Twelve questions to ask a metal 3D printing supplier before sending them a part

Ordering a metal printed part for the first time presents a problem that ordering a machined part doesn't: you don't yet know what a reasonable order size is. And a supplier who refuses to answer these twelve questions is more informative than one who answers them all.

It helps you choose a shop floor and, above all, helps you know what you're comparing when you have two quotes in front of you that are 40% different.

About the material

1. Which alloy exactly, and from which powder supplier? "Stainless steel" is not sufficient. "316L" is acceptable, and even better, the reference number and manufacturer of the powder. Two 316L powders from different suppliers will not produce the same properties.

2. Can you give me the batch certificate? It should be yes, no question about it and free of charge. If the answer is "we don't provide it," the part is not traceable and has no regulatory value.

3. How many times has this powder been reused, and what criteria do you use to dispose of it? This is the least asked question, yet it's the biggest difference between a serious shop floor and one that isn't. A good answer includes the number of cycles, a criterion—particle size, oxygen, flowability—and who measures it. This is explained in powder reuse.

About the process

4. What parameters will you use to manufacture my part, and are they qualified for this alloy? You don't need the parameter set—that's its value—but you do need to know that one exists, that it's fixed, and that it's not improvised on a part-by-part basis.

5. In what orientation will you place it, and why? The orientation determines cost, lead time, finish, and properties. A shop floor that can't explain it to you hasn't considered it. It's in anisotropy and orientation.

6. What record of the process do you keep, and will you give it to me if I ask for it? If one day it is necessary to demonstrate how that part was manufactured, either the record exists or it doesn't.

About what arrives at your table

7. Does the price include post-processing, and if so, which one exactly? Herein lies half the difference between quotes. Stress relief, platform trimming, support removal, shot blasting, machining of functional surfaces: each one incurs a cost and a timeframe, and sometimes "printed part" means it arrives with the supports in place.

8. What tolerances do you guarantee in the rough and which only with machining? An honest answer distinguishes between the two. If they promise hundredths of a millimeter in all dimensions without any machining, something doesn't add up. It's in tolerances and finish.

9. How do you check that the part is okay, and what report will I receive? There's a big difference, and a big price, between "by eye" and a dimensional report with tomography.

About the treatment

10. What lead time, and what portion of that lead time is machine queue? An unbroken lead time cannot be negotiated. With a breakdown, you know what can be shortened. It's in actual lead times.

11. What happens to my geometry? How long do you store it, who sees it, do you use it for anything else? You're sending intellectual property to a company that probably also manufactures for your competition. The right answer is specific: how long, who has access, and what gets deleted. Ideally, this information should be included in the terms of service, not just in an email.

12. What if the part is defective? Who is responsible for what, within what timeframe is it redone, and what happens if the problem was in the design rather than the manufacturing? It's important to have this clear beforehand, not afterward.

The three answers that should raise a light

• "Our parameters are secret, and we can't say anything about the process." The parameters may be theirs; the lack of information about the process is another matter.
• "We'll do it just like machining, don't worry." An additively manufactured part is not a machined part. Whoever says that hasn't redesigned anything, and you're the one paying for the result.
• "Fixed price without seeing the geometry." Either they have a huge markup, or they're going to renegotiate halfway through.

And one they're going to do to you

“What does the part have to withstand?” If they don't ask, that's bad. And if they do ask, have the answer ready: it's the information that most changes the outcome and is least often included in the first email. How to properly prepare this request is explained in how to order a printed part.

If you want a cost reference before talking to anyone, the quote calculator gives it to you with the geometry you already have, and with the assumptions in view so you can compare it with what they offer you.

Those that have to do with your file and who sees it, developed, in send your part to a stranger.