Wirtgen Group has unveiled the "Mill-Trace" intelligent profiling and control system for its W 200 Fi large-diameter cold milling machines. In highway rehabilitation, achieving a precise milling depth is critical to remove only the damaged asphalt layer without cutting into the structural base course. Traditionally, this requires setting up a physical stringline or relying on ultrasonic sensors that track the existing road surface. However, if the road surface is severely rutted, tracking the surface results in an uneven milled surface, requiring excessive amounts of new asphalt to level it during repaving.
The Mill-Trace system eliminates stringlines and surface-tracking limitations by integrating two distinct sensor arrays. The engineering core is a "Downward-Facing Ground-Penetrating Radar (GPR)" integrated into the milling rotor hood. This GPR scans the subsurface density profile up to 30 cm ahead of the cutting drum, distinguishing the dense asphalt layer from the softer aggregate base in real-time.
Coupled with a "360-Degree 3D Laser Scanner" mounted on the rear of the machine, the system builds a digital elevation model of the road. The ECU uses the GPR data to establish the exact depth of the asphalt-to-base boundary and uses the laser data to modulate the hydraulic side plates and rotor depth. The breakthrough innovation is the "Substrate Protection Algorithm." If the GPR detects a sudden thinning of the asphalt layer (e.g., a previous patch where new asphalt was laid directly over the base), the system automatically raises the milling drum by 5 mm in that specific zone to prevent gouging the base material. Furthermore, the system features "Micro-Texture Smoothing." Instead of rigidly holding a flat plane, the system allows minute variations in depth (±2mm) to follow the structural contours of the road, preventing the creation of shear planes that cause delamination. This single-pass precision milling reduces milling time by 30% and cuts new asphalt overlay material costs by 18%.
