I once trusted a factory that promised 50,000 parts a month—only to find out their actual capacity was less than 20,000.
To secure long-term supply of custom metal parts from Vietnam, you must confirm production capacity using real data, audits, and contractual guarantees—not assumptions or sales claims.
In this guide, I’ll show you how I confirm whether a supplier can truly support recurring, high-volume orders.
What signals show actual production volume capability?
I’ve seen fancy brochures claim “1 million parts per year,” but when I asked for machine uptime or output logs, there was nothing.
To assess a factory’s real production capacity, I request documents like machine lists, operator counts, production logs, and run-rate data 1 for similar parts.
Factory Data I Always Request
| Category | What I Ask For |
|---|---|
| Machine Inventory | Model, type, year, throughput/hour, number of units |
| Shift Schedule | Number of shifts per day, shift length, working days per month |
| Operator Count | Number of skilled workers per process (CNC, welding, stamping, etc.) |
| Monthly Output History | Units produced per part family over the last 6–12 months |
| Downtime / Maintenance Logs | Machine availability, breakdown records 9 |
If I’m evaluating a stamping supplier 2, I don’t just want their tonnage rating. I ask how many strokes per minute their press runs, how often dies are changed, and what average scrap rate they see.
I also use this formula to cross-check capacity:
Monthly Capacity = (Available Minutes per Month) x (Parts per Minute) x (Machine Utilization %)
This tells me if they can realistically hit my volume, especially when I factor in setup times and maintenance downtime.
How to check machine uptime and utilization?
I’ve seen a factory with 10 CNC machines—only 4 were operational during my call. The rest were down or waiting for operators.
Machine quantity means little without uptime and utilization data. That’s why I verify metrics like OEE (Overall Equipment Effectiveness) 3 and ask for recent production dashboards 10.
Machine Utilization Metrics I Analyze
| Metric | What It Tells Me |
|---|---|
| Availability (%) | Downtime vs scheduled run time |
| Performance (%) | Actual speed vs theoretical cycle time |
| Quality Rate (%) | Good parts vs total parts produced |
| OEE (%) | Overall performance (Availability × Performance × Quality) |
Let’s say the supplier runs 2 shifts of 8 hours each, 26 days per month. That’s 416 hours. If their CNC machine runs 60% of that time, with 90% yield and 85% cycle efficiency, the real output is much lower than advertised.
Here’s an example of an OEE table I request:
Sample OEE Table
| Machine ID | Availability | Performance | Quality | OEE % |
|---|---|---|---|---|
| CNC-01 | 85% | 90% | 98% | 75% |
| CNC-02 | 60% | 80% | 95% | 45.6% |
| Stamping-A | 92% | 85% | 96% | 74.9% |
Factories that track and share OEE data transparently give me confidence—they usually understand capacity planning 4 and have a data-driven mindset.
Can lead time history indicate capacity reliability?
One of the smartest ways I evaluate capacity is by tracking actual vs promised lead times on similar projects.
Yes — lead time history 5 is a real-world indicator of a supplier’s capacity load and reliability. Consistent delays usually mean they’re overbooked or poorly managed.
What I Track About Lead Times
| Item | Why It Matters |
|---|---|
| Promised vs Actual Lead Times | Consistency shows stability in planning |
| Rush Order Flexibility | How quickly can they handle a last-minute batch? |
| Average Production Cycle Time | By product type—reveals baseline capability |
| Bottleneck Step Duration | E.g. heat treatment, plating, CMM—are these causing delay? |
| Delivery Deviation Logs | If they log late reasons, it’s a good sign of discipline |
If a factory claims they can deliver 10,000 parts/month, but takes 7 weeks to ship 3,000 pieces, I know they’re stretched. If they miss deadlines but blame “unexpected power outages” or “labor shortages” every time, that’s a red flag.
I often plot a simple Gantt chart 6 or spreadsheet showing:
- Quoted lead time
- Actual delivery date
- Reason for deviation (if any)
- Feedback from QC or shipping logs
Consistent alignment between promise and performance builds trust.
What contracts or agreements ensure long-term capacity?
I’ve helped clients who initially received great service—until the factory got busier with a bigger client. Then my client’s orders were delayed or deprioritized.
To ensure consistent long-term supply, I lock in capacity with written agreements, minimum quantity clauses, and lead time penalties 7.
Contract Terms I Use for Capacity Assurance
| Clause Type | Description |
|---|---|
| Minimum Monthly Volume | Supplier agrees to reserve enough capacity to fulfill it |
| Lead Time Guarantee | Defines maximum days from PO to shipment |
| Penalty for Late Delivery | Financial or priority penalties for missed deadlines |
| Exclusive Line or Tool Usage | Assigns dedicated equipment or tools for your parts |
| Expansion Timeline Clause | If supplier promises to scale up, define date + outcome |
| First-Right Scheduling | Buyer gets priority in peak season or limited capacity |
I always clarify: capacity = actual throughput, not a theoretical claim. If the supplier says they’re expanding, I request:
- Investment plan (machinery, staff)
- Timeline for implementation
- Proof of down payments or orders
- Floor layout for new lines
- Staff hiring roadmap
Without clear commitments, “we will scale up if needed” is just a placeholder promise.
To double-check these commitments, I often request a supplier audit 8 to validate the factory’s claims before signing.
Conclusion
In Vietnam—and anywhere—capacity isn’t what the factory says, it’s what they can prove.
Get the data. Run a test. Audit the shop. Lock it in writing. That’s how you secure long-term supply without getting blindsided by bottlenecks or broken promises.
Footnotes
1. Learn how production capacity is calculated and analyzed. ↩︎
2. Basics of metal stamping and capacity considerations. ↩︎
3. Guide to understanding OEE and machine effectiveness. ↩︎
4. What capacity planning means in manufacturing. ↩︎
5. How lead times reflect supply chain reliability. ↩︎
6. Explanation of Gantt charts for project tracking. ↩︎
7. Example clauses in supplier capacity agreements. ↩︎
8. Why supplier audits help validate manufacturing claims. ↩︎
9. Importance of downtime and maintenance logs in capacity checks. ↩︎
10. Benefits of using production dashboards for transparency. ↩︎
