In this article, we will explore the stone slab manufacturing process, detailing the procedures and methods in stone extraction and processing.
Stone Extraction
The raw materials used for processing decorative stone are rectangular stone blocks with specific dimensions, commonly known as rough blocks. Traditionally, these rough blocks were extracted from stone quarries using manual methods, now the process has largely transitioned to mechanization.
Process flow
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Raw rock separation: drilling and blasting, mechanical separation;
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Block processing: cutting and shaping;
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Lifting and transporting;
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Stacking at the storage area;
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Waste removal.
Extraction methods
Due to variations in geological conditions, stone types, and the degree of mechanization in quarries, diverse mining techniques and processes have developed. Each stone extraction method possesses distinct characteristics, and the primary techniques for extracting stone can be categorized into five types:
Splitting
This method involves using basic tools or machinery to separate the stone from the parent rock. There are two primary types: manual splitting and hydraulic splitting.
Blasting
This technique employs controlled blasting principles, utilizing various explosives and ignition methods to separate stone from the parent rock. A key feature of this method is that the extracted stone does not produce blast fractures, ensuring that the yield of rough blocks is not compromised by the blasting process. There are four types of blasting methods:
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Black powder blasting
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Metal fuel blasting
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Detonating cord blasting
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Static (silent) blasting
Mechanical sawing
This method primarily employs stone saw machines, complemented by other specialized extraction tools. Depending on the type and technical capabilities of the saw machines, sawing can be categorized into four types:
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Wire saw machine
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Diamond wire saw machine
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Chain saw machine
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Circular saw machine
Jet cutting
This technique utilizes thermal or hydraulic energy for cutting. It employs flame cutting machines or high-pressure water jet cutting machines.
Methods combined
This method involves utilizing two or more extraction methods. It is uncommon to rely on a single method for the stone extraction process, as different sections of the same rock body may exhibit varying characteristics. Even within the same section, the extraction method may differ depending on the specific part being extracted. For example, flame cutting machines are primarily used for vertical cuts and are rarely employed for horizontal extraction. The combination of methods can vary based on the specific conditions of the quarry, including:
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Diamond wire saw combined with splitting or blasting.
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Wire saw combined with blasting.
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Diamond wire saw combined with chain saw or circular saw machines.
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Jet cutting combined with splitting or blasting.
Stone Processing
Stone processing refers to the process of transporting rough stone blocks to a processing factory and transforming them into finished stone products. This process can be broadly divided into three main steps: rough block sawing, slab grinding and polishing, and cutting the finished products.
Sawing rough block
Rough block sawing involves securing the rough block on a workbench, which then moves beneath a circular saw machine, frame saw, or diamond wire saw. The saw machine either rotates the circular saw blade or reciprocates the saw wire to cut through the rough block.
Circular saw machine: This machine features a circular blade with alloy blocks embedded with diamond particles along the outer edge. The blade is mounted on a spindle and driven by a motor, enabling it to rotate in circular movements. The diamond segments on the edge harness kinetic energy from linear speed to effectively cut through stone, allowing for the splitting of stone such as granite, marble, and sandstone.
Frame saw: This specialized device is designed for cutting granite. It features a set of parallel saw blades fixed to a frame that moves in a slight oscillating motion, driven by a connecting rod powered by a motor. While the saw blades contact the rough block, their lower edges do not contain hard materials for cutting. Instead, they utilize a sand slot and a water slot. The cutting action is achieved through the application of alloy sand, which the saw blades drive and press against the rock. The advantage of using a frame saw is its ability to cut large rough blocks, resulting in larger slabs with greater flatness.
Diamond frame saw: This saw has a structure similar to that of the sand saw, but instead of oscillating, the frame moves horizontally in a reciprocating motion. It does not require the application of alloy sand, as diamond segments are welded to the lower edge of the saw blades for direct cutting of the rock. The diamond frame saw is specifically designed for cutting marble blocks.
Grinding and polishing semi-finished slabs
This step involves the procedures of unifying thickness, milling, coarse grinding, fine grinding, and polishing.
The slabs cut from rough blocks often have issues with inaccurate thickness and unevenness, which need to be tuned using milling heads or grinding rollers to meet standard requirements.
Coarse grinding is performed using relatively rough abrasives, followed by a fine grinding process. Both stages involve securing abrasives onto a horizontal grinding plate that rotates, generating friction against the stone surface to achieve a smooth, honed finish. The abrasives used in both coarse and fine grinding are typically artificial diamond or corundum. The grinding blocks are usually made from cement, dolomite, or, preferably, resin-based materials.
Polishing involves the use of specialized polishing abrasives on the finely ground stone surface to achieve a mirror-like finish. During the stone processing, when using a hand-held grinding machine, different types of abrasive modules for coarse grinding, fine grinding, and polishing must be replaced as needed. The processed slabs remain stationary while the hand-held machine applies manual pressure and friction through the interchangeable abrasive modules. In an automated production line, stone slabs are placed on the conveyor belt of a continuous grinding machine. This machine is an integrated unit equipped with more than ten grinding heads with abrasive modules from the coarsest thickness milling head to finest polishing module.
The semi-finished stone products, after their rough surfaces and irregular edges have been ground and polished, are known as "rough polished slabs." Depending on the strength and crack situation of the rough slabs, reinforcement methods are required. These methods include adhering mesh to the back of the rough slabs and filling cracks and holes to enhance the usability of the stone slabs.
Cutting rough polished slabs
The semi-finished rough polished slabs have undefined dimensions and irregular edges. This step involves cutting the slabs to the required specifications and shapes for construction projects, ensuring they align with design and installation requirements. Specifications are based on design drawings, which may include squares, rectangles, polygons, arcs, and other shapes. Cutting machines are used to perform these cuts. The resulting slabs are then further processed for edge and corner finishing before inspection, packaging, and shipment.
Surface treatments
The surface finishes of stone can be categorized into two main types: smooth and rough.
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Smooth Finishes: This category includes polished and honed finishes.
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Rough Finishes: This category includes natural cleft, flamed, antique, bush-hammered, and rough-picked finishes.
For more information about each type of stone finish treatment, please refer to the article "An Introduction to Different Types of Stone Finishes."
