Almost every team that develops more complex electronic devices reaches a point where they need to design the cable connections to their PCBs, including its manufacturing documentation. I have encountered a variety of approaches to handle this task. From creating documentation in common office software such as MS Word or Visio to designing harnesses in AutoCAD or using dedicated tools for cable and harness design.

Among Altium Designer users, it is, quite understandably, a popular approach to directly use the schematic editor to design the wiring harness. Since it is not intended for this use, users encounter several obstacles. The main one is that the wires themselves are not included in the bill of materials, which must then be created manually. Over time, of course, users have found a way to get around this and other limitations as well [1]. However, even then, the support of harness design is minimal in the design environment.

This has changed with Altium Designer PRO 23, in which Altium has introduced a new type of project - The Harness project [2] with direct support for the design of cable harnesses, including the generation of their complete manufacturing documentation. The addition of Harness projects is a continuation of the development of so-called Multi-board projects in Altium Designer, which allow multiple PCBs and their assembly to be captured directly in Altium Designer in a common 3D environment. These multi-board assemblies were previously limited to board-to-board arrangements, i.e. the case where one board is plugged directly into the connector of another board. This significantly limited the use of multi-board assemblies. Harness projects have eliminated this limitation and allow for cable-connected board assemblies.  

Wiring editor
Depending on whether the Harness project is set up on its own or as part of a Multi-board project, the way in which the wiring of the cable harness is created differs. For an individual Harness project, the user manually controls the entire design. In the case when a Harness project is part of a Multi-board project, the harness connectors from the connected assembly are loaded into the wiring editor and these connectors already indicate to the user (similarly to the nets on an unrouted PCB) which connector pins need to be interconnected and the system monitors whether the Harness project corresponds to the Multi-board project in this respect.

The actual wiring design is similar to the design of the circuits in the schematic editor, however, there are changes that are worth noting. The connectors are standard components from the Altium Designer library, but in the editor, they allow the definition of associated components (e.g., separately purchased parts of the connector used to screw it to the board) and crimps. These are also separately purchased parts, but in this case, they are tied directly to a specific pin of the connector (e.g., used for crimps).

There are also differences in the wiring. Each wire has its own parameters such as color, cross-section area, and purchase number. In addition, they are included in the final bill of materials (BOM). They can also be inserted as parts from a library where all their parameters are defined in advance. 

Wirings can be bundled with the Harness Cable object to form a cable, which again is included in the BOM (only the cable, the separate wires that form the cable are no longer listed in the BOM). In the schematic editor of a regular PCB project, the connection of multiple wires is represented by a signal junction, which has no physical representation on the PCB. In the wiring editor in a Harness project, this wire connection is represented by a Splice object (see SPL1 to SPL5 in the wiring diagram), which represents the terminal block that is physically used to connect multiple wires.

The editor also includes solutions for shielding and twisting of wirings or for branching wirings with continuous crimp taps (another type of Splice object).

Wiring of a simple cable harness with Splices