Harness Printer — Malachi Espinola

The problem

Wire harnesses are still built by hand, on form boards, one wire at a time. They are slow, easy to get wrong, and bad for high-mix production.

The V1 harness printer gantry — V1. Built in a living room.

Wire laid across the pegboard — A finished path.

Close-up of extruded wire routed between pegs — Held by tension alone.

Schematic to machine path

The goal is an ECAD harness file in, machine code out. We built the machine code side, but not the ECAD slicer — that is saved for V2.

Design to slicing to execution pipeline diagram — Design → slice → execute.

Custom GUI with a wire path drawn on the pegboard — Paths drawn in a custom GUI.

Plot of planned vertices against actual coordinates — Peg path collapsed to bend vertices.

Tensioning

Feedrate control is the most important aspect. Too little wire and the head drags pegs out of the board; too much and the harness goes slack.

Plots of feed distance buffers across moves — Desired, minimum, and actual feed across every move.

The machine

Ten steppers across three CNC shields, with an Arduino Giga running the event loop. The PC slices the path into machine code, then sends it to the Arduino.

Belt drive feeding wire.

Rotary cutter.

CAD of the full feed system — Full feed system.

Cross section of the feed and cutter — Feed and cutter, cross section.

Wiring diagram of controller, shields and motors — Ten steppers, three shields, one Giga.

Embedded software architecture diagram — Machine manager owns the loop.

What V1 taught us, and V2

The pegs were too small and too constrained, which made starting and ending a wire the hardest part of any run. Extrusion also put the crimps at risk. Cutting and crimping are already well handled by existing machines, so V2 leaves them alone and focuses on routing and assembly. It drops the pegboard for two robotic arms, one carrying a pinch grip and one carrying the extrusion head, with vision as a cross check.

Built with my brother, a mechanical engineer at SpaceX.

CAD render of the V2 dual-arm concept — V2 concept.

← All work