Additive manufacturing

This category covers additively manufactured metal and polymer parts for aerospace and defense: powder bed fusion, directed energy deposition, binder jetting and the post-processing that finishes them. A shop that only machines belongs in precision machining, and a shop that only inspects belongs in NDT. The distinction that matters commercially is that in additive the material is created at the same time as the part, on that machine, in that build, which makes the process the product.

Qualification is machine, parameter and powder together

Ask which machine the part will be built on, and then ask what happens if it is built on the identical machine next to it. A serious supplier will already know, because it has run the comparison. Ask how the powder is controlled: lot traceability, sieving, reuse policy, the number of reuse cycles allowed and the chemistry check that permits another cycle. Ask what the build parameters are locked to and what the change control is when the machine manufacturer issues a firmware update. Ask what witness coupons are built with each job, what is tested, and what the acceptance criteria are. NASA publishes an additive manufacturing standard for spaceflight systems through its technical standards system, which is a useful public reference point for what a mature qualification framework asks of a supplier.¹ Ask which framework the supplier works to and how it differs from that one.

Post-processing is not a detail

Most of the properties a designer wanted arrive after the build. Ask about stress relief, hot isostatic pressing, support removal, machining of interfaces, surface finish and the internal passages nobody can reach. Ask what non-destructive testing is applied, at what stage, and whether computed tomography is used or claimed. Ask what the defect acceptance criteria are, in writing, and who signs them off. Ask who performs each of those steps, because a printing shop that subcontracts every downstream process is selling you a supply chain, not a part.

What lets the part fly

Producing an article that is reasonably likely to be installed on a type certificated product is only lawful through defined routes: under a type certificate, under an FAA production approval, as a standard part to a government or industry specification, as a commercial part, by an owner or operator for their own product, by an appropriately rated certificate holder consuming it in a repair, or in another manner the FAA approves.² If the parts feed a production line, the production approval holder's quality system must control design data, documents and suppliers, including a supplier reporting process for nonconforming articles.³ Settle before the order which of those routes your parts travel and what evidence has to arrive with them. For defense work, check that the specifications called out on the drawing are current in the government's standardization register, where documents show as active, inactive or cancelled with their dates.⁴

Questions that sort suppliers

Ask how many of this part number the shop has built, on which machines, over what period. Ask for the powder lot traceability record from a recent job. Ask what the scrap rate is on a comparable part and what caused the last rejection. Ask what happens to your build files and parameters if you take the work elsewhere.