Reverse engineering is a subject that offers significant benefits in the overall effort to reduce the time-to-market for new products, yet the same term is also used to describe the practice whereby an existing product is copied by first finding out how it works and then producing a low-cost ‘look-alike’ or competing product that offers similar functionality. For the purposes of this article, we will consider only the legitimate use of three-dimensional scanning systems and software as part of the new product development process. Related applications are the inspection of first-off parts from new tooling, and the inspection of the tooling itself.

The most common application for reverse engineering is where a product is under development and the external form is refined manually, perhaps using clay or foam. To create the tooling necessary to manufacture the final form, the traditional approach involves manual measurements and a degree of interpolation between the measured points to create a close approximation to the desired surface. Not only is this time-consuming and expensive, but it is also prone to errors.

Hand-operated or automated touch-probes reduce both the time required and the risk of errors, thereby offering significant advantages over the manual technique. Furthermore, because the data is collected electronically, it is relatively easy to import this into a computer system that converts the data into a usable digital format.

A major breakthrough, however, came about when non-contact, laser-based measurement techniques were introduced. These can potentially gather data for millions of points on the surface in just a few seconds, making this by far the quickest method. Once again, the data can be readily be imported into a software package so that it can be converted into a digitised surface model.

Depending on the application and, in particular, the size of the object being scanned, the laser-based device can either be mounted statically – perhaps with the target object rotated on a turntable – or the laser system can be handheld, such as Creaform’s new Handyscan 3D (Fig.1).

The Handyscan 3D is available in Europe through a network of distributors, including Unimatic Engineers in the UK. The device is pointed towards the object to be scanned and moved around so that a self-positioning cross-hair sweeping laser is moved over the object's entire surface. This generates a constant stream of positional data, the initial value of which is used as a datum from which all other data are measured. Software instantly collates the data into a 3D scan or virtual model of the object. A surface optimisation algorithm, together with other features of the program, ensures an accurate scan, while rendering for real-time visualisation maximises user-friendliness.

It is claimed that the Handyscan 3D digitising software is easy to learn and simple to integrate with existing systems through its Windows compatibility and ability to export files in standard formats such as Geomagic Studio and Qualify. Other applications planned for imminent integration include Polyworks, Catia v5, Prelude Inspection and Rapidform.

One example of the static type of laser scanner is the recently launched Konica Minolta Vivid 9i. This unit is suitable for high-precision 3D measurement of a wide range of items including cast, forged, pressed, and moulded plastic components, as well as dies and mould tools. The new hardware design is said to improve measurement accuracy fourfold compared with the preceding models from Konica Minolta; maximum accuracy is now 0.05mm in the X, Y and Z axes under standard conditions at a distance of 0.6m (Fig.2). Using the marker registration tool (which is available separately), even large objects – such as car panels – can be measured with high precision (Fig.3). One of the notable features of the Vivid9i is that the lens can be changed, enabling different sized objects to be scanned.

Conversion software

Included with the Vivid9i hardware is the Polygon Editing Software version 2.00. The higher processing speed and enhanced measurement GUI (graphical user interface) allow for quicker and easier merging and editing of large amounts of measurement data.

Within the field of reverse engineering, software to process the data is just as important as the scanning hardware. While some of these software tools are designed for use across a broad base of CAD, solid modelling and surface modelling packages, others are suitable for use only with one.

In February 2007, for example, Nextengine released its new Rapidworks software package with special features for Solidworks users. Rapidworks offers a comprehensive suite of tools to allow designers to take raw points and turn them into idealised Solidworks SLDPRT part files. The output is a fully parametric solid model with a true Feature Tree, all built on technology from RapidformXOR.

Alongside Rapidworks, Nextengine’s Scanstudio Pro is for engineers who want Nurbs surfacing and automatic spline output from points. It also features a comparison tool to analyse differences between as-built and CAD models.

Nextengine’s full-colour 3D scanner with multi-laser precision simply connects to the USB port of a computer, making it practical and cost-effective for the user to scan complex shapes at his or her desk.

Another software package that integrates with Solidworks – and Autodesk Inventor 11 – but that takes scanned data from a variety of hardware, is DezignworksV8.0, the latest reverse engineering software product from Creative Dezign Concepts. Engineers and designers can use Dezignworks and Solidworks or Autodesk Inventor to capture data from existing parts directly within the CAD environment.

With Dezignworks’ patent-pending data collection method, all the movement of the device is stored and can be reused again and again without the need to re-digitise the model. During the digitising procedure, the data can be exported and used to compare the information with an existing model or imported back into the CAD package to create a mesh.