What to Send a Factory Before Production — And Why Most Designers Send Too Little

The files are ready. The factory has been selected. It's time to move. Most designers at this stage do one of two things: they send a 3D model with a note saying "let me know if you have any questions," or they forward a drawing and wait for the factory to tell them what else they need.

Both approaches produce the same outcome. The factory makes assumptions about everything that wasn't specified — material grade, surface finish, acceptable tolerances, which surfaces matter — and builds accordingly. The first sample comes back wrong in ways that could have been prevented. Not because the factory was careless, but because you gave them incomplete information and they filled in the gaps with their own judgment.Factories don't ask questions. Not the ones you need them to ask. They're optimizing for throughput, not for design intent. The completeness of what you send determines whether you get what you imagined.Here's what should go to a factory before production begins.

Technical drawings — not just 3D files

A 3D model is a design artifact. A technical drawing is a manufacturing instruction. They serve different purposes, and a factory needs both.The drawings should include every critical dimension with its tolerance, reference planes and datum points, thread specifications and hole callouts, and a general tolerance block that covers everything not individually annotated. The tolerance block is what most designers skip. It's also the fallback for every dimension you didn't specifically call out — which means it silently governs most of your product.If your drawing has no general tolerance block, the factory applies its own standard. That standard may or may not match what you need.

A material specification

"Stainless steel" is not a material specification. "Stainless steel 304, sheet, 1.5mm, 2B finish, ASTM A240" is. The difference determines whether you get what you intended or what the factory had in their warehouse from the last order.For every material in your product, specify: the grade or alloy, the applicable standard, the form (sheet, tube, bar, casting), and any pre-processing requirements. If you don't know the standard, find it — or ask someone who does, before the order is placed.

A surface finish specification — with a reference sample

This is the most consistently under-specified element in any design package, and the most common source of sample disappointment."Matte black powder coat" is the beginning of a specification. RAL 9005, matte (20 GU), textured effect, with a physical color reference panel provided to factory — that's a specification.Surface finish requires: the specific color reference (RAL number or physical swatch), the effect type (matte, gloss, textured, fine texture), the gloss level in measured GU units where consistency matters, and a physical reference sample that the factory retains as a production standard. Words describing color and finish are almost entirely unreliable across language and cultural context. The word "warm" means something different in Shenzhen than it does in Copenhagen.A physical sample is worth more than any paragraph of description. Send one, or make it the first thing you establish in the sampling process.

A cosmetic surface map

Not every surface on your product matters equally. The top face of a table matters. The underside of the frame mostly doesn't. The inside of a drawer back definitely doesn't.Defining this explicitly — which surfaces are A-grade (visually critical, closest inspection), B-grade (visible but functional), and C-grade (hidden or non-critical) — gives the factory a quality framework that prevents over-inspection in some areas and under-inspection in others. Without it, the factory either inspects everything uniformly (slow, expensive, and often still wrong) or makes its own judgments about what you care about (unreliable).A one-page cosmetic map drawn over a product rendering takes twenty minutes to produce and prevents the kind of surface quality disputes that can stall a production run.

Assembly and fit requirements

If your product assembles from multiple components, define how they should fit: clearance tolerances between mating parts, functional requirements for anything that moves, and the assembly sequence if it's non-obvious. "The lid should close with resistance but not force" is useful. "The tolerances on the hinge pocket are ±0.3mm" is more useful.If you don't specify this and a fit problem shows up in the sample, you'll spend two rounds of sampling determining what the requirement should have been in the first place.

What you're actually doing

A specification isn't paperwork. It's the document that makes shared reality possible between a designer who thinks in form and a factory that thinks in tolerances.A factory cannot build to your intention. It can only build to your specification. Every question your spec doesn't answer gets answered by the factory — and not always the way you would answer it.The work of writing a complete pre-production package almost always takes less time than the work of recovering from the preventable sample rounds it would have avoided. Two hours of documentation, three weeks of time.