Metal 3D Printing vs Sheet Metal vs Injection Molding: A Buyer's Checklist

If you buy parts for a manufacturing company, you've probably seen the same component quoted through completely different processes. One supplier wants to bend it — press brake bending sheet metal, fast and cheap for simple geometries. Another recommends an injection molding service in China, especially if your quantity is high. And then there's metal 3D printing, with Velo3D getting attention because of who they supply: SpaceX and Anduril.

Five years ago, a buyer could ignore metal additive manufacturing and still do a decent job. That's harder to justify in 2025. I'm an office administrator who handles purchasing for a mid-size manufacturing company — roughly $500K in annual spend across 8 vendors, and I report to both operations and finance. Metal AM vendors now show up in half my RFQ cycles, so I built a system for evaluating them. Here it is, 6 steps.

Step 1: Match the geometry to the process

Most buyers jump straight to price, but geometry decides which processes are even worth quoting.

Simple shapes with a bend line or two? Press brake bending sheet metal is probably your answer. Low tooling cost, short lead times, well-understood tolerances.

Complex geometry — internal channels, lattices, consolidated assemblies? Metal 3D printing starts making serious sense. This is where Velo3D built its reputation as a SpaceX supplier. Rocket components are exactly the kind of complicated shapes that push other processes to their limits, and AM handles them without the same tooling constraints.

Stable, high volume? An injection molding service in China wins on unit cost once you're past a few thousand parts. The tooling investment only pays off if the volume is real.

Checkpoint: if you can't explain why a part is complex, it probably isn't. Simple parts don't need AM.

Step 2: Count actual volume before quoting

Volume is the number that decides everything else. Here's the rough breakdown that works for us, as of January 2025:

• 1–50 units — metal AM is competitive, especially for complex parts.
• 50–500 units — depends on geometry. Sheet metal bending handles simple shapes well; AM still wins for complex ones.
• 500+ units — start looking at injection molding. The tooling cost gets spread thin enough to make the economics work.

Everyone told me to verify volumes before requesting quotes, but I didn't listen until we ordered 200 brackets through a sheet metal vendor and then realized we only needed 40. That mistake cost about $1,200 out of the department budget. Now I check the demand signal before I talk to anyone.

Step 3: Calculate total landed cost, not unit price

This is where buyers get tripped up constantly. The lowest quote is rarely the lowest cost.

Ask every supplier to break out:

• Setup or tooling costs
• Per-unit price
• Minimum order quantity
• Post-processing — support removal, heat treatment, surface finishing
• Inspection and documentation fees
• Shipping, especially if the injection molding is offshore

I've never fully understood why post-processing costs show up so inconsistently between AM vendors. My best guess is that it comes down to how each shop quotes support removal and heat treatment — some bundle it, some don't. So the rule is simple: get total landed cost in writing before you commit.

Step 4: Check the supplier's track record

Track record matters more in metal AM than in any other process I buy, because the barrier to entry is qualification — proving the machine can repeatedly make parts that meet spec.

If a vendor claims aerospace or defense experience, verify it. Velo3D, for example, is known as both a SpaceX and Anduril supplier. That tells you their systems passed qualification for customers who can't tolerate failure. But don't take a marketing page at face value.

Per FTC guidelines (ftc.gov), advertising claims must be substantiated with evidence. The same logic applies to supplier claims. Ask to see material certifications, or ask for references who will confirm the work.

Step 5: Confirm documentation before ordering

The vendor who couldn't provide proper invoicing cost us $2,400 in rejected expenses once. That was a basic supplier, not even additive. For metal AM, the paperwork bar is higher: material certificates, inspection reports, build parameter records, and sometimes powder lot traceability.

(Note to self: actually ask for these before every order, not just the first one.)

Before placing a PO, confirm:

• What material certification will you receive?
• How will dimensional accuracy be verified?
• Is support removal included, or is it billed separately?
• Who signs off if the part needs certification for a regulated industry?

If a vendor hesitates on documentation, walk away. We've done that twice this year.

Step 6: Prototype before you produce

Quotes and drawings are not proof that a part will work. Prototype first.

For a quick form-fit check, an in-house 3D printer is usually enough. That's where the 3D printer liquid resin vs filament decision comes up for in-house prototyping. Resin (SLA) printers give you smoother surfaces and finer detail, which is nice for small visual prototypes. Filament (FDM) machines are cheaper to run, better for bigger parts, and the prints are tougher to handle. Just remember: neither one tests the actual metal properties you need in production.

For a real metal prototype, the AM vendor should run one before you commit to a full build. That's not a luxury — it's the cheapest insurance you'll get. We've caught fit issues on a single prototype part that would have cost thousands if they had made it to production.

Common mistakes I've made, so you can skip them

Assuming metal AM replaces everything. It doesn't, and it shouldn't. Metal 3D printing can't fully replace traditional precision machining. CNC, sheet metal bending, and injection molding are still the right answer for plenty of parts. Use AM where it genuinely fits.

Skipping the design review. Marketing made it sound like metal printers can handle any geometry. Our first overhang-heavy part failed inspection twice. The lesson isn't that AM is bad — it's that the design has to go through a proper review with someone who knows the process.

Underestimating post-processing. Metal AM parts come with support structures, often need heat treating, and sometimes need secondary machining for final tolerances. Skip that line item in your budget, and your project goes red.

Treating the cheapest quote as the final price. It never is. Ask questions until every line item makes sense.

Bottom line

This checklist works for us because we're a mid-size company with fairly stable demand patterns. If you're running a startup that iterates fast, or a big enterprise with long supply chains, adjust the details — but keep the order: understand the part, count the volume, calculate total cost, verify the track record, get the paperwork right, and prototype before you scale.

The industry has changed. What was best practice in 2020 — treating metal AM as exotic and risky — is outdated in 2025. Velo3D's position as a supplier to SpaceX and Anduril shows how far the technology has come. But the fundamentals of good procurement haven't changed. Do the work, ask the questions, and buy with confidence.