Hand-drawn digital fabrication: calibrating a visual communication method for robotic on-site fabrication.

According to the 2016 Mckinsey report, the global construction industry is one of the least productive (The Construction Productivity Imperative, McKinsey Report, 2016), which can be attributed to a minimal implementation of digital and automation technology (Berger Digtization in the Construction industry-Building Europe's road to "Construction 4.0 THINK/ACT-BEYOND MAINSTREAM, 2015). This research argues that this relates to the skill base of construction workers since very few, if any, can operate digital fabrication systems. Here, a digital model is considered foundational knowledge and is used to communicate with a fabrication unit. The difficulty lies in communicating the digital model to the fabrication machine, which arguably requires a level of specialist knowledge. However, history shows that other methods of communicating complex construction information have existed, such as 1:1 on-site drawing, which used to be made by architects or construction workers to communicate complex information related to constructing jigs or building components (The Tracing Floor of York Minster." In Studies in the History of Civil Engineering, 1:81-86. The Engineering of Medieval Cathedrals. Routledge, 1997). We propose an alternative where we learn from history and amalgamate that knowledge with a robotic framework. We present the calibration process behind a parametric visual feedback method for robotic fabrication that detects on-object hand-drawn markings and allows us to assign digital information to detected markings. The technique is demonstrated through a 1:2 prototype that is fabricated using an ABB IRB 120 robot arm.