Xometry Ordering FAQ: Instant Quotes, Gas Assist Injection Molding, Large CNC Machining, and Laser Welding Lessons

Some background: I'm a mechanical design engineer. I've been ordering custom parts through Xometry since 2019, and before that I spent two years trying to avoid online manufacturing platforms. That didn't last. I've personally made (and documented) 9 significant ordering mistakes, totaling roughly $12,400 in wasted budget and rework. Now I maintain our team's pre-order checklist, and this is the FAQ I wish I'd been given at the start.

1. Is Xometry's instant quote the final price?

Short answer: Yes, if you uploaded the same file you plan to manufacture and checked every requirement. The quoting engine is good—uncomfortably good at catching geometry issues. But it can't read your mind.

In 2021, I ordered 250 machined brackets with a note on the drawing: “tap these holes.” I didn't specify thread depth, and the note wasn't in the CAD model. The parts came back with no tapped holes. $890 of parts, plus a one-week delay, plus a customer who stopped returning my emails. The quote was accurate for the file I uploaded. The file was wrong.

Now I treat the quote as a starting point, not a guarantee. I ask “What's NOT included?” before I ask “What's the price?” Total cost of ownership includes base price, setup fees, shipping, rush fees, and potential redo costs. The lowest quoted price isn't always the lowest total cost. People think expensive vendors deliver better quality. Actually, vendors who deliver quality can charge more. The causation runs the other way.

I don't have hard data on how often quote changes happen across the platform. What I can say anecdotally is that most increases I've seen trace back to missing surface finish, secondary operations, or tolerances.

2. What does “Xometry your manufacturing delivery service” actually mean?

I think that phrase is a paraphrase of Xometry's core model: upload a part, get an instant quote, and Xometry routes the job to a vetted manufacturer, then handles delivery. You're not renting a machine from one factory. You're tapping into a network that covers CNC machining, 3D printing, injection molding, sheet metal, and more.

This has a huge advantage: capacity. If one shop is overloaded, the job can move to another that isn't. But it also means you have to be specific about what delivery means to you. Xometry's quoted lead time is a business-day estimate. Shipping is separate. As of Q4 2024, I always check the quoted delivery date before accepting a quote—because overnight shipping doesn't matter if the part spends four days in queued production.

The value of a quoted turnaround date isn't just speed. It's certainty. For production schedules, knowing when a part arrives is often worth more than a lower price with an “estimated” delivery window.

3. When should I consider gas assist injection molding service at Xometry?

Gas assist injection molding is for parts that need thick sections, hollow channels, or ribbed structures without sink marks. It's a specialty process, not a magic price-break option. It shines when you're consolidating multiple parts into one or adding stiffness without a solid thick wall.

I tried it on a small plastic part in 2022 because I wanted to look clever. The gas channel design was wrong—too sharp, too thin—and the part failed structural testing. $1,200 in mold mods plus a two-week reschedule. The lesson: gas assist is a solution to a specific problem, not a way to impress anyone.

That said, Xometry's DFM feedback on injection molding is genuinely useful. It flagged my problem before manufacturing kicked off. I just didn't want to listen. If the system says “consider a different geometry,” consider it. This was true for me three years ago, and it's still true today.

4. Can I use Xometry for medium to large part CNC machining services?

Yes. I've ordered aluminum parts with envelopes around 36 x 24 x 8 inches. The quoting engine asks for stock size and available travel, so it can match you with a shop that has the right machine. I don't have hard data on the absolute maximum envelope—it depends on material, weight, and machine access. But “medium to large” is not a problem for the network, as long as you define what you mean.

Be prepared to state the obvious. I once approved a quote for a large part but didn't specify that it had to be machined from a single billet. The shop welded two smaller pieces together. Strong? Maybe. Accepted by my client? No. The redo cost $3,200, and my credibility took a hit.

When in doubt, add a note: No welding. No stitching. Single material. The extra ten seconds saves a week.

5. Should I search for injection molding in South Dakota or use Xometry?

I understand why people search for “injection molding in South Dakota.” Local communication, less shipping, and the feeling that you can drive to the shop if something goes wrong. I get it. But “local” and “reliable” are not the same thing.

The “local is always better” thinking comes from an era when you had to stand next to the machine to catch errors. That's changed. A well-managed remote vendor can often beat a nearby one on speed and consistency if your files are right. Xometry's network includes qualified shops across the US; depending on your zip code, some may even be in South Dakota. The platform doesn't care about state lines.

To be fair, there are legit reasons to go local: a true prototype meeting, same-day physical inspection, or volume under 25 parts where setup dominates the cost. For standard production quantities, search the way that solves the problem, not the way that feels safe.

6. How do I use a laser welding machine? (And what NOT to do)

The basics are not complicated. Clean the metal. Set the focus. Set pulse width and peak power. Test on scrap. Check penetration from the back side. Before you know it, you're welding.

But “not complicated” doesn't mean “easy.” In September 2022, I watched a technician ruin 37 stainless steel parts because he skipped the cleaning step. Oil from his fingers created porosity, the weld looked gray, and every part failed pressure testing. The problem wasn't the machine. The problem was prep.

If you've been searching “how to use laser welding machine” and want a checklist, here's mine:

• Clean the joint. No oil. No paint. No fingerprints.
• Set focus according to the nozzle distance—don't guess.
• Keep the weld direction consistent.
• Use shielding gas, but don't crank it. Too much flow creates turbulence.
• Check the back side of the weld. The front can look perfect while the back is cold.

I wish I'd tracked focus offset more carefully when I started. What I can say anecdotally is that most “bad weld” problems I've seen were actually bad prep problems. The machine just did what it was told.