When to Combine 3D Scanning and Probing for FAI, Deep Holes, Datums, and Critical Features

A single drawing for a machined housing can carry a cast organic fillet, a blind bore 40 mm deep, and three datum holes that the entire GD&T scheme references. One inspection method rarely covers all three well. The fillet needs full surface coverage to catch local high and low spots against CAD. The blind bore needs a probe tip that can reach past the point where a scanner loses line of sight. The datum holes need position data precise enough to hold up as the reference frame for every other callout on the report.

Trying to force one instrument to do all three jobs is where first article inspections go sideways. This guide breaks down which features belong to a 3D scanner, which belong to a contact probe, and how to combine both into a single workflow that produces one traceable report instead of two disconnected data sets.
 

Two Ways of Capturing a Point, Not Two Tiers of Accuracy

A 3D scanner is a non-contact optical instrument. It projects laser lines or structured light onto a surface and reconstructs geometry from what its cameras see, which means it captures thousands of points per second across an entire surface, but only the surface it has a direct line of sight to.

A contact probe, whether mounted on a portable arm like SCANOLOGY's AccuArm or a fixed CMM, physically touches the part. It records one coordinate per touch, with no line-of-sight requirement, because the probe tip goes wherever the operator can physically place it.

The two methods report accuracy under different test standards and different metrics, so a scanner's point accuracy figure and a probe's point-to-point error figure are not a straight apples-to-apples comparison. What matters more than comparing the numbers is what each one answers: a scanner tells you how an entire surface compares to nominal, and a probe tells you the exact coordinate of one specific point a scanner may not be able to see at all.
 

Why Freeform Surfaces Belong to the Scanner

Cast fillets, sculpted panels, and organic transitions do not have a finite list of points worth measuring. Every square millimeter of the surface could be the spot where the part deviates from CAD, and there is no way to know which spot that is until you look at the whole thing.

A scanner is built for exactly that kind of coverage. SCANOLOGY's SIMSCAN-S Gen2 captures up to 8.1 million measurements per second at 0.015 mm accuracy, and KSCAN-E reaches 8.29 million measurements per second across a scan area up to 1440 by 1000 mm per frame, both per current product specifications. A full pass over a housing's exterior takes a fraction of the time a point-by-point probe program would need to approximate the same coverage, and the output is a complete deviation map rather than a sample.

SIMSCAN-S Gen2 is the SCANOLOGY scanner intended for small parts with fine detail, connector housings, small castings, and machined brackets under roughly 700 mm. For mid-size mechanical components with mixed surface density, KSCAN-E covers more area per frame without giving up accuracy.
 

Why Deep Holes, Blind Bores, and Datums Belong to the Probe

A scanner needs to see a surface to measure it, and a hole deep enough that the scanner's cameras cannot see its far wall or floor will not return usable data for that feature, no matter how accurate the scanner is on open surfaces. This is a physical limit of triangulation-based optical measurement, not a software gap that a firmware update fixes.

KSCAN-E does push that limit further than a standard optical head. Its deep-hole scanning mode uses a single blue laser line to reach into features such as engine cylinders and internal grooves on cast parts, according to the current product specifications. That extends the range of holes a scanner can capture directly, but a single laser line still needs a path in and a return signal out, and a sufficiently deep blind bore, an undercut pocket, or a datum feature buried behind a wall of material still sits outside what any optical scan head can resolve.

Contact probing closes that gap. AccuArm's published performance characteristics associated with ISO 10360-12 for its 6-axis, 2 m reach, S-grade configuration list a SPAT of 0.016 mm, an EUni of 0.022 mm, and a PFORM of 0.015 mm, per SCANOLOGY's current AccuArm specifications, and its 360-degree joint rotation lets the probe tip swing into a bore or boss from a new angle without unclamping the part. A probe tip goes exactly where a datum plane or bolt circle needs it touched, which is the same reason fixed CMMs have relied on contact probing for datum work for decades.

Building the Hybrid Workflow

Most shops run the same sequence: scan first, then probe. Scan the part's full exterior with SIMSCAN-S Gen2 or KSCAN-E and align the mesh to CAD, which immediately shows every surface deviation across the part in one pass. That same alignment becomes the coordinate frame for the probe step, so nothing has to be re-registered later.

