Paving the way to a successful partnership
01 May 2012
Every year, thousands of kilometres of streets and roads are added to the landscape and paving machines have a pivotal role to play in all this activity. Transferring up to 1,100 tons of asphalt per hour is a huge deal and one of the reasons why Dynapac paid so much attention to the hydraulic control systems at the heart of its latest generation of pavers.
A successful 20 year long collaboration ensured that Rexroth was again appointed hydraulics control system supply partner when Dynapac set out to develop its latest generation of asphalt paving machines, examples of which attracted big crowds at last month’s Intermat show in Paris. Both electromechanical and PLC based modular control systems have been developed for the first six versions of the new paver, which have been received enthusiastically by the industry.
Dynapac’s Thomas Muller, who oversaw Rexroth’s role in the project, pays tribute to their design partnership: “The ultimate result was a hydraulic concept that is convincing not only because of its high performance, but also because of its ease of maintenance. Wherever possible, all the hydraulic components are grouped together in the machine to achieve good accessibility.”
Rexroth’s central electronic system enabled Dynapac to reduce both energy consumption and noise emissions. In the two smaller versions of the new paver, the system is used to control the electro-hydraulic propulsion drive, while in the four larger versions, the controls mimic the entire machine.
A large share of the development work, consuming several man-years of work, was devoted to adapting the control functions to meet specific needs. This effort paid off as the developers avoided having to use separate electronic units that might otherwise have required different interfaces and tools. Rexroth’s central electronic system allows third-party systems, such as regulators for tamping beam heating and functions, to be easily integrated. Only one more process computer is needed – one for levelling – and this is also capable of exchanging information with Rexroth’s central electronic unit.
Rexroth’s central electronic concept also simplifies operation for the road building crew. For example, the driver can select ‘Variospeed’ mode, in which the speed of the diesel engine is automatically matched to current power demand. The same operating principle is used for the hydraulically driven fan, which always regulates itself to the appropriate duty point. This not only makes the paving machine more economical; it is also easier on the ears, both for the road crew and those living near the construction site.
A ‘Safe Impact’ function also facilitates paving material refills during operation. Normally, when a truck filling the supply hopper bumps the paver during docking, the impact causes unevenness in the road surface. The new pavers provide an optional, hydraulically damped advancing roller that absorbs this shock to ensure a flat and level wearing course. And in the operator’s cab, user-friendless is the order of the day. In its PLC-controlled machines Dynapac has implemented an intuitive operating menu for the driver, presented via a full colour display.
All the road construction contractors that were invited to test machines from the pre-production series were enthusiastic to a man. And surprisingly, there was praise from an entirely unexpected quarter, as product manager Volker Behrens recalls: “We even received compliments from the competition!”
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