Stone mining with the diamond wire saw machine:
Basic information about the quarry:
1.1 Basic information about the stone in the quarry (provided by the client)
1.2 Current basic mining conditions of the quarry (provided by the client)
Advantages of diamond bead wire saw in stone mining:
Compared to traditional mining methods, using the wire saw has the following advantages:
(1) Wide adaptability: The wire saw is suitable for all types of quarries.
(2) Powerful and efficient: It allows for deep cutting up to 10-20 meters or even deeper, compared to conventional mining, which is generally limited to 10 meters or less. The cutting speed is also faster, typically 4-5 m2/h, which is 2-3 times faster than conventional cutting.
(3) Capable of cutting in various directions: The wire saw can perform vertical, horizontal, and inclined cutting, as well as blind cutting.
(4) High yield and low overall cost: The wire saw produces very smooth and non-damaging cutting surfaces, and the saw kerf is small (about 11mm), reducing resource waste.
(5) Safety and environmental friendly: The wire sawing process is noise-free and dust-free, with a high level of automation and low labor intensity for workers. In contrast, conventional cutting generates a lot of noise and dust, with higher labor intensity and lower safety.
Brief description of the diamond bead wire saw cutting process:
3.1 Requirements for infrastructure during wire sawing
Power supply: The wire saw machine, air compressor, multifunctional rock drilling machine, down-the-hole drill, etc., all require a power supply of 380V. The power consumption will depend on the number of machines used. For example, for a 37KW wire saw machine and associated equipment, the total power requirement should be around 60KW. For larger-scale operations, a 100KVA transformer can be added. In the initial stages to save investment, a diesel generator can be used for power supply.
Water source and supply capacity: Cooling water is required during wire sawing to protect the wire saw and the machine. The water consumption will depend on the number of machines used. Each wire saw machine requires around 0.5-1 ton of cooling water per hour. Adequate water source and supply capacity should be ensured. If possible, a recirculating water system can be set up to ensure a continuous water supply.
Accessible roads: The quarry must have an accessible road for transportation of various mining equipment and stone materials, with the capacity to accommodate trucks with a load of 20 tons or more.
3.2 Stone cutting process with the diamond bead wire saw:
3.2.1 Preparatory work:
Stripping the mountain: Remove the overlying soil, weathered layers, interlayers, and surrounding rocks that have no mining value to expose the stone deposit and prepare for mining. Special attention should be paid to the protection of the stone deposit, and blasting vibrations that may affect the integrity and blockiness of the stone should be avoided.
Constructing the working platform: After the stone is exposed, an appropriate working platform suitable for the wire saw machine needs to be excavated. The width of the platform is generally about 6 meters, and the length depends on the topography of the mountain. The height of the mining benches should be between 5 to 10 meters. Drilling and expansive agent methods can be used for excavation, while granite can be excavated using blasting if the slope is relatively gentle.
3.2.2 Pre-mining preparations:
(1) Drilling: Drilling is a crucial preparatory work, and if not done properly, it can directly affect the threading of the diamond bead rope, the service life of the rope, and the cutting efficiency. To cut a large block, three holes are required, including one vertical hole and two horizontal holes intersecting each other. If the three holes do not intersect at one point, it will complicate the threading of the diamond bead rope, and it may not be able to pass through, requiring re-drilling, thus reducing production efficiency. Therefore, drilling must be carried out according to the operating procedures and actual conditions. Drilling equipment can include multifunctional rock drilling machines, down-the-hole drills, manual rock drilling machines, etc.
(2) Threading: The manual threading method is used, where one end of the rope is fixed to a thin steel wire rope, and the other end of the thin steel wire rope is connected to a multi-strand soft line (usually used as a hoisting line). The diamond bead rope is threaded into the vertical hole and pulled out from the horizontal hole using a metal hook, and then the thin steel wire rope is pulled out with the diamond bead rope.
(3) Wire saw machine installation: After threading, the equipment track is first laid, and the track should be parallel to the horizontal hole. The track's levelness should be measured using a leveling ruler and adjusted to meet the requirements. Then, the wire saw machine is hoisted onto the track, the rope saw is hung, and the power is connected. Due to the weight of the equipment and the need to move the equipment after cutting one surface, methods such as mast crane, forklift, loader, or excavator can be used to move the sawing machine.
