Absolute precision

Citation

(1998), "Absolute precision", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 5. https://doi.org/10.1108/aeat.1998.12770eab.008

Absolute precision

Absolute precision

Keywords Machining, Neos Robotics, Precision instruments, Robots

Absolute precision while machining bulky work pieces can reportedly be achieved by a new method that combines the Swedish Tricept robot with a vision system for CCD camera positioning, report Neos Robotics of Sweden. Scrapping of expensive components owing to exceeding error tolerances is said to be completely eliminated with this new technology, that goes under the name of TI² (Plate 6).

This method is believed to have great potential within aircraft manufacturing.

Plate 6 The TI² robot cell is being steered to find the absolutely correct position for machining, in accordance with the CAD model desired value, including corrections for the true measured actual value

Boeing (USA) has recently negotiated delivery of the first robot cell.

TI² stands for the Tricept robot system, the Imetric measurement system and the Igrip computer simulation. Tricept is the Swedish element and is represented by a new, three-armed ballscrew-driven industrial robot with high positional accuracy and impressive press power at its head (up to 15,000N vertically).

The robot's inventor is Karl-Erik Neumann, MD for the Swedish company Neos Robotics. Metric SA is a Swiss company specialising in photogrammetry and camera-based measuring systems, while Igrip's simulation software (developed by American Deneb) is marketed and developed in Scandinavia by the Finnish firm Tehdasmallit Oy.

Together these companies have developed an advanced flexible manufacturing system (FMS). The true positions of the physical components and their dimensions are determined, and compared with the absolutely perfect theoretical measurements stored in the computer-aided design (CAD), so that the robot machining processes can be corrected to produce the equivalent correct components.

Previously, expensive jigs had to be made to ensure that the correct tolerances were met, but these are no longer necessary. The camera measurement system permits continuous correction of the tool head position, taking into account the dimension changes that can arise owing to temperature changes in the work being machined.

This is particularly valuable within the aircraft manufacturing industry, where heating of large aluminium work pieces causes the material to expand during machining, and can lead to expensive scrapping and loss of time for machining expensive replacement components.

Even free-standing objects, such as a fuselage, can be worked on quite comfortably.

The tremendous potential of the TI² system has already attracted the attention of the US aviation group Boeing, which has arranged to receive the first robot cell.

Eric Whinnem, who leads the Boeing R&D operations in this field, has come to this conclusion: "This new technology is almost as large an innovative step within the aviation industry, as was the introduction of duralumin stressed-skin construction in its day". Responsible for the negotiations was purchasing manager Sandy S. Cunningham, Boeing Military Transport Aircraft, R&D Aircraft Derivatives: "There is great potential within our manufacturing group for this new technology, and production technicians are now coming from our civil and military facilities all over the USA to study it."

Unlike conventional industrial robots with jointed arms, the Tricept movement range is completely free from oscillation or swinging that can detract from positional precision.

Because a Tricept can be controlled via off-line programming, expensive down-time for reprogramming is avoided. In principle just alter the program and change the tool.

For further information contact Neos Robotics AB, VD Karl-Erik Neumann. Tel: + 46 8 630 03 75; Fax: + 46 8 630 03 79; E-mail: showroom@neosrobotics.com