Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
  • B23D61/00—Tools for sawing machines or sawing devices; Clamping devices for these tools
  • B23D61/18—Sawing tools of special type, e.g. wire saw strands, saw blades or saw wire equipped with diamonds or other abrasive particles in selected individual positions
  • B23D61/185—Saw wires; Saw cables; Twisted saw strips

Definitions

• Sawing by wire in the presence of abrasive is generally carried out by alternating or continuous displacement of a wire pressed against a workpiece to be sawn and previously impregnated with an abrasive generally in suspension in the form of an abrasive slip.
• the part of the workpiece to be cut in contact with the wire and the abrasive defines a sawing area.
• the sawing efficiency depends on the relative speed of the abrasive on the surface of the workpiece while the wire wear depends on the relative speed of the abrasive with respect to the wire. We therefore see that we will have maximum efficiency when the speed of the abrasive will equal that of the wire. In this case the wear of the wire will tend towards zero. So this is the ideal case.
• the surface of the wire will be passive as regards the transport of the abrasive in the sawing zone and there is relatively little or no possibility of varying the carrying factors if not with the aid of slips having wettability factors favoring the adhesion of the abrasive grains on the wire and not on the workpiece. Apart from that there is no possibility of modifying the distribution of the relative speeds of the abrasive with respect to the wire or with respect to the workpiece to be sawn.
• the abrasive slip generally consists of a mixture of lift liquid and an abrasive solid. More particularly, this mixture can consist of an aqueous medium or of oil with silicon or boron carbides, or alumina oxides. There may also be agents surfactants such as carboxymethyl cellulose or glycerin etc. Diamond paste can also be considered.
• Saw wires are generally made of high-strength spring steel with a diameter between 0.1 and 0.2 mm.
• the smooth stretching surface does not favor the attachment of the abrasive. The result will therefore be of average efficiency or even simply mediocre.
• the object of the invention is therefore to remedy this shortcoming by using a wire of high mechanical strength while having an active surface promoting the carrying and or the adhesion of the abrasive.
• a surface can act either by carrying abrasive in a texture imprinted in the thread or by implanting grains of abrasive in soft parts of the same surface.
• the choice of the working mode of the wire with an active surface will therefore depend, among other things, on the application, the material to be sawn and the abrasive in slip or not.
• the wire acts by carrying away in a surface texture
• the abrasive will then spread along the sawing area.
• the micro-cavities will act as local micro-distributors of abrasive and will thus improve its efficiency.
• a periodic variation of the diameter of the wire will give the same results, the abrasive penetrating with the parts of wire of minimum diameter is acting with the parts of maximum diameter where the pressure in the sawing zone is maximum one will use in generally this mode in the presence of abrasive slip.
• the wire When using the implantation mode, the wire must have either locally or over its entire surface more tender areas which will act by allowing the abrasive grains to hang on the active surface of the wire in the area of sawing giving the maximum speed in relation to the workpiece and almost zero speed compared to the wire, which is close to the ideal case.
• This can be achieved by coating the wire with a softer material allowing implantation. Synthetic material such as polyurethane or nylon may do the trick. You can also use a softer metal like copper.
• the thickness must be compatible with the size of the abrasive grains used. Indeed, a layer that is too thick does nothing for the process, just as a layer that is much thinner than the average diameter of the abrasive grains will have no effect.
• a good layer is between 0.1 and 10 times the average diameter of the abrasive grains.
• Another possibility is to create a wire with a gradient of radially variable hardness, for example by using a material whose composition varies as a function of the distance from the core. The core being the hardest or the most mechanically resistant and the surface most prone to the implantation of abrasive grains and their removal.
• a kevlar thread with a nylon coating. Nylon as an active surface facilitating implantation and kevlar giving it mechanical resistance.
• an optical fiber thread could be envisaged with an active surface in the form of a polyurethane coating.
• the choice of the base material will be dictated by its availability in great length and its mechanical resistance whereas the choice of that of the surface apart from the characteristics already mentioned will have to have a good adhesion on the base surface.
• the implantation mode will be used indifferently with a slip or abrasive pastes, as well as with a dry abrasive.
• Sawing devices using passive wires are already known and used especially in the industry of electronic components, ferrites, quartz and silica, for obtaining thin slices of materials such as silicon (poly or monocrystalline), or new materials such as GaAs, InP, GGG or also quartz, synthetic sapphire, or even ceramic.
• silicon poly or monocrystalline
• new materials such as GaAs, InP, GGG or also quartz, synthetic sapphire, or even ceramic.
• the high price of these materials makes wire sawing more attractive compared to other techniques such as diamond disc sawing.
• the wire sawing technique requires perfect control of the abrasive supply. This contribution without control with a passive wire, does not allow all the performances that the technique of wire sawing can bring.
• the object of the invention is to remedy the aforementioned drawbacks by providing a wire with an active surface maximizing the relative speed of the abrasive grains with respect to the surface of the material to be sawn and minimizing this same speed with respect to the wire.
• the wire therefore sees its lifespan increase in time as the sawing efficiency.
• Fig. 1 - Figure 1 represents an active wire surface with micro-cavities 1
• Fig. 2 - Figure 2 shows an active wire surface with micro-cavities in the form of streaks 2
• Fig 3 - Figure 3 shows an active wire surface with corrugations 3 whose length is relatively large compared to the wire diameter.
• FIG. 4 - Figure 4a shows the section of a wire whose active surface is produced by a layer 4 softer than the core 5 while FIG. 4b achieves the same goal by having a gradient of hardness H which is radially variable.
• the aspect carried by the abrasive by the surface of the wire must be kept in the spirit of having an increase in the relative speed compared to the workpiece or a decrease in the relative speed compared to the wire to improve the sawing effect.
• this liquid could be an instant adhesive, for example.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)

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Publications (1)

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Cited By (9)

Citations (4)

• 1989
  • 1989-04-19 CH CH148589A patent/CH680658A5/fr not_active IP Right Cessation
• 1990
  • 1990-04-17 WO PCT/CH1990/000103 patent/WO1990012670A1/fr not_active Ceased

Patent Citations (4)

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