(4) Water supply connection and installation of cooling water pipes: Two water pipes need to be configured—one set at the entrance hole position of the rope and the other at the exit position of the rope. The inlet position and outlet direction of the water should be constantly adjusted as the cutting progresses.
3.2.3 Stone cutting:
When using the wire saw to extract raw blocks, the horizontal plane must be cut first, followed by the vertical plane to ensure smooth cutting. Cutting the vertical plane first and then the horizontal plane can easily cause the stone to fracture, compress the diamond bead rope, and result in motor slippage and damage to the flywheel. In severe cases, the wire saw may be scrapped.
The commonly used cutting methods with the wire saw are as follows:
a) Vertical cutting method
b) Horizontal cutting method
c) 90-degree cutting method
d) Blind cutting method
Production capacity estimation, equipment, and personnel configuration:
The equipment and personnel should be configured based on the set production capacity. Since the quarry did not provide a specific production capacity target, we can only assume that one wire saw machine is the main equipment and consider the most reasonable auxiliary equipment and personnel configuration, and calculate the production capacity. If the quarry needs to increase production capacity, the required configuration can be replicated accordingly.
Using the diamond wire saw machine:
The diamond bead wire saw machine can be operated using either the circular sawing method or the downward pressure sawing method. These two methods use different equipment, operating conditions, and processes.
(1) Circular sawing method:
This method is also known as the rope sawing method. In essence, a closed loop of diamond bead wire surrounds the stone being cut. With the help of the rotation and movement of the wire saw machine, the diamond bead wire saws through the rock. The cutting curve length and radius of curvature vary from large to small. This method can be used for both cutting the working face and shaping the cut stones. It is applied independently during the cutting process.
During the cutting process, the wire saw can be used for vertical and horizontal cuts. For vertical cuts, the machine can perform cutting from a position above the machine in the horizontal direction. It can also perform cutting from a position below the machine in the horizontal direction.
The process for the circular sawing method is as follows: Drilling - Threading - Sawing
Drilling: Holes are drilled at the designated positions on the cutting face. For vertical cutting, one vertical hole and one horizontal hole that are mutually perpendicular and intersect should be drilled. The hole diameter is usually 40-70mm. Vertical holes can be drilled using a drilling machine, and horizontal holes can be drilled using a horizontal guide groove rock drilling machine. The guide groove rock drilling machine can drill holes slightly higher than the ground, and a leveling rod on the equipment can ensure accurate alignment with the vertical holes.
Threading: After the two threading holes are connected, the diamond bead wire is threaded into the vertical hole and pulled out from the horizontal hole with a metal hook to form a continuous loop. The loop is then placed on the driving wheel of the diamond wire saw machine. The diamond bead wire is stretched out to ensure that the two guide wheels are in the same plane and correctly oriented, without any deviation. Sawing: The cutting operation is performed according to the operating requirements and steps.
(2) Downward pressure sawing method:
This method is also known as the pressing rope sawing method. In essence, the diamond bead wire is driven by the driving rope wheel of the saw machine and is pressed down into the hole using a multi-purpose drilling machine or a cutting work column to achieve sawing and feeding. The cutting curve is limited by the length of the working face, and the length and radius of curvature do not vary greatly. The rock being cut is located below the diamond bead wire. This method is only suitable for cutting the working face and cannot be used for shaping cut stones.
This method must be used in conjunction with a multi-purpose drilling machine or a cutting work column. It can only perform vertical cutting.
Based on the equipment used, the following approaches can be used:
Cutting with one multi-purpose drilling machine or cutting work column: When the cutting face has a wide open area suitable for placing the diamond wire saw machine, only one hole needs to be drilled, and it can be used in conjunction with the drilling machine for cutting. (As shown in Figure 1-37) When the rock has natural bedding planes, this method is more suitable.
Cutting with two multi-purpose drilling machines or cutting work columns: When the length of the working face is sufficient and cutting needs to be done parallel to the top line of the step, two drilling machines can be used for work. In this case, the drilling machine and the wire saw machine are arranged in a straight line. If there is no ditch, two holes need to be drilled, and two drilling machines can be installed to work together. (As shown in Figure 1-38) If there is a ditch, the drilling machine (or cutting work column) can be placed in the ditch to work together.
