A wire saw is a saw that uses a metal wire or cable for mechanical cutting of bulk solid material such as stone, wood, glass, ferrites, concrete, metals, crystals etc.. Industrial wire saws are usually powered. There are also hand-powered survivalist wire saws suitable for cutting tree branches. Wire saws are classified as continuous (or endless, or loop) or oscillating (or reciprocating). Sometimes the wire itself is referred to as a "blade". Wire saws are similar in principle to band saws or reciprocating saws, but they use abrasion to cut rather than saw teeth. Depending on the application, diamond material may or may not be used as an abrasive. The wire can have one strand or many strands braided together (cable). A single-strand saw can be roughened to be abrasive, abrasive compounds can be bonded to the cable, or diamond-impregnated beads (and spacers) can be threaded on the cable. Wire saws are often cooled and lubricated by water or oil.
Types
The simplest type of wire saw is the inexpensive "survivalist" (emergency) type intended for sawing branches which are sold in hunting and climbing shops. Continuous type wire saws are used to cut walls and other large constructions. Continuous type saws are used to cut silicon wafers for the semiconductor and photovoltaics industry. Diamond-impregnated wire saws are used in machine shops to cut metal parts. Precision wire saws are used in laboratories to cut fragile crystals, substrates, and other materials. In addition, the technology can be used for disassembling advanced research structures. For example, Bluegrass Companies designed and fabricated a diamond wire sawing method to dismantle the Tokamak Fusion Test Reactor for the Princeton plasma physics laboratory. Based upon the demonstration at PPPL on the TFTR surrogate, the diamond wire cutting technology is superior to the baseline technology for both cost and safety considerations. The combination of void filling with this cutting technology will significantly reduce personnel radiation exposure through shielding, remote operation (normal application of this technology), and radionuclide stabilization”. Both continuous and oscillating type saws are used to cut intricate shapes in stained glass.
Materials
Stone
Mining and quarrying industries commonly use a wire saw to cut hard stone into large blocks that can then be shipped to processing plants to be further refined (in the case of ore dressing) or shipped to distributors (in the case of granite or marble for building). These wire saws are large machines that use diamond-impregnated beads on a cable. The saws allow the bottom of a quarry slab to be cut free (after the cable is passed through access drill holes); with the bottom cut, back and side charges (explosives) can cleanly cleave the slab. Quarry saws on this principle date back centuries; before the era of steel cables with diamond cutters, there were fiber ropes that drew sand through the kerf. The sand (flushed with water) cut the stone (albeit more slowly than diamond does today).
Foam Foam manufacturers commonly use an abrasive wire saw, either manual or automatic, to cut foam to certain sizes or certain profiles (shapes). Foam saws are used in many industries, include housing (insulation, pipe insulation), furniture (couches, couch cushions, chair cushions), and entertainment (foam fingers, foam accessories). Abrasive-wire cutting is often done with a computer numerical control device that automatically cuts the pattern (or patterns) that are specified in a two-dimensional (2D) CAD/CAM drawing. The materials to be cut can range from polystyrene, polyethylene, and polyurethane, to high-density or rigid types of foam, such as cellular glass (e.g., Foamglas®). Oscillating saws are used to cut foam rubber.
Semiconductors In the semiconductor industry, multi-wire saws are used to cut cylindrical ingots of silicon boules into thin wafers. Thin wire is used to minimize the loss of material. For example, the Peter Wolters DW 291 has a minimum wire diameter of 40 μm and can cut an 860mm work piece into 100 μm wafers.
Advantages and disadvantages One major advantage of wire saws is their smaller kerf, as compared to a blade. Another is the precision of the cut. Their main disadvantage is the slower speed. Other disadvantages include a greater chance the wire will break and any surface imperfections can cause errors in the cut.
Diamond wire cutting Diamond wire cutting (DWC) is the process of using wire of various diameters and lengths, impregnated with diamond dust of various sizes to cut through materials. Because of the hardness of diamonds, this cutting technique can cut through almost any material that is softer than the diamond abrasive. DWC is also practical and less expensive than some other cutting techniques, for example, thin diamond wire cost around 10-20 cents per foot ($0.7/m) in 2005 for 140 to 500 micrometer diameter wire, to manufacture and sells around $1.25 a foot ($4.10/m) or more, compared to solid diamond impregnated blade cutters costing thousands of dollars. Thus a 1,000 foot (300 m) spool of diamond wire costs around $200 to manufacture and sells for around $1,250. Selling cost may vary because of wire grade and demand. Other diamond wire cutting can use shaped diamond rings threaded through cables. These larger cables are used to cut concrete and other large projects.
Advantages DWC produces less kerf and wasted materials compared to solid blades (slurry wire may be similar). On very expensive materials, this could save hundreds or thousands of dollars of waste. Unlike slurry saws that use bare wire and contain the cutting material in the cutting fluid, DWC uses only water or some fluid to lubricate, cool the cut, and remove debris. On some materials DWC may not need water or cutting fluid, thus leaving a clean dry cut.
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