# Concepts by milestone

> For agents: start with the [agent guide](https://parol6.build/llms.txt). Every page is Markdown by default; add `Accept: text/html` for HTML.

**Stub.** This page gathers the Concepts section of each milestone. Each milestone page explains its concepts with citations. Single terms live in the [glossary](/glossary).

## M1. Bench it

The robot system and its 10 ms packet cycle, steppers and drivers at 32 microsteps, why the E-stop is normally closed, and why the mains switch is the stop that still works. See [M1 concepts](/lore/m1-bench-it#concepts).

## M2. One joint end to end

Planetary gearbox ratio and step math, backlash, how an inductive sensor sees a steel screw head, couplers and threadlocker, and why the parts are printed in PETG. See [M2 concepts](/lore/m2-one-joint#concepts).

## M3. The whole arm moves

Joint numbering, limits and directions, kinematics, homing as the only position reference, and how an open-loop stepper loses steps. See [M3 concepts](/lore/m3-whole-arm#concepts).

## M4. Pick and place

The tool frame and the TCP, joint moves and Cartesian moves, what a repeatability of 0.1 mm means, and the 10 ms packet cycle. See [M4 concepts](/lore/m4-pick-and-place#concepts).

## M5. Touch the skiff

**Our design.** Coordinate frames and registration, Eurorack mechanics, and why compliance matters. See [M5 concepts](/lore/m5-touch-the-skiff#concepts).

## M6. Patch a cable

**Our design.** Peg-in-hole insertion, spiral-search and wiggle strategies, and detection without a force sensor. See [M6 concepts](/lore/m6-patch-a-cable#concepts).

## M7. Play it

**Our design.** Sequencing against a musical clock, MIDI and CV control, and handling failure mid-performance. See [M7 concepts](/lore/m7-play-it#concepts).

## Terms

- **mental model**: the why behind a step. Every milestone page gives its concepts their own section, apart from the how-to steps, following [four-component instructional design](https://www.4cid.org/).

## Sources

1. [Four-Component Instructional Design](https://www.4cid.org/)
   4C/ID. Why each milestone separates the concepts from the how-to steps. Accessed 2026-11-07.

2. [Drives, ratios and resolution, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/03-technical-data/drives-and-ratios/)
   Source Robotics. Steps, microsteps, gear ratios and open loop. Accessed 2026-11-07.

3. [Homing, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/05-operation/homing/)
   Source Robotics. Homing as the only position reference. Accessed 2026-11-07.

## Lore on this page

- [The PAROL6 milestones](/lore/milestones)
- [M1. Bench it: power, one motor, a safe stop](/lore/m1-bench-it)
- [M2. One joint end to end: the wrist and joint 6](/lore/m2-one-joint)
- [M3. The whole arm moves](/lore/m3-whole-arm)
- [M4. Pick and place, repeatably](/lore/m4-pick-and-place)
- [M5. Touch the skiff](/lore/m5-touch-the-skiff)
- [The skiff target](/lore/skiff-target)
- [M6. Patch a cable](/lore/m6-patch-a-cable)

## What links here

- Agent guide → Joel builds a PAROL6 robot arm, one sourced and filmed milestone at a time. → [Read page](https://parol6.build/llms.txt)

- Change log → What changed in the files served here, newest first. → [Read page](https://parol6.build/log)

- Full agent guide → Joel builds a PAROL6 robot arm, one sourced and filmed milestone at a time. → [Read page](https://parol6.build/llms-full.txt)

- PAROL6 build → Joel builds a PAROL6 robot arm, one sourced and filmed milestone at a time. → [Read page](https://parol6.build/)

- PAROL6 wiki | PAROL6 build → The PAROL6 build wiki: the milestones, their videos and the official sources behind them. → [Read page](https://parol6.build/lore)

- Purpose of the PAROL6 build wiki (VISION.md) → What the PAROL6 build wiki is for and who it serves. → [Read page](https://parol6.build/VISION.md)

- Source change history (log.md) → The generated change log as Markdown. → [Read page](https://parol6.build/log.md)

- The PAROL6 milestones → Seven milestones take the build from a bare control board to a robot arm that plays a Eurorack skiff. → [Read page](https://parol6.build/lore/milestones)