Xi Peng Xu

The Effects of Swarf in the Diamond Sawing of Granite

The present study was undertaken to examine the effects of swarf in circular sawing of granite with a diamond segmented blade. Measurements were made of the horizontal and vertical force components and the power over a wide range of sawing conditions. Cal culated tangential and normal force components, force ratio and specific energy were subseque ntly used to evaluate the effects of swarf. Two separated sawing tests were arranged to study the influences of machining parameters and the time-dependent nature of the sawing process. Additi onal tests were conducted to compare the effects of swarf under different lubrication conditions i ncluding two extreme cases dry sawing and grease lubrication. It was found that the sawing swarf was responsible not only for the shift in the location of the line of action of the resultant force but also for the change of force ratio. The effect of the swarf was governed by contact length, lubricant viscos ity, and diamond protrusion height beyond the bond matrix. Introduction Diamond impregnated segments used for circular sawing of granite co sist of randomly dispersed and randomly oriented diamond crystals embedded in a metal matrix. It is well known t hat the erosion of the segment matrix through abrasion gives rise to diamond protrusion, and hence an eff icient cutting process. Therefore, the matrix and the diamond wear rates should be appr opri tely matched in sawing in order to facilitate constant efficient cutting as well as minimize the wear of the diamond segments. A physical model indicating the interactions at the sawblade-grani te interface in circular sawing is illustrated in Fig.1. Fig.1 Illustration of the interactions at the sawblade-granite interface duri ng sawing During the past 30 years, extensive research has been conducted on the m echanisms of segment wear in the sawing of natural rock materials through observing the m orphologies of worn segments [1-5]. It was pointed out by many studies that the primary mode of diam ond tool wear in circular sawing is diamond breakdown due to impact and fatigue, with the secondary mode being tool wear through abrasion of the matrix [2-5]. It is found that the grain fract u e and wear by friction are the main mechanisms causing diamond wear, whereas the coolant together w ith the swarf (chips) form an Granite Force Fracture surface Diamond Bond

Analysis on the Fracture Failure of Brazed Diamonds in Wire Sawing

An investigation was undertaken to elucidate the mechanisms for the fracture failure of brazed diamonds in wire sawing. Diamonds were brazed by high-frequency induction in vacuum. The changes of compressive strength and the appearances of the diamonds at different brazing temperatures were obtained. The morphologies of the diamonds after sawing were also observed. Together with the stress analysis of a brazed grit, it is found that the fracture failure of brazed grit is the result of the brittle fracture happening on the root section of the grit, the interface between the grit and the brazing alloy. The degradation of mechanical properties of grits in brazing is a key factor to the reduction of their resistance to fracture. Lower machining forces as well as grit exposure are in favor of preventing grits from fracture.

Analysis of the Breakage of Diamond Wire Saws in Sawing of Stone

An investigation is reported on the breakage of the diamond wire saw during stone processing. A Lot of breaken wire samples were collected from factories and observed macroscopically and microscopically. The results indicate that the breakages were mainly fatigue failure. And statistic of results show that all the breakage sites centralize on two sections. Reasons for the two break sections are also discussed in detail. Furthermore, sawing experiment was conducted to study the effect of the process parameters and the results reveal that the breakage of the wire saw is sensitive to the processing parameters. Finally, some proposals for manufacture and application were presented.

Experimental Investigation of Intermittent Rotary Ultrasonic Machining

Rotary ultrasonic machining (RUM) is considered as an effective machining method, which has been utilized to machine hard and brittle materials such as advanced ceramics. In order to improve the hole wall surface quality during RUM, it is important to wash away swarf in the gap between the tool and the workpiece as fast as possible. In this paper, a new machine process – intermittent rotary ultrasonic machining (IRUM) – is introduced for the first time. The cutting force, surface roughness and coolant flow rate in conventional rotary ultrasonic machining (CRUM) process and IRUM process are compared. It is found that compared with CRUM, the output coolant flow rate could be increased significantly by using the IRUM method. It is also found that the surface roughness of workpiece can be improved significantly in IRUM.

Improvement of the Performance of Diamond Segments for Rock Sawing, Part 1: Effects of Segment Components

