Kalmar has introduced the "Spreader-3D" load center mapping system for its DRG450 series heavy reach stackers. In busy port and rail terminals, reach stackers handle 40-ton shipping containers. While the external dimensions of a container are fixed, the internal center of gravity (CG) is entirely unknown. If a 40-ton container is loaded with heavy steel coils at the far door end, the CG is offset by up to 1.5 meters from the container's geometric center. When the reach stacker extends the boom to place this container on the top row of a stack, the offset CG causes a massive lateral and longitudinal tipping moment that can flip the 80-ton machine.
The Spreader-3D system integrates a "Ground-Penetrating Radar Array" into the spreader twist-lock housing. The engineering breakthrough is the "Density and CG Tomography." When the spreader locks onto the container, the radar emits a low-frequency pulse that penetrates the steel container walls and reflects off the internal cargo. By analyzing the reflection coefficients, the system calculates the mass distribution along the length of the container and locates the exact longitudinal and lateral CG.
If the CG is offset by more than 500 millimeters, the system engages "Dynamic Suspension Pre-Load." The ECU commands the reach stacker's rear oscillating axle lock to engage, freezing the chassis. Simultaneously, the hydraulic suspension cylinders on the heavy front drive axle increase their pre-load pressure by 30% to counter the tipping moment. Furthermore, the system automatically limits the boom extension speed. If the operator attempts to extend the boom beyond the safe CG envelope for that specific container, the system halts the boom extension and commands the operator to re-orient the container. This 3D payload mapping eliminates the blind-lift tip-over risk and allows operators to safely handle eccentrically loaded containers at maximum reach, increasing terminal stacking density by 15%.
