Questions to Ask Before Choosing a Manufacturing Partner
Choosing a manufacturing partner usually starts with the wrong question: “Can you make this part?”
Almost every shop with a mill and a lathe will say yes. That’s not the question that protects your production schedule six months from now. The questions that matter are the ones that reveal how a partner operates when things don’t go according to plan. Because at some point, they won’t.
Use this vendor vetting checklist before you commit a part line to a new manufacturing partner.
1. What’s your minimum batch size?
Some shops are built for high-volume runs and treat anything under a few hundred units as a scheduling inconvenience: you’ll get pushed to the back of the queue every time a bigger job comes in. Others are set up to run small batches efficiently and won’t punish you for ordering 25 brackets instead of 2,500.
Get specific: What’s the smallest order you’ll take without it becoming a pricing or lead-time penalty? If the answer is vague, that’s your answer.
2. Can you prototype, or only produce?
There’s a real difference between a shop that can machine a part from a finished print and one that can work with you through iterations: adjusting tolerances, testing material substitutions, catching design-for-manufacturing issues before you commit to a production run.
If you’re still finalizing a design, you want the second kind. Ask how many prototype revisions they typically run before a part goes to production, and whether that’s billed separately or built into the relationship.
3. What’s your turnaround time under normal load, and under strain?
Every vendor quotes a best-case lead time. Fewer will tell you what happens to that number when their shop is at capacity, a machine goes down, or a rush order from another customer jumps the queue.
Ask what their lead times looked like during their busiest stretch in the past year, not just their advertised average. If they can’t answer that specifically, they may not be tracking it, which tells you something valuable on its own.
4. What quality checks happen on a part before it ships?
You don’t need a manufacturing partner with a formal certified quality system to get a reliable part. Plenty of shops without ISO certification run tight, well-documented processes. But you do need to know specifically what inspection happens, at what stage, and what’s recorded.
Press them for specifics: Is there in-process inspection or only final inspection? Are dimensional checks documented per batch, or spot-checked? Who signs off before a part ships? Vague answers here (“we’re really careful”) are not a substitute for a described process.
5. What happens when something goes wrong?
Every vendor will tell you their defect rate is low. Find out instead how they’ve handled it when a batch didn’t meet spec. Did they catch it internally or did the customer catch it? What was the corrective action? A vendor with a real answer to this question, even an uncomfortable one, is more trustworthy than one who claims it’s never happened.
None of these questions are complicated. But most buyers don’t ask them until after a manufacturing partner relationship has already gone sideways: a missed batch, an undocumented defect, a material substitution nobody flagged. Keep this vendor vetting checklist handy the next time you’re evaluating a new partner. Asking upfront costs you one conversation. Not asking can cost you a production schedule.