Technical · Tolerances · UK

3D Printing Tolerances & Accuracy

Q: What tolerance can you hold on a 3D printed part?

Our standard tolerance is +/-0.3 mm for parts up to 100 mm in size. For larger dimensions it is generally calculated as +/-0.3 mm for the first 100 mm, plus an additional +/-0.1% for every 100 mm thereafter. So a 300 mm dimension carries roughly +/-0.5 mm, and a 900 mm dimension roughly +/-1.1 mm. These are general tolerances for a well-designed part in a standard grade.

Our standard tolerance is ±0.3 mm up to 100 mm, then ±0.3 mm for the first 100 mm plus a further ±0.1% for every 100 mm after that. That is the number, published up front rather than buried in terms. Below: what it means on a real part, why additive tolerance works differently from machining, and how we hit tighter figures when a fit genuinely demands it.

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3D printing tolerances · additive manufacturing accuracy · dimensional tolerance UK · 024 7736 0144

±0.3 mm

Standard, to 100 mm

±0.1%

Added per 100 mm beyond

ISO 9001

Inspection under certification

1–4

PPAP levels approved

The rule

What tolerance can RYSE 3D hold?

±0.3 mm for parts up to 100 mm.

Beyond that: ±0.3 mm for the first 100 mm, plus ±0.1% for every 100 mm thereafter.

The percentage matters more than people expect. It is applied to the dimension, not the part, so a long thin bracket and a large boxy housing are treated on the dimension being measured. Worked through, on a nominal dimension:

Nominal dimension	Standard tolerance	How it is built up
50 mm	±0.3 mm	Under 100 mm — the flat figure applies
100 mm	±0.3 mm	At the threshold — still the flat figure
200 mm	±0.4 mm	0.3 mm + 0.1% of the additional 100 mm
300 mm	±0.5 mm	0.3 mm + 0.1% of the additional 200 mm
500 mm	±0.7 mm	0.3 mm + 0.1% of the additional 400 mm
900 mm	±1.1 mm	0.3 mm + 0.1% of the additional 800 mm

These are general tolerances for a well-designed part in a standard grade. They are not a guarantee for every feature on every geometry — read the next section before you design to them. Reviewed by the RYSE 3D engineering team · August 2026.

Why it works this way

Additive tolerance is not machining tolerance

A milled part starts as solid stock and has material removed by a tool whose position is known to microns. A printed part is built up from powder or filament that is melted, fused and then cooled — and cooling is where the dimensional story actually happens. The machine is not the limiting factor. Thermal behaviour is.

That is why additive tolerance scales with size while machining tolerance largely does not. A 20 mm feature has very little material shrinking around it. A 500 mm feature has a great deal, and every millimetre of that length contributes a small amount of thermal contraction. The ±0.1% term is that reality expressed as a number, rather than a promise nobody could keep.

It also means that the same nominal dimension can behave differently on two different parts, depending on wall thickness, how much material surrounds it, where it sits in the build and which way up it was printed. Anyone quoting a single tight figure for every part in every material is quoting a machine specification, not a part specification.

What moves the number

Six things that affect accuracy on your part

If a dimension is critical, these are the levers — and the ones we adjust when you tell us which faces matter.

Part size

The dominant factor, and the reason the rule scales. More length means more material contracting as it cools. Large-format parts carry proportionally more deviation than small ones — which is arithmetic, not a quality problem.

Wall thickness and uniformity

Thick sections hold heat longer than thin ones and shrink differently. A part with wildly varying section will move more than one with even walls — which is why uniform thickness is the first rule in every design guide we publish.

Orientation in the build

Holes and pins are most accurate with their axes in Z, and circular features lying in the XY plane tend to come out slightly elliptical. We set orientation, but if a bore has to be round, say so and we will stand it up.

Material grade

Filled grades are more dimensionally stable under heat than unfilled ones. Elastomers move most. PA11 is more warp-prone across large cross sections than PA12. The grade you choose changes what is achievable before anything else does.

Feature geometry

A hole through a thin wall is more accurate than the same hole through a thick one. Deep pockets, long unsupported spans and sharp section changes all reduce local accuracy relative to the general figure.

Post-processing

Some finishes are dimensionally neutral and some are not. Black dyeing adds nothing measurable. Vapour smoothing reflows the surface. Painting adds a physical layer to every coated face. Tell us the finish at quote, not after.

Tighter than standard

How we hold a fit the process cannot

Plenty of parts have one or two features that genuinely need to be tighter than ±0.3 mm — a bearing seat, a sealing face, a dowel location, a bore that has to be round. The answer is not to promise a tolerance the process will not repeat. It is to print near-net and machine the features that matter.

That means designing in machining stock on the critical faces, printing the part, then finishing those features conventionally. You get additive geometry everywhere it helps and machined accuracy exactly where it is needed, on one part, from one supplier. It costs more per part than printing alone, and considerably less than tooling.