An investigation is reported on how to improve the performance of diamond-impregnated segments for the circular sawing of natural rock materials. T hese serial papers consist of three parts. Part 1 is concerned with the service performance of diamond segments fabricated at a wide range of conditions. The service performance of the segments was evaluated in terms of t he characteristics of segment wear and the consumed power. The worn surfaces of the seg m nts were monitored in an effort to relate the working surface state of the segments w ith their service performance. The percentage of diamond working conditions on the worn segment surfaces w s found to be closely related to the wear performance of the segments and the consume d pow r. The diamond working conditions and hence the segment performance are attributed to t he combined effects of such parameters as grain size, concentration and quality of diamonds, proper ties of bond matrix and granite. Introduction It is estimated that one of the biggest consumptions of synthetic di amond abrasive lies in the processing of rock materials, in which case sawing is perhaps the most important with regard to the production cost and efficiency. The tools most widely used for primary s wing are circular saw blades with diamond impregnated segments. With the increasing use of natural rock materials as decorative materials around the world, there is a great demand on opt imizing the wear behavior of diamond sawblades so as to reduce the overall production cost. Diamond impregnated segments consist of randomly dispersed diamond cr ystals embedded in a metal matrix. As sawing proceeds the segments wear down and new iamonds emerge from the matrix and cut the workpiece. During the sawing process, the main role of the metal bond matrix is to ensure maximum cutting productivity of the diamond by holding it fir mly until it is worn out. Generally speaking, the matrix and the diamond wear rates should be appropriately matched in order to facilitate constant efficient cutting as well as mi ni ze the wear of the diamond segments. Unfortunately, diamond segments that are popularly used in the practica l fields of producing granite products are frequently worn in unexpected modes, in which case diamond gr its prematurely fail either through pop-out or by fracture and the bond matrix wears much slowe r or faster than diamond grits. A fundamental understanding of what mainly affects the wear of diamond segments is required in order to provide a technological basis for optimizing the design of diamond segments and consequently improving their performance. These serial papers consist of three parts. Part 1 is mainly de vote to elucidate the influences of segment components including the compositions of bond matrix, diamond grit s ize, and the concentration and quality of diamond grits, on the performance of diamond se gments fabricated and used under different conditions. Coupled with the findings of this first part, Part 2 will focus on studying the mechanisms for the retention of coated diamond grits, whereas an attempt is to be made in Part 3 to improve the performance of bond matrix through an addi tion of rare earth elements. It is hoped that the findings of these serial papers ca n provide more technical supports for the selection of diamond grits and optimal design of the compositions of bond matrix in order to improve the performance of diamond segments for the sawing of natural rock materia ls. Key Engineering Materials Online: 2003-09-15 ISSN: 1662-9795, Vol. 250, pp 46-53 doi:10.4028/www.scie tific.net/KEM.250.46

Fabrication of Ultra-Fine Abrasive Polishing Pads by Gel Technique

In this paper, an experimental study was carried out to fabricate a new kind of ultra-fine abrasive polishing pad by means of gel technology. The polishing pad was then used to polish silicon wafer on a nano-polishing machine. Optical microscope and ZYGO 3D surface analyzer were applied to observe the surface morphologies of the silicon wafer. Meanwhile, surface morphology of ultra-fine abrasive polishing pad was observed by ESEM. No obvious gathering of ultra-fine grains were found on the ultra-fine abrasive pad. The surface roughness (Ra) of the silicon wafer was reduced to 0.3nm after being polished by the abrasives with average grain size of 10μm. Mirror surface can be realized after being polished with the polishing pad.

Polishing Silicon Wafers with the Nanodiamond Abrasive Tools Prepared by Sol-Gel Technique

In this paper, in order to avoid aggregate of nanodiamonds and reduce the damage problem caused by the hard abrasives during polishing, a kind of ultra-fine nanodiamond abrasive polishing pad was fabricated by means of sol-gel technology. The polishing pad was then used to polish silicon wafer on a nano-polishing machine. The surface morphologies and roughness were measured by both optical microscope and atomic force microscope (AFM). It is found that it was easy to machine the silicon wafer to mirror surface after polishing with the nanodiamond pad. And the surface roughness of the silicon wafer was reduced to 0.402 nm.

A Comparative Study on the Dressing of Metal-Bonded Diamond Saws

An investigation is reported of the dressing of metal-bonded diamond saw blades with four different dressing methods – stirring the blade segments in rock slurries, surface grinding the blade segments with Al2O3 wheels, dressing the blade segments with SiC wheels, and dressing the blades through sawing of refractory materials. The surfaces of dressed blade segments were examined by a scanning electron microscope. The protrusion of the diamond grits on the dressed segments was quantitatively assessed using a digital optical microscope. The vertical and horizontal force components and the spindle power were measured in the refractory sawing. The grit protrusion generated by the stirring method was found to be the highest and most diamond grits remained their original crystal shapes. But it took a quite long period to let the diamond grits protrude from the bond matrix. The protrusion produced by the surface grinding ranked the lowest among the four methods. The height of grit protrusion for either SiC dressing or refractory sawing was found to be about 20% of the diamond average size, which might be an optimal point with respect to the segment sawing performance. Force analysis indicated that the force per diamond grit in refractory sawing was much lower than the diamond compressive strength. The changes of spindle power in the sawing of refractory materials can be used to in-process monitor the dressing process. Introduction Circular sawing with diamond impregnated segments mounted on a circular steel core is the most extensively used process for natural stone materials. In newly fabricated segments, diamond grits are usually embedded and covered by the metal bond matrix. Although new diamonds can emerge from the matrix while the segments wear down and cut the stone workpiece as sawing proceeds, they need to be dressed before sawing to achieve an efficient cutting in most cases. Since the dressing of metal-bonded diamond wheels is regarded as the key technology in high-performance, high-speed and high-precision grinding processes, tremendous studies have been conducted on the dressing of diamond wheels for grinding ceramics and steels [1-2]. In the field of rock sawing, however, much fewer studies covered this topic in the past few decades. In an early study on the dressing of diamond saw blades [3], Wright and Ford investigated the selection of dressing wheels and the effects of grit sizes. They developed a special-purpose dressing rig, which consisted of a grinding wheel mounted on a spindle and driven through an electric motor. Unlike previous studies, this present investigation focuses on the comparison of four different methods for dressing diamond a kind of saw blade segment. It is hoped this work will be of benefit to the choice and improvement of dressing methods for metal-bonded diamond tools widely used in the processing of stone materials. Experimental Fabrication of Metal-bonded Diamond Saws. Iron, copper, tin, cobalt and nickel were used as the constituent metal powders for the manufacturing of diamond segments, in which case iron was about 50% wt. The diamond segments were fabricated on an automatic hot pressing machine installed with an infrared device for monitoring sintering temperature. Diamond of 40/45 (355-425μm) US mesh Key Engineering Materials Online: 2006-02-15 ISSN: 1662-9795, Vols. 304-305, pp 19-23 doi:10.4028/www.scientific.net/KEM.304-305.19

