> Historical R3 button reference, retained for unchanged button mechanisms. Use the R3.1 root START_HERE and assembly for current files and light placement; R3 filenames and package paths below are historical.

# R3 button assembly and adjustment

All dimensions are millimetres. Values below describe the nominal CAD configuration, not measured LIDUOLE specifications. Named film/shim thicknesses are total installed thickness, including any adhesive. Do not add an unaccounted adhesive layer.

## Installed configuration

| Interface | PTT | Volume up/down | Front |
|---|---:|---:|---:|
| Selected nominal switch size | 6 x 6 x 6 | 6 x 6 x 5 | 12 x 12 x 4.3 |
| Estimated travel to electrical operation | 0.25 | 0.25 | 0.30 |
| Seat shim | 0.40 | 0.40 | 0.40 |
| Compliant contact thickness | 0.25 | 0.20 | 0.25 |
| Nominal released contact gap | 0.15 | 0.15 | 0.15 |
| Travel-stop shim | 0.10 | 0.10 | 0.10 |
| Nominal exterior key stroke to stop | 0.45 | 0.45 | 0.50 |
| Side cradle backing film | 0.15 | 0.15 | n/a |
| Side rear keeper pad, installed | 0.50 | 0.50 | n/a |

The click travel is an analogy, not a permitted maximum stroke. With an undeformed contact, the default geometry provides 0.05 mm beyond the analogous click position. Actual pad compression, switch force, operating point and permissible overtravel must be established on the bench. The stop geometry is not evidence that this extra stroke is safe for a particular sample.

## How adjustment works

- Seat alternatives: 0.20, 0.30, 0.40 and 0.50 mm. Increasing the seat by 0.10 mm moves the switch 0.10 mm toward the external key and reduces the rest gap by 0.10 mm. Decreasing the seat does the opposite. The assembly reference switch stays at the default pose; selecting a different shim requires repositioning the switch in CAD or measuring the corresponding physical stack.
- Contact alternatives: PTT/front 0.15, 0.25 and 0.35 mm; volume 0.10, 0.20 and 0.30 mm. A thicker contact reduces the released gap. Contact alternatives replace the installed contact, rather than sitting on top of it.
- Stop alternatives: 0.05, 0.10 and 0.15 mm. Side key stroke is `0.55 - stop thickness`; front key stroke is `0.60 - stop thickness`. The thicker stop produces less key motion. Use a matched pair of stop shims on each key.
- Do not independently choose the thickest seat and thickest contact. Their effects add. In the nominal model, `released gap = 0.15 - (seat - 0.40) - (contact - default contact)`. A negative result means preload. Avoid unintended preload or a switch held electrically closed.
- The backing films locate the cradles against the inner load spines; the two front pins locate each cradle laterally. Rear pads take up the closure stack. Installed pad thickness is modeled; free thickness, compression set and clamping force are not qualified.

## Suggested first assembly

1. Deburr the prototype carriers, contact lands, cassette grooves and locating holes. Verify there is no flash or print support in the side passages. Keep hard particles away from switch plungers.
2. Select one actual 6 x 6 x 6 PTT, two actual 6 x 6 x 5 volume switches, and one actual 12 x 12 x 4.3 front switch. Confirm momentary action and identify the electrical contact pairs with a meter; pin positions in these reference models are not an electrical pinout.
3. Trial the switches in the cradles and clamp before connecting the harness. Check lead projection and the soldered/insulated joint against the provided clearance channels. Keep solder and adhesive out of the switch body and moving contact.
4. Fit the selected seat shims. The default is 0.40 mm. Attach the compliant contacts on their flat carrier lands using an attachment method compatible with the chosen elastomer and carrier; account for bond thickness in the total stack. A loose or detached small contact is not an acceptable build.
5. Insert the side cradles from the rear onto their locating pins and backing strips. Fit the rear pads and close the shell evenly. The PTT cradle is centred at Y=17 mm, not the previous Y=12 mm location.
6. Fit the front switch, bearing ring and revised clamp with its existing two screws. Stop columns face the rear of the round key. Confirm screws seat correctly without pulling the clamp out of alignment.
7. Begin a gentle bench check with the thicker 0.15 mm stop shims (shorter stroke), then adjust in small increments only as needed. Watch electrical state while releasing and pressing. Stop if a key binds, stays operated, the switch moves in its holder, or the stop is not reached consistently. Establish the sample's permissible travel before relying on an end stop to protect it.
8. Once the centre press works, test edges and ends of each key, especially the long PTT. Repeat with the shell fully closed, the real wiring dressed, and screws tightened consistently. Check automatic return, no sustained activation, no rattling, and no lead chafing. Compare the feel of both volume buttons.

## Prototype materials and fabrication

Rigid carriers, cradles and clamp are small mechanical fit parts. Use a dimensionally controlled prototype process agreed with RPS; confirm thin walls and locating pins survive the chosen material/process. The volume cradle has a local 0.40 mm retaining lip; it should be evaluated as a fit prototype and is not a released urethane wall specification. The enclosure retains its established exterior material/finish direction, while the new internal features still require casting and shrink/tolerance review before a batch.

Bearing/stop shims can be cut from suitable measured film or shim stock using the DXF profiles. Contact and rear-pad pieces require compliant material, rather than rigid print resin. Select pad hardness, free thickness, attachment, compression and return behaviour with physical switch samples. CAD colours are identification only. A nominal interference-free fit is not a tolerance or material test.

## Record the accepted stack

For each control record: actual body/overall height, terminal envelope after wiring, seat thickness, total contact thickness, released gap, stop thickness, key movement to electrical operation, movement to stop, return behaviour, edge-press behaviour, and final material/adhesive. Keep one accepted sample assembly as the comparison reference before committing to the casting batch.