# M6. Patch a cable

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

**Whole task:** grip a 3.5 mm patch cable, insert it into a target jack, verify it is patched, and pull it back out.

**Our design.** The PAROL6 manual stops at pick-and-place, so this milestone is ours.

## Parts

- A cable-holding gripper: TPU 75A fingers, or a printed plug holder on a compliant mount ([Custom tools](https://docs.source-robotics.com/PAROL-docs/1.1/end-effectors/custom-tools/)).
- Patch cables.
- A cable rack or nest to pick from.

## Concepts

- **Peg-in-hole insertion:** chamfers, lateral compliance, and why open-loop steppers cannot feel force. An overloaded stepper loses steps silently ([Drives, ratios and resolution](https://docs.source-robotics.com/PAROL-docs/1.1/03-technical-data/drives-and-ratios/)).
- **Spiral-search and wiggle strategies.**
- **Detection without a force sensor.** Verify the patch electrically: send an LFO through the new cable and read it at the destination. Our design.

## How-to

- Our insertion routine, written as a completion task on the [Python API](https://docs.source-robotics.com/PAROL-docs/1.1/programming/02-python-api/).
- The measured jack positions from [M5](/lore/m5-touch-the-skiff).

## Practice

- Insertion trials across jack positions.
- Failure-mode drills: a missed jack, a cable caught on a knob.

## Done check

Nine of 10 inserts and 10 of 10 removals across three different jacks, each verified electrically. No damage to the jacks.

## Terms

- **peg-in-hole**: the robotics name for inserting one part into a close-fitting hole, here a 3.5 mm plug into a jack. Our design; the PAROL6 docs do not cover it.
- **spiral search**: moving the plug in a widening spiral around the expected jack position until it drops in. Our design.

## Video

[The M6 video](/lore/video-m6) is planned.

## Sources

1. [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. Overloaded steppers lose steps silently, so the arm cannot feel force. Accessed 2026-11-07.

2. [Custom tools, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/end-effectors/custom-tools/)
   Source Robotics. Mounting a custom cable-holding gripper. Accessed 2026-11-07.

3. [Python API, PAROL6 docs 1.1](https://docs.source-robotics.com/PAROL-docs/1.1/programming/02-python-api/)
   Source Robotics. Scripted motion for the insertion routine. Accessed 2026-11-07.

## Lore on this page

- [The PAROL6 milestones](/lore/milestones)
- [M5. Touch the skiff](/lore/m5-touch-the-skiff)

## 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)

- Build steps by milestone → The official how-to pages for each milestone, in build order, gathered from the milestone pages. → [Read page](https://parol6.build/lore/build-steps)

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

- Concepts by milestone → The mental models each milestone teaches, gathered from the milestone pages, with the glossary for single terms. → [Read page](https://parol6.build/lore/concepts)

- 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)

- M6 video: Patch a cable → The video for milestone 6 is planned and not yet recorded. → [Read page](https://parol6.build/lore/video-m6)

- M7. Play it → The capstone milestone runs a script that patches cables and moves knobs on cue to perform a short written piece. → [Read page](https://parol6.build/lore/m7-play-it)

- Milestone videos → Each milestone ends in one video, and every video is planned until Joel publishes it. → [Read page](https://parol6.build/lore/videos)

- 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)

- Parts by milestone → What goes on the bench at each milestone, gathered from the milestone pages and the official bill of materials. → [Read page](https://parol6.build/lore/parts)

- 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)