Cold Milling Is One of the First Measures Taken When a Roadway or Traffic Area Needs to Be Rehabilitated.
By Mark S. Kuhar
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| Modern cold milling machines like the powerful large cold mills from Wirtgen improve the quality and cost-effectiveness of complete road rehabilitation. |
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| Selective milling: With the help of modern machine technology, the surface, binder and base courses can be removed separately and also returned to the material cycle separately. This increases the sustainability of RAP recycling. |
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| To increase productivity and area output, the Wirtgen compact cold milling machine W 150 CFi can be equipped with 6-ft (1,800-mm) wide milling drums by means of a housing extension. Customers therefore profit from a wider range of applications. |
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| The RAP loading systems of Wirtgen’s W 50 Ri small milling machine offer maximum functionality. A large slewing angle, the practical quick-release coupling and the hydraulically operated folding conveyor simplify the working processes enormously. |
At World of Asphalt/AGG1 2019 Wirtgen presented the 40-hp (298-kW) compact cold milling machine W 150 CFi, mounted with 6-ft. (1,800-mm) drum assembly, and the small milling machine W 50 Ri.
Aged asphalt pavements are being removed from every type of roadway, from dual-lane highways in rural areas to urban pavements with multiple manholes and inlets, to shopping center parking lots with concrete “islands” with acute curb radii.
Market-Driven Innovations
Wirtgen offers the most extensive line-up of cold milling machines in the industry, the company stated, with milling widths from 0.55 in. (14 mm) to 14.4 ft. (4.40 m). Customers can choose from over 30 different machine types, each also available with a variety of milling widths.
The lower performance class starts with the small 60-hp (45-kW) milling machines and extends through compact machines with engine outputs of between 344 and 400 hp (257 and 298 kW), to large milling machines in the upper performance class offering power reserves of up to 1,009 hp (753 kW). The high level of customer-oriented design expertise guarantees market-driven innovations. The new solutions developed at the brand headquarters in Windhagen are founded on practical know-how and core competencies in leveling, control and cutting technology.
Key Impact
Cold milling is one of the first measures taken when a roadway or traffic area needs to be rehabilitated. The condition of the milled surface has a key impact on the quality of the new surface courses, their service qualities and on the economical and efficient execution of the other construction measures. An evenly milled surface, true to line and level, is a crucial factor when it comes to paving surface courses of uniform thickness and avoiding costly correction measures in the form of asphalt leveling courses.
Milling Layers Separately, Recycling Economically
The progressive automation of technical processes, in particular, plays a key role in optimizing the milling result. To achieve optimum results, the leveling parameters for the respective machine are saved, linked to the LEVEL PRO automatic leveling system and retrieved during the working process.
Nowadays, the widest variety of pavement layers are removed and separated in highly selective processes. The removal of problematic construction materials is possible, as is the standard separation of premium-quality surface courses with a high bitumen content, or the removal of road markings prior to the actual separate milling of the asphalt courses. The surface, binder and base courses can be returned separately to the material cycle, increasing the sustainability of RAP recycling.
Selective milling does not entail significant time disadvantages. Due to the shallower milling depth, the cold milling machines work more quickly when removing the individual layers than when removing the complete pavement at maximum milling depth in a single pass. Milling off surfaces in two or three layers can sometimes be just as fast – in some cases even faster – than complete pavement removal, depending on the type of machine and pavement and on ambient conditions. Modern cold milling machines also have been specifically tuned to typical selective milling.
Always on the Level
One of the decisive factors in milling a surface true to line and level is precision leveling. The purpose of leveling is to regulate the milling depth and slope automatically and as precisely as possible based on a reference line. In the field, it has become standard practice to copy an existing surface by scanning a reference line.
But teamed with a wide range of sensors, the Wirtgen Multiplex leveling system can do much more than simple copying. Three sensors on each side of the machine scan the height at wide intervals along the same reference line. The automatic leveling system averages the three measurements to create a perfectly even milled surface, while meeting the target milling depth. This is a highly effective way of leveling out longitudinal undulations. What is more, defined surface profiles can be created, such as specified cross slopes or crowns.
Completely new surface profiles can be created by means of 3D milling. A new digital surface profile generated on the computer can be transferred directly to the Wirtgen cold milling machine using 3D leveling systems. Increased quality and cost-effectiveness are major benefits offered by 3D milling technology.
Multifunctional Armrest
A highlight of the small milling machines is the ergonomically designed multifunctional armrest. With it, the operator can call up all the important information he needs to see on the color display, including the acquisition and visualization of all job data. Four “favorites” buttons integrated in the armrest can be programmed with any of 20 different functions. The operator can also intuitively control the height of the machine from the multifunctional armrest.
New Milling Drum Assembly
The W 150 CFi can now also be equipped with a 6-ft. (1800-mm) milling drum assembly. Customers therefore profit from a wider range of applications. The most powerful machine in the compact milling machine class with its 400 hp (298 kW) engine power, it now achieves even greater productivity and area output.
The W 150 CFi can tackle a wide array of different jobs, ranging from classic small milling machine applications such as partial road surface repairs to the removal of entire road pavements. The milling machine is therefore especially suitable for large-scale projects in confined spaces such as on urban job sites. Particularly in such conditions, the sophisticated visibility concept combined with the camera systems help the machine operator to maneuver the milling machine.
Cutting Technology: A Wide Range of Efficient Applications
The powerful “heart” of the cold milling machine – the milling drum assembly with all the cutting technology components – also has a critical bearing on the quality, costs and performance of the milling process. Here too, as technology leader Wirtgen is continually developing cost-efficient solutions. Different milling drums support a wide range of milling applications on different road surfaces.
The standard milling drums, for example, offer tool spacings of 0.5 in. (12 mm), 0.6 in. (15 mm) or 0.7 in. (18 mm). Fine milling drums usually have a tool spacing of 8 mm; in micro-fine milling drums the tooling space is 0.2 in. (6 mm). The ECO Cutter milling drums developed by Wirtgen are designed for maximum milling output. They can even mill extremely hard materials such as concrete or rock cost-efficiently. Cold milling machines are also frequently used to dig trenches for pipe laying or, when fitted with a deep milling unit and narrow cutting wheel, to mill slots. In short, the range of applications is immense.
Wirtgen, www.wirtgen-group.com/america