Almost every stamping shop advertises secondary operations for metal stampings as an in-house capability, and almost every stamping shop subcontracts some of them. That’s not a contradiction, it’s good manufacturing: the press floor earns its money making parts, and the question is which post-press work belongs beside it. This guide is about where welding falls, written from the side that receives the parts.
Weighing whether to send welding out? We weld stampings for shops across Southern California and ship nationally, running TIG, MIG and resistance spot welding in one shop. See welding for metal stamping companies or request a quote.
What a secondary operation actually is
Everything done to a part after it leaves the press. The standard list runs: deburring, tapping and drilling, machining, welding, assembly and sub-assembly, heat treating, plating, painting and powder coating, and final inspection. Nothing about the term implies the work is minor. On plenty of programs the secondary operations cost more than the stamping.
The cost comparison most shops get wrong
The in-house argument is usually made on piece price, and piece price flatters whatever you already own. The presses are bought, the building is leased, the welder is on payroll, so an in-house weld looks nearly free. The costs that don’t appear in that number:
- Queue time. A weld cell with a three-week backlog adds three weeks to every assembly that touches it, whatever the piece price says.
- Scrap value. A burned-through weld doesn’t scrap a weld. It scraps a part that already carries material, press time and tooling amortization.
- Certification. Holding a certified welder, and the procedure and continuity records behind them, is a real annual cost that gets charged to one or two programs.
- Capacity you can’t flex. One welder is either idle or overloaded. Outside capacity scales with the order book.
- Floor space. A weld cell with screens, extraction and a fixture rack occupies space that could hold a press.
Compare total cost per shipped assembly, including the parts you lose and the days you wait. That’s the number the customer feels.
What stamping shops typically keep
Deburring, tapping, basic assembly and inspection almost always stay in house. They’re fast, low-risk, need no certification, and they keep the part moving. Plating, painting and heat treating almost always go out, because the capital and the permitting make no sense below very high volume.
Welding is the one that genuinely sits on the line, and it splits by the kind of weld rather than by the shop.
Where welding splits
Usually worth keeping in house: resistance welding that is already running at volume. If you own the spot welder, the fixture is built and you’re attaching hardware to thousands of identical brackets, nothing is gained by moving it. The cycle is seconds and the cost per joint is already as low as it will go.
Usually worth sending out: anything of the following kind, whatever the process:
- Assemblies with position requirements. Two or three stampings that must become one component with squareness or hole position that holds.
- Unforgiving alloys. Thin-wall stainless, aluminum, titanium and nickel alloys, where a single bad weld scraps a costly part.
- Certified welds. The print flows down a welding specification and you don’t hold it.
- Cosmetic welds. Parts that get polished, plated or powder coated, where the finish magnifies every defect in the weld underneath.
- Leak-tight and sanitary joints. Continuous seams, back purged where the back side matters. See weld heat tint and back purging.
- Pre-production assemblies. Samples needed before the die exists, built from laser-cut or soft-tooled parts.
The dividing line is not the process, and it isn’t difficulty. It’s whether the operation rewards equipment you already own and a cycle you’ve already proved, or whether it rewards control, judgement and a fixture built for one job. A supplier who runs resistance spot welding and TIG can take a mixed assembly whole, rather than handing it back half-finished for you to close out.
How to spec welding on a stamped part
Most requote cycles come from prints that under-specify the weld. Six things make a stamping weldable to a predictable price:
- Use weld symbols, not notes. “Weld here” is not a requirement. A symbol gives size, length, pitch and side, and it’s what gets quoted and inspected.
- Size the weld to the load, not to the metal. Oversized welds on thin material add heat, distortion and cost without adding strength. This is the single most common waste on stamped assemblies.
- Call out which features must hold position, and relative to what. Welding moves metal, and a supplier who knows the critical dimension can fixture for it. A supplier who doesn’t will protect the wrong thing.
- Choose datums that survive welding. Reference features that stay stable, not a surface that will pull.
- Design the joint for fit-up. Tabs, slots and notches that self-locate improve repeatability far more than tightening the tolerance on the stamping does.
- State the downstream finish. A weld destined for polishing or plating is welded differently from one that gets painted or left raw.
More on the fixturing and sequencing side in sheet metal welding.
What to send with the parts
The print or STEP file, the material and gauge, the quantity now and the expected annual volume, any specification that applies, the features that must hold position, the downstream finish, and the inspection records your customer requires. If there’s a first article or PPAP-style submission behind it, say so at quote time rather than after the parts are welded.
Five questions worth asking a subcontract welder
- What certifications do you actually hold? A specific standard, not “certified welders”.
- How do you control distortion on gauge material? Fixturing and sequencing should come up without prompting.
- Will you weld a first article and let us approve it before the run?
- What records can you supply? Inspection results, traceability, a certificate of conformance.
- Do you work with our customers directly? The answer should be no. Your account is yours.
Those five separate a supplier who can hold a program from one who can weld.
The arrangement that usually works
Keep the operations that reward volume, send out the ones that reward control, and treat the outside welder as an extension of the floor rather than a vendor of last resort. In practice that means one supplier who knows your parts, holds your fixtures between releases, and quotes per part on repeat work. See production welding for how repeat runs are set up, or send a print and we’ll tell you honestly which side of the line your part belongs on.