ABOUT THIS BUILD

The inspiration and goals behind the J-4.2 project

The Movie

In the 1986 film Short Circuit, a military robot designated Number 5 is struck by lightning and becomes sentient. He escapes the lab, befriends Ally Sheedy's character, and proves that he's alive — not just a machine following programming. The robot became one of the most beloved in cinema history, and inspired our J-4.2 build.

The Build

This project is a full-size, functional replica of J-4.2 built over 12 weeks using a combination of CNC machining, laser cutting, 3D printing, welding, and modern electronics. The goal isn't just a static prop — it's a working robot with:

  • Tracked locomotion (stair-climbing dolly base)
  • Articulated head with camera eyes and LED iris
  • Moving arms with tendon-driven fingers
  • Speech synthesis and voice recognition
  • Computer vision via Raspberry Pi 5 + Google Coral
  • Remote control + autonomous behaviors

The Approach

The build follows a 3-tier system across 3 months:

  • Month 1 (Skeleton): Frame, chassis, structure, basic mechanics
  • Month 2 (Organs & Nervous System): Electronics, wiring, software, head assembly
  • Month 3 (Evolution): Cosmetics, advanced features, tracked drive, calibration

The Equipment

This build leverages production-grade fabrication equipment including a Laguna SmartShop EX laser cutter, Colex SharpCut 5x10' CNC router, Creality K1 Max 3D printer with CFS-C multi-color kit, Creality RaptorX 3D scanner, and full MIG/TIG/stick welding capability. Most builders have a 3D printer — this shop can fabricate 80%+ of J-4.2's parts in-house.

Open Source

This build is based on the OpenSAINT project by Input-Inc, with modifications for the dolly-based platform, K1 Max print bed constraints, and custom electronics architecture. The build plan, parts list, and progress are documented here for anyone who wants to follow along or build their own.

Sister Projects

Short Circuit is the umbrella brand for our maker projects. In addition to the J-4.2 robot build, we're developing tools and documentation for the fabrication equipment used in the shop:

  • Colex Forge — CNC toolpath generation, feeds & speeds calculators, and machine profiles for the Colex SharpCut 5x10' flatbed router. Material libraries, cut optimization, and production workflow documentation.