Aerospace Sheet Metal Fabrication and Welded Assemblies

What aerospace sheet metal fabrication covers

It covers formed and welded hardware cut from sheet, plate, tube and structural shapes: brackets, enclosures, chassis, ducts, frames and welded assemblies for flight, test and ground use. What makes it aerospace work is not the press brake. It is the drawing control, the material and temper callouts, the weld code and the records that prove each of them.

Jobs we see buyers send out fall into four groups:

• Formed details. Brackets, clips, angles, doublers, shields and cover plates, often in aluminum or 300 series stainless.
• Enclosures and chassis. Electronics boxes, panels and racks with inserted threaded hardware, cutouts and a finish.
• Welded assemblies. Ducts, tanks, housings, brackets with welded gussets and subassemblies that are finish machined after welding.
• Frames and structures. Test stand frames, equipment skids, carts, platforms and the welded structure inside ground support equipment.

A fabricated part is often cheaper and faster than the same shape hogged from plate, but it brings its own risks: springback, distortion, weld quality and finish entrapment. The sections below cover what to put in the request so those risks are priced and controlled from the start.

Material and temper: say how the part should be formed

Name the alloy, the temper the sheet is bought in and the temper the finished part must be in. When those two tempers differ, the forming and heat treat sequence is part of the job and the shop has to plan for it.

Two points catch buyers late. First, a part formed soft and heat treated afterward needs a heat treat certificate and hardness or conductivity results in the package, not just the sheet mill cert. Second, published minimum bend radii vary between producers, so put the radius and its tolerance on the drawing rather than leaving it to the shop's chart. Bend radius rules, grain direction and flat pattern practice are explained on our sheet metal and welding process page, and alloy tradeoffs on the aluminum alloys page and the titanium alloys page.

Which weld code to put on the drawing

Pick the code by what the hardware is and what it carries, then require every weld record to that same code. The code decides how procedures and welders are qualified, how welds are inspected and what discontinuities are accepted, so it changes both price and supplier choice.

A complete weld note names the code and edition, the weld class where the code has classes (D17.1 does), and any inspection beyond the code minimum. Writing only "weld per AWS" leaves the shop to choose, and two shops will choose differently. The D17.1 weld classes and what each one requires are covered on the process page, so this page stays on what to buy and what to accept.

Mixed structures are common. A stand might be welded to D1.1, while the stainless interface plate that bolts to flight hardware is welded to D17.1. That is fine, as long as the drawing makes the boundary explicit and the weld map shows which joints fall under which code.

Welder and procedure qualification: what to ask for

Ask for proof that the procedure was qualified, the welder was qualified to that procedure and the welder's qualification covers the material, process and position used on your part. Those three records answer most audit questions about a weld.

• Welding procedure specification (WPS). The written instructions for the joint: process, filler, shielding, preheat, interpass limits and technique.
• Procedure qualification record (PQR). The test welds and results that back up the WPS. Every WPS used on your part should trace to a PQR under the same code.
• Welder or welding operator qualification. The record that the person, or the operator of an automatic system, passed the test for that process, material group, thickness range and position.
• Weld map or traveler. A drawing or table that ties each joint to the WPS used and the welder who made it.

When you qualify a new source, ask for a sample WPS and PQR for your alloy and thickness before award. A shop that welds 6061 to D1.2 every week may have nothing qualified for 2219 or titanium, and qualifying a new procedure adds test coupons, lab time and weeks to the first order. Find that out at quote time, not after the PO is placed.

Weld inspection and acceptance

Every weld gets a visual inspection. Surface and volumetric methods are added by weld class or by drawing note, and acceptance limits come from the code class tables or the drawing, not from the inspector's judgment.

Be specific about sampling. "Radiograph 100 percent of Class A butt welds" is inspectable. "Radiograph as required" is not. If penetrant or radiography is needed, the NDT provider and its level of certification should be flowed down the same way the weld code is. Method detail lives on our nondestructive testing page.

One sequencing point: penetrant inspection should be done before a coating or paint closes the surface. If the drawing calls for NDT after finish, flag it, because most sources will want to inspect before.

Flatness, distortion and post-weld machining

If a flatness or position tolerance on a weldment matters, say whether it applies before or after welding, and whether machining after welding is allowed. Welds shrink as they cool, and a drawing that assumes no distortion either gets fixtured heavily or gets pushed back.

• Machine after weld. For mounting faces, bores and interface patterns, the usual answer is to weld with stock left on, stress relieve if the procedure calls for it, then finish machine. Show the machined surfaces clearly so the fabricator and the machinist agree on datums.
• Straightening. Some shops correct distortion by flame or mechanical straightening. On heat treated aluminum and precipitation hardening steels that can change properties, so state whether it is permitted.
• Formed part flatness. Large formed panels relax after cutting and forming. Put a flatness callout on panels that mate to other hardware, and state the restraint condition for measurement if the part is flexible.
• Measurement setup. Large frames may need a coordinate measuring arm or laser tracker rather than a surface plate. Ask how the source will measure the tightest tolerance on the weldment.

Distortion is also a lead time issue. A weldment that has to come back for machining is now two jobs at two shops, which is one reason buyers use a single sourcing point for fabricated and machined work.

Inserted hardware: self-clinching nuts, studs and standoffs

Call out the exact hardware part number, the sheet material and hardness, and when in the sequence the hardware goes in. Self-clinching hardware only holds when it is harder than the sheet it is pressed into.

Self-clinching nuts are covered by NAS standard NASM45938, which superseded military specification MIL-N-45938, and the major manufacturer publishes which of its parts conform to each NASM45938 slash sheet. When your program requires NASM parts, put the NASM number on the drawing rather than a commercial catalog number, and ask for the hardware certs in the package.

