LSR injection moulding
Two-part liquid silicone metered, mixed, injected cold and cured hot. The cleanest route we have for medical, wearable and electronics parts at…
See the serviceProject record · Haptics · LSR
A haptics brand's silicone diaphragm.
A precision-shaped silicone diaphragm that generates haptic feedback in a small consumer device. Prototype casting proved the design; production LSR held it stable across millions.
The brief
A diaphragm whose deflection had to be repeatable to the human touch.
A haptics-focused consumer brand had prototyped a small silicone diaphragm — the acoustic-adjacent element that produces tactile feedback in a hand-held device. Prototype casting had validated the concept; user testing had confirmed the haptic profile.
For production, the challenge was consistency. Haptic feedback is generated by the diaphragm deflecting under a fast air pulse. If the diaphragm stiffness varies part to part, the feedback varies. Users describe the device as inconsistent. Reviews reflect it.
They needed a production route that would hold diaphragm stiffness within a tight window across every part in every batch — for the life of the product.
The problem
Diaphragm stiffness depends on wall thickness, grade, and cure — all three had to be locked.
Cast prototypes were made one at a time, weighed for material, hand-poured, and cured on the bench. Every part was slightly different. That was fine for prototype: overall haptic character was consistent even if individual parts varied.
At production volume, individual variation stops being averaged out — every user experiences their own device, not the fleet average. Wall thickness variation of even a small percentage translates directly into perceived stiffness variation.
The route had to be LSR with tight cavity dimensional control, a grade whose cure kinetics were well-characterised, and a cure cycle held to specification. All three interlocked; getting one wrong would show in the finished part.
What we changed
We tooled LSR to a tight cavity spec, verified stiffness on real parts, and locked cure.
The design was correct. The route change did the rest.
Cavity finish specified for dimensional control
The cavity was machined and polished to hold diaphragm wall thickness to a defined tolerance. Cavity wear tracked to protect the tolerance across tool life.
Grade selected on cure kinetics
LSR grade chosen for well-characterised cure — repeatable material behaviour across batches, minimal cure-condition sensitivity.
Sample parts stiffness-tested
First production samples deflection-tested individually. Distribution measured; grade and cure adjusted where needed to centre and tighten the distribution.
Cure cycle formally locked
Cure time, temperature and pressure documented. Any deviation requires quality sign-off before the batch continues.
Golden sample plus stiffness reference
First production batch established the golden sample and a stiffness distribution. Both retained as programme references.
Rolling batches to spec
Each batch first-off checked for both dimensional and haptic performance. Any drift caught before the batch ships.
The commercial shape
Tooling paid for itself in the first year; consistency stabilised the product.
LSR multi-cavity tooling investment recovered inside twelve months on the initial volume forecast. Actual volumes ran ahead of forecast; payback was faster.
Per-part cost dropped substantially versus what cast prototype production had cost per unit. More importantly, the product's user rating stabilised — the 'inconsistent feedback' complaints in early reviews disappeared once production LSR parts replaced the pilot cast parts.
The tool has since produced several million parts. Diaphragm stiffness distribution remains within the initial reference. No refurb required so far; scheduled inspection continues at defined cycle intervals.
“The reviews stopped saying it was inconsistent about six weeks after the LSR parts started shipping.”
Services used
How this programme was actually delivered.
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