Print, build, first motion

Build the arm, zero every joint, and prove it stops.

Print and build the arm and its props, set up the servos, and put the safety supervisor in front of every powered move. Then make the first real moves on the servos’ stock loops: a wave, a drawing and a melody.

Written lesson + build labEvidence-based gate

The goal for this build

What you’ll be able to do.

Print, assemble and weigh the arm, its tools and its test props, and record them as built.
Give every servo its ID, its zero and its startup registers, and prove each write by reading it back.
Put the safety supervisor in front of every powered move, and show on video that its latch holds.
Calibrate the webcam and locate the arm’s base, so the camera can check the encoders.

What to have ready

Module 6 gate passed, including the trainer’s review of the wiring plan before the first power-on
The Module 6 test joint, which stays assembled as the pendulum bench
The hardware kit, a printer with a 180 × 180 mm bed or a print service, a soldering iron, and a scale that reads to 0.1 g
Forward kinematics from Module 1, and the inverse kinematics and stock baseline from Module 2

Download the course starter ↓

Free account

Read the lesson, run the lab, pass the gate.

The whole course is free. Create an account to unlock the lesson, the build lab, the task and the gate command for this module, and to download the starter kit.

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03 / Prove it

Keep the evidence.
Then run the gate.

What you ship

A moving arm, a build log with photos, and the wiring plan updated to the wiring as built
A BOM with weighed, not datasheet, masses
The calibration file, plus the round-trip, zero-gauge and repeatability logs
The failsafe log with its video
Videos of the first wave, the first drawing and the first melody, with the drawing scanned

Module 07 gateEvidence required

A fixed tag filmed for 30 s gives the camera noise for Module 8.
Round-trip test, signs: with torque off, each hand-moved joint moves the webcam’s tag in the direction the forward kinematics predicts, and by within 10% of the predicted distance.
Round-trip test, zero offsets: with the zero gauge fitted, every calibrated arm joint reads within 1° of zero.
Returning to a taught pose 10 times, the gripper tag stays within 2 mm of its mean position, or within three times the fixed tag’s standard deviation if that is larger.
The failsafe test passes on video, with the arm holding a pose: opening the kill switch drops it limp into its rest pose and latches the supervisor; closing the switch moves nothing until the learner re-arms, after which the read-back is clean and the arm starts from where it lies.
In the same filmed test, a temperature limit set below the present temperature latches, a goal below the table latches without being sent, and stopping the app leaves the arm holding until the kill switch drops it.
The arm holds the stretched pose with 150 g for 30 s without an overload trip.
The first figure-eight is drawn on stock settings and scanned.

With a free account: the gate command and how to record your evidence.

The story behind the build

Episode companions.

EP 08Printing and building it: the first wave and the first drawing

Written companions are available now. Recordings and customer access are forthcoming.

Made it through the lesson?

Save your reading progress here. Record your gate result in your project.