Points that cause rework:

• Sheet hardness. Manufacturer data for stainless self-clinching nuts limits use to sheet at or below a stated hardness, for example HRB 70 for some 300 series parts. Hardware cannot be clinched into sheet that is too hard, which rules out some heat treated or cold worked material.
• Sequence versus finish. Inserting before anodize or plating can trap solution around the hardware. Inserting after finish can crack or scrape the coating. Agree the order with the source and state it.
• Edge distance and sheet thickness. Each part has a minimum sheet thickness and centerline to edge distance. Holes near bends or edges can distort when the hardware is pressed.
• Verification. For critical hardware, ask for push-out or torque-out testing on a sample from the lot.

Finishes on fabricated parts

Specify the finish, the class or type, and any masking, and think about how the finish reaches every surface of a welded or formed part. Fabrications create finish problems that solid machined parts do not.

• Entrapment. Lap joints, skip welds, spot welds and hemmed edges trap anodize and plating solutions, which bleed out later as corrosion. Continuous seal welds or a design change are often better than hoping the rinse gets it out.
• Weld zones. Weld metal and heat affected zones can anodize to a different color than base metal. If appearance matters, say so and ask for a sample.
• Stainless. Heat tint and embedded iron from forming tools need removal. Passivation is common, and some programs also require pickling of weld areas.
• Paint and powder on GSE. Outdoor equipment near the coast needs a coating system chosen for salt exposure, with surface preparation spelled out, not a default shop paint.

Anodize, conversion coating, passivation and paint specifications are compared on our surface finishing page, and post-forming heat treat controls on the heat treatment page.

First article inspection on fabrications

A first article inspection to AS9102 applies to a fabricated part the same way it applies to a machined one: every characteristic on the drawing, every material and process callout, and a record that ties them together. Fabrications just have more ways to drift between the first part and the tenth.

What makes fabrication FAI different:

• Formed dimensions depend on tooling and material lot, so a change of brake tooling or sheet supplier can be a reason for a new or partial FAI.
• Weld procedures, welders and NDT sources are part of the process record. Ask that the FAI identify them.
• Heat treat after forming, finish and hardware insertion are separate operations, often at separate suppliers, and each needs its cert in the FAI.
• Large weldments may need several measurement methods, which should be stated on the inspection report.

Our AS9102 first article guide explains the forms and when a new FAI is triggered.

What to put in a sheet metal or weldment RFQ

Send the drawing at its released revision, the material and temper in and out, the weld code and class, the inspection, the finish and the quantity. A fabricator can quote a bracket in an hour; what stalls the quote is not knowing which rules apply.

1. Drawing and 3D model, revision letter stated, with flat patterns marked reference unless controlled
2. Material specification, temper as bought and temper as delivered, and heat treat specification if forming is done soft
3. Weld code, edition and class, plus a weld map if the assembly has more than a few joints
4. NDT method and sampling, and acceptance basis if it differs from the code
5. Flatness and post-weld machining requirements
6. Inserted hardware part numbers and installation sequence
7. Finish specification, type or class, masking and color
8. FAI requirement, certificate of conformance and any other certs
9. Quantity, release schedule and need date
10. Export control status of the drawings

Our aerospace RFQ checklist covers the general items, and the GSE cost guide explains how weld, test and coating choices drive price on larger structures. If the drawings are export controlled or proprietary, read our confidentiality page and the controlled programs process before sending anything.

How Aerospace Sourcing handles a fabrication job

We do not run a fabrication shop. We match your job to fabricators whose weld qualifications, forming capability and quality system fit it, and we manage the work through delivery.

• One quote, one lead time, one point of contact and one purchase order, even when a fabricator, a heat treater, a finisher and an NDT lab are all involved
• Weld code, class, inspection, heat treat and finish requirements flowed down to each supplier
• Every supplier signs a flow-down NDA before seeing your data and does not learn the end customer unless you approve
• Paperwork checked before shipment, with a certificate of conformance on every order and other certs when your request requires them

We do not promise a supplier for every job. If a part needs a qualified procedure no one we can match holds, we will say so instead of guessing.

Request a sheet metal or welding quote

Use the sheet metal fabrication quote form. It is preset for formed and welded parts, so the weld code, temper and finish questions are asked up front, which is what lets a fabricator price the job without a round of clarifications. A person replies within one business day, and rush requests are prioritized.

Questions

Related

• Ground Support Equipment Fabrication for Launch and Spacecraft Programs
• AS9102 First Article Inspection: A Buyer's Guide
• Aerospace RFQ Checklist for Machined and Fabricated Parts
• What Custom Ground Support Equipment Costs, and Why

Sources

• ANSI Blog: AWS D17.1:2024 Fusion Welding for Aerospace Applications
• AWS: D1.2/D1.2M:2026 Structural Welding Code, Aluminum
• AWS: D1.6 Structural Welding Code, Stainless Steel, scope
• SAE: AMS 2770 Heat Treatment of Wrought Aluminum Alloy Parts
• SAE: AMS 2681 Electron Beam Welding
• SAE: AMS 2680 Electron Beam Welding for Fatigue Critical Applications
• Aircraft Materials: 17-4PH sheet and plate (AMS 5604) forming and heat treat data
• Revista de Metalurgia: deformation temperature and springback of Ti-6Al-4V sheet
• ASTM E1417/E1417M-21e1 Standard Practice for Liquid Penetrant Testing
• NZ CAA Continuing Airworthiness Notice 02-005 on ASTM E1417 Type II penetrant
• PennEngineering: self-clinching nut conforming to NASM45938/4
• PEM nut and NASM45938 history