Welded, cast and milled components from two to twenty metres can only be inspected with tape measure, plumb line and square at considerable expense of time — and some dimensions not at all.
Three characteristics usually decide whether a photogrammetric measurement is superior to conventional inspection: the component is too large or too heavy to be brought to a measuring device. The required dimensions depend on each other spatially, so individual lengths are not enough. Or the inspection has to be documented — for the end customer, as an as-built record or as the basis for subsequent machining.
Photogrammetry captures the component from photographs — where it stands — and derives its geometry from them, including a nominal/actual comparison against the CAD model. The measuring setup comes to the component, not the other way round. The system weighs around ten kilograms, works without contact and is insensitive to impact, vibration and changing temperatures. Forklift traffic in the hall does not affect the result.
It is not only individual points that are measured, but geometric elements — and dimensions derived from them that a length measurement cannot provide:
The relevant locations on the component are fitted with self-adhesive measuring targets; adapters are added for edges, bores and flange rims. One operator walks around the component with the camera and photographs it from all angles — depending on the object, a few dozen to more than a hundred images.
The software detects the targets in all photographs, identifies them by their individual patterns and calculates the 3D coordinates and camera positions from them. The evaluation takes place directly on site. Measuring a propeller takes about half an hour; a tank cylinder with around 400 targets takes correspondingly longer.
Turbine housings at Siemens in Mülheim. The housing parts of modern gas and steam turbines measure between 2 × 2 × 1 m and 5 × 5 × 3 m and weigh several tonnes. In the past they were aligned and scribed on the marking-out table with tape measure, plumb line and square — a procedure proven over decades, but very time-consuming. Today the photogrammetric measurement supplies the machining allowance and the reference locations for alignment on the CNC machine.
Tank construction. With welded tanks up to ten metres in size, the position of the flanges determines whether the component fits into its installation environment. The main cylinder is fitted with about 400 targets, the flange rims are probed using adapters. The flange centre points in the cylinder coordinate system yield roundness, tilt and spatial angles — as as-built documentation for the end customer.
Ship propellers at Otto Piening GmbH. The manufacturer needed a portable coordinate measuring machine for production, research, field repairs and the reverse engineering of existing propellers. The size of the propellers is unlimited, and concealed geometries are captured as well. The integrated CAD comparison makes deviations from the nominal geometry immediately visible.
Linearis3D Photogrammetry Professional is used for quality assurance. In accordance with VDI 2634 it achieves a length measurement error of 0.03 mm within a measuring volume of one cubic metre and works on objects up to twenty metres and beyond. Accuracies down to the hundredth-of-a-millimetre range are achievable. The system can be used in bright sunlight as well as in darkness, and in confined surroundings.
We will advise you on which measured values matter — and recommend the right system.
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