How to order a printed metal part without making a mistake

Ordering a printed metal part for the first time has a challenge that no one warns you about: it's not like ordering a machined part. A dimensioned drawing, which in machining is all the necessary information, here only provides half the information — and what's missing is precisely what determines the price.

This is the list of what to send, in what format, and how to read what they send back to you.

The file: sends geometry, not a mesh

The difference between STEP and STL isn't just a technical detail. An STL file is an approximation: cylinders cease to be cylinders and become prisms with many faces. For a bracket or fairing, this doesn't matter; for a bearing housing, it does—and to make matters worse, the error can no longer be corrected afterward because the exact geometry was lost during export.

The rule: send STEP files whenever possible. If you only have STL files, say so, so the recipient knows that the surface they see is an approximation of the one you had.

What else needs to be sent besides geometry

Geometry determines the shape of the part. Price and delivery time depend on six other factors:

1. What the part does. The most useful phrase in the entire email. "It's a support that doesn't touch anything" and "it's a housing that rotates at 8,000 rpm" are two different parts with the same shape, and they don't cost the same.

2. The material. And if you haven't decided yet, specify the conditions: service temperature, whether weight matters, whether there is corrosion, whether it will come into contact with the human body. With that information, the choice is made—it's the decision tree for 316L, Inconel 718, or Ti-6Al-4V.

3. How many. One, ten, and five hundred are three different projects. And if there's going to be repetition, say so from the beginning: change how the build is prepared.

4. Which faces do something. This is the one that involves the most money and the one that almost never gets done. Mark the three or four functional surfaces with their actual tolerance, and explicitly accept the overall rough tolerance for everything else. A drawing with two hundredths of a millimeter tolerance across the entire part multiplies the budget without improving anything — it's developed in tolerances and finish.

5. The finish you need, per side. Not for the entire part.

6. By when, and what happens if it's late. A realistic deadline allows for proposing alternatives; a simple "by now" doesn't.

And two that only apply sometimes, but if they do apply, are the first: if you need certificates or traceability —and what type—, and if the geometry is confidential, to sign the agreement before the file is moved.

How to read the quote you receive back

An additive manufacturing quote includes items that don't exist in machining. Check that they are included, because what isn't listed will appear later.

If one quote is much cheaper than another, it's almost always because it includes less, not because it manufactures better.

The five mistakes that delay an order by a week

Only send the plan. Without a 3D model, we can't even begin calculations. It's the number one reason for return emails requesting additional information.

Include machining tolerances across the entire part. Either the price will be absurd, or someone will have to call you to ask which tolerances actually matter. It's better to specify them yourself.

Not saying what the part does. Without that, the person quoting has to guess, and guesses are always made on a high note.

Ordering one when you'll need fifty. The price of the first one and the fiftieth are not the same, and neither are the manufacturing methods. Mentioning this upfront usually lowers the price of both.

Sending the geometry without a confidentiality agreement, and realizing it later. It can be fixed in five minutes before, but not after.

What to ask a supplier before sending them anything

Five questions. The answers speak louder than any catalog:

1. What machine and process will you use to manufacture it? If the answer is vague, you're going to subcontract it, which isn't necessarily a bad thing—but it's good to know.
2. How many times have you made a part like this in this material? Experience with that material is what prevents surprises.
3. What do you measure before delivery, and what do you send me in writing?
4. If the part is defective, what happens? Especially if there's a network or subcontracting involved.
5. What do you do with my file when the job is finished?

How we approach it

The quote calculator gives you an estimate without you having to contact anyone: you upload the geometry and it generates an estimate. It's an estimate, not a quote — the firm price requires inspecting the part, and we state this within the tool itself.

If you prefer to skip this step, in print your part there is a form with the fields from this list already filled in, which is the fastest way to make sure you don't forget anything.

And if the part is important and you want to see it before committing, at the open days you can bring it and make it in front of you.

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What can be ordered in raw form and what needs machining is listed under tolerances and finish. Whether your part is a candidate for printing is listed under five parts you shouldn't print. And whether it's more advantageous to buy a machine rather than order parts is listed under buy machine or buy service.

How to export the mesh so the estimate is realistic, in preparing the file: STL, 3MF and why the mesh matters. And what happens to your geometry when you send it externally, in sending your part to a stranger.