Cutting head (mining)

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Cross cutting heads on a TSM
Longitudinal cutting head on the front of a TSM

A cutting head is a mining tool with which the working face is machined during the mechanical drive-up of the road . In order to be able to carry out the cutting work, the cutting heads are equipped with cutting chisels. Cutting heads are used on circumferential milling machines such as roadheaders or continuous miners . They are also used on the drilling unit of manhole lowering systems .

construction

There are two types of cutting heads, transverse cutting heads and longitudinal cutting heads. Cross cutting heads have a cylindrical geometry. The cutting heads are attached to the side of the machine's boom so that they rotate axially across the direction of advance. Rip heads are mounted on the top of the boom in front of the head and move radially around the boom. The axis of rotation for longitudinal cutting heads is orthogonal to the swivel direction. Chisel pockets are welded to the cutting heads at a certain distance. These chisel pockets are used to hold the cutting chisels. The chisel pockets are designed so that the chisels can rotate in the chisel pocket. The chisel pockets are welded to the cutting head in such a way that the cutting bits are held at a certain angle. In the case of cross cutting heads, the wear of the chisel tips can be minimized by setting the angle of attack to the axis of rotation accordingly. The cutting heads are equipped with an internal nozzle to cool the chisel tips and to combat dust. Here, a water pump is used to pump water through channels in the chisels.

Cutting chisel

There are different types of chisels that have to be matched to the respective type of rock. Flat chisels or round chisels are used on partial headers. Continuous miners are usually equipped with pointed chisels or with truncated cone chisels. All chisels are equipped with a carbide tip. Flat and round chisels are used for rock with low strength. Pointed chisels have a cylindrical chisel shaft and a conical chisel point. Truncated cone chisels have a similar shank to pointed chisels, but the chisel tip has a circular, concave surface. They have a longer service life than pointed chisels.

Working method

Due to the concentric movement of the cutting head, grooves are cut in the rock and the remaining rock ribs are then broken away by so-called displacers. In the case of cross cutting heads, due to the cylindrical geometry of the cutting heads, steps are cut into the joints when cutting the rock. The machine must be moved so that these stages can be eliminated again. The debris in front of the machine is transported onto the loading table by the rotation of the cutting heads. Longitudinal cutting heads have a conical shape with cutting bits arranged in a spiral. With longitudinal cutting heads, a flat cutting profile can be created in the area of ​​the ridges and joints . Longitudinal cutting heads do not throw the separated rock directly onto the machine's loading table, but onto the bottom .

Tool wear

Depending on the load, the cutting heads and, in particular, the chisels will wear out accordingly. The degree of wear of the chisels depends on the abrasiveness of the rock to be cut, the strength of the chisel material, the quality of the materials and the service life of the tools. With certain types of rock, e.g. B. clay or silt, it comes in connection with water that the cutting head sticks to the rock mass. As a result, the chisels can no longer rotate in the chisel pocket and are worn on one side. This leads to one-sided wear and thus to premature failure of the chisel. Depending on the respective load, there is abrasive wear, wear due to brittle fracture or thermal wear. The abrasive wear occurs due to the sliding contact between the rock surface and the tool. This leads to a continuous material removal. Brittle fractures are caused by high stresses with impact loads. Thermal wear is caused by high temperatures. There are also forms of wear due to contact between the tool surface and intermediate materials such as flushing media in combination with substances carried along.

Explosion protection

In the underground area , escaping mine gas in connection with the formation of sparks during the cutting process can ignite the mine gas and lead to other consequences such as a firedamp explosion . In order to dilute the methane emissions that occur, additional ventilation measures must be taken in the area of ​​the cutting heads. This can be achieved using additional air nozzles, air / water jets and jet blocks. In the area of ​​the face, the methane content of the weather must be recorded and evaluated. If certain limit values ​​are exceeded, the cutting heads may no longer be operated. Appropriate spray systems must be used to cool the cutting heads.

Individual evidence

  1. ↑ a b c d e Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7
  2. ↑ a b c d e f g Eric Drüppel: Development of a concept for the cutting extraction in rock salt. Dissertation 2010, Rheinisch-Westfälische Technische Hochschule Aachen
  3. ^ Heinrich Otto Buja: Engineering handbook mining technology, deposits and extraction technology. 1st edition, Beuth Verlag GmbH Berlin-Vienna-Zurich, Berlin 2013, ISBN 978-3-410-22618-5 , pp. 254-256.
  4. ^ A b c Heinz M. Hiersig (Ed.): VDI-Lexikon Maschinenbau. VDI-Verlag GmbH, Düsseldorf 1995, ISBN 9783540621331
  5. ↑ a b c d e Maxim Vorona: Optimization of the cutting process and prognosis of the relevant working parameters when destroying rock, taking into account the bit wear. Dissertation 2012, Technical University Bergakademie Freiberg
  6. ↑ a b c d e Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1
  7. ↑ a b c d Klaus Eichler: Rock and tunnel construction. Expert Verlag, Renningen-Malmsheim 2000, ISBN 3-8169-1741-0
  8. ↑ a b Friedrich Brune: Experience with the use of a roadheading machine in Tübingen. In: Deilmann-Haniel GmbH. (Ed.): Our company, company magazine for the companies of the Deilmann-Haniel Group. No. 14, printed by A. Heilendorn (Bentheim), Dortmund September 1974, pp. 24-28
  9. ↑ a b c d e f g Kurosch Thuro: Geological-rock-mechanical basics of the rock solution in tunnel construction. Habilitation thesis 2002, ETH Zurich, ISSN  1430-5674
  10. ↑ Horst Roschlau, Wolfram Heintze: Bergmaschinentechnik. VEB German publishing house for basic industry, Leipzig 1977
  11. ↑ a b Gerhard Girmscheid: Construction and construction in tunnel construction. Ernst & Sohn Verlag for Architecture and Technical Sciences GmbH and Co.KG., Berlin 2008, ISBN 978-3-433-01852-1

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