Top Precision Completely without Stringlines: Wirtgen Slipform Paver SP 25i with AutoPilot Field Rover

In the past, stringlines always had to be set up expensively and time-consumingly for the construction of concrete sections. These caused obstructions during installation and had to be removed again at the end of the project. Those days are now over because the AutoPilot from Wirtgen with Field Rover heralds a new era. The satellite-aided navigation system controls the steering and cross slope of the slipform paver fully automatically – without the effort of creating a digital terrain model.

Wirtgen AutoPilot Field Rover receives bauma Innovation Award 2013

The AutoPilot Field Rover has been on the market since the beginning of the year and has now won the bauma Innovation Award 2013. Wirtgen offers this new technology for the SP 15 and SP 15i as well as the SP 25 and SP 25i pavers. It can also be retrofitted to these machines. "These slipform pavers are excellently suited for the offset installation of monolithic sections or the constructions of narrow road surfaces. And these are ideal jobs for the AutoPilot," Martin Datzert, sales and application specialist for slipform pavers at Wirtgen Windhagen Vertriebs- und Service GmbH explains. He knows the possibilities of the system because, together with the Wirtgen GmbH developers team, he supervised construction sites at which the AutoPilot and Field Rover were in operation immediately before its market launch. The following two examples show that installation without stringlines works even under different basic conditions. These range from a three meter wide road surface for a cycle path to the concrete protection wall on a freeway.

The AutoPilot Field Rover won the bauma Innovation Award in the "Component" category. The jury praised the Field Rover as a trailblazing development for road construction.

The AutoPilot Field Rover won the bauma Innovation Award in the "Component" category. The jury praised the Field Rover as a trailblazing development for road construction.

3,500 meters of perfection without a stringline

In February 2013, VSB infra GmbH & Co. KG, Dortmund, became the first German company to buy an SP 25i with AutoPilot. Managing Director Kay Petersen and his team have thoroughly tested the new technology in advance, in the construction of a 3.5 kilometer long concrete protection wall on the A7 freeway near Bockenem among other projects. The 90 centimeter high wall with step profile was built parallel to the new road surface. VSB infra completely dispended with the use of stringlines.

Instead, construction manager Thorsten Kräutner recorded measuring points at intervals of 20 meters with the Field Rover a few days before beginning construction. "It's quite simple: As is normal with surveying, the stretch along which the construction is to be laid is plotted with the survey pole. Individual measuring points are defined. The software in the Field Rover computes the course of the reference line from these – the virtual stringline so to speak. In this way the user can quite easily create his own digital terrain model with the Field Rover," slipform paver specialist Datzert, who is the contact person for concrete pavers in Germany, explains.

"The recorded data can be viewed on the Field Rover display and re-edited if necessary," the developer and survey engineer Matthias Fritz from Wirtgen GmbH adds. "When everything is perfect, you transfer the data from the Field Rover to the slipform paver by USB stick." When starting work, the Wirtgen slipform paver moves automatically to the defined starting point and works from there along the reference line with millimeter accuracy.

Enormous time saving

"The big advantage of this method is that there is no stringline to obstruct the team around the paver. The concrete mixers also have more room to maneuver. This makes the work much easier and quicker," says Dipl.-Ing. Petersen as he recalls his first experiences with the new system. But for him, other aspects are also relevant: "The time for setting the lines is saved. This is noticeable above all for radii, for example at roundabouts. The points are recorded with the Field Rover in no time at all – not like before where the surveying and setting of the lines took just as much time as the construction." The data recording is particularly fast when the concrete profile is to be built on existing road sides. The user can then record the data on site and transfer them to the paver within minutes.

Goodbye to trip hazards

Böhling Bauunternehmen GmbH in Friedeburg in Northern Germany used the system in Bosse at the southern perimeter of the Lüneburg Heath. Here, a three meter wide dyke path was constructed along the river Aller with various slopes, bends with slight elevations and long straights. One day before beginning construction, Wirtgen specialist Matthias Fritz together with Franck Alberts, foreman at Böhling, went along the track and recorded about 60 measuring points along the two kilometer long stretch with the Field Rover. "A certain preparation time is necessary even with the Field Rover but it is much quicker and less personnel-intensive than all the other available methods," Martin Datzert knows.

No stringline obstructed the construction of this concrete protection wall. The VSB infra construction team enjoyed the freedom of movement just as much as the concrete mixer drivers – they can maneuver in front of the paver much better without a stringline.

No stringline obstructed the construction of this concrete protection wall. The VSB infra construction team enjoyed the freedom of movement just as much as the concrete mixer drivers – they can maneuver in front of the paver much better without a stringline.

As soon as the data are transferred to the paver and the SP 25i is installing the concrete profile, it constantly compares the current position with the nominal data. At a reference station set up at the side of the construction site the paver receives a DGPS signal which gives the position precisely with an accuracy of one centimeter. The paver control system generates the steering signals from the differences between the nominal and actual data. The driver no longer has to intervene.

Construction of a cycle path in Bosse in the Lüneburg Heath: Bends with tight radii are also possible without a stringline with the Wirtgen AutoPilot.

Construction of a cycle path in Bosse in the Lüneburg Heath: Bends with tight radii are also possible without a stringline with the Wirtgen AutoPilot.

On this principle the AutoPilot also took over the control of steering and cross slope on the construction site in Bosse – even in the bends. Machine operator Torsten Fabricius always had the position and the current parameters in view on the display but was able to concentrate totally on the coordination with the concrete mixer and his colleagues on the ground. They, on the other hand, appreciated being able to work without stringlines as did the drivers of the concrete mixers.

The machine operator can see the status of the AutoPilot on a separate display the whole time.

The machine operator can see the status of the AutoPilot on a separate display the whole time.

Sensors for height adjustment

While the AutoPilot steers, the height adjustment is controlled by an additional sensor. This may be an ultrasound sensor or a ski sensor, a laser receiver or a total station depending on the nature of the ground and the local topography. A laser sensor was used on the dyke path construction site. A different story on the freeway construction site: VSB infra scanned the new road surface with an ultrasound sensor – an ideal reference.

The AutoPilot steered the SP 25i from Wirtgen in the construction of the three meter wide dyke path by Böhling Bauunternehmung GmbH. The height was controlled by a laser transmitter with the appropriate receiver on the paver.

The AutoPilot steered the SP 25i from Wirtgen in the construction of the three meter wide dyke path by Böhling Bauunternehmung GmbH. The height was controlled by a laser transmitter with the appropriate receiver on the paver.

Convincing new paver generation

When testing the AutoPilot, VSB infra GmbH & Co. KG and Böhling Bauunternehmen GmbH were also able to judge the new SP 25i. Managing Director Egon Böhling especially praised the new, very accurate steering and the many sophisticated details. Managing Director Kay Petersen was thrilled with the convenient operation of the slipform paver, its high transport and maneuvering speed and the economical engine concept. These were just some of his reasons for deciding to buy a machine immediately after the tests. VSB infra is therefore the first company in Germany to use the AutoPilot and, as Petersen says, "the system convinced me one hundred percent."

With the purchase of the machine, Wirtgen trainers provided AutoPilot training for the entire construction team of VSB infra Kay Petersen knows why: "It is not just the construction managers, who will record the data with the Field Rover later, who need to be familiar with the system. The foremen and machine operators also have to know how the AutoPilot works and what it can do. When that is the case, we can exploit all the economical advantages and produce optimum quality."

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