JP2008515643A - Hard material processing apparatus and processing method using laser having irradiance in the range of 106 to 109 Wcm-2 and repetition rate in the range of 10 to 50 kHz - Google Patents

Hard material processing apparatus and processing method using laser having irradiance in the range of 106 to 109 Wcm-2 and repetition rate in the range of 10 to 50 kHz Download PDF

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JP2008515643A
JP2008515643A JP2007535239A JP2007535239A JP2008515643A JP 2008515643 A JP2008515643 A JP 2008515643A JP 2007535239 A JP2007535239 A JP 2007535239A JP 2007535239 A JP2007535239 A JP 2007535239A JP 2008515643 A JP2008515643 A JP 2008515643A
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range
irradiance
material
khz
method
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ウェンドランド、ジョゼフ
ハリソン、ポール
ヘンリー、マシュー
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パワーレイズ・リミテッド
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Priority to GB0511966A priority patent/GB0511966D0/en
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Priority to PCT/GB2005/003855 priority patent/WO2006038017A2/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/142Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor for the removal of by-products
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • B23K26/0648Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/0665Shaping the laser beam, e.g. by masks or multi-focusing by beam condensation on the workpiece, e.g. for focusing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/12Working by laser beam, e.g. welding, cutting or boring in a special atmosphere, e.g. in an enclosure
    • B23K26/123Working by laser beam, e.g. welding, cutting or boring in a special atmosphere, e.g. in an enclosure in an atmosphere of particular gases
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36Removing material
    • B23K26/40Removing material taking account of the properties of the material involved
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00Articles made by soldering, welding or cutting
    • B23K2101/002Drill-bits
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00Articles made by soldering, welding or cutting
    • B23K2101/34Coated articles, e.g. plated or painted; Surface treated articles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00Materials to be soldered, welded or cut
    • B23K2103/50Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26

Abstract

Hard material processing apparatus and processing method using laser having irradiance in the range of 10 6 to 10 9 Wcm -2 and repetition rate in the range of 10 to 50 kHz The processing apparatus comprises a laser (10) that generates a high repetition rate, high irradiance laser pulse that is scanned over the material using a scanner (20) for laser milling or laser cutting applications.
[Selection] Figure 1

Description

  The present invention relates to an apparatus for processing hard materials.

  Ultra-hard materials such as polycrystalline diamond (PCD), natural diamond and tungsten carbide (WC) have numerous industrial applications. These include machining tools as well as solid substrates for microelectronics in extreme environment applications. However, there are many problems in processing these materials.

  PCD cutting tools are commonly used to process non-ferrous metals, wood and rubber. PCD blanks are cut to a specific shape and brazed to individual holders incorporated in a cutting tool (often having multiple PCD cutting edges in one tool). A polycrystalline diamond cutting tool blank can be considered as a composite material that combines the hardness, wear resistance, resistance resistance and thermal conductivity of diamond with the toughness of WC. A PCD is a very hard, interdigitated mass of diamond particles that are randomly oriented within a metal matrix. This is made by sintering selected diamond particles at high pressure and high temperature. The sintering process is precisely controlled within the diamond stable region, resulting in a very hard wear resistant structure. These properties are most often used in cutting tools that process a wide range of materials, as well as applications for wear parts. In these applications, these properties contribute to increased tool life and provide additional technical advantages such as machining reliability and high precision machining tolerances.

  However, even during the life of the tool, the cutting edge wears out (although at a slower rate of wear than conventional cutting tools), so the cutting edge of the PCD cutting edge must be sharpened. If this is not done, dimensional tolerances increase and cutting quality decreases.

  Known solutions for extending the life of PCD cutting tools include electric discharge machines (EDM) in which wire electrodes cut diamond by electric discharge machining. The problem with this known solution is that it is slow and can only cut simple shapes. Other known prior art suffers from problems such as the need for lubricating oil and excessive tool wear.

  Furthermore, another method for cutting diamond using a laser has been proposed. The prior art includes the use of flash pumped solid state lasers (FPSSL). Flash lamp pumped solid state lasers (FPSSL) have been operating in the industry for over 20 years, operating at hundreds of hertz, with pulse durations of milliseconds, and widely used to provide high power but low power density (irradiance) Has been used. However, this mechanism suffers from the problem of low power and low efficiency.

  The invention is clearly set forth in the appended claims.

  Next, an embodiment of the present invention will be described by way of example with reference to the drawings.

For example, the hardness is 250 kg. hardness exceeding mm 2 (Vickers hardness value), more preferably 500 kg. It exceeds mm 2, even more preferably 1000 kg. Processing can be performed on materials having a hardness exceeding mm 2 . Specifically, the hardness of WC is 1730 kg. mm 2 and the hardness of PCD is 5098 kg. a mm 2.

