The big, new W 250 cold milling machine from Wirtgen America Inc. was introduced to North America at Conexpo-Con/AGG 2011 in Las Vegas in March.
It joins two new large cold mills introduced in 2010: the new W 200 single engine model — which is a large but compact milling machine that can be equipped with milling drum assemblies of 59, 79, or 87 in. (150, 200 or 221 cm) working width — and the similarly sized W 210 dual engine model, offering more power at lower fuel consumption.
The launch of the W 250 marks the advent of a high-performance cold milling machine with a maximum power rating of 980 hp (730.5 kW). The new large milling machine can remove up to 1,300 tons (1,179 t) of asphalt per hour.
Like the W 210, the W 250 incorporates Wirtgen’s dual engine concept, which allows milling with one engine at 610 hp (454 kW), or milling with two engines at a more powerful 980 hp (730 kW). Six different milling widths ranging from 87 in. to 14.4 ft. (221 cm to 4.4 m).
The W 250 also is equipped with WIDRIVE, the intelligent Wirtgen machine management system, which not only eases the workload of the operator, but also guarantees fuel efficient and environmentally compatible milling, according to the manufacturer.
The W 250 is able to mill large job sites on dual-lane highways — or airport runways — at top speed. The Wirtgen W 250 can remove asphalt layers with a milling depth of up to 13.8 in. (35 cm) — and tough portland cement concrete pavements — at a high advance rate.
WIDRIVE: Intelligent Machine Management
In addition to removing complete pavement sections in a single pass, individual layers also can be removed very economically. The intelligent WIDRIVE machine management system, the three selectable milling drum speeds and the dual engine concept keep the operating costs low.
The dual engine concept in the W 250 essentially gives the owner two machines in one: a high-performance milling machine with the full power of its two engines, and a cost-efficient mid-range milling machine that can operate with the reduced power of just one engine to economically remove softer asphalt surface courses or porous asphalt, for example, or for travel, according to the manufacturer.
In order to optimize fuel consumption, milling output and the overall efficiency of the W 250, by using a selector switch, the machine operator can set the most suitable milling drum speed for the job at hand directly from the operator’s platform.
This means that the ideal milling output can be achieved even under unpredictable milling conditions, by directly switching to the optimal speeds during the milling process.
For example, in the case of standard milling jobs, such as removal of a surface course, the W 250 operates with the medium milling drum speed of 1,800 rpm, producing the milled asphalt in desired particle sizes. When removing thin surfaces at the maximum advance rate, the high milling drum speed of 2,000 rpm can be selected, producing a superior milling texture. And to achieve maximum milling output while keeping costs low, the lowest speed of 1,600 rpm can be the right choice for complete removal, as it guarantees reduced fuel consumption and low cutting tool wear.
The standard milling width of the W 250 is 7.2 ft. (2.20 m). This can be optionally extended by fitting the machine with additional milling drum units for working widths of 8.2 ft. (2.50 m), 10.2 ft. (3.10 m), 11.5 ft. (3.50 m), 12.5 ft. (3.80 m), up to a maximum 14.4 ft. (4.40 m).
Optimal Work Environment
The W 250 operating platform provides the operator with an optimal work environment, which speeds productivity and provides an abundance of operating information.
Part of this intuitive operating environment — a multifunctional control display — operates as a practical information hub. It can be swung to the left or right of the operator — together with the level pro control panel — and displays operating status and servicing data in an easily comprehensible way.
The control display provides user-friendly diagnostic options with clear graphics for identifying the source of any problem. Another handy function is the logging of job data: at the end of the day, the log can show how many trucks have been loaded and the overall tonnage that was achieved.
Like the W 200 and W 210 cold mills, the new W 250’s parallel-to-surface (PTS) system automatically aligns the W 250 parallel to the road surface. The system ensures simple, accurate operation of the machine in demanding profiling jobs. PTS also assists the operator with positioning the machine in the milled cut to initiate the milling process. In automatic mode, the system takes care of all the steps that the operator would otherwise need to select manually one after another; the need for repetitious manual correction is eliminated.
The operator activates the integral level pro control system at the flick of a switch, and all four crawler track units of the large milling machine are lowered simultaneously at high speed. When the milling drum unit reaches the surface to be milled, the lowering speed is reduced and the milling drum slowly penetrates the material down to the set depth. The automatic process helps to prevent excessive cutting tool wear or even tool failure when commencing the milling operation.
The same applies when the W 250 is aligned transverse to the direction of travel. In many cases, cold milling machines need to overcome significant differences in height when being moved into or out of the milled cut. The integrated four-fold, full-floating axle balances out all four track units quickly and reliably to reduce the machine’s lateral inclination to a minimum. This lends a high degree of stability to the large milling machine.
The W 250’s intelligent speed control (ISC) system ensures maximum traction. The ISC system is particularly useful for highly demanding milling jobs. Just like the traction control system of a car, ISC prevents crawler track slip and ensures perfect traction of all track units to achieve maximum milling performance, reducing track pad wear, according to the manufacturer.
When negotiating bends, the ISC system automatically increases the speed of the outer crawler tracks, depending on the steering angle. As a result, even extremely narrow bends can be milled using the all-track drive. Automatic adjustment of the advance rate to match the diesel engine load always ensures maximum performance yet quiet operation of the machine.
A vacuum cutting system will remove dust, fines and smoke from the cutter chamber and extract it out the conveyor, keeping the machine cleaner and prolonging component life.
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