For the extraction of medium hard rock cutting machines such as road headers, continuous miners or longwall shearers are often used. The defining parts of these machines are one or more rotary drums equipped with picks. While the picks are in interaction with the rock they emit a wide variety of physical effects like vibration, transient shock emissions, infrared emission, or others which can be analyzed to derive present machine parameters, present tool conditions as well as properties of the material actually being cut.

The objective of the present paper is an analysis of these emissions investigating if and how they can be used for status monitoring of the cutting process under laboratory as well as under real conditions. In this case, real conditions refer primarily to cutting speed and cutting forces.

1 Introduction

The automation of mining machinery is a major task in the modern mining industry in order to increase safety and productivity. In many industrial branches partially or fully automated machines and processes are common and lead to highly efficient operations. The mining industry is facing difficulties due to the rough conditions in the mining environment, and, therefore, high demands on machine safety are formulated.

Extraction machines like road-headers, continuous miners or long wall shearers are often used to extract coal, salt or ore. The cutting process is of special interest because its optimization and monitoring are the key factors for minimizing the energy input and maximizing the equipment durability. Especially to be emphasized as a major task are the material identification and the condition monitoring of cutting tools. Material identification or "boundary layer detection" is fundamental for a highly automated machine. Sharp picks are vital for effective cutting. Worn or even damaged picks cause higher cutting forces, increase airborne dust and decrease the cutting efficiency. Additionally, they can lead to tool holder damage and drum damage.

Depending on the cutting conditions encountered in the mine, different types of picks can be used. The conventional chisel pick is used in coal ploughs. Most modern extraction machines use point-attack type picks. The point-attack pick is renowned for being robust and hard wearing since it is self-sharpening. Shearer loaders or continuous miners are equipped with cutter drums. The cutting drums rotate about a horizontal axis and are equipped with point-attack picks. As the drum rotates, the picks start to cut with zero depth of cut as they enter the coal at roof or floor, and the depth of cut increases to a maximum at mid-drum level and then decreases until the pick exits at zero depth of cut.

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