The box arrived, you opened it, and the parts are not what you had in your head. They are too small, or the holes are tight, or the surface looks nothing like the render, or there are eighteen of them instead of twenty. A 3D printing order that comes back wrong is common enough that every established service bureau has a process for it — and the outcome depends almost entirely on what you do in the next hour, before you send an email. This guide covers how to inspect what arrived, how to work out whether the defect belongs to the shop or to the specification, what recourse is realistic, and how to write the next order so the same thing cannot happen. If the answer turns out to be that you need a different shop, browse the 3D printing provider directory and start the next quote properly.
Measure Before You Argue
The single thing that changes how this goes is whether you are holding measurements or impressions. "These are too small" invites a debate. "The 12.00 mm bore measures 11.62, 11.58 and 11.64 across three parts, against a drawing callout of 12.00 +0.10/-0.05" ends one.
Fifteen minutes, on arrival, before the parts go in a drawer:
- Photograph them as they came out of the box, with the packing slip in one frame. If the box is damaged, photograph that first — carrier damage is a different claim with a shorter clock.
- Measure the two or three dimensions you actually care about with calipers, on at least three parts, and write the numbers next to the nominal. Three parts tells you whether you have a process offset or a one-off.
- Check the quantity against the packing slip, not against your memory of the order.
- Try the fit if there is a mating part. A bore that measures correctly and still will not accept a shaft is useful information, not a contradiction — see why 3D printed parts don't fit together for where that error usually lives.
- Keep everything, including the box and the failed parts. A shop assessing a remake will often ask for them back.
Then do the less pleasant half: re-read your own RFQ, your file and the quote you accepted. A surprising share of wrong orders are correct orders against a specification that did not say what the buyer meant.
The Five Ways an Order Actually Goes Wrong
| What you are seeing |
Most likely cause |
Who owns it |
What to ask for |
| Dimensions off by a consistent amount |
Process capability, shrinkage or a tolerance you never specified |
You, unless a tolerance was called out and missed |
Re-quote with tolerances on the critical features |
| One feature wrong, the rest right |
Orientation, support contact or a bore that printed undersize |
Shared — flag it, most shops will adjust and rerun |
Remake with the feature marked critical |
| Material feels or behaves differently |
A grade substitution, or a family named instead of a grade |
The shop if a grade was specified, you if it was not |
The material certificate or batch record |
| Surface finish below expectation |
As-printed was quoted, finishing was assumed |
Almost always you |
A finishing quote, priced separately |
| Wrong revision, wrong scale, short quantity |
File handling or picking error at either end |
Whoever sent or picked wrong — the file hash settles it |
Immediate remake, no argument |
The scale error deserves its own warning because it is the one that looks most like malice and almost never is. A model exported in inches and interpreted as millimetres comes back at 1/25.4 scale, and a model exported with no unit declared can go either way. STL carries no units at all, which is the root of it — STL vs STEP files for 3D printing explains why sending a solid model removes this entire failure mode.
Material substitution is the one worth being firm about. If you asked for PA12 and received PA11, or asked for a specific high-temperature grade and received a generic one, that is not a close-enough swap: the mechanical and thermal behaviour differ, and the part may pass inspection and fail in service. Name grades rather than families when you order, which is the discipline how to choose a 3D printing material is built around.
Whose Mistake Was It, Honestly
Shops apply one test, and knowing it saves you a round of email: did we miss your written specification, or did your specification miss what you needed?
Anything in the first category is a defect. A dimension outside a stated tolerance, a material other than the one named, a quantity short of the purchase order, a finish below an agreed sample, damage in transit on the shop's packaging. Expect a remake or a credit, and expect a reasonable provider to offer it without a fight.
Anything in the second category is a re-quote, however frustrating that is. The part is dimensionally fine and still too weak, because the load was never stated. The bore is on nominal and the shaft does not fit, because no clearance was designed in. The finish is as-printed because finishing was never ordered. The part warped because the geometry invites it. None of these are the shop's error, and treating them as one is the fastest way to lose the goodwill you will want for the actual defects.
The grey middle is real too. A shop that printed a thin unsupported boss exactly as modelled, watched it fail, and shipped it anyway did nothing contractually wrong and still did not behave like a good supplier. That is a judgment call about who you want to work with rather than a claim — and it is the signal to read when you decide whether to reorder. Tolerances and accuracy in 3D printing sets out what each process can actually hold, which is the reference that tells you whether your expectation was reasonable in the first place.
What Recourse Looks Like, and How Long You Have
Custom parts are not a normal return. They were made to your file, they cannot be resold, and almost no bureau accepts a change-of-mind return on them. What you have instead is a defect claim, and it runs on a clock: most terms give you between 5 and 15 days from delivery to report a problem, after which the order is treated as accepted.
That clock is why the inspection happens on arrival rather than the week you need the parts. If you ordered three weeks early, inspect three weeks early.
A workable claim, in the order a shop wants to receive it: the order number, the specific requirement from the RFQ or drawing, the measured or photographed deviation, the quantity affected, and what you want — remake, credit or partial. Ask for one outcome rather than listing grievances. Keep it to the parts that are genuinely out of spec; bundling in the ones that merely disappointed you weakens the whole claim.
Pay attention to what comes back. A shop that asks for your measurement method and the parts back is running a quality process. A shop that offers a discount on your next order instead of fixing this one is managing you. The qualifying questions in how to choose a 3D printing service are worth re-reading at this point, because the response to a problem tells you more about a supplier than the original quote did.
Re-Spec So It Cannot Happen Again
Most repeat buyers stop having this problem after they change four lines in how they order:
Mark two or three critical dimensions and tolerance them. Not every dimension — tolerancing a whole part is how you buy an expensive part slowly. Pick the bore, the mating face and the overall length that actually matter, give each a band, and explicitly state that everything else is nominal.
Name the material by grade. "Nylon" is a family. "PA12, SLS" is an order. Add the colour and any certificate you need in the same line.
State the finish level as a separate item. As-printed, supports removed and witness marks sanded, or fully finished are three different prices and three different parts. Post-processing and finishing services covers what shops offer and what each step costs you in time.
Ask for a first article. One part, inspected and reported, before the balance of the quantity runs. It adds a few days and it converts a twenty-part mistake into a one-part mistake. On any repeating order it pays for itself the first time it catches something.
Sending the same package to every provider also makes the next quotes comparable — how to prepare your files for a 3D printing quote has the checklist, and if certification or traceability is part of the requirement, 3D printing service certifications explains which ones mean a documented inspection process rather than a logo.
When to Change Provider
Once is a problem. Twice with the same root cause is a pattern, and the pattern usually means the shop is not running the process you need — a hobby-grade machine quoting industrial tolerances, no inspection step, or a subcontractor you were never told about.
Change providers when the shop cannot tell you how a part was measured, when the same defect survives a remake, when the material certificate does not arrive, or when the answer to "who actually printed this" is unclear. None of those are recoverable by complaining harder.
Get the Next Order Quoted Properly
Take the specification you have just rewritten — critical dimensions, material grade, finish level, first-article request — and put it in front of two or three shops. Browse 3D printing providers, send the same package to each, and read the questions that come back as the real evaluation: a provider who asks which dimensions are critical and what the part has to survive is telling you they inspect before they ship. The cost of the first bad order is sunk. The cost of the second one is a choice.
Related Resources
Hero photo: Greg Rosenke via Unsplash.