The process for the downward pressure sawing method is as follows: Drilling - Sawing. As this method only requires drilling a vertical hole and not a horizontal hole, the threading process is not necessary.
Operating Techniques:
(1) Control of cutting curve radius:
When using the circular sawing method, the cutting curve length and radius of curvature vary from large to small, resulting in changing bending stress on the wire. The bending stress of the steel wire is related to the ratio of drum diameter (D) to wire diameter (d). When D/d is less than or equal to 60, reducing D/d will cause a sharp increase in the bending stress of the steel wire.
For the diamond bead wire, its diameter is 4-5mm. Although the flexibility and maximum bending stress of the wire have been considered in the design of the diamond wire saw machine, during the cutting process, the wire may experience significant impact stress when in contact with sharp edges and hard enclosing bodies of the rock. Especially when the cutting curve has a large radius, excessive bending of the wire can cause a rapid increase in bending stress, leading to wire breakage. After the wire breaks, five diamond beads will scatter and be lost, increasing the production cost. Therefore, controlling the cutting curve's radius is of great significance.
To address this, the following measures can be taken:
When cutting large rock masses vertically, sharp edges of the rock should be processed first. During threading, allow the wire to come out of the wire rope drum naturally and extend toward the top of the rock mass. The upper front guide wheel of the wire saw machine may not be used at this stage. During horizontal cutting, the wire will surround four sharp edges at the beginning. An additional auxiliary guide wheel can be used to open the wire and reduce the increase of bending stress on the steel wire.
When the cutting face is about 30cm away from the edge of the rock, the cutting should be stopped to prevent excessive bending stress due to the small bending radius. The initial distance between the saw machine and the working face can be used to tighten the wire rope, but excessive tension should be avoided to prevent difficulties during startup and damage to the diamond beads.
(2) Control of feed rate:
The feed rate has a significant impact on cutting efficiency and the wear rate of the wire. The feed rate is related to the linear speed of the wire rope drum and its rearward movement speed on the guide rail. The tension of the wire rope ensures the necessary pressure during cutting. While maintaining the cutting pressure, the increase in traction force of the steel wire due to the increase in cutting pressure will also increase the wire's bending stress. Excessive bending stress may lead to wire breakage. Increased traction speed of the wire rope under constant cutting pressure can improve cutting efficiency but also increase the wire's bending stress. On the contrary, if the cutting pressure is too small, the cutting efficiency will be reduced, which is also undesirable. The feed rate depends on the performance of the wire saw machine, the quality of the wire rope, and the hardness of the stone, among other factors. Different feed rates may be used at different cutting stages. Generally, at the beginning of the cutting process, the feed rate is set at 3/4 of the normal feed rate. When the depth of the saw cut reaches 100mm or more, and the cutting curve is relatively smooth, the feed rate can be increased to the normal value. The feed rate should be reduced at the end of the cutting process. During operation, closely monitor and control the instrument to keep the pressure value in the optimal state for cutting. For diamond wire saw machines with electronic automatic control, automatic control during work is reliable.
(3) Control of water supply:
Constant water supply during the cutting process is essential. In addition to washing away and removing mud from the saw cuts, the water also serves to cool the diamond wire, prolonging its service life. As diamond is composed of carbon atoms, heating can reduce its physical properties. When the temperature rises to around 950 degrees Celsius, it will be oxidized (fine diamond powder can burn to produce carbon dioxide) and lose its cutting ability. Therefore, providing an adequate amount of cooling water and ensuring proper supply are essential to improving cutting quality and reducing wire wear.
The cooling water flow should not be less than 15 liters per minute. The quality of the water is also important, and soft water without precipitates is preferred, especially for stone that can generate adhesive and abrasive mud during cutting. When adding water, the water flow should be directed into the saw cuts from the threading direction.
Maintenance and Safety:
(1) Regularly inspect the joint of the wire rope and other components for integrity. The driving rope wheel and guide rail of the wire saw should be kept clean and wiped with gasoline in a timely manner. Lubricating oil should not be used to avoid rock dust adhesion.
(2) Change the oil every four months.
(3) Regular maintenance is required, with minor repairs every six months and major repairs every two years.
