Open Duck Mini

Print the standard parts before selecting modifications

The print guide calls for standard PLA at 15% infill, except the two foot-bottom pads, which use TPU at 40%. It lists quantities for each named part. Keep that list alongside the preserved STL files: the repository also contains optional modifications and simulation meshes, so printing every mesh would not produce one coherent robot. We have preserved the repository at an immutable commit, including its print files and policy files; we have not exported the external standard Onshape assembly. [S005] [S010]

Configure the motors before mechanical assembly. The BOM identifies fourteen Feetech STS3215 servos specifically in the 7.4 V version, plus two small antenna servos, a Pi Zero 2 W, BNO055 IMU and a Waveshare bus-servo adapter. Assembly requires soldering, M3 inserts and threadlocker on specified metal connections. The guide still leaves the overall M3 screw quantity unspecified, so it is not yet a complete purchasing checklist. [S006] [S007] [S008]

The spreadsheet is more useful than the headline price

The README's under-$400 ambition is not a delivered build quote. The captured spreadsheet is denominated in euros: its main total is €398.10, rising to €432.34 with the listed expression package. Its lower €331.10 estimate assumes, among other things, existing PLA and a cheap IMU alternative that the author says still needs testing. Do not use that lower column as a verified equivalent build. [S001] [S008]

The sheet includes cells, a holder, BMS, regulator and charger, but it does not establish a complete delivered price including tools, shipping, tax and all fasteners. Several expression parts require buying packs larger than the quantity used; camera and microphone integration are marked unfinished in the captured sheet. The exact expression configuration therefore needs reconciliation before ordering. [S006] [S008]

Match the runtime, policy and calibration

The separate runtime instructions use Raspberry Pi OS Lite 64-bit and the v2 branch. They cover I2C, controller pairing, motor checks and a per-robot duck_config.json. That file records expression options, IMU orientation and measured joint offsets. The instructions link a walking-policy file from a moving branch; preserve the selected runtime commit and policy checksum together before comparing results across builds. Both repositories are now held locally, but we have not established a tested compatible combination. [S009]

Check IMU orientation explicitly: the assembly guide notes that its photographs show the IMU upside down and explains that configuration must match its installation. The runtime also labels head control experimental and warns that it can damage the head. These are practical limits to retain in any demonstration or support plan. No walking, calibration or hardware test has been performed for this profile. [S006] [S009]