Is UHPC Panel Drilling Prone to Cracking? — Key Crack-Prevention Techniques in the Drilling Process

Drilling UHPC panels does carry a risk of cracking, but this risk can be completely avoided through scientific process control. Based on 28 years of processing experience, Qinglong Group has found that cracking mainly occurs when the hole diameter is too small, the feed rate is too fast, or cooling is insufficient. By optimizing drill bit selection, machining parameters, and cooling methods, the cracking rate can be kept below 0.1%.

Drill bit selection is the foundation of crack prevention. Diamond thin-wall drill bits are preferred, with a diamond grit size of 50/60 mesh and a concentration of 75%, to ensure sharp cutting. Testing by Qinglong Group in a Shenzhen project found that cutting force is minimized when the drill bit lip angle is 15°-20°. For panels thicker than 30mm, stepped drill bits are used to enlarge holes in stages, avoiding stress concentration from single-step forming. The ratio of drill bit diameter to panel thickness is kept within 1:3; for example, a 20mm-thick panel requires a minimum hole diameter of ≥6mm.

Machining parameters are precisely controlled: feed rate of 0.5-1mm/s and rotation speed of 800-1200rpm. In a Hainan project, Qinglong Group used CNC drilling machines equipped with pressure sensors to monitor cutting force in real time, with automatic adjustment when pressure exceeds the set value (e.g., 200N). A cooling system is indispensable; water cooling is used with a flow rate of ≥5L/min to keep the temperature below 60°C. After machining, hole edges are chamfered by 0.5mm to eliminate micro-cracks.

Reinforced areas are pre-treated. A backing plate is attached to the back of drilling positions to prevent exit-edge chipping. For dense hole groups, a skip-drilling process is adopted with intervals of ≥30 seconds to avoid heat accumulation. Through these measures, Qinglong Group has achieved zero cracking in the drilling of thousands of square meters of UHPC panels.