Interpretation: The application prospect of diamond grinding tools in stone

The use of diamond abrasive tools in all areas of the stone processing industry has steadily increased. The main driver of this growth is the overall reduction in costs due to improvements in diamond synthesis technology, tool manufacturing technology and machine tool design. These improvements have resulted in a significant increase in stone utilization and production from the initial stage of production to the final processing. These advances have comprehensively affected the increase in diamond consumption and replaced traditional abrasive tools in a variety of current and newly developed processes. This paper examines the technological advances in stone processing that have indeed contributed to the growing market for natural stone used as interior and exterior decorative building materials.

The availability of natural stone for construction and decoration is different for most countries with large stocks of raw materials. Until now, many smaller stone producing countries have processed stone mainly for local consumption without opening up the export market. In recent years, the global market has begun to undergo significant changes.

The amount of stone used for processing has increased significantly. In 1998, the global mining volume was about 47.4 million tons, an increase of 48% over 1997.

In 1993, there were only three countries with a stone extraction capacity of more than 2 million tons. They were Italy, Spain and China, with output of 7.5 million tons, 3.4 million tons and 2.5 million tons respectively. After 5 years, the number of such countries has increased to 7: Italy leads with 7.5 million tons; China rises to second place with output of 6 million tons; Spain ranks third with 4.5 million tons, and India ranks fourth Its output is 2.4 million tons. The other three countries sharing the remaining 2 million tons of markets are Brazil, Portugal and Greece.

The share of global production for these countries is the intercontinental distribution of global production.

Stone processing
The total amount of stone processed by finishing and semi-finished products in 14 major countries in 1998 was comparable to the level of nearly 15.2 million tons in 1997. This makes the stone processing volume of these 14 major countries account for 71.5% of the world.

In this group, its development has changed. Material processing is growing in most countries, but as expected, the reduction in stone processing is reflected in the amount of production, with Japan, South Korea and Taiwan showing a downward trend in processing.

Stone processing is creating a clear global landscape. Three countries control the world market, namely Italy, China and Spain. In 1998, these three countries accounted for the global natural stone processing volume (top 14):

The processing volume of stone is 39.5%. Surveys in these areas show that there are significant differences between the methods and technologies used in Europe and China. Cultural, economic structures, fundamental and technological differences have led to the development of industries using different processing techniques and equipment and tool design standards, as well as different requirements for the performance of diamonds in these tools.

Comparison of stone processing technology between China and Europe
Recently, China has emerged as a leader in the mining and processing of stone. Today, China produces 240 different varieties of granite, accounting for 65% of its output [3], 60 varieties of marble and 10 varieties of slate. In 1998, 160 billion square meters of various stone plates were produced for domestic and export markets. There are about 500 companies with the ability to mine and process local stone, and the number of companies is increasing. The rhythm of this number change is also obvious, however, the sharp increase in production has not been reflected in the investment in machine tool technology. Most processing equipment still uses old-fashioned, outdated production methods.

The mining method uses a blasting method, which means that only 5% to 8% of the stone can be used for processing.

Many of the selected blocks are often returned from the process because there are many cracks and defects that occur during blasting.

The main use of Chinese granite is as floor tiles and facing tiles. The Chinese market does not match the use of such products. Because at the world level, these stones are still basically used in well-known buildings, not standard civil buildings. In China, stone competes directly with other civil building materials such as ceramics, cement and wood. To be treated as such, the quality of the finish and dimensional accuracy of the stone used for this purpose is of course lower than the quality requirements of the stone used in the West for well-known construction projects.

The main difference in this regard is the labor market, where labor costs are significantly lower than in Europe; they are also reflected in sawmill investment, automation and overall labor productivity. When mining stones, China used a blasting method that produced irregularly shaped stones that were small enough to be shipped in small trucks and then transported to the processing plant over short distances. Generally, the processing of panels for floor tiles and tiled tiles is generally based on a domestic reciprocating multi-saw system. The system has five combinations of five 1 m diameter and five 1.6 m diameter saw blades. . The productivity of the saw is low because the amount of cutting is limited by the power of the equipment and simple tooling techniques. Typical process parameters for processing ordinary granite are as follows:

Cutting speed around the saw blade: (saw blade with a diameter of 1 m) 27 m/s, (saw blade with a diameter of 1.6 m) 17 m/s
Sawing depth: 1mm
Feeding speed: 5m/min
Sawing efficiency: 50cm2/min or 0.3m2/h per saw blade
Saw machine production efficiency: 24m2 / working day (8 hours per working day)

The stone is then removed from the saw and the sawn stone is manually placed on a spiral-arm polisher and polished with a conventional abrasive. After polishing, these long slabs are cut to the final size on a manual cutter.

