A welding robot was designed as part of a project for the development of a novel geothermal drilling process, to position tubes reaching a length of up to 12m and bond them with a force of more than 2,000kN. To minimise the development risk for the welding robot based on a hexapod manipulator, Hydrive supported several project phases with extensive simulations. This enabled us to validate the basic concept early on without incurring additional expenses for hardware.
Earth drilling for geothermal sources is characterised by the use of borehole casing which is to enhance the persistence of a borehole several kilometres deep. After drilling, a casing made of special steel is positioned inside the borehole and widened to allow a continuous support at maximal inner diameter. The construction of a tubular string from individual tubes that have been screwed together carries a high risk of leakage and loss of stability during production and is relatively expensive.
The development of a novel geothermal drilling process [1, 2] aims at reducing the costs of the wellbore construction by 30% and the entire lifecicle cost by about 50%. A fusion press welding process development delivers tighter, ridgid and reliable tubular connections.
A welding robot was designed as part of this development project to position the 12 m tubing (max. diameter: 300 mm, max. wall thickness: 25.4 mm) along the string at a distance of 5 mm from each other, to melt the ends of the tubes and bond them with a force of more than 2,000kN.
To meet the demanding requirements of the welding process, the welding robot including drives and control needs to be extremely dynamic and accurate. These strict requirements and the high costs that arise mainly due to the strong forces required and the wide measurements of the welding robot lead to a very high development risk.
To minimise the development risk for the welding robot based on a hexapod manipulator, Hydrive supported several project phases with extensive simulations. This enabled the early correction and validation of the basic concept (layout, dimensioning, etc.) without incurring additional hardware costs. During the design and construction of the prototype we were able to optimise the controls using a wide range of real-life disturbance effects and develop the control software. This approach presents an opportunity to considerably shorten development times and create a more mature prototype, which in turn allows concentrating on process optimisation and industrialisation of this new geothermal drilling process early on.
 D. Brouwer, J. Lehr, B. Denkena, H.-C. Mohring, K. Litwinski:
Positioning system and method for automated alignment and connection of components, Patent WO 2013/086326 A1, 13.06.2013
 Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Project No. 0325073, „Konzept, Entwicklung, Fertigung, und Test eines innovativen und kostengünstigen Geothermie-Verrohrungssystems“