Assemble the Mechanism¶
Coming soon. A step-by-step guide with photos will be written from the reference build. Until then, the draft below gives the order, reconstructed from the parts and screw list and not yet checked against a build. Corrections and photos are welcome.
Mk3: this draft order was written for the Mk2 and is not yet checked on the Mk3. The Mk3 is standalone: the board and the power boards go inside the clamp's technical cavity, which the printed door closes, and the USB-C connector is the only connector left outside.
You need the printed parts and the parts below. The servos are wired in Wire the electronics.
Parts to buy¶
| Qty | Part | Notes |
|---|---|---|
| 1 | 608 skateboard bearing | |
| 27–28 | 6 mm balls | Between the top plate and the rotor plate. 6 mm airsoft BBs do the job very well. The Mk2 uses 16–24 steel balls of 4 mm instead. |
| 4 | M3×8 button-head screws | Horizontal servo mounting |
| 2 | M3×25 button-head screws | Lower plate of the horizontal axis to the ball track |
| 1 | M3×8 countersunk screw | Horizontal servo shaft plate |
| 1 | M3×20 countersunk screw | Vertical servo shaft |
| 4 | M3×8 button-head screws | Vertical servo mounting |
| 3 | M3×30 countersunk screws | Bearing to the vertical shaft |
| 1 | A toy wand | Any cat wand with a stick that fits the arm |
Draft assembly order
### Before you start - [Print](print.md) every part in [`stls/mk3/`](https://github.com/vistorx/CatWandConnect/tree/main/stls/mk3) (or [`stls/mk2/`](https://github.com/vistorx/CatWandConnect/tree/main/stls/mk2) for the previous Mechanism). - Clean the ball track and the bearing seat of strings and elephant's foot, so the balls roll freely. - Plug each servo into a powered, flashed board and let the robot Stow once, so both servos sit at their Stow position before you fit the arm. This keeps the arm centred within its range. ### Steps 1. **Bearing.** Press the 608 bearing into its seat. It should sit flush and turn without rubbing. 2. **Ball track.** Lay the 6 mm balls in the track between the top plate and the rotor plate: 27 to 28, until the plate turns smoothly without play. On the Mk2: 16–24 steel balls of 4 mm. 3. **Horizontal servo.** Mount it with four M3×8 button-head screws, then fix the horizontal servo shaft plate with the M3×8 countersunk screw. 4. **Horizontal axis.** Fix the lower plate of the horizontal axis to the ball track with the two M3×25 button-head screws. 5. **Vertical servo.** Mount it with four M3×8 button-head screws, and fix its shaft with the M3×20 countersunk screw. 6. **Bearing to the vertical shaft.** Fix it with the three M3×30 countersunk screws. 7. **Arm and wand.** Fit the arm and attach the wand. 8. **Clamp.** Fix the robot in place with the clamp and its screw. ### Checks - Unpowered, both axes turn by hand without binding, and the bearing doesn't rub anything. - No screw crushes a printed part. Tighten until snug, not more. - Route the servo cables so they can't snag as the axes move. - Power up and stay close: the wand should crawl to its Stow position. Then try the joystick gently. See the [acceptance checklist](acceptance-checklist.md).Next: Wire the electronics.