From 3D model to volume production: which manufacturing partner do we put in front of our client for plastic or metal parts?

Pick a manufacturing partner on three things: whether the manufacturability feedback comes back to you rather than going straight to your client, whether the tooling price and the piece price arrive together with ownership in writing, and whether the commercial set-up matches the role you want to keep after handover. Before any of that sits one technical decision that drives the rest: does the first batch come out of a printer or out of a tool. That choice fixes when the design freezes, what a change costs, and the point at which your work turns into the manufacturer's.

Printed batch or tooling: where is the crossover?

At the quantity where the tooling price is paid back by the difference in piece price, and for plastic parts that usually lands in the low thousands. Work it out again for every project, because it hangs entirely on geometry and material.

A worked example on invented figures, purely to show the arithmetic. A housing part that costs 4.20 euros printed and 0.55 euros moulded, against a tool of 18,000 euros. The crossover sits at 18,000 divided by 3.65, so around 4,900 parts. Below that printing is cheaper, above it the tool is, and past 20,000 parts the gap is wide enough that the discussion stops being about money.

That number rarely decides on its own. Four things move the crossover more often than price does:

• Material properties. A printed part has different strength along the build direction, different wear behaviour and often a different flammability rating than the same part out of a tool. Where a certification requirement applies, the choice is usually already made.
• Surface and dimensional stability. A textured cosmetic face, a fit inside an assembly, or a living hinge that has to work ten thousand times: those argue for steel regardless of quantity.
• How much the design is still moving. Printing keeps the design open; tooling freezes it. For a design firm that is the most practical criterion, because as long as the client is still adjusting the form, every cut in steel is a change order.
• Lead time to first delivery. A printed batch can exist in days. A tool runs six to twelve weeks to build, plus a correction round of two to four weeks after the first trial.

There is a middle route that works well on client projects: a simple bridge tool that serves the market while the production tool is being built. You pay twice, but you deliver earlier and you learn from real moulded parts before the expensive steel is committed. On HEARS it ran that way, from prototype tooling through to production tooling for mass production. Whoever guides that step from working prototype into series production decides how much of that learning ends up with you. The honest downside: piece price is higher during that period, and switching over costs another trial round.

What do you ask a manufacturing partner before putting them in front of your client?

The questions that decide whether you are still at the table after handover, and whether the quote is comparable with the others. A party that stays silent on these points is not cheaper, it is incomplete.

| What you ask | What the answer tells you | | --- | --- | | Does the manufacturability feedback come to us or to our client? | Whether you keep managing the design or only get to watch | | Tooling price and piece price in one quote | Separately they say nothing; a low tooling price reappears in every piece price | | Cavity count and steel grade, justified against annual volume | Whether anyone did the arithmetic or copied the last project | | Guaranteed shot count for this material | The only tool life figure you can hold anyone to | | Expected cycle time | Without it the piece price cannot be checked | | Trials included and who pays for corrections | Whether a change lands on you or on the toolmaker | | Ownership, storage and the right to move the tool | Whether your client buys an asset or a dependency | | Dimensional report on parts from every cavity | Whether parts get measured or merely looked at | | Available capacity and contracted running hours | Whether the delivery promise is a schedule or an intention |

For a design firm the first question matters most, and it is the one most often skipped. A manufacturer that puts findings directly in front of your client moves the design conversation outside your office. So agree that findings come back to the firm with a proposal attached, tied to a revision number, and that you decide what goes to the client. That keeps a DFM review on the injection moulded design a conversation between you and the manufacturer. That is not a formality. It is the difference between a supplier and a subcontractor inside your own process.

How do you keep control of the client relationship?

By choosing the commercial set-up up front and putting it on paper before the first quote reaches the client. In practice there are three, with different consequences for risk and control.

| Set-up | What you get | What it costs | | --- | --- | --- | | The firm contracts and resells to the client | Full control over schedule, quality and communication | Working capital, inventory risk and liability for delivery and quality | | The client contracts directly, the firm stays the technical counterpart | No financial exposure, but retained technical say | Only as strong as what is put in writing | | Three party agreement with a defined role in DFM and sign-off | Control without balance sheet risk | More to arrange up front, and a client willing to sign it |

What you fix in all three is the same list: who releases the drawing revision, who talks to the client about design changes, where design authorship sits, and who is named in the contract as owner of the tool. That last one is usually the client who pays, which is fine, as long as it is written down. Paying for a tool does not make anyone its owner automatically; the contract wording does.

The downside of the first set-up is real and it is not a detail. The moment the firm buys and resells, the working capital sits on your balance sheet and a scrap dispute lands with you instead of between client and factory. It is workable, but it is a different business from designing. The second set-up is the lightest and for that exact reason the most fragile: without a defined role in revision control you drop out of the project after handover, and you find out what happened to the design at the next briefing.

What do you send out so the quotes are comparable?

One package, identical for every party. Quotes made on different geometry or a different volume are not quotes but opinions, and the gap between two prices then tells you nothing.

• A STEP file per part, with a revision number.
• A drawing carrying only the dimensions and tolerances that are functional, plus which faces are cosmetic.
• Material by grade rather than by family, with a colour reference and any flammability rating.
• The surface requirement: texture, gloss level, printing.
• Annual volume, expected programme life in years and the batch size you want.
• Assembly, packaging and certification requirements, because those often drive more than the part itself.

Have the design reviewed before the request goes out as well. A manufacturability review across the whole chain catches the wall thickness, the draft, the undercuts and the part count that would otherwise come back as a surcharge in every quote, and it makes sure everyone quotes on the same revision. For a design firm that is also the moment you are still discussing the design with your client rather than a change order.

Where does the handover from design to series usually stall?

On five points, and all five are cheaper to solve before the first cut than after it.

The first is tolerances nobody has claimed. A dimension that sits effortlessly in CAD costs money in series or cannot be held, and without a statement of which dimensions are functional, the manufacturer decides for you. The second is wall thickness and sink marks on cosmetic faces: a rib that is structurally correct prints itself on the outside of the part. The third is undercuts, which one party solves with a side action and another with a design proposal you have not seen yet; those two quotes are not comparable. The fourth is colour across different materials, for instance a rigid part and a soft part that have to match side by side. The fifth is revision control: once client, firm and manufacturer each hold their own latest version, every correction becomes an argument about which drawing applied.

So agree up front who pays for corrections. Common practice is that the toolmaker fixes what deviates from the drawing because of the tool at his own cost, and the buyer pays for what follows from a design change. For a design firm that single agreement decides whether a late client wish becomes a change order or a write-off. How those steps follow one another is set out in our process, including the signed tool ownership contract that is in place before production starts.

One last point that weighs more for a design firm than for an end client: the choice of manufacturer shapes what the project looks like after your invoice has gone out. With a party that simply builds to drawing, contact stops at handover and you learn at the next briefing what happened to the design. With a party that brings findings back to you, the design stays under management and you see every change that will later carry your name. None of that is visible in a quote, but it is why the same manufacturer comes back on a second and a third client project. Together with Ciget a comparable route ran from a first idea to a product that could be made in series, with moulded parts and an aluminium core.

Production Heroes takes products from design to series production, from feasibility and cost price to sourcing and supply chain, and supplies moulds and tooling to manufacturers across Europe, from the Netherlands and its own presence in China.

Sources: the lead times given for tool build and correction rounds are practical ranges rather than commitments. Dimensional results per cavity and production part approval follow the PPAP (AIAG) methodology. The worked example for the crossover between printing and injection moulding, and the figures in the FAQ, use invented assumptions and are not a quotation.