Splitting a critical part between two qualified suppliers sounds simple. The hard part is making both sources produce the same drawing. We run dual sourcing when the volume and the risk both justify it.
Dual sourcing is not insurance against everything. It targets a specific set of failures.
A small shop takes on a bigger customer, loses a machinist, or gets bought out. Your open PO sits in a queue you cannot see. By the time you learn the truth, the assembly date has already passed and the only fix is air freight or a line stop.
A 5-axis spindle needs a rebuild. The part only runs on that one machine because nobody wrote a second process. Two to six weeks of capacity disappears, and no amount of expediting brings it back.
The machining is fine. The 17-4PH bar or the 7075 plate is not. A mill allocation, a heat-treat queue, or a plating line shutdown holds up a part that was otherwise ready to ship.
Most buyers learn about single-source exposure during an audit or a line-down meeting. By then the mitigation is expensive. A cost and capacity review done early is far cheaper than a recovery plan.
Two sources only work when both build to the same controlled process.
A backup supplier discovered during a crisis is not a backup. It is a new project with a new first article, a new fixture, and a new set of questions. That takes weeks you do not have.
So the second source gets qualified while volume is normal: same drawing, same material certs, same inspection plan. First article parts from both sources are measured against the same critical dimensions. If the two processes disagree, we change the process, not the print.
A common mistake is to give 50% to each supplier and treat them as equals. In practice one site should carry the process knowledge and the other should carry surge capacity. The lead site owns the program; the second site ramps when demand moves.
Typical split is 70/30 or 80/20, with the smaller share kept live by a minimum monthly quantity. That keeps the second source warm without paying for idle capacity. When the lead site slips, the second site is already making the same part on the same revision.
Use this to decide per part number, not per company. Most programs land in the middle column.
| Part or program profile | Single source is fine | Dual source is worth it |
|---|---|---|
| Annual volume | Under 200 pieces | 1,000 pieces or more |
| Line-down impact | Prototype or spares | Feeds a running assembly line |
| Tooling cost | High fixture or die cost | Low fixture, standard workholding |
| Material risk | Stocked domestic alloy | Long-lead or allocated alloy |
| Drawing stability | Still changing every build | Frozen revision, ECO controlled |
| Qualification effort | Simple 3-axis geometry | 5-axis or tight tolerance features |
| Changeover cost | Full day of setup | Under 2 hours of setup |
Every process below can be quoted from a single plant or split across sites when the volume justifies it.
16 simultaneous 5-axis centers. Complex geometry, undercuts and compound angles in one setup, which keeps datum stack-up low and makes a second source easier to qualify.
12 four-axis mills for prismatic parts with features on multiple faces. Good fit for splitting volume because setup is short and repeatable.
27 three-axis machines. The easiest process to duplicate at a second site: standard vises, standard fixtures, predictable cycle times.
16 mill-turn centers handle turned parts with milled features. One chucking means one source of concentricity, which simplifies cross-site comparison.
Bridge parts for line-down situations and design checks. Useful when you need something in hand before the production source is qualified.
Anodizing, plating, powder coating, black oxide, blasting and laser marking. Finishing is often the second bottleneck, so we plan it as a separate capacity line.
Same tolerance and inspection standard applies to the lead site and the backup site.
| Item | Range or standard | Notes |
|---|---|---|
| General tolerance | ±0.005 mm | ±0.0002 in |
| Fine surface finish | Ra 0.2–0.8 μm | On request |
| Standard finish | Ra 0.8–1.6 μm | Default production finish |
| As-machined finish | Ra 1.6–3.2 μm | Non-critical faces |
| Maximum part size | 4,000 mm | 4,000 × 400 × 150 mm travel |
| Rotary table | Ø400 mm | For mill-turn work |
| Inspection | 100% before shipment | Reports on request |
| Materials | Aluminium, stainless, steel, copper, titanium | Plus engineering plastics |
The numbers below are the ones that decide whether a split program holds tolerance across two sites.
We have run split production for long enough to know which parts tolerate it and which do not. That judgment is the useful part.
Capacity spread over three wholly-owned plants in Dongguan and Singapore, so a spindle rebuild does not stop a program.
Both sources are measured against the same critical dimensions. If one drifts, we fix the process before shipping.
First article and production parts released against the same inspection plan, whether they come from plant one or plant three.
Send a drawing and get a quotation plus manufacturability notes within 12 hours, including a view on whether splitting makes sense.
Parts ship in 3–5 days once production starts. Production can begin within 24 hours of a released order.
Programs need traceable material, documented inspection and a source that survives an audit. We hold the process on both sites and report critical dimensions per lot.
Line-side fixtures cannot arrive late. Volume is split so a tooling failure at one plant does not stop the assembly line at the customer.
Cleanliness, documented material certs and a stable revision are the requirements. Two qualified sources reduce the risk of a single plant going quiet.
Large aluminium frames and plates with long lead times on material. Splitting the machining and holding a material buffer at each site keeps the build on schedule.
Start with parts that feed a running line and have a low changeover cost. Annual volume above 1,000 pieces is a reasonable threshold because the second qualification effort is amortized.
Leave prototypes, one-off spares and parts with heavy dedicated tooling on a single source. Qualifying a second site for those costs more than the risk it removes.
Not if the process is controlled. Both sites work from the same frozen drawing revision and the same inspection plan. Critical dimensions are compared on first articles before the second source is released.
Where the two sites differ is in workholding and machine selection. Those are allowed to differ. The measured output is not.
Most programs work well at 70/30 or 80/20. The lead site keeps the process knowledge and the main volume. The second site holds surge capacity and a minimum monthly quantity so the line does not go cold.
A straight 50/50 split doubles the management effort for the same total output and makes it harder to tell which site owns a quality issue.
Usually yes, by a small amount, because setup and inspection are duplicated across sites. The size of the increase depends on how much setup the part needs.
Parts with under two hours of setup absorb the split well. Parts that need a full day of fixture work do not, and we will say so in the quote.
For a part we already run, the second site needs a first article build and inspection. Quotation and DFM analysis come back within 12 hours, and production can start within 24 hours of release.
The first article itself is the long step, because it has to be measured and compared, not just made.
Yes. Each site holds its own fixtures, its own CAM programs and its own material buffer. Neither depends on the other for tooling or stock.
A spindle failure or a material delay at one plant does not interrupt the other. That independence is the whole point of the arrangement.
The same quality system applies across our plants: ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022.
Inspection follows the same sequence everywhere: raw material check, in-process monitoring, and final inspection before shipment. Reports are available on request.
Then we run a single source and reduce risk another way: keep a finished-goods buffer, hold raw material, or qualify a second process on the same machine family.
Dual sourcing is a tool, not a policy. We use it where it removes real exposure and skip it where it only adds paperwork.
We will tell you whether your part benefits from a second source, what the split would cost, and what the qualification step looks like.
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