Is Drilling UHPC Panels Prone to Cracking? An Analysis of Brittleness Control and Precision Cutting Techniques

Due to UHPC's extremely high density and brittleness, post-machining operations such as drilling and cutting do indeed carry a risk of edge chipping or micro-cracking if not handled properly. This risk mainly stems from localized stress concentration and thermal damage caused by high-speed friction. However, through 28 years of process accumulation, Qinglong Group has developed a mature machining control system that keeps the cracking risk close to zero. Our core strategies are: "specialized tooling, low-speed cooling, and pre-reinforcement," ensuring that every machining operation is precise and damage-free.

Tool selection is the first line of defense against cracking. Given UHPC's high hardness (Mohs hardness can reach 6-7), diamond-coated drill bits, saw blades, or waterjets must be used. For example, for hole drilling, we use impregnated diamond thin-wall core bits, in which the diamond particles are evenly distributed throughout the bit matrix; as they grind the UHPC, they wear down slowly themselves, always maintaining a sharp cutting surface. We strictly prohibit the use of ordinary carbide tools, as they dull easily and can induce impact stress within the material. In waterjet cutting, we use ultra-high-pressure water flow (above 380MPa) mixed with fine-grain garnet sand to achieve "cold" cutting, completely eliminating thermal stress.

Precise control of machining parameters is the second line of defense. When drilling, we follow the principle of "low speed, gradual feed, and continuous cooling." The drill speed is typically controlled at 500-800 rpm, the feed rate is kept stable, and coolant (usually a water-based solution) is continuously applied to flush the drill bit and hole wall, reducing friction temperature and carrying away debris. For example, when installing undercut anchors for a large UHPC curtain wall project, we machined tens of thousands of installation holes using CNC drilling machines with preset parameters, without a single case of edge chipping. For cutting, the peripheral speed of circular saws must be precisely controlled, and dedicated clamps are used to reduce panel vibration.

For particularly thin panels (e.g., ≤20mm) or those with complex shapes, we perform local reinforcement treatment on the designated areas before machining, or reserve hole and cutout positions in low-stress areas of the panel at the design stage. In the production of large UHPC openwork screens for a project in Shenzhen, all the intricate hollow-out patterns were cut in a single pass in the factory using CNC waterjets, with smooth edges and no chipping whatsoever—thanks to earlier optimization simulations of panel fixing methods and cutting paths. Therefore, as long as scientific principles of material properties and machining processes are followed, drilling and cutting UHPC panels can be both highly efficient and completely damage-free.