Linear cutting of Helidon sandstone was conducted to investigate the effect of pick geometries and pick orientations on pick performance, using a conical pick (C1) and a pyramid pick with different orientations (P1: a pyramidal surface in parallel with the rock surface to cut; and P3: a pyramidal surface in 45 degrees with the rock surface to cut). It was found that the pyramid pick P1 can produce the largest fragments and consumes the least specific energy. With increasing the depth of cut, the specific energy decreases for all picks. It was also found that in all the cases there is a critical speed of cut at which the specific energy is minimal. The study concluded that pick profile does affect the pick cutting performance and that P1 is the most desirable orientation.
Pointed picks have been widely used in the mechanical excavation of rocks, where the performance of a pick is often assessed by the specific energy consumed. It was reported that the coarseness of the chips is descendingly related to the specific energy [1]. Investigations based on linear rock cutting tests revealed that the texture coefficient and feldspar content of sandstones influenced the rock cuttability and the assessment by specific energy is highly reliable [2]. It has been demonstrated [3] that when using conical picks, changing the included angle of the pick could improve the cutting efficiency or cutting performance in terms of pick life, dust generation and energy consumptions. A comparable experimental study with sharp and blunt picks [4] showed that dust generation could be related to specific energy. However, the previous studies have been on the cutting conditions using conical picks with different included angles [3]. The aim of this paper is to investigate the geometry and orientation effect involving both pyramidal and conical picks [5-6].
Fig.1 shows the experimental setup of the linear cutting tests. A pick was held static, while the rock sample fixed on the machine table approached the pick horizontally to realize the cutting. The cutting forces were measured by the dynamometers attached to the pick holder. Two types of cutting picks were used, which are conical (C1) and pyramid (P1 and P3). Picks P1 and P3 have the same geometry and dimensions but their orientations relative to the rock sample surface were different, as illustrated in Fig.2, where P1 had a pyramidal surface in parallel with the rock surface to cut (see section B-B) and P3 had its pyramidal surfaces in 45 degrees with the rock surface to cut (see section C-C). The rock sample for the tests was Helidon sandstone from a local quarry in Brisbane Australia whose dimensions were Length × Width × Height = 1700mm × 450mm × 450mm. Some properties of the sandstone are listed in Table 1 below.
Fig.3 schematically illustrates the cutting process, where ? stands for the half included angle of a pick, a is the angle of attack, ß is the clearance angle and h is the depth of cut. ,
