Submitted by Olaf Schwittay, Bosch Rexroth AG, Lohr, Germany. For more information, visit www.boschrexroth-us.com.
With a length of five meters, but just 1.80 meters wide, the Dynapac Citypaver SD1800 from Atlas Copco is ideally suited to tight construction site environments and movement in heavily built-up city centers. The Citypaver uses the Hydrotrac GFT 8000 transmission units from Bosch Rexroth. This modular drive series combines two- and three-stage planetary gearboxes with axial-piston motors to create an individually adapted drive package for mobile working machines.
Efficient Hydraulics Cut Fuel Consumption
As with any new mobile working machine development, reduced exhaust emissions and lower fuel consumption were both part of the specification. The power of the 54 kW diesel engine is intelligently distributed to the paver functions, minimizing power losses. Both the hydrostatic drive concept and the thermostatically controlled fan and load dependent hydraulic pumps contribute to this.
Instead of using fixed-displacement pumps, the Citypaver uses compact A1VO variable-displacement axial-piston pumps from Bosch Rexroth. This variable-displacment feature enables energy savings of 10 to 15%. A further increase in energy efficiency is achieved through load sensing and independent flow sharing. The hydrostatic travel drive and working hydraulics are networked with a state-of-the-art control unit via CANbus.
For machine control, the Dynapac group uses two Rexroth modular BODAS RC28 mobile controllers in a master-slave configuration. Combining the two controllers provides greater freedom in terms of the driving and working functions while complying with functional safety requirements.
Complex Functions at the Push of a Button
For the first time in this class, the new Citypaver uses the entire functionality of Dynapac’s PaveManager 2.0 operating system, which users are familiar with from the company’s larger SD pavers.
Thiberio Tanus, the product manager for the Compact and Citypavers, offers, “It was an explicit objective of the new development to adapt the operation and comfort of the large machines for the smaller Citypavers as far as possible.” PaveManager 2.0 automates road paver functions, such as the recording of laying parameters, storage of laying progress, and automatic settings for straight crossfall angle and slope.
Dynapac uses Rexroth’s configurable BODAS DI4 display for monitoring and controlling operation. This opens up a wide range of options for custom visualization and function assignment, which Dynapac fully utilizes. In addition to two hard keys for set functions, 12 freely programmable function buttons are available. In addition, the driver can intuitively select functions without visual contact with the control panel using a turn/push button.
A new SetAssist function lets the machine operator save the position of the screw conveyor and slab at the push of a button before moving the paver from one section to the next. The innovative TruckAssist system supports correct and safe docking of trucks on the paver. The display also simplifies commissioning and service.
With no need for an external diagnostic unit, authorized maintenance engineers or operators can use the display to access the BODAS controllers integrated into the machine in master mode, and to read active and saved faults. This accelerates diagnosis. The service engineer can load new parameters for the BODAS controllers or transfer new sequence programs using the integrated USB interface.
Finally, the display ensures short standstill periods, for example, because the joystick can be calibrated using the display after replacement. Anup Jacob, group leader for the Compact and Citypaver at Dynapac, is overall very positive: “When it comes to programming and parameterizing the control units, Rexroth brought their extensive experience with travel drives on large machines to bear and supported us the whole way, from design to commissioning.”
Click here to watch a short video describing the Dynapac Citypaver SD1800 from Atlas Copco.