Outsourcing Cable Harnessing: A Guide for Machine Builders

It’s Day 2 of your Factory Acceptance Test (FAT). The machine is built, but the vision system is dropping packets. A tech spends four hours tracing the cable, only to find a “pigtail” shield termination inside the cabinet. The machine is supposed to be identical to the last one, but the wiring is not.

This single, inconsistent crimp—a 10-second manual task on the shop floor—has just halted a multi-million-dollar machine’s acceptance test and put the entire delivery schedule at risk.

This is the “wiring bottleneck.” In modern machine building, wiring is one of the last “manual craft” tasks. It is highly variable, difficult to control on a busy floor, and a primary source of “ghost” faults that derail FAT and SAT (Site Acceptance Test). When building one or two machines, this is an annoyance. When scaling to 10, 50, or 100 units, this variability becomes a critical commercial failure. The solution is often to move from wiring to manufacturing.

The In-House vs. Outsourced Decision

For OEMs and system integrators, the triggers to move from in-house wiring to outsourced, pre-assembled harnesses are nearly always commercial. This “make vs. buy” decision is a common strategic challenge, as discussed by publications like Control Engineering.

Keep it In-House If…	Outsource It If…
You are building a one-off prototype or in a rapid R&D loop where the design changes daily.	You are building repeatable machines, lines, or multi-site rollouts.
You have a dedicated, skilled wiring team with zero production bottlenecks.	You have labour constraints or your skilled techs are wasting time on repetitive tasks.
Quality is managed, but some rework at FAT is an accepted part of the process.	Reducing FAT/SAT rework to zero and demanding 100% first-pass yield is a priority.
You manage a complex, multi-vendor component list for every build.	You want to simplify your BoM into a single, kitted part number for an entire assembly.

Key Considerations for Successful Outsourcing

Once the decision leans towards outsourcing, the process relies on three key areas of collaboration.

Consideration 1: The ‘Frozen’ Blueprint as a Foundation

Chaos cannot be outsourced. A partner cannot build a reliable harness from an inconsistent drawing. The first step is “freezing” the design into a reusable blueprint.

• BoM Finalisation: This involves specifying the exact cable families, such as ÖLFLEX® for motion, ETHERLINE® for data, and SKINTOP® glands.
• Connector Conventions: A clear definition is needed, e.g., “M12 X-coded for all field sensors. EPIC® rectangular for main cabinet disconnects.”
• Standardised Labelling: A logical label map ([MachineZone]-[DeviceType]-[ID]) becomes part of the deliverable.
• The Acceptance Pack: This defines “done” and includes items like a photo of correct routing, a signed-off continuity test sheet, and proof of 360° EMC termination.

Consideration 2: Moving Quality from Inspection to Manufacturing

A major benefit of outsourcing is moving quality from an inspection step (at FAT) to a manufacturing step.

A harness built in-house is subject to the shop floor: time pressure, component swaps, and inconsistent habits (like the pigtail). A pre-assembled ÖLFLEX® CONNECT harness, by contrast, is built in a dedicated, controlled cell.

• EMC is Guaranteed: 360° EMC terminations can be mandated and tested before shipping.
• Yield is 100%: The harness is electrically tested for continuity and pinout.
• Tools are Correct: Specialist partners use calibrated crimp tools and test boards, eliminating the variability of a hand-tool in the field.

This single change can recover days from a FAT/SAT schedule by eliminating the “ghost” fault-finding loop.

Consideration 3: The Logistics and Supply Chain Benefits

The final win is logistics. An in-house wiring process requires managing dozens of part numbers: bulk cable drums, connectors, glands, labels, and heat-shrink.

Outsourcing converts this entire list into one part number.

• Before: 20+ component SKUs
• After: 1 SKU: “Machine 01 – Gantry Harness”

This single part number can then be integrated into a “just-in-time” (JIT) delivery flow. Instead of a pallet of bulk drums, a single, pre-labelled kit arrives for “Machine 07 / Bay 3,” sequenced to the build schedule. This eliminates on-site cutting waste, stock-holding, and hours of “hunting and gathering” by the assembly team.

The Bottom Line: From Craft to “Copy-Paste”

In-house wiring is often perfect for R&D and one-off custom prototypes where the design is fluid. But the moment replication is required—whether for 10 machines or 10 sites—that variability becomes the biggest risk.

Outsourcing harnessing is not just buying a cable. It is a strategic decision to de-risk the schedule, guarantee quality, and convert wiring from a manual craft into a predictable, reliable, “copy-paste” manufacturing step.

Frequently Asked Questions (FAQ)

Isn’t outsourced harnessing more expensive? The comparison should focus on Total Cost, not just the part price.

• In-House Cost: Part cost + Purchasing labour + Kitting labour + Wiring labour + Cost of Rework + Cost of FAT Delay.
• Outsourced Cost: Price of single kitted part. For any repeatable build, the outsourced model is almost always cheaper by reducing labour, rework, and schedule risk.

What if my design changes? This is a common process managed by version control. You work with your partner to update the frozen spec. The next delivery is “Gantry Harness v1.1.” This ensures the change is documented and replicated perfectly across all future builds.

Can I trust the quality of an outside partner? Quality is managed through verification, not just trust. The “Acceptance Pack” (Consideration 1) is key. By requiring 100% electrical testing, EMC validation, and documentation, you receive a warrantied assembly that is often more reliable than a unit wired under time pressure on the shop floor.