RU2044645C1 - Method to produce cylindrical pieces from stone blocks - Google Patents

Abstract

FIELD: stone-working and pulp and paper industries. SUBSTANCE: method is used for production of large size lengthened pieces, made of blocks of stone, for example, granite blanks of press shafts for paper-making machines or columns. Using boring diamond crown they drill in stone blocks holes, corresponding outer diameter of the crown with depth that corresponds given length of piece and simultaneous creation of cylindrical form of the piece. In the case process of working is exercised with mechanical speed of 0.2 0.25 m/h and rate of crown rotation of 100-130 turns per minute. EFFECT: increased efficiency. 1 dwg, 1 tbl

Description

 The invention relates to stone processing, pulp and paper and mining, and is intended for the manufacture of large long cylindrical products, in particular granite press rolls for paper machines.

 It is known that the quality of paper largely depends on the material of which the press roll is made, the purity of processing of its outer surface, and also on the accuracy of its geometry.

In this regard, strict technological requirements are imposed on the press shafts, providing:
a) the correct cylindrical shape with an allowance of not more than 5-10 mm per diameter;
b) smoothly polished outer surface with a purity of processing 7-8 accuracy class;
c) the possibility of processing and polishing the surface of the shaft;
d) good water absorption of the material from which the shaft is made;
d) high wear resistance of the shaft, depending on the hardness of the material.

 All these requirements are best met by granite.

 A known method of manufacturing cylindrical products from a stone block using a hollow core drill with a diamond crown, which consists in the fact that a shaft with a diameter corresponding to the internal diameter of the diamond crown and a depth corresponding to a given length of the product is drilled in the stone block, while simultaneously drilling shaft carry out processing of its outer surface.

 This method does not provide the specified surface finish of the resulting shaft.

 For this, the process of drilling a shaft from a block of stone is carried out at a feed rate of a drill of 0.2-0.25 m / h and with a rotational speed of the drill of 100-130 rpm.

 In the manufacture of products with a rotation frequency of less than 100 rpm and a drill feed speed below 0.2 m / h, the contact time of diamond cutters with the outer surface of the product increases, which leads to a significant reduction in the diameter of the product beyond the allowable parameters.

 With an increase in the rotational speed above 130 rpm and a mechanical speed above 0.25 m / h, vibration of the drill string appears. As a result of this, deep furrows appear on the outer surface of the product, reducing the surface finish and the quality of the product.

 The drawing shows a device for implementing the proposed method.

 The granite blanks of the press shafts of paper machines were manufactured in bench conditions using a device that included a drilling rig 1 with a lead pipe 2 and a projectile 3 consisting of a core pipe 4 equipped with a diamond crown 5 with an outer diameter of 634 mm and an inner diameter of 606 mm.

 The device is equipped with removable ball-bearing lunettes 6, installed with the possibility of interaction with the outer surface of the core pipe 4 and mounted on the container 7 with a granite block 9. The container 7 is fixed in the pit 10 using spacers 8. The length of the core pipe 4 corresponds to the length of the shaft being manufactured and is 3 , 0 m.

 Preparation for work and the work of the projectile was carried out as follows.

 The lead pipe 2 was connected to the projectile 3, the core tube 4 was centered at the mouth of the granite block using lunettes 6, and using an external trigger mechanism, it was lowered onto a pre-centered and leveled granite block 30. Deviation of the axis of the projectile 3 from the center of the granite block 30 when installing it on the upper concrete cushion was 9 mm, which corresponds to the permissible. The NB-3 mud pump was turned on, the rotator and the process of drilling the billet of the press shaft from the granite block began.

 Drill bit 5, rotating together with pipe 4, destroyed the outer surface of granite by drilling a hole to a depth corresponding to the length of the shaft blank. At the same time as the hole was drilled, a cylindrical core was formed in the granite block 30, i.e. the shaft itself, the outer surface of which during its manufacturing was polished with a diamond crown 5.

 Process water and cutting fluid (coolant) supplied by the NB-3 pump (not shown) were used as flushing fluid.

To determine the most optimal modes of drilling a shaft blank, the process was carried out in several modes:
1. Drilling began at a rotational speed of 90 rpm, a mechanical speed of 0.15 m / h and an axial load of 1000 kgf. The flow rate of the flushing fluid was 120 l / min. Drilled 240 mm of granite.

 2. Drilling was carried out with a rotation speed of 100 rpm, a mechanical speed of 0.2 m / h with an axial load of 1000 kgf and a coolant flow rate of 120 l / min. Drilled 1000 mm of granite.

 3. Drilling was carried out with a rotation speed of 120 rpm, a mechanical speed of 0.23 m / h, an axial load of 1000 kgf and a coolant flow rate of 120 l / min. 1880 mm drilled.

 4. Drilling was carried out with a rotation speed of 130 rpm, a mechanical speed of 0.25 m / h, an axial load of 1000 kgf and the same coolant flow rate of 120 l / min. 2480 mm drilled.

 5. Drilling was carried out with a rotational speed of the projectile of 150 rpm, a mechanical speed of 0.3 m / h. A 3000 mm shaft is drilled.

 The shaft was removed from the container and a study was made of its outer surface for compliance with a given diameter and cleanliness of processing.

 The research results are summarized in table.

 The table shows that the best conditions for drilling the shaft, as well as the cleanliness of the processing of its outer surface are carried out within the values of the mechanical velocity of the projectile 0.2-0.25 m / h and a rotation frequency of 100-120 rpm. Significantly worse shaft parameters are found beyond the specified limits. By reducing the speed to 0.15 m / h and the rotational speed to 90 rpm, the contact time of diamond cutters with the shaft surface increases. In this regard, the shaft diameter is reduced to 590.17 mm, which is beyond the permissible 10 mm, with an inner diameter of the crown of 606 mm, since a depression appears on the surface of the shaft. At the same time, at a rotation speed of 150 rpm and a mechanical speed of 0.30 m / h as a result of projectile vibrations, the shaft surface becomes uneven, wavy, which also leads to a decrease in the shaft diameter, but its value lies within the permissible parameters.

 Thus, through the use of the proposed method, it was possible to significantly improve the manufacturing quality of the granite shaft by increasing the frequency of its processing in comparison with the prototype.

Claims (1)

 METHOD FOR PRODUCING CYLINDRICAL PRODUCTS FROM A STONE BLOCK using a hollow core drill with a diamond crown, which consists in drilling a shaft in a stone block with a diameter corresponding to the inner diameter of the diamond crown and to a depth corresponding to a given length of the product, while simultaneously drilling the shaft carry out the processing of its outer surface, characterized in that the process of drilling a shaft from a block of stone is carried out at a feed rate of a drill of 0.2 0.25 m / h and a rotational speed of order 100 130 rpm

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