What we need from you is which dimensions are critical — at quote, not at inspection. Mark them on the drawing or say so in the notes. We will plan orientation, allow stock and inspect against them. Finding out afterwards that a bore was critical is the single most common cause of a part being remade.

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Inspection

How parts are checked before they ship

A tolerance is only worth what the inspection behind it is worth.

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ISO 9001 certified quality system

Inspection runs under an independently certified quality management system covering every part from quote through to delivery, with traceability on each job.

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PPAP level 1–4 approved

Production part approval to automotive standards, for programmes that need documented, repeatable process control rather than a certificate of conformity alone.

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3D scanning on site

Parts are verified against the CAD before they ship, which matters most on freeform geometry where a caliper has nothing useful to measure between.

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Critical dimensions inspected to drawing

Where you have identified critical features, those are the ones checked and reported — not a general dimensional sample that happens to miss the fit you cared about.

Need a specific inspection regime, a first article report or documentation for an approval pack? Tell us at quote and we will confirm what we can provide before you commit.

Honest limits

Where we will tell you additive is the wrong answer

We would rather lose the job than deliver a part that will not gauge.

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Fits measured in hundredths

If the drawing calls for ±0.05 mm across the whole part, printing alone will not do it in any polymer process. Near-net plus machining will — or the part belongs on a mill.

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Tight tolerances on very large parts

At 900 mm the standard figure is ±1.1 mm. If a metre-long part needs to hold a few tenths across its length, additive is not the process, whatever the marketing says.

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Elastomers to a rigid spec

TPU parts move more than nylon, both in the build and in service under load. Dimensioning a flexible part to a rigid tolerance misunderstands what the material does.

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Tolerances quoted after finishing is chosen

A coated part is a different size from an uncoated one. If a fit is critical and the part is being painted, that has to be designed for, not discovered.

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Unstated critical features

We inspect to the standard tolerance unless told otherwise. If a dimension matters and nobody flagged it, it gets treated like every other dimension on the part.

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Metal-grade structural fits

We are a polymer bureau. Where thermal expansion in service would open a fit beyond its allowance, a polymer part is the wrong answer regardless of how accurately it was printed.

FAQ

Tolerances & accuracy FAQ

What tolerance can you hold on a 3D printed part?

Our standard tolerance is ±0.3 mm for parts up to 100 mm in size. For larger dimensions it is generally calculated as ±0.3 mm for the first 100 mm, plus an additional ±0.1% for every 100 mm thereafter. So a 300 mm dimension carries roughly ±0.5 mm, and a 900 mm dimension roughly ±1.1 mm. These are general tolerances for a well-designed part in a standard grade.

Why does 3D printing tolerance get looser on bigger parts?

Because the limiting factor is thermal, not mechanical. A printed part is fused from powder or filament and then cools, and cooling causes contraction. A 20 mm feature has very little material shrinking around it; a 500 mm feature has a great deal, and each additional length contributes more contraction. Machining removes material from stock at a known tool position, so it does not scale the same way.

Can you hold tighter tolerances than ±0.3 mm?

On specific features, yes — by printing near-net and machining the critical faces conventionally. That is the honest route to a bearing seat, a sealing face or a precise bore, and it gives you additive geometry everywhere it helps with machined accuracy exactly where it is needed. Identify the critical dimensions at quote and we will allow stock, plan orientation and inspect against them.

Does the material affect dimensional accuracy?

Yes. Filled grades such as PA12-GF and the carbon-filled nylons are more dimensionally stable under heat than unfilled grades. PA11 is more prone to warping across large cross sections than PA12. Elastomers such as TPU move most, both during the build and in service under load. The grade is chosen for the application first, but it does change what is dimensionally achievable.

Does part orientation change accuracy?

Considerably. Holes and pins are most accurate with their axes oriented in Z, and circular features lying in the XY plane tend to elongate slightly into an ellipse. Surface finish also depends on which way a face points. We set orientation as part of build preparation, but tell us which feature or face is critical and we will optimise the build around it.

Will finishing change the dimensions of my part?

It depends on the finish. Black dyeing adds no measurable thickness at all, which is why it is the default on parts that still have to fit something. Vapour smoothing reflows the surface. Painting adds a physical layer to every coated face and has to be accounted for on mating surfaces. Tell us the finish and the critical dimensions together at quote.

How do you inspect parts before they ship?

Under our ISO 9001 certified quality system, with PPAP level 1 to 4 approval available for programmes that need documented process control. We 3D scan on site to verify parts against the CAD, which matters most on freeform geometry, and where you have identified critical dimensions those are the features inspected and reported.

Ready when you are

Tell us which dimensions matter.

Free design review with every quote — we will tell you what the process will hold on your geometry, and what needs machining, before anything is printed.

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Our own ISO 9001 facility in Shipston-on-Stour, Warwickshire. Mon–Thurs 8am–4pm, Fri 8am–2pm. Call 024 7736 0144 or email hello@ryse3d.com.