Helicoidal saw
The helicoidal saw , also known as a wire rope saw , is a tool that is used to extract rough blocks in quarries. It is a special form of wire saw .
Definition of terms
The name comes from the Greek word helix for a twist or spiral. This describes the special functionality, the continuous, endless rope. A helicoid is a spiral line in geometry.
Foreign language terms are: engl. helicoidal wire saw , French fil hélicoïdal or Italian filo elicoidale .
functionality
Based on the wire saw principle, a steel cable up to 1,500 m long is moved by an electric motor over a special pulley system. The modern diamond wire saw in the natural stone industry is a technological modification of this functional principle and is used in block extraction with a favorable cost-benefit ratio. The difference to the diamond wire is that the steel wires of the helicoidal saw do not have any diamond segments and in the narrower sense are actually not a sawing tool, but a transport system for the sawing elements. For this purpose, when this saw is in operation, a mixture of quartz sand (occasionally also silicon carbide) and water is fed into the sawing zone at the entry point of the rope in the mining front. The moving rope pulls this water-sand mixture through the sawing zone in the rock. In this way, a saw cut is created which, depending on the “hardness”, i.e. the mineral composition of the rock, can be more or less time-consuming.
The positioning of the pulleys is necessary for the correct guidance of the rope to and in the holes. It also ensures that the rope can be fed into the quarry from a central drive station without hindering further activities and transport movements. For this reason it is necessary to set up pulleys on raised points in the quarry. This also enables the simultaneous operation of several sawing points with a single drive. In the immediate area of the sawing zone, pulleys are mounted on a support frame (feed controller) so that the advance is secured in a forced direction. These saw stands with pulley also enable the continuous height or depth offset of the running rope.
Depending on the rock and the quality of the abrasive (quartz sand and other materials), an hourly cutting depth of 5 to 30 cm can be achieved.
Requirements for operation
The following materials, preparatory work and facilities are essential for operating a helicoidal saw:
- sufficient stocks of water and quartz sand (abrasive)
- oblong holes drilled in the rock at right angles to each other
- a sophisticated system of deflection rollers with clamping parts (clamping carriage) and support elements (feed regulator)
- a powerful drive unit
The elongated holes in the rock are drilled with carbide-tipped drills or core drilling tools, depending on the required diameter. The position of these holes determines the size of the raw blocks to be extracted. The rope is inserted through these holes before the sawing work begins and its ends are screwed together at the end.
In addition, specific safety regulations must be observed when operating helicoidal saws, as considerable forces are released when taut ropes are torn and the rope ends whipping around in an uncontrolled manner can have a destructive effect.
history
Since ancient times , useful rock has been extracted in quarries by mechanical handwork and various blasting techniques ( fire setting and explosives). The helicoid saw developed in the course of the gradual mechanization of natural stone mining in the 19th century.
The negative effects of blasting techniques were recognized early on, which, depending on the intensity, produced cracks of different lengths in the rock, which turned out to be very harmful for further processing.
Until the 19th century, natural stone was extracted by means of manual drilling, wedge and cutting work. These methods are very laborious and time consuming. It was not until the manufacture of tear-resistant steel cables and the development of modern drive technologies that helicoidal saws were used in quarries. The principle of this sawing technique is still old and the use of the gate is very obvious. It has been practiced for centuries in small workshops using hand-operated thread saws. Small stone workpieces were divided by the pendulum movement of a relatively resistant tendon. Various grain sizes of very hard minerals (mostly emery made from corundum powder) were used as sawmill.
In 1854, the French engineer Eugène Chevalier developed the wire saw for cutting stone. The same invention was made in 1854 by Georges Hermann, about the progress of which nothing is known. The helicoid saw was improved around 1880 by the Belgian engineers Paulin Gay and Michel Thonar. Today (2008) the rope consists of three wires of particularly resilient steel. The overall diameter is often 6 mm.
But mainly Pellegrini in Sant'Ambrogio di Valpolicella , the Veronese marble quarrying area , made outstanding contributions to the development of the helicoidal saw . For this reason, the colloquial and internationally common term Pellegrini saw has established itself for a long time .
In the most recent epoch, since 1977, the use of this saw has declined because diamond wire saws are being used more and more frequently in quarries. With the first saws with diamond wires, their cutting performance was 2 to 3 square meters in marble and today it is 12 to 15 square meters per hour. Furthermore, the technical effort involved in sawing is lower.
literature
- Franco Cucchi, Santo Gerdol et al .: The natural stone from the Trieste Karst. Camera di Commercio Industria Artigianato e Agricoltura, Trieste 1989
- M. Darras: La Marbrerie . Dunod et Pinat, Paris 1912
- Raymond Perrier: Les roches ornementales . Ternay 2004, ISBN 2-9508992-6-9
- Richard Thiele: Stone carving in architecture . Fachbuchverlag, Leipzig 1957
Web links
- Description of the helicoid saw (French)
- Use of the helicoid saw in the Carrara region (French)
Individual evidence
- ↑ Stone . Magazine for stone. No. 01/2009, p. 53