  In general, the present invention relates to a laser configured to process hard materials such as natural diamond, PCD, WC, etc., with a very high repetition rate and irradiance using a pulsed laser. Within a specific range of parameters, each value has been specified with a very effective operation. As described in more detail below, it has been found that in one embodiment, a diode pumped solid state laser (DPSSL) can achieve the desired performance.

  Two specific machining applications for the apparatus of the present invention are described below: cutting an initial tool shape and maintaining the sharpness of the tool.

  An apparatus for shaping or milling a hard material is shown in FIG. The laser 10 generates a pulse beam. The pulsed beam is redirected by mirrors 12, 14 and through an optical array 16, 18 with a telescope (beam expander) to a scanner 20 that moves the beam across the target (eg, PCD material to be milled). Led. The beam passes through a shaping or clip aperture or a stop 24, 26, 28, 30. Further, for example, an alignment laser 32 such as a HeNe alignment laser generates an alignment beam that is coaxial with the pulse beam by mirrors 34 and 36. The mirror 36 is in the optical path of the pulsed laser beam, but can be removed when alignment is complete. A diaphragm 23 is used in association with the HeNe alignment beam to assist in alignment using the back reflector.

  The laser milling method uses a Starlase AO2 Nd: YAG Q-switched DPSSL available from Powerlase Limited, Crawley, West Sussex, West Sussex, at a fundamental wavelength of 1064 nm. Yes. This pulsed laser provides an average power of up to 220 W with repetition rates and pulse durations in the range of 3-50 kHz and 20-200 ns, respectively. The output beam power is changed using any suitable attenuator (not shown), then collimated using Galilei telescopes 16 and 18 and galvanometer scanner 20 (Munich, Germany). Guided to ScanLab HurryScan 25 available from Scanlab GmbH. The scanner is fitted with an f-θ telecentric objective with a focal length of 80 mm with a work target area of 25 × 25 mm. All processing operations are performed in air at standard ambient conditions and do not use gas assist.

  In operation, the system is first aligned using the alignment laser 32 and the removable mirror 36 is removed. Next, the pulsed laser 10 is activated and performs the operating cycle described in more detail below. A pulsed beam is scanned across the target by the scanner 20.

  The scanner 20 will be understood in more detail from FIG. In FIG. 7, the scanner includes steering mirrors 50 and 52 and a flat field lens 54. As can be seen from the inset 56, as a result of scanning the pulse beam, overlapping laser pulses are achieved, allowing any desired complex cutting shape. The scanning speed is determined as a function of the laser repetition rate and the spatial overlap of the laser pulses. The degree of pulse overlap is used to control the amount of “heat” received by any particular portion of the target. When the laser pulse illuminates the target, the material is heated, a portion of the material evaporates, and after the pulse, the target begins to cool. During this cooling process, if the next pulse arrives and there is an overlap, the material will reach the evaporation point earlier than the first pulse (the material temperature after the first pulse is higher than the ambient temperature) As a result, the laser pulse becomes effective by evaporation. However, this process has its limitations. If excess residual heat energy is left (stored) in the target, the material becomes a liquid and a molten pool is formed. This is quite difficult to control and is therefore undesirable in a milling process. Furthermore, by carefully controlling the overlap, the quality of the material surface after the milling process has been completed can be controlled. The greater the overlap, the smoother the finish. Accordingly, an appropriate scanning speed for a given setting can be determined by experimentation to achieve a desired level of milling.

  The specific operating parameters selected are described herein in connection with two specific materials, PCD and WC. For example, a laser can be used to mill a material such as the material shown in FIG. 2 (and cut as described in more detail below). This material includes a PCD layer 200 on a WC substrate 210 and forms a composite material 220 with a cutting edge 230 to be cut / milled and a taper angle θ240. Laser cutting and milling processes must achieve and maintain a cut that can use PCD as a cutting tool. FIG. 2 shows the sharp cutting edge 230 required on the diamond side of the PCD material. The cutting edge must be exactly straight and have the smallest possible radius. This sharp cutting edge is only needed on the cutting surface 250 and not on the other side of the PCD part.

  The exact operating parameters depend on the material, factors such as thermal conductivity, density, heat capacity, evaporation temperature, specific heat of evaporation and reflectivity of the target surface, as well as the preferred range of specific materials as described below. ing.

When milling PCD, the preferred irradiance range is 10 7 to 10 9 Wcm −2 , more preferably 100 MWcm −2 to 200 MWcm −2 . A preferable pulse duration is 47 ns to 160 ns, more preferably 120 ns to 160 ns. A preferable repetition rate is in the range of 10 kHz (47 ns) to 50 kHz (160 ns), more preferably 40 kHz (120 ns) to 50 kHz (160 ns). A removal rate of up to 9 mm 3 / min is achieved using the above-described specific laser device, but the removal rate can be increased by using a high-power laser. FIG. 3 shows in more detail the removal rate achieved at irradiance with a repetition rate in the range of 10-50 kHz.

