3D scan accuracy vs. finished-part tolerance

Scanner accuracy, data resolution and part tolerance answer different questions. Agree drawing requirements, accessible surfaces and how the finished part will be checked before reconstruction. A scanner specification alone does not determine fit.

Specification value and object size

Shining3D specifies EinScan Rigil Laser HD volumetric accuracy up to 0.04 mm + 0.06 mm/m. These examples substitute object sizes into that formula; they are not results of measuring our parts:

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  100 mm bracket: 0.046 mm.
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  300 mm housing: 0.058 mm.
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  500 mm body: 0.070 mm.
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  One-metre frame: 0.100 mm.

The formula value increases with size. Suitability depends on the required tolerance, surface, settings, access and alignment of scans. It is not a guaranteed error for every reading or a certificate for a particular part. The size of a scanned object also does not establish whether it fits a printer.

Resolution refers to mesh density

The finest published Laser HD resolution setting is 0.05 mm. It describes data density, not a guarantee that an edge, slot or marking of that size will be captured correctly. Surface and visibility matter as well.

A denser mesh is not proof of a more accurate dimension. Increasing resolution does not recover missing data from inside an inaccessible hole.

Part tolerances are not set by the scanner

A tolerance defines permitted dimensional or geometric variation from a design. The part's function and documentation set it, rather than the scanner or printer. A scan records a worn part's current state; original tolerances need a drawing, mating part or other agreed evidence.

We do not declare one ± value for every print. Reconstruction, orientation, finishing and measurement conditions affect the result. Design guidance gives recommendations for model features; it does not replace drawing requirements or inspection of the finished part.

For a critical fit, agree dimensions, measurement datums and a trial in the intended assembly. Polyamide dimensions change with moisture, as explained in the moisture and fit guide. A trial checks assumptions; it does not recover lost documentation.

What realistically ruins a scan

Before work, assess the reading and access to the surface:

1. 1.
   Gloss and transparency may leave missing data. The manufacturer's documentation recommends suitable preparation; we agree any scanning spray and permission before use.
2. 2.
   Black colour alone does not determine whether spray is needed. Rigil can scan dark and metal surfaces without spray, but reflections, shape and settings still need assessment.
3. 3.
   Optical scanning needs a visible surface. We do not claim to measure closed interiors or an inaccessible hole bottom. Filling gaps in a mesh is reconstruction, not a new measurement.
4. 4.
   Movement, deformation of a soft part and difficult tracking may change recorded geometry. Wear is the original's actual condition; any shape correction is agreed using available evidence.

When to choose manual measurement

A plate, sleeve or spacer can often be described with a few dimensions. Consider manual measurement, selecting a method for the requirement and access. Scanning may provide useful data for free-form surfaces or a complex housing. Neither method is always faster, cheaper or suitable.

A mesh, CAD reconstruction and report are different deliverables. See scope and pricing on the 3D scanning page; CAD modelling and later printing are quoted separately.

When a report is needed instead of a model

Comparison with supplied CAD shows deviations on scanned surfaces. Agree areas, sections and alignment datums before work; the alignment method affects interpretation of the map. Areas without data remain outside measurement and do not demonstrate conformity.

A report supports geometry comparison but is neither a calibration certificate nor a coordinate-measuring-machine report. If the recipient requires a particular procedure, uncertainty statement or quality documentation, state those requirements before quotation.

Three numbers, three different questions

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  Volumetric accuracy: the value published for a particular mode and object size. It does not replace checking a specific reading.
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  Resolution: how densely data is recorded. It does not guarantee capture of a feature or dimension.
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  Part tolerance: variation permitted by the design. Check the finished part against those requirements.

Send photographs with a ruler, overall dimensions, the required file and critical requirements. A report also needs CAD and the areas to inspect. Send photographs and a brief, read about part reconstruction or check scanner specifications.

Sources: Shining3D: EinScan Rigil specification, Shining3D: scan preparation. Manufacturer data describes the device; service scope and requirements are agreed for each job.