Second-source qualification: proving an alternate shop can build the same part

Company approval and part approval answer different questions

A capability assessment tells you the shop has presses of the right tonnage, a quality system and someone competent running it. Part qualification asks something narrower: can this shop hold this tolerance, on this material, at this rate, repeatably. The evidence is dimensional and statistical rather than organisational. Many buyers stop at the first exercise and are surprised when the first production lot from an approved supplier is rejected. Treat the company assessment as the gate that lets a supplier be considered, and the part programme as the thing that lets an order be released. They usually sit with different people and should not be merged into one sign-off.

Where the alternate will quietly differ from the incumbent

Drawings capture geometry and material grade. They rarely capture the sequence of operations, the fixturing, the coolant, the tool path, the annealing step someone added years ago, or the fact that the incumbent buys bar from one mill because another mill's chemistry machines badly. A new source will reinvent all of that, legitimately, and the resulting part can be dimensionally conforming yet behave differently in assembly or in the field. Before qualification starts, walk the incumbent's process and write down what is not on the drawing. Anything you cannot explain becomes a risk item for the alternate's first article review.

Tooling for the alternate is a decision, not a detail

Three routes exist: transfer the existing tool, build a duplicate, or let the alternate design its own. A transferred tool preserves geometry but leaves you with no capacity if the tool is damaged, and it must be reproved in a press it was never set up for. A duplicate costs money and introduces cavity-to-cavity variation you now have to manage in the field. A supplier-designed tool gives the best process fit and the least comparability. Whichever route you take, decide who pays and who holds title before the tool is cut, and record the cavity identification scheme so returns can be traced back.

A qualified alternate that never runs stops being qualified

Approval decays. Operators leave, machines get repurposed, the plating subcontractor changes hands, the material grade gets substituted. A source that has not produced your part for a long stretch is an unproven source with a certificate attached. The usual remedy is to route a share of volume through the alternate rather than holding it purely as a standby, even where the piece price is unattractive, because the difference buys a live capability. Where volume genuinely cannot be split, agree a periodic requalification run and treat the cost of that run as part of the insurance you are buying.

Counting the real cost before you commit to a second source

The visible items are duplicate tooling, sample parts, test and laboratory work, engineering hours and travel. The less visible ones are customer approval fees in regulated sectors, split volume pushing both suppliers below their efficient batch size, additional inventory locations, and the ongoing quality workload of managing two processes rather than one. Set against that, price the exposure you are removing: what a stoppage on this part actually costs in lost output and customer penalty. Qualification is rarely worth it for a catalogue item with several stockists, and almost always worth it for a tooled part with a long recovery.

Frequently asked questions

Do we need to requalify a part if only the sub-tier changes?

Usually yes, where the sub-tier performs a special process. Heat treatment, plating, anodising, welding, painting and sterilisation all change material properties in ways that final dimensional inspection will not detect. A supplier switching plating lines can produce parts that measure identically and corrode differently. Build the requirement into the agreement so the supplier must notify you before changing any named sub-tier, then decide the scope of requalification case by case rather than granting a blanket exemption.

How much volume should go to the second source once it is approved?

Enough that the process stays alive and the people running it stay familiar with the part. A trickle of occasional orders leaves you with a source that will need a warm-up period exactly when you have no time for one. The split is a commercial judgement: too small and the alternate loses interest and efficiency, too even and you lose whatever price the incumbent gives for scale. Many manufacturers settle on a clear majority with the primary and a steady, predictable remainder with the alternate.

Can we qualify a second source using the incumbent's inspection data?

No. The incumbent's capability data describes the incumbent's process, and the whole point of qualification is to establish that a different process reaches the same result. What the incumbent's data is useful for is defining the qualification itself: it shows which characteristics actually vary, which have historically caused rejections, and which are comfortably held. Use it to focus the alternate's measurement plan on the features that matter, rather than demanding a full dimensional report on every feature on the drawing.