Production of Diamond Sawblades for Stone Sawing Applications

The objective in writing this article is to acquaint the reader with the processes involved in the production of diamond sawblades, used extensively in stone cutting oper ations, but also in diverse construction jobs, road repair, sawing ceramics, etc. For reasons of space, its technical contents relate mainly to the design and fabricate]on of diamond im pregnated segments. Great emphasis is placed on providing guidelines for the selection of metall ic matrix and diamond abrasives. The sawblade assembling and finishing steps are also r eviewed, but, as they have only been given condensed accounts, the reader is encouraged to consult the rel evant source literature included in the comprehensive list of references. Historical Background The modern application of diamond tools is roughly a century old although the early use of diamond as an engraving tool goes back to 350 BC [1]. The first diamond circular sawblades for cutting stone were developed by Felix Fromholt in France in 1885. Fourte en years later, a large diameter blade was first used in practice in the Euville stone quarries. The early blades used carbonados set around their periphery and were utilised to cut limestone s and marbles during the construction of large buildings in Paris. Progress in the tool production r outes, by making good use of powder metallurgy techniques, resulted in developing diamond grit impre gnated sawblades to be finally put into operation around 1940 [1]. Further developments in the tool manufacturing technology may chiefly be attributed to the invention of synthetic diamond. Natural diamond has been used for centuries a nd efforts to manufacture synthetic crystals also date back at least sever al hundred years. They had remained fruitless until 1953, when positive and fully reproducible results were obtained by a team of researchers at ASEA [2]. Quite independently, and entirely without knowledge of what ASEA had been doing, General Electric announced its capability to manufacture synthetic diamonds on an industrial scale in 1955 [3]. While ASEA kept the diamond experiments secret, GE was first to apply for a patent and described the process in the scientific lite ratur . Therefore the invention has officially been attributed to GE. Permanent progress in the manufacturing technologies fostered the commercial importance of synthetic grits, which in the early 1990’s constituted around 90% of al l industrial diamonds consumed [2]. Over the past four decades, modern production techniques based on dia mond tooling have widely been employed in the stone and construction industries, road r epair, machining of glass and ceramics, grinding of metals, woodworking, finishing of plastic and rubber components, etc. enabling to do the job faster, more accurately and at less cost. N owadays the market for diamond tools continues to grow rapidly. Figures revealed currently indic ate that the demand for diamond abrasives reached a volume of 700 million carat in 1997, with Europe being th largest market [4]. Interestingly, the production of sawblades for stone cutting and const ruction applications has been identified as the biggest segment accounting for 50% of the overall consumption of industrial diamonds in Europe [4]. The current trend is to diversify into applicati ons still dominated by traditional abrasives with particular interest in developing linear blades for sawing granite as well as in applying diamond grits on a broader scale in the surface finishing operations [5] . Diamond Tool Design and Fabrication A typical fabrication process, commonly used in the manufacture of diamond impregnated Key Engineering Materials Online: 2003-09-15 ISSN: 1662-9795, Vol. 250, pp 1-12 doi:10.4028/www.scie tific.net/KEM.250.1

A Comparative Study of Stone Sawing with Thin and Normal Blades

In this paper, an experimental study was conducted to compare the sawing of granite with thin and normal blades. The power drawn by the spindle and horizontal and vertical forces were measured. The width of sawing slot on the granite was examined after sawing. For both blades, power and forces increase with the depth of cut. The width of sawing slots for the thin blade was about 75% of the normal blade. The width of sawing slots for either thin or normal blade sawing became narrower in larger depth of cut.