Dan Kitchen, 5 Oct 2026
Questions to Answer Before You Build a Prototype
Who buys it, how it ships, what it must cost, how it is assembled, what happens if it sells. Five answers that change a prototype's design.
Most people treat a prototype as an engineering problem. Make it work on the bench, then work out how to sell it. I think that order costs money, because the business questions change the design, and changing a design after it has been built is the expensive way to learn.
Before the first prototype, answer five questions: who buys it, how it is packed and shipped, what it has to cost, how it is put together, and what happens if it sells. You don't need perfect answers. Rough ones will still move the design.
Who buys it, and who uses it?
They are often different people. A tool paid for by a school and used by a ten-year-old has to survive being dropped and still make sense to the person signing the purchase order. A professional tool can be heavier and plainer if it does the job.
How it changes the design: the answer sets wall thickness, finish, colour, and how much the part can cost to make.
How will it be packed and shipped?
If it ships by courier, the size of the box often sets the cost more than the weight does, because carriers charge by dimensional weight. A part a few millimetres too long can push the whole product into a bigger carton.
How it changes the design: it can change the product's length, whether it folds, or whether it ships in pieces and goes together at the other end.
What does it have to cost?
Work back from the price someone will pay, less what the seller and the box take. That number decides the process. A part that has to cost very little in volume points toward molding, and machining only makes sense where the numbers allow it.
How it changes the design: a part headed for a mold needs draft on its walls, even wall thickness and no needless undercuts from the first version.
Will it be assembled by hand or by machine?
Engineers call this design for assembly, or DFA. Fewer parts, parts that only fit one way, and joints that snap together instead of screwing all cut assembly time, whoever does the assembling. If you'll be putting the first few hundred together yourself at a kitchen table, that matters more than it sounds.
How it changes the design: part count, fasteners, and whether two parts become one.
What happens if it sells?
If the honest answer is that it could sell in volume, design the prototype as if a mold is coming.
How it changes the design: draft, even walls and features a mold can release, so the first molded version refines the prototype rather than replacing it. The choice of mold is covered in aluminum or steel mold, choosing for your stage.
Why a shop asks
We ask these because we run a product business of our own. Through our sister company, Make Stuff Move, we design products, have them made, kit them, pack them and sell them. Make Stuff Move's products are used in over 30 school boards.
At Make Stuff Move we standardised on one shipping case that holds different inner box set-ups, of 10, 15 or 25 units. That one case made packing predictable and repeatable.
That experience comes into a project even when our part of the job is a small piece of the whole. We don't build online stores or run marketing, and you'll want someone else for those.
Plenty of good shops will make exactly what's on the drawing without asking any of this. If your answers are already settled, that may be all you need.
Write your answers down, even rough ones, before anyone cuts metal. Together they are the brief for the prototype.
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