Why Instant Quoting Doesn't Work for Heavy Weldments
If you buy machined parts, you have probably become used to uploading a STEP file and having a price back before you have closed the tab. That model is now a large and growing business. Xometry reported roughly $687 million of revenue for 2025, of which about $630 million came through its marketplace, up 30 % year on year, with close to 5,000 active suppliers and more than 85,000 active buyers. Protolabs' CNC machining line was its largest and fastest growing in 2026.
It works. For a bracket, a housing, a shaft, a sheet metal panel — it works very well, and a fabricator who tells you otherwise is protecting something.
But there is a boundary, and it is not vague. It is published, in inches, by the platforms themselves.
The boundary, in numbers
Xometry publishes its CNC machining size limitations. The milling work envelope is a machine travel of 64 in × 32 in × 38 in — about 1,626 × 813 × 965 mm. Turning goes up to about 18 in diameter. The same guidance notes that travel is not the same as maximum part size: deep features need long tooling, which eats into the usable envelope before you reach the stated numbers.
That is a machine roughly one and a half metres across its longest axis.
A crusher feed chute is longer than that. So is a gearbox housing for a mill drive, a slew bearing support, a press frame, a conveyor drive base, a boom section. The moment your part does not fit inside that box, you have left the market that instant quoting serves — not because the algorithm is bad, but because there is no machine on the other side of it.
Why the algorithm cannot follow you past the boundary
It would be easy to assume this is a temporary limitation and that the envelopes will grow. They will, a little. But the deeper reason instant quoting stops at heavy weldments is not machine size. It is that the cost of a large fabricated part is not a function of its geometry.
An instant quote is fundamentally a volumetric calculation: material removed, tool paths, setup count, finish. Feed it a solid model and it can compute all of those to a useful accuracy.
Now consider what actually determines the cost of a five-tonne welded and machined assembly:
The weld sequence. How the part is welded determines how much it distorts, which determines how much stock has to be left for machining, which determines the cycle time. Two engineers can look at the same drawing and propose sequences that differ by 20 % in cost. No geometry parser sees this.
Whether it is stress-relieved, and when. A weldment that is machined before stress relief will move afterwards. Getting this order wrong does not show up as a cost — it shows up as a part that measures correctly on Tuesday and is out of tolerance the following month. The decision is a process decision, not a geometric one.
How many times it is picked up. The tolerance you can hold across a large assembly is governed mostly by how many separate setups it goes through and what it is referenced from each time. A part machined in one setup off a machined datum behaves completely differently from the same part machined in three setups off a welded edge.
Handling and fixturing. Every crane lift is time. Every custom fixture is cost. Neither is visible in a STEP file.
The inspection level. UT on full-penetration welds versus visual only can be a double-digit percentage of the price of the part. The drawing may specify it; often it does not, and the answer has to be asked for.
What the drawing does not say. On heavy fabricated parts, the most expensive item in a quotation is frequently the ambiguity — a datum that moves, a tolerance that cannot be held on the specified feature, a radius too tight for the grade. These need someone to notice them and raise them *before* the price is fixed.
An algorithm that returned a number for a part like this would not be fast. It would be wrong, in one of two directions: low enough that somebody loses money and the relationship, or high enough that nobody orders.
What a quotation for a heavy weldment should contain instead
If not a number in ten seconds, then what? A quotation on this kind of work should be a document you can put straight into your purchasing system, with eight things in it:
- Technical understanding confirmed — the supplier restating what they think you asked for. This is where drawing ambiguities surface.
- The proposed process route — how it will be made, in what order, and why.
- Material proposal and equivalency note — what grade, from where, and if substituted, on what basis.
- Price breakdown — material, machining, surface treatment, inspection, packing, transport, itemised.
- Lead time with milestones, not one number.
- Inspection plan and the documents you will receive.
- Packing and Incoterms.
- Validity and assumptions.
The reason to want all of this is not thoroughness for its own sake. It is that the quotation is the only chance to find out what the supplier actually understood before money is committed. A price on its own tells you nothing about whether they read the drawing.
What is a reasonable turnaround, then
Instant quoting reset everybody's expectations, and the reset was healthy. Three days for a price on a part somebody can look at in twenty minutes is not defensible.
A workable standard for heavy fabrication looks like this:
- Within four working hours: acknowledgement, and a first read of the drawing. Either it is inside the supplier's envelope or it is not, and you should be told that immediately.
- Within forty-eight hours: a full quotation, if the drawing package is complete.
- Within four working hours, if the package is not complete: a specific, itemised list of what is missing and why each item is needed. Not "please provide more information."
That is fast enough to compete and slow enough to be right.
Where the two markets meet
None of this is an argument against instant quoting. If your part fits in the envelope and is a standard machining job, use the platforms — the price will be competitive and the process is genuinely better than sending emails.
The argument is narrower: know which side of the line your part is on, and stop expecting the tooling from one side to work on the other. A supplier who offers instant online pricing on twenty-tonne weldments is either quoting from a lookup table that will be renegotiated later, or has not thought about it.
If you want to know which side you are on before you talk to anybody, the honest version of an instant quote for this kind of work is a capability check: material, thickness, size, weight, tightest tolerance — and an answer that says yes, needs review, or no, with a reason.
We publish ours, including the point at which we say no and what kind of shop you should be looking for instead.
FAQ
Why won't you give me an instant price? Because on parts this size the cost is set by the weld sequence, the number of setups and the inspection level, none of which are in the CAD file. A number produced without those decisions is a guess. You would get it faster and it would be wrong.
How large a part can typical instant-quote platforms handle? Xometry's published CNC milling travel is 64 × 32 × 38 inches, with turning to about 18 inches diameter, and the guidance notes that travel is not the same as usable part size. Past that, quoting goes to a person somewhere regardless of what the interface looks like.
How fast can you actually quote? Acknowledgement within four working hours, full quotation within forty-eight when the drawing package is complete. If something on the drawing is ambiguous you hear about it in the first four hours, not on day three.
What makes a drawing package "complete"? A 2D drawing with tolerances and datums, the material grade or standard, the quantity, the surface and heat treatment requirement, and the inspection level. A 3D model on its own is not enough — the model does not say which features matter.
Sources Xometry investor relations, full-year 2025 and Q1 2026 results; Xometry published CNC machining size limitations; Protolabs quarterly results, 2026.