Due to the low level of automation and low sawing efficiency used, the requirements for diamond saw blades are not high, so the variety and size of the abrasives seen in this use are different from those commonly used in Europe. Since the sawing efficiency is much slower, the grain size of the abrasive particles is correspondingly finer, and the diamond particle size used in this application is usually 50 to 70 mesh. At this sawing efficiency, the load on the saw blade is low, so the performance of the diamond used is very different from the diamond performance used in similar applications in Europe. The diamond grades required are very irregular, fragile abrasive particles, which enable the saw blade to be sharpened under normal conditions.

The situation in Europe is different for a number of reasons. Europeans have higher living standards than China, so labor costs in Europe are much higher. In order for European major stone producers to be competitive, they must focus on processing, which optimizes productivity and maximizes the yield of raw materials. These methods focus on converting the mined stones into the final product as much as possible while minimizing energy consumption and minimizing unnecessary stone waste. These methods require sawing technology with high speed operation and sophisticated tools that maintain automatic operation for long periods of time. In the 1990s, technology development of machine tools and diamond tools was carried out in Europe, which promoted an increase in production efficiency and a significant reduction in the cost of stone processing.

If we compare the technology used in Europe and the technology in China when producing modular veneers, we can see that there is a big difference between machine tool technology and productivity. In Europe, the production of these tiled tiles is almost fully automated, using efficient machine design and automated handling equipment. The latest equipment for this type of production, 80 pieces of saw blades with a diameter of 1 m can be mounted on a single spindle.

Machine and tool design allows for faster cutting efficiency with typical usage as follows:

Cutting speed around the saw blade: 25 ~ 35m / s
Sawing depth: 1mm
Feeding speed: 17m/min
Cutting efficiency: 170cm2/min per piece or 1.02m2/h
Machine tool production capacity: 640m2 / working day (8 hours per working day)

Under these conditions, the waste must also be miniaturized in order to maximize the output of the product. As a representative example, the width of the saw blade is less than 10mm, while that of China is 12-15mm. Material handling and processing time optimization is also the key to maximizing productivity, so the stone is sawn into sheets and automatically transferred to an automated machine for the second step.

Due to the very high cutting efficiency, the requirements for diamond tools are very high. The grade and particle size of diamond abrasives in this type of application is quite different from that used in China. Due to the high cutting efficiency, the grain size of the diamond abrasive is naturally coarser, and the most common diamond particle size is 30 to 50 mesh. In the case of high cutting efficiency, the load acting on the tool is correspondingly larger, and thus the performance requirements for the diamond are quite different. Typical requirements for diamonds are: good consistency, high strength, and massive particles that allow the tool to maintain a very sharp state with high processing efficiency. At the same time, performance stability can be maintained for a long time under high load use conditions.

Application prospect of diamond in granite processing
In order to further increase productivity, various studies have focused on improving the economics of stone processing. In addition to improving the output of materials and reducing the cost of scrap, diamond manufacturers, machine tool builders and tool manufacturers are increasing the productivity of machine tools. A lot of research has been done to match the tools. One of the studies identified the current level of production capacity of marble processing machines. The most efficient granite saws currently used in Europe are only about 4% more productive than marble processing. In general, when the depth of cut is greater than 25 mm, it is unlikely to be used for processing granite, as this will result in a large amount of heat and overload of the diamond tool.

A diamond partner, a diamond tool manufacturer, a machine tool builder, a saw blade matrix manufacturer and a European partner international organization, a research institute, began researching a new world of stone processing. Emphasis is placed on finding ways to solve problems, as well as a comprehensive assessment of technology, the economy and the environment, and the approximation of the problem. The goal of this program is to develop the subsystems of the processing system to meet the needs of deep conditions, that is, the depth of cut ranges from 100 to 300 mm. It includes an efficient diamond circular saw blade and an improved system for lubrication at the tool and workpiece interface to ensure stable operation over time. Because this is a basic requirement for a highly automated process. The research work is carried out in two phases:

1. Conduct laboratory tests to obtain some basic information (material properties, cutting forces, temperature and vibration) as the basic data that must be improved when designing machine tools and tools.

