CAD User Online Article Archive

Review

All that glitters!

From CAD User Mechanical Magazine Vol 18 No 06 - JUNE/JULY 2005

3D Scanners latest hand-held laser scanner, ModelMaker Z, provides superior dark or shiny surface data capture.

It was back in 1995 that 3D Scanners came up with the first hand held laser scanner- a device that combined the flexibility of the digital probe for getting into those awkward spots on the model – and the accuracy of lasers. The ModelMaker has, since then, come to be regarded as the standard 3D data capture tool within the industry for reverse engineering, computational fluid dynamics, rapid prototyping and many other 3D measurement tasks – as evidenced by over 95% of the world’s automotive companies who use them in their design studios and on the shop floor.

Now comes ModelMaker Z – the fifth generation 3D scanner from the company and the successor to the W. X and Y range. ModelMaker Z comes with enhanced ability to scan shiny or black surfaces – improved datuming and new macro functions amongst a range of other enhancements. The scanner is located on the end of an articulated and pivoted arm that allows it to be manually positioned at any point around the model, capturing its x,y,z position and an I,j,k vector for each profile, enabling the exact position of the model profile to be transmitted via the scanning head back to the computer.

The hand-held scanner is capable of capturing up to thirty profiles and positioning them in 3D space each second, producing a high accuracy, high density 3D point cloud. It also comes as three separate models, the ModelMaker Z35, providing the highest resolution with a scan range of 50 x 35 mm along the Z and Y axes, for small, detaile dobjects, the general purpose Z70 with scan ranges of 100 x 70 mm, and the high speed Z140 which scans at a range of 150 x 140 mm, which allows larger objects to be scanned efficiently. At a scanning speed of over 23,000 points per second, the ModelMaker range is the fastest- and lightest - group of hand held scanners on the market.

The ModelMaker sensor projects a laser stripe across the object to be scanned, whic is viewed by a camera so that height variations in the object can be seen as changes in the shape of the line. Each viewed stripe forms a profile which is built up from several hundred measured points. The stripes are merged to produce the 3D simulations of the model.

ESP

Scanning shiny and dark surfaces may appear to be quite straightforward – to human sight - but, to a laser device, the qualities of such surfaces present quite serious problems of reflection and absorption of light. Laser scanning, using the technology described above, or, like other laser scanning devices, measuring the distance between the scanning head and the object by measuring the amount of time it takes for the light to hit the object and return, are susceptible to abnormal surfaces, and features, such as shiny or a dark surfaces, can interfere with the reflection.

It is only through using technology such as ESP – Enhanced Sensor Performance (not extra-sensory perception) that accurate readings can be achieved - providing ModelMaker Z with unsurpassed scanning capabilities of difficult surfaces. Using ESP technology, the sensor detects the changes in the surface reflection of the object and makes the relevant compensations between the laser head and the KUBE software. The tool’s capabilities can be further refined by users, allowing them to optimise ESP’s performance through a simple set of automated controls.

KUBE 9

ModelMaker Z is basically a scanning system, the handheld scanner being merely the data capturing device of a complete hardware and software solution.. Kube, the scanning and data processing software, has been under development by 3D Scanners for as long as the Modelmaker has been around

Kube also provides advanced tools for establishing the datum point of the scan, or for creating entities such as points, lines, planes, circles, spheres and cylinders, used to re-align or re-register the co-ordinates of the scan, so that it can either be used directly with data models for quality control, or for exporting the scanned data to another CAD system. The high accuracy exchangeable mechanical probe can also be used to align data to alternative co-ordinate systems.
Kube is also used for ‘snapping’ together overlapping scan data sets – even where no comparable reference points are available in the scanned data. The aim being, of course, to provide a location for the data in 3D space, and to enable multiple scans to be linked together.

Data Capture and Preparation

The software also allows the user to control the scanner remotely using an arm driven menu system. Moving the arm up and down highlights the functions, each of which can be selected from buttons on the arm. Being a mechanical system, as well, automatic tracking and adjustment maintains the sensor systems, continually optimising the scanning performance.

Scanning is pretty fast, as well. Laser scanners can capture far more data than is normally required, as most jobs don’t need the scanner’s maximum resolution. Pre-processing the data as it arrives, a real-time job that is normally handled manually in other 3D software, helps users prepare the data for faster down-stream processing.

Users can also ‘select’ the type of data they want by creating scanning profiles. To provide a 3D scan, the ModelMaker takes 2D scans in U and V directions, which, when merged create the 3D mesh. Preliminary scans produce raw stripe data – extremely raw, because it has been produced manually as the operator passes the scanning head around the model at – to the computer – vastly varying speeds and distances, the distance between each of the lines being governed by how fast the hand travels over the object. The software is then used to sample the data, and to merge series of data scans, discarding any data that overlaps, possibly up to 40-50%, and superfluous data, ending up with a uniform polygon mesh. Several sub-processes are involved – 2D sampling, optimise and polygon reduction.

Scan data to CAD Inspection

One of the most effective uses of the ModelMaker is in scan to CAD inspection – scanning a prototype product to ascertain whether it conforms to the data in the manufacturing drawing. Normally a task that requires specialised software – but, in the case of ModelMaker and KUBE, as straightforward routine. KUBE inspection is an ideal ‘shop-floor’ tool, providing only essential inspection functions in a simple to use format. KUBE inspection can be used on-line to provide instant feedback from the model, or off-line to generate electronic or printed reports.

Output from KUBE inspection includes, besides rapid scan to CAD comparisons, quick bitmaps generating ‘snapshots’, pick point error flags displaying deviation details, coloured sectional inspection with ‘whisker’ style graphical output, histogram for displaying statistical data and the ability to generate PDF or HTML reports using defined templates - with a single click.

www.3dscanners.com

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