When you send a contract manufacturer your CAD files, engineering drawings, and product specifications, you might expect them to review everything and simply come back with a price. But if they do that without asking questions, I would be concerned.
A drawing gives us important information, but it does not necessarily tell us everything we need to know about how the product is supposed to work, where it will be used, how parts interact, or what is genuinely critical to quality.
“If the contract manufacturer is not asking questions, that’s a red flag.”
At Agilian, this kind of questioning is an important part of our contract manufacturing process. Before assumptions get built into the product, we want to understand what you actually need. That thinking also sits naturally alongside our DFX, Industrialization, and NPI support.
What questions should a contract manufacturer ask you?
The first question is about function. What does the product do, and what does each part need to do?
Then comes the environment. Will it be used indoors or outdoors? At high or low temperatures? What about humidity, UV exposure, chemical contact, high loads, or repeated bending?
These questions matter because they can influence material selection, surface finish requirements, and other manufacturing decisions.
Your manufacturer should also understand mating parts. Is something a sliding fit, friction fit, snap fit, or clearance fit? What happens when tolerances stack up across several parts?
This is where manufacturing tolerances and tolerance stack-up become important.
Quantity matters, too. Are we making one prototype, a golden sample, or a million units a year? The answer can change the manufacturing approach and process selection.
And then there is quality.
“What is your inspection criteria? Now, if this question is not asked by your contract manufacturer, please, you ask the question because this is super, super important.”
We need to know what is acceptable to you.
“No scratches anywhere,” for example, could mean rejecting a part because of a mark on an internal surface nobody will ever see. Your inspection criteria and cosmetic inspection criteria need to be specific.
That is why detailed 2D manufacturing drawings are so important. Tolerances, mating relationships, surface finish, roughness, welding requirements, and CTQ (critical to quality) characteristics should be called out.
If the drawing cannot contain everything, provide supporting documentation or assembly instructions.
You can learn more about this stage in Agilian’s New Product Introduction process.
What should you ask your contract manufacturer?
This is not one-way traffic.
As a buyer, you should also ask questions.
Ask whether your manufacturer has enough information. If you do not understand the proposed material, ask them to explain it. If something on an engineering drawing makes no sense to you, ask what it means.
“Always, always, always ask questions, particularly if you don’t understand something.”
A capable contract manufacturer should be able to explain the reasoning behind its recommendations, not expect you simply to accept them.
That matters when you are evaluating a contract manufacturer because the quality of the answers can tell you a lot about their engineering depth.
For more on supplier due diligence, this QualityInspection.org guide covers 11 questions to answer before working with a contract manufacturer in China.
How do you identify an experienced manufacturer?
Do not judge a manufacturer simply by the number of questions it asks. Look at the quality of the questions.
Let’s take the example of GD&T.
An inexperienced manufacturer might simply say, “No problems, we’ve got it.”
An experienced contract manufacturer goes deeper: does the datum structure actually make functional sense?
The same applies to materials. Rather than automatically selecting ABS, a capable team asks about function, environment, humidity, assembly, and whether another polymer or even metal would make more sense.
This is part of design for manufacturing (DFM) and reducing manufacturing risk before production begins.
It is also the approach we want customers to experience when working with Agilian: not simply accepting a specification and moving ahead, but questioning the details that need to be understood before manufacturing.
I can sum it up neatly like this:
“Smart questions at the start are cheaper than solving problems at the end.”
Manufacturing needs to be a two-way conversation.
Ask questions, expect questions, and pay close attention to the quality of the answers you receive.
P.S.
I discuss questions to and from manufacturers in more detail on the Sofeast podcast. Watch and listen to the episode here.