2. Development of tools and machine tool components (saw blade agglomeration, lubrication and finishing systems) based on the first phase data. In the first phase, one of the keys to the design of the project was to use a small saw blade simulation to examine the force of the machining, the temperature at the interface of the tool and the workpiece (grinding zone), and the vibration characteristics. When using a small saw blade, it is important that the system characteristics match the actual use condition characteristics in industrial applications. To meet this requirement, many authors have proposed various sawing models. Two major variables in the system are recognized, namely cutting speed (Vc) and depth of cut (ae).

Using these parameters and information about the tool geometry, a simplified model formula for a circular saw blade sawing can be proposed.

Heq=aeVft/Vcλ

Using this formula, it is possible to reproduce conditions and forces that are similar under normal conditions in industrial applications.

Measurement of cutting temperature and cutting force under deep sawing conditions
Deep sawing was performed using a small laboratory test to measure the heat and cutting forces generated in the cutting zone. This information is necessary to determine the lubrication equipment for large-scale production saws and to predict the cutting forces that diamond tools can withstand during processing. High strength diamond is used with a particle size of 30/40 and a particle count of 660 ± 30 per carat. First sawn medium-hard Italian granite, and then saw more difficult to process Indian red granite, which is one of the most difficult materials. In the sawing test, the sawing depth was maintained at 90 mm, and the feed speed was adjusted to vary between the mildest cutting conditions of 100 cm 2 /min and the worst conditions of 600 cm 2 /min. This condition can meet the production efficiency of 380 cm 2 /min to 1000 cm 2 /min set by industrial production. The temperature measurement results were obtained. As expected, the cutting temperature as the sawing efficiency increases is also increasing, but even at the highest speeds, the resulting cutting temperature is still below 200 °C. Use a dynamometer to measure normal and tangential forces in machining, helping to develop sawmill designs and tool sizes for the largest sizes. The analysis of the cutting forces and the investigation of the diamond wear process determined that the work should be carried out in that section within the scope of the process. This is the key to maintaining uniform wear of the diamond and adjusting the exposure height required by the diamond to complete the cutting of the material.

Granite deep saw processing requirements
Based on the information obtained in the first phase, specially designed processing equipment related to the deep sawing process is determined. Consider the design of the diamond saw blade, focusing on the following tool design requirements. The tool specifications and processing conditions must be such that the thickness of the chip is achieved when the material removal rate and diamond exposure height match. In the case of deep sawing, unlike the case where the chip thickness is too small, the main aspect of concern is that if the cutting parameters are too large, the thickness of the chips will exceed the exposed height of the diamond. In this case, since the diamond particles show excessive brittleness, the gap between the workpiece and the bonding agent is insufficient and a catastrophic failure occurs. This will cause an increase in the normal force, causing a catastrophic failure of the tool. On the other hand, the project plan focuses on various requirements such as machine stability and lubrication power, which are considered when the final assembly of the deep saw is made.

Prospects of deep sawing process
These experiments show the potential for today's high-strength synthetic diamonds. When attention is directed to the machining process, the machine tool, the optimization of the machining parameters, and the design of the saw blade, it is possible to build a system that can break through the current limitations of conventional systems. The advantages of this system will be realized in the near future when the machine tool builder developed a dedicated deep-cut sawing machine in 2000. Based on this situation, it is possible to predict a complete processing system using the most intense synthetic diamond of the current strength, which can effectively achieve a great increase in production efficiency.

Prospects for the use of diamond wire saws in stone processing
Diamond wire saws are recognized in the stone processing industry for processing and mining granite and marble blocks. In Europe, diamond wire saws have been designated as standard mining tools for marble and are effectively entering the mining of granite. The use of diamond wire saws is also increasing. Wire saws are now found in many applications in granite and marble processing. In the early 1990s, the use of fixed diamond wire saws was limited to a handful of stone processors who had used this technique to make stones. Since then, there has been a big difference in technology.

In 1997, a fairly new idea was commercialized on a CNC-controlled wire saw, which had the ability to saw the rather complex shapes used in construction. Combining the latest machine concept, machine control technology and modern diamond tools into a comprehensive device that can be processed into a variety of shapes according to the design, which must be costly before. The introduction of this diamond wire saw relieves the architects and designers from the technical and cost barriers to achieving the shape design of their interior and exterior stone finishing projects.

