Flex-arm key plate
- One molded part, no mat, lowest part count
- Slots around every key mean the plate itself cannot seal
- Arm roots see a flex cycle on every press; a tough, fatigue-resistant resin matters
Molded part guide: keypads
Injection Molded Keypads
On a twelve-key pad, users notice the one key that feels different. It is usually a corner key, and the reason is usually that the frame holding all twelve is not flat once it is screwed down.
Consistency
Every key has to feel like its neighbor
A keypad multiplies every tolerance in a single button by the number of keys.
A keypad is a grid of buttons that share one frame, one set of switches or domes, and usually one seal. Each key on its own may be well designed, but the user compares them side by side. A key that sits proud, feels stiffer, or clicks earlier stands out immediately, and on a keypad it is almost always a key at the edge or corner.
The frame is the common cause. Molded frames with many key holes rarely come out perfectly flat, and screws around the perimeter pull them down at the corners while the middle stays where it was. Keys over the high spots are preloaded against their domes; keys over the low spots have extra free travel before they click. Flatness after assembly matters more than flatness on the inspection table.
The holes themselves create a second problem. Melt splits around every key opening and rejoins on the other side, so the narrow webs between neighboring keys are full of knit lines. Those webs are also where the frame flexes when screws are tightened, which is why cracks on keypad frames tend to run from one key hole to the next.
Architectures
Three common keypad constructions
The construction decides which part carries the feel and which carries the seal.
| Construction | What the molded parts do | Watch for |
|---|---|---|
| Rigid caps through a bezel, over a key mat | Bezel locates caps; caps press the mat; frame clamps the mat edge to seal | Bezel flatness sets both key feel and seal compression |
| One-piece plate with flex-arm keys | Each key is a tab on its own arm, cut free by a U-shaped slot | Arm length sets feel, so keys with different arms feel different |
| Printed overlay on a molded backer | Molded plate supports the overlay and positions the domes | Backer must be flat and free of sink under every key |
Flatness and sealing
Keeping the frame flat once it is screwed down
The seal and the key feel both depend on the frame staying flat between fasteners.
- Add fasteners or clamp points so the frame cannot bow between them and open the seal
- A stiffening flange around the perimeter resists bow better than a thicker plate
- Gate so the knit lines between key holes fall where the frame is not flexed by the screws
- Check key height against the bezel on an assembled unit, not on a loose frame
Choosing a construction
Flex-arm key plate versus caps over a key mat
One is a single molded part. The other is a small assembly that seals better.
Caps over a key mat
- The mat gives the return force and can seal the whole front
- Key feel is more even, because every key presses the same mat geometry
- Silicone mats come from a separate process; NetProto does not quote them
Drawing
What to send for a keypad review
The frame is reviewed as part of a stack, so send the stack.
Frame or bezel CAD, key caps, and the housing they fasten to
Mat, dome sheet, or overlay drawings from the vendor
Fastener positions and the clamp method at the seal
Whether the front must pass a water or dust ingress test, and which one
Legend artwork per key and the marking method
Which keys are backlit and where the LEDs sit on the board
Keep reading
Related guides
Single buttons, front panels, and the defects behind uneven keys.
Buttons
Guide, stop, and gap on one key.
ButtonsBezels
The trim that locates the caps.
BezelsLight pipes
Backlighting individual keys.
Light pipesInstrument panels
Keypads inside a larger control face.
Instrument panelsElectronic enclosures
Sealed housings behind the keypad.
Electronic enclosuresWeld lines
Knit lines in the webs between keys.
Weld linesSharp corner stress
Cracks at flex-arm roots.
Sharp corner stressPolycarbonate
Tough frames and translucent caps.
PolycarbonateMolded parts hub
Every part-type guide, grouped by family.
Molded parts hubKeycaps
Individual caps with legends and stems.
KeycapsFAQ
Questions about molded keypads
Only the corner keys feel wrong. Why?
The frame is usually bowing when screwed down, so corner keys sit closer to or farther from their domes than center keys. Measure key height on an assembled unit and add stiffness or clamp points before changing individual keys.
Cracks run between key holes after assembly. What causes that?
The webs between holes carry knit lines and flex when the frame is tightened. Moving the gate, widening the webs, or reducing the bow that the screws force into the frame all help.
Can NetProto supply the silicone key mat?
No. NetProto does not quote silicone mats. We mold the rigid frame, bezel, and caps around the mat you specify from your mat vendor.
Can one tool make several keypad layouts?
A family mold can combine several parts that share a resin. Layout variants that differ only in legends can often share one tool, with the difference applied by printing or laser marking.
Next step
Quote the keypad as a full front stack
Upload frame, caps, housing, and mat or overlay drawings. DFM feedback covers frame bow, knit lines between keys, and key height.