Seal — moulded perimeter bead, evenly compressed, so fluid cannot reach the contact area.
Two keypads, two specifications
| Requirement | Medical infusion pump keypad | Outdoor payment terminal keypad |
|---|---|---|
| Priority | Silence, wipeability, unambiguous press | UV stability, temperature range, vandal resistance |
| Compound | 50 Shore A, addition cure, post-cured | UV-stabilised, carbon black or pigmented package |
| Dome | Shallow travel, raised locating ring | Deeper travel, high actuation force, metal dome option |
| Legend | Moulded or two-part ink with full cure | Moulded or laser-etched; print chalks outdoors |
| Sealing | Perimeter bead, IP-rated against cleaning fluids | Gasket plus vented housing for temperature swings |
| Validation | Wipe cycles, compression set, force curve | QUV, salt spray, thermal cycling, impact |
| Typical risk | Compression set from over-compression | Legend fading and seal hardening |
The outdoor payment terminal keypad and its different enemies
A payment terminal on a forecourt or a station platform meets sun, frost, rain and a user who may strike the key with a coin or a key. The silicone body copes; the legend and the seal do not. Printed characters chalk and fade within a season in strong UV, and a gasket that hardens at minus twenty lets water past in the first cold snap.
The answers are unglamorous. Mould the characters, or etch them, so there is no ink film to chalk. Use a UV-stabilised compound; carbon black is the most cost-effective option and the reason most outdoor keypads are dark. Then design a gasket with a compression range that still seals when the material stiffens in the cold, and add a vent so the housing does not pull water in as it cools at night.
What both programmes had in common
Different markets, same four disciplines, and each one is a place where a rushed programme loses money.
A written force target
Both keypads were specified by actuation force and travel, not by adjectives. The curve was measured on production parts, not on a sample.
A legend method chosen with the tool
Neither programme could change its legend after the cavity was cut without cost, so the method was fixed early.
A sealing strategy with an owner
The perimeter bead belonged to the keypad, the gasket to the housing, and the interface was reviewed once, together.
Validation before volume
Wipe cycles for the pump, UV and thermal cycling for the terminal, both run before the first production order.
What a custom keypad programme needs from you
Two drawings and one protocol start a programme properly. The key layout drawing fixes the legends, the key sizes and the spacing; the housing drawing fixes the aperture, the retention and the sealing interface. The protocol list — what the device is cleaned with, or where it is installed — fixes the compound and the validation plan.
Then agree the sampling route. A single-cavity prototype settles the dome and the legend, a small pilot confirms colour and force spread across a panel, and only then is a multi-cavity tool justified. Programmes that skip the middle step usually end up paying for it in a production tool modification, which costs more than the pilot by an order of magnitude.
Questions these two programmes raised
Can one keypad design serve both medical and outdoor use?
Rarely. The sealing, the legend method and the force target diverge, and a compromise part usually fails one of the two specifications. It is cheaper to keep two cavities than to defend one part against two validation sets.
How do we make a keypad quieter without losing feel?
Reduce dome height, soften the compound slightly, and add a raised locating ring so the finger still finds the key. Measure the result on a force-displacement curve; noise is subjective, travel is not.
Do payment terminals need metal domes?
Not always, but a high actuation force and a robust legend matter more than on a consumer keypad. Where vandalism is a real risk, a metal dome under a silicone overlay is the more durable construction.
What documentation should accompany a medical keypad?
Material declaration on the finished part, force-curve data, wipe-cycle results, compression set and lot traceability. The same pack, at a lower intensity, is useful for an outdoor terminal.
Send the layout and the cleaning protocol
FromRubber builds medical and outdoor keypads in Dongguan, from single-cavity prototypes through multi-cavity production tools, with moulded legends, sealed perimeters and measured force curves. Send the key layout, the housing aperture and the environment the device will live in; we will return a construction proposal and the validation plan that supports it.
Request a keypad case reviewRelated reading: how keypad quality control works in production and industrial grade silicone keypads.