Granite large-size sheets of 10 to 40 mm thick can only be completed with a conventional steel sand saw. Due to the design of the saw blade base and the associated groove width limitations, it is absolutely impossible to machine with a circular saw blade. The replacement of this outdated technology with a diamond wire saw has been thought for many years, but it was not possible until the tooling of diamonds in 1997. This saw is specifically designed to replace traditional frame saws with high-grade diamond wire saws. The diamond sawing machine using 10 diamond wire saws with a diameter of 8 mm is equivalent to two conventional frame saws, while the surface morphology of the processed slabs is improved, and the amount of waste stone and power consumption are reduced. . An improvement in surface quality alone means that the subsequent grinding process is reduced by nearly 20%.

The success of this processing concept relies to a large extent on the performance of tools called diamond wire saws. Two factors are the key to the success of this application. First, the diameter of the rope directly determines the practicality of the workpiece material. Initially, diamond wire saws used to process granite were 10 to 12 mm in diameter, but today, the smallest diameter range is 6 to 8 mm. Followed by the actual performance of the diamond wire saw. This can be measured in two ways. First, the diamond wire saw must reach a certain cutting rate, and this efficiency can be maintained for a long time, and it must also bring other advantages brought about by it, such as reducing power consumption and material waste. In order to achieve these advantages, diamond technology has taken a step forward. Early electroplated diamond wire saws used in marble mining used irregular natural diamond abrasives or relatively easy-to-cut low-medium-strength diamonds. Today's diamond wire saws use fairly complete wear-resistant materials for high strength. The advantages of regular shaped synthetic diamond products are fully utilized.

DEBID studied the application of diamond wire saws over the past decade. Research has focused on the details of the application, especially the interaction between tools, workpieces and machine design. This process allows DEBID to focus its attention on research methods to produce synthetic diamond products that fully meet future market needs, including product and particle size, strength, thermal stability and properties.

The field test was carried out using a wire saw device from DEBID in the UK, according to a certain procedure. The configuration of the wire saw machine is as close as possible to the environmental conditions normally produced.

Through the analysis of experimental data in the past decade, a large number of observation reports have shown that the trend has been confirmed. Some of the observed trends are not tool performance, but are specific to the wire saw process. Early diamond wire saws were electroplated for sawing marble, followed by binders and sintered beads for granite. The latest developments in today's manufacturing technology can be seen in the beading produced by hot isostatic pressing. It brings a new field of mass production of powder metallurgy diamond tools. A significant improvement in the density and consistency of the sinter is also seen. Finally, single or multi-layer brazed diamond tools have been introduced which provide advantages over existing diamond tools in terms of diamond abrasive grain exposure height and bond fastness. This result standardizes the tool, which increases the amount of wire saw production and reduces costs to a certain extent.

The processing data is processed to generate an accurate expression of the tool's performance, including two items, namely the achievable cutting efficiency and tool life under fixed processing power conditions. Different from the selection and processing parameters of the workpiece, the factors affecting the performance of the tool are the technical conditions of the diamond brand, its particle size distribution, the binder powder metallurgy raw material and the manufacturing method.

These variables, when several different wire saws are evaluated under the same conditions of use, have an interesting situation, and the productivity of the application is particularly interesting.

During the ten-year examination, the sawing efficiency achieved by this application was stably maintained in the range of 170 to 250 cm 2 /min. With this conclusion, it can be concluded that the use of diamond wire saws in this field has significant benefits. Diamond wire saws have achieved this growth as performance improvements result in cost reductions, including improved tool life and, therefore, direct reduction in processing costs. At the beginning of the study, the industry standard index for the service life of a diamond wire saw with a diameter of 10 mm was 5 m2/m (wire saw), and by the end of the study, this index had doubled. CM (19*2) significantly reduced the processing cost, thus promoting the growth of the application.

As can be seen, despite some current economic turmoil, stone processing continues to grow steadily. In almost all countries with suitable natural resources, there is no doubt that the exploitation and processing of stone is growing. But most of the final stone products are produced in three major countries, spanning two continents. There are a large number of economic and technical differences between the two continents. As a result, there are huge differences in the technical requirements for machine tools, tools, and diamond products. As European countries struggle to maintain their cost competitiveness, a number of attempts have been made in technology development, which is continually improving the practicality of the workpiece. These advances can be seen through the growth of diamond wire saw applications, the use of high-precision machine tools, the ability to perform large depths of cut and precision sawing, and the development and utilization of multiple wire saws. The increase in production is mainly from three regions where cost reduction can be achieved.