The discovery of Isel and their gantry base provided high precision table movements over a wide range of motion at a very economical cost. As a result they were able to introduce a series of 3D laser digitisers at half the price of what used to be their lowest cost product. The new product filled an important gap in their capability by allowing them to offer a very accurate reverse engineering tool at a price that can be afforded by small and medium sized shops.

Their software engineers had developed line-sensor technology dramatically reducing scanning time by collecting data substantially faster than conventional measuring technologies. The technology uses laser triangulation, an active stereoscopic technique where the distance of the object is computed by means of a directional light source and a video camera. The scanner emits a Class II laser light, which scans an object. The scanning systems use a line range profiling that spreads the laser beam into a line and collects data up to 100 times faster than point range sensors and up to 15,000 co-ordinates per second. Using triangulation-based technologies 3D co-ordinate locations lying on the surface of the object are captured by a sensor on a charge coupled device in the probe according to scan density and pattern parameters set by the user. This means details of the object’s shape and finish is captured with high accuracy.

High density, true surface information permits exact duplication of complex shapes and the digitising eliminates the inaccuracies of mechanical probe offsets deflection, vector analysis, and probe size or shape. Laser scanning non-contact technology also allows difficult materials such as clay, fabric, wood, foam, plaster, glass, metal, and plastic to be scanned without damage to the surface of the object. A laser beam is projected from the sensor head onto a scanning object. The object scatters the light, which is then collected by a video camera located at a known triangulation distance from the laser. Using trigonometry, the 3D spatial (XYZ) co-ordinates of a surface point are calculated. The charge coupled device camera’s 2D array captures the surface profile’s image and digitises all data points along the laser. With specialised inspection software from solution partners the laser scan data can be easily compared to a CAD file enabling deviations from nominal to be graphically displayed. Other software programs allow NURBS surfaces to be applied to the scan data to create a CAD Model of the scanned object. STL and CNC tool paths can be derived from the scan data for duplication and manufacturing.

The 3D laser digitising systems are used for rapid inspection applications including computer-aided verification and quality control, reverse engineering, rapid prototyping and manufacturing. Typical parts scanned include plastic and rubber components, EDM electrodes, extrusions, mould, dies and castings. The systems scanning speed and accuracy are ideal for quality inspection. By scanning an existing product or tool, editing, and outputting the scan data to a CAD system, improved product designs can be completed very quickly therefore reducing the design cycle time. Models that have been produced by a sculptor or rapid prototyping system can also be scanned for input into CAD.

Although very successful the need for a lower cost alternative-scanning tool for reverse engineering was identified. All the machines previously used servo controls while other machines were available at a lower price but they had manual motion to control the scanning head. The problem with this approach is that manual motion introduces jerkiness and instability that reduces the accuracy of the resulting 3D model. What they require was a motion control system that would provide the accuracy of servo control at an economical cost. The Isel gantry was the answer offering travel ranging from 200 x 250 130 mm up to 1400 x 2400 x 500 mm and a mechanical system delivering durable, play-free motion that is rigid and stable. Yet the cost was low enough enabling them to introduce a new line of machines that each cost about 50% less than existing machines of comparable size. The benefit of using Isel was that not only did they supply machines for CNC applications they also made them available for other OEM applications such as scanning and inspection.

Each Isel gantry base incorporates a tough linear motion system for high load-carrying capacity, rigidity and positioning accuracy. Heavy cast aluminium side plates support the X axis providing increased stiffness and all axes include a home reference switch and a far end limit switch with +0.01mm repeatability. The profile rail and bearing block systems produce very smooth, play-free motion, thus facilitating high accuracy cuts or scans. Another appealing feature of the machine was its use of anti-backlash ball screws the same as those used in high-end machining centres. These screws have excellent power transmission due to the rolling ball contract between the nut and screws, which also feature extremely small backlash. Rolling ball contact between the nut and screw provides excellent rigidity ensuring long life because wear is considerably lower than ACME screws and nuts, which have sliding friction contact. This type of contact ensures low friction, low wear and long life. The ball screws also contribute to the bases exceptionally high positioning accuracy per axis of 0.10mm/300mm, resolution of 0.01mm and repeatability per axis of 0.01mm.

It took just one week to complete the design of the new laser scanner, the process primarily consisting of integrating the existing scanner head and software with the Isel gantry base. The result is a new series of 3D laser digitisers, which scan parts from all orientations and then easily transfer the data back into a common co-ordinate system. The machine control software controls scanning motion, sensor settings and also contains advanced data-editing automation features.

These laser scanners have already established a large base of new customers in a wide range of different industries and customer feedback reports they can produce the finished product between 1/20 and 1/10 of the time they took when they were creating CAD models by hand.

Micromech is the UK systems and distributor for Isel, if you wish to find out more about these cost effective, quality machines then contact Alan Spinks on 01376 333333 or alan@micromech.co.uk for further details.

‘Affordable Automation’