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Levelling system LEVEL PRO / LEVEL PRO PLUS

Levelling in an automated process

In cutting and milling, it is crucial to remove pavements to the specified depth. The intuitive WIRTGEN LEVEL PRO / LEVEL PRO PLUS levelling technology can be relied on to precisely maintain the preset cutting and milling depth. The hightech system is fully integrated into the machine’s overall management system.

LEVEL PRO / LEVEL PRO PLUS continuously reconciles the actual cutting and milling depth with the preset target value. Any deviations detected by the system are levelled out dynamically by means of proportional control. The actual cutting and milling depth is determined by means of optical or mechanical sensors scanning a reference surface.

- The new LEVEL PRO / LEVEL PRO PLUS levelling system offers intuitive, one-hand operation via a rotary control and free menu configuration.

- Full integration of the LEVEL PRO / LEVEL PRO PLUS levelling system into the machine management system allows a high degree of automation.

- The LEVEL PRO / LEVEL PRO PLUS levelling system offers many complementary and automated features which relieve the operator of a part of his workload. This also results in a faster progress of operations.

LEVEL PRO / LEVEL PRO PLUS screen for small milling machines	LEVEL PRO / LEVEL PRO PLUS screen for large milling machines

The machine is adjusted in height via the lifting columns of the front and rear wheel or track units, all of which are interlinked hydraulically. If one of the wheel or track units climbs over a hump or drops into a dip, the resulting difference in height is levelled out automatically by the remaining three wheel or track units. This fourfold full-floating feature enables the machine to always align itself to the ground automatically, which results in significantly improved machine stability.

Closely linked to this feature is the PTS system (Parallel To Surface) integrated in the levelling system, which aligns the machine parallel to the ground surface during the milling process and supports the operator in positioning the machine in the milling cut.

The integrated auto-start feature allows the wheel or track units to be lowered to the specified depth simultaneously at the mere push of a button; the milling drum penetrates the material more slowly as a result. Manual adjustment of the rear wheel or track units to maintain the specified working depth is no longer required. Operation of the machine is simplified considerably at the same time.

Automatic level and cross slope control

Paving thickness accurate to the millimetre

The levelling control system governs the paving thickness of concrete profiles in accordance with a specified reference. Slipform pavers typically use mechanical systems scanning a stringline to effect horizontal position and level control.

Stringless 3D control systems have also proven their worth in recent years, however, and are sometimes even a requirement today in tender specifications. 3D control offers many advantages over stringline control – the ideal paving line, for instance, need not be transferred to the actual construction site by means of a wire but is available as a computer model. This digital terrain model is used to define the set positions of the machine which are then monitored using optical measuring systems such as a motorized total station and prism. A wide variety of concrete profiles can thus be produced to precision in a simple and efficient process.

Level control using stringline

A stringline is carefully installed and tensioned along the entire length of the concrete profile or slab to be produced prior to commencing the paving operation. It will provide the specified paving level. Two separate sensors carried by the slipform paver normally guide off the stringline for level control – one sensor for the front tracks, a second one for the rear tracks. While the slipform paver keeps moving forward, both sensors scan the stringline and continuously send pertinent level details to the paver’s control system. These level details are not absolute values, however, but merely the deviations from the set value that is provided by the stringline.

  

 

 

 

The control system receives the measured results, and in case of any deviation actuates the relevant hydraulic cylinders to compensate by adjusting the level of the machine including the mould. This matching process takes place around 40 times per second. The side of the paver carrying the mould is immediately raised or lowered by the resulting difference between the actual and set values. The opposite side of the machine is balanced in level by means of a second control loop with integrated slope sensor.

Level control using a 3D system

With stringless systems, the computer of the 3D control system feeds the paver’s control system with the specified parameters of level and horizontal position of the concrete profile to be built. The 3D system uses a special interface to communicate with the controller of the slipform paver.

Two prisms are typically installed on the slipform paver which have direct visual contact to a total station each, reflecting their optical beam. The total station keeps determining the prism’s current 3D position. The measured results are transmitted by radio to the system computer on the paver. Two multi-axial slope sensors integrated in the machine additionally determine the paver’s longitudinal and cross slope.

 

 

 

 

The system computer uses these parameters to calculate the machine’s actual position and direction of travel. The position data are continuously compared with the design data of the concrete profile stored in the system computer as a digital model. Any deviations are immediately forwarded by the system computer to the paver’s machine control system. The paver’s control system then initiates the required corrections in level, slope and steering angle of the track units. This procedure enables the production of concrete profiles that meet the specified requirements with great accuracy.

Electronic slope control

Perfect paving results are guaranteed thanks to the electronic slope control developed by WIRTGEN on the basis of the “Rapid Slope” cross slope sensor. Optimized control technology enables the innovative slope control system to achieve as yet unmatched dynamics and precision. Significantly shorter machine response times are refl ected in the precision and quality of the completed concrete product. The WIRTGEN cross slope system can be relied on to quickly level out any vibrations or ground irregularities.

High-precision cutting depth control

Selective mining driven to the max

Precise control of the cutting depth is a vital requirement that surface miners need to meet for selective mining, the production of level surfaces, and grading. Cutting depth and cross slope are set and controlled via the hydraulic height adjustment feature of the track units.

Control systems

- Manual or automatic adjustment of the cutting depth using the hydraulic height adjustment feature of the track systems.

- Cutting depth control by scanning the level of an existing surface using sensors installed at the side plate.

- One or two masts equipped with laser receivers can be installed on the left and right side of the machine. These laser receivers are connected to the automatic cutting depth controller. Hence very levelled horizontal surfaces and slopes can be generated.

- When a GPS receiver is connected to the automatic cutting depth controller, predefined profiles can be cut after programming the receiver accordingly.