Dual sourcing: running two qualified sources for one part

What the split is buying

An allocation across two sources buys three distinct things: continuity if one fails, a live price reference, and the ability to scale when demand surges. Which of the three you value most should shape the structure. Continuity requires the smaller supplier to be able to absorb the whole volume within an acceptable ramp; a price reference needs far less; surge capacity requires reserved headroom that must be paid for whether or not it is used.

Balanced or primary-and-secondary

An even split preserves symmetry and keeps both suppliers engaged, at the cost of leverage and of duplicated setup. A dominant-and-supporting arrangement keeps most of the scale advantage while maintaining a warm alternative. The supporting share still has to be large enough that the supplier keeps qualified staff, current tooling and an active account, otherwise the arrangement provides paperwork rather than protection.

Costs that surface later

Beyond price, expect duplicated tooling and validation, two sets of process controls to monitor, additional inbound consignments, and the quality variation that comes from two processes producing nominally identical parts. Assembly issues traced to source-specific variation are a recurring surprise. These costs should be entered into the sourcing case from the outset, because discovering them afterwards is what leads businesses to quietly abandon the second source.

Testing that the fallback works

The arrangement is only proven when the secondary source has produced at volume recently. Scheduled switching of a defined portion, periodic requalification runs and an agreed ramp plan with notice periods turn a theoretical fallback into a tested one. Without that, the first genuine test happens during the disruption the arrangement was bought to survive, which is the least forgiving moment to discover a lapsed approval.

Frequently asked questions

Does dual sourcing always raise unit cost?

Usually, through lost volume discounts and duplicated setup, though not always: competitive tension can offset part of it, and in tight markets holding two allocations can secure supply that a single relationship would not. The comparison should be against the expected cost of an interruption, not against price alone.

What minimum share keeps a second source viable?

Enough that the supplier retains trained people, maintained tooling and a live commercial relationship, and enough that a ramp to full volume is a scale-up rather than a restart. The precise share depends on the process, but token allocations reliably fail this test.

Is dual sourcing appropriate for every critical part?

No. Where tooling is prohibitively expensive, the technology is proprietary or the qualified supplier base is genuinely tiny, other protections — buffer stock, contractual capacity reservations, design change to a more available part — may deliver more continuity per unit of spend.