A New Test Bench System for Hammer Drills: Validation for Handle Vibration

Abstract

Workers' can be exposed to high levels of hand vibration when drilling into concrete or rock using hammer drills; exposures that can cause hand arm vibration syndrome. Exposure levels may be reduced by different drill and bit designs and drilling methods, but these interventions have not been systematically evaluated. The purpose of this project was to develop a robotic test bench system for measuring handle vibration on drills in order to compare differences in drill designs, power sources, bit designs and drilling methods. The test bench is a departure from the ISO method for measuring drill handle vibration (ISO 28927-10), which requires drilling by humans. The test bench system was designed to repeatedly drill into concrete blocks under force control while productivity and handle vibration were measured. Handle vibration levels with different drills and bit sizes were similar to those collected following ISO methods. A new robotic test bench system for measuring handle vibration is presented and validated against ISO methods and demonstrates dynamic properties similar to human drilling.

Keywords: Hand-Arm-Vibration Syndrome; Musculoskeletal Disorders; Occupational Health; Tool Design; Vibration.

Figure 1

Manual drilling with pneumatic rock drill for structural work.

Figure 2

Drawing of test bench system and corresponding mechanical mass-spring model with a hammer drill (a). The drill handle is clamped to a fixture (c) with rubber-foam between the clamp and the handle. The chuck rests on a rubber-foam support. In the model, m1 includes plate d, vertical bar b, and fixture c; k2, m2 and c2 are the rubber-foam interface. The stiff spring is k1; dampener c1 is the friction between d and f. The linear actuator (g) drives the whole assembly toward the concrete block.

Figure 3

Test bench system with a Hilti TE7 drill. Drill handle is secured to a vertical bar with hose clamps with rubber-foam between the clamps and handle. After each hole is drilled the concrete block is released and the block is advanced and secured for the next hole. The mannequin is located above the linear actuator and is positioned for noise and dust sampling.