Design and Development of a Shape Measurement System for 3D Construction Printing with a Manipulator (2024-10)¶

We describe a 3D construction printing system comprising an industrial robot with a six-degrees-of-freedom manipulator and a pump that supplies mortar. Printing is realized by linking the manipulator to the pump. To measure and evaluate printed object shapes, we attached a time-of-flight camera with ±2-mm measurement accuracy to an end effector mounted on the manipulator, thereby acquiring point-cloud data for printed objects. Using software developed to control the manipulator, and an open-source robotics middleware suite as the robot operating system, we merge the obtained point clouds. After printing mortar objects, we use the developed system to measure their shapes. Experimental results show that point clouds for printed objects have errors of 0 to 10 mm, while data from a conventional stationary 3D laser scanner has measurement accuracy of ±1 mm. Although merged point clouds show increased errors, measurement times decreased to approximately one-sixth those of conventional scanners. The increased error is likely due to factors such as the manipulator’s weight and its installation at the end effector and the sensor. We use a total station to measure deflections to confirm the manipulator’s positioning accuracy.