  More than expected, a particularly good performance result is obtained by the above-mentioned parameter range. This is due to the physical mechanism that occurs during laser milling. In this physical mechanism, the laser pulse creates an initial melting stage in which the surface of the workpiece rises to the vapor temperature, and then a material removal stage with controlled evaporation. In particular, laser pulses are powerful enough (ie, have sufficient irradiance), have sufficient pulse duration, and raise the temperature of the material above the melting point to the vapor point of the material (near the boiling point) I have to let it. From this point in the pulse duration, evaporation occurs and material is removed from the target in a controlled manner.

  Consequently, the control parameters for removing material by polishing are the irradiance or power density of the pulse and the pulse duration. In some cases, the pulse duration is directly related to the laser repetition rate. When the repetition rate is high, the pulse length is long, and when the repetition rate is low, the pulse length is short. Therefore, in the above-described embodiment, the above-described repetition rate range forms a management parameter based on a direct relationship with the pulse duration. However, in other embodiments, the pulse duration itself can be appropriately controlled independently of the laser repetition rate to achieve the desired processing conditions.

  The importance of irradiance rather than just pulse energy arises. The reason for this is that by reducing the conduction loss of the target material to the volume, less energy is actually processed, and in order to be able to actually form a molten pool of liquid, This is because the pulse energy must be concentrated in a pulse of time (on the order of nanoseconds). In the case of PCD, it has been found that irradiance levels below the lower limit of the specific range described above have little effect on the material other than melting the material due to the limited material removal. On the contrary, the upper limit of the pulse irradiance is determined by the plasma absorption effect that blocks the beam to be delivered to the target (laser induced absorption wave (LAW)).

  Similarly, as the laser repetition rate increases, the pulse duration increases, but the irradiance and pulse energy decrease, so the maximum repetition rate limit is determined by the low irradiance threshold. Similarly, since the laser pulse irradiance increases at a low repetition rate until the absorbing plasma is generated as described above, the lower limit of the pulse repetition rate is also determined by the beginning of the LAW. But yet another factor must be considered. That is, as the laser repetition rate decreases, the pulse duration decreases and the irradiance increases. Although material removal per pulse increases with increasing irradiance (because the material reaches the evaporation temperature faster), the pulse duration decreases, and this increased removal rate helps to reduce time. Furthermore, when the repetition rate decreases, the removal amount for each pulse increases, but since the number of pulses decreases, the overall removal amount may not increase.

  Thus, it has been found that fast repetition rate is a major factor in achieving the fastest PCD removal rate. It has also been found that the greater the laser repetition rate, the smoother the bottom of the milled area. This result shows that the best laser milling conditions are determined and that the high power nanosecond-kilohertz operating area is effective for milling PCD.

Turning now to WC, a lower removal rate is achieved than with PCD. A high removal rate is achieved with a low frequency repetition rate (with high pulse irradiance), whereas a maximum repetition rate of 50 kHz does not remove any material, thus eliminating removal with available pulse irradiance. May not be available. Referring to FIG. 4, the relationship between pulse irradiance and removal rate is shown in various repetition rate ranges. Surprisingly, the preferred range for irradiance is 10 8 Wcm −2 to 10 9 Wcm −2 , more preferably, pulse duration 47 ns to 160 ns, more preferably 500 ns to 700 MWcm for 120 ns to 160 ns. -2 , the repetition rate is 10 to 50 kHz (47 to 160 ns), more preferably 10 to 30 kHz, and the highest removal rate is in the range of 10 to 20 kHz (47 to 63 ns).

  This is due to the underlying physical mechanism as described above. At 50 kHz, the pulse is relatively long but the pulse irradiance is small and in many cases the evaporation temperature for WC is not achieved within the pulse duration. The material removal stage is reached only when the pulse irradiance is maximum. In fact, the removal rate usually drops to zero at a repetition rate of 50 kHz and the pulse irradiance is not sufficient for the material to reach this evaporation temperature. Therefore, neither evaporation nor material removal takes place. This means that the minimum pulse irradiance boundary condition has not been reached. Only when the repetition rate is low, material is removed. In this case, the pulse irradiance level is high enough to reach the evaporation temperature within the pulse duration. For example, at 30 kHz, the pulse duration is shorter, but the pulse irradiance is much larger and reaches the material removal stage faster within the pulse duration.

  It is important to note that in both these cases the laser output power will be the same. This can significantly improve the material removal rate by maintaining the laser output power and changing other laser parameters.

  Next, focusing on another application of the tool, cutting will be described below with reference to FIG. FIG. 5 shows a laser cutting device having the same characteristics as the laser cutting device shown in FIG. 1, and like reference numerals relate to like parts. The main difference is that a gas-assisted cutting head 40 is provided.

  The laser drilling and cutting method uses a higher power Starlase AO4