Next, identify which callouts on the drawing the scan could not resolve with confidence. Anything the scan could not resolve cleanly, typically a blind bore, an internal boss, or a datum feature blocked from the scanner's line of sight, gets probed next. AccuArm probes those specific points directly on the same part, in the same setup, without moving it to a different station.

Because AccuArm pairs with SCANOLOGY's scanners on DefinSight, SCANOLOGY's own metrology software platform, the probed coordinates and the scan mesh can land in one aligned file, removing the manual step of exporting two separate data sets and reconciling them in a spreadsheet before the report goes out.
 

What This Looks Like on an AS9102 First Article Report

AS9102 first article inspection requires each design characteristic to carry a traceable, individually reported result on Form 3, most commonly tracked against a ballooned drawing that numbers every callout. The standard does not require every characteristic to be measured with the same method, and mixing methods across one report is normal, not a compromise.

A cast profile characteristic can get its result from the scan-to-CAD deviation map. A bore position or a datum feature gets its result from the probed coordinate. Form 3 requires each numbered characteristic to trace back to a specific, documented measurement, and a merged scan-and-probe data set in DefinSight supports that traceability for both types of characteristics without forcing either one into the wrong method just to keep the report format consistent.
 

One Dataset, One Report

The reporting stage is where a hybrid workflow either saves time or creates extra work, depending on whether the scan and probe data are already connected. If the scan lives in one software package and the probe data lives in another, someone has to manually match coordinates between two files before the report can go out, and that step is where transcription errors creep into first article reports.

DefinSight handles scanning, meshing, alignment, probing, and inspection in one interface, which means a single report can carry both a full-surface color deviation map and discrete GD&T results on probed features, pulled from the same aligned dataset. To share a quick color map with a customer or supplier without opening the full metrology license, SCANOLOGY's free ScanViewer covers distance checks and deviation visualization.

Matching the Workflow to the Part

A part that is entirely freeform surface, such as a sheet metal panel or a cast cover with no internal features, rarely needs a probe at all. Scan it, align it to CAD, and the deviation map carries the inspection result.

A part that is mostly discrete features, such as a fixture plate with a handful of tapped holes and no organic surfaces, may not need a scanner. Probe the holes directly and the point data carries the inspection result.

Most real parts need both approaches, especially castings, machined housings, and anything with a sculpted exterior alongside a functional bore or datum scheme. That is the part that benefits from a hybrid workflow: scan the surfaces with SIMSCAN-S Gen2 or KSCAN-E, probe the features the scan cannot measure reliably with AccuArm, and let both feed one DefinSight report from a single setup.
 

Frequently Asked Questions

Can a 3D scanner measure a deep hole at all?
It depends on the depth relative to the hole's diameter and whether the scanner has a line of sight to the far wall. KSCAN-E's deep-hole scanning mode uses a single laser line to reach further into features like engine cylinders and cast internal grooves than a standard scan pass, but a sufficiently deep blind bore or an occluded datum feature still needs a contact probe.

Does combining scanning and probing require two separate reports?
No. AccuArm and SCANOLOGY's scanners share the DefinSight platform, so probed coordinates and scan data land in one aligned file, and a single report can include both a full-surface deviation map and discrete GD&T results on probed features.

Does AS9102 require every characteristic to be measured with the same method?
No. AS9102 Form 3 requires each numbered design characteristic to carry a traceable, individually reported measurement result. It does not mandate a single measurement method across the report, which is why mixing scan-based profile results with probe-based position results on the same first article report is standard practice, not a workaround.

What size part is a good fit for SIMSCAN-S Gen2 versus KSCAN-E?
SIMSCAN-S Gen2 is built for small parts with fine detail, roughly up to 700 mm, where its 0.015 mm accuracy and compact form factor make it easy to work around tight features. KSCAN-E covers a larger scan area per frame, up to 1440 by 1000 mm, which suits mid-size mechanical components and housings with mixed surface density.

When should a fixed CMM still be used instead of AccuArm?
For the small number of features on a drawing that require very low measurement uncertainty, a fixed CMM in a controlled lab remains the reference instrument. AccuArm's published EUni of 0.022 mm at 2 m reach, S grade, may be suitable for selected datum and bore measurements after a task-specific capability and uncertainty assessment, though the final call on any specific feature still depends on feature strategy and the shop's own uncertainty budget, not the MPE figure alone.