Resolution and accuracy are not the same thing
This is the confusion that costs the most money. Resolution is how often a point is taken: it sets the detail captured. Accuracy is how closely that point matches reality: it sets whether you can judge a dimension with it. A unit can have fine resolution and mediocre accuracy, and in the brochure both appear as small numbers that look good.
If your problem is copying a geometry, resolution rules. If your problem is deciding whether the part conforms, accuracy rules — and with it the measurement judgement, without which no equipment will save you.
The small print on the spec sheet
An accuracy of "0.02 mm" is measured under laboratory conditions, on a calibration artefact, at a specific standoff and a specific temperature. Your plant is none of those. Always ask over what volume that figure was measured and what happens when the part is twice as large: on many units the error grows with volume, and that does not appear on the cover page.
Technologies, and what each is for
- Structured light. Very good detail on small and medium parts, fast, sensitive to ambient light and shiny surfaces.
- Handheld laser. More tolerant of shop lighting and difficult surfaces, comfortable on large parts, typically target-based.
- Measuring arm. For when you need to touch specific points with traceability rather than capture whole surfaces.
- Photogrammetry. A complement for very large parts, to control drift across a long scan.
The right question is not which is best, but which solves your parts. A plant digitising body panels and one inspecting connectors need different equipment, and the more expensive of the two may be the wrong one.
The cost almost nobody adds up
Software. Many units are quoted with a basic licence, while the functions you will actually use — advanced alignment, CAD comparison, reporting — live in a separate module, sometimes on annual renewal. Always ask for the quotation with the software you need for the real work, not the one that merely starts the unit.
Ask these before signing
- Over what volume was the accuracy figure in the brochure measured?
- Which software modules are included and which renew?
- Who backs the warranty, and within what response time?
- Is the training on my parts or on a demonstration figurine?
- What computer is actually required for my point cloud sizes?
If a supplier dodges any of the five, that is information in itself. We answer them in writing in the quotation.
And if the answer is not to buy
It happens, and we say so. One project a year neither amortises equipment nor keeps the operator in practice; in that case the scanning service works out better and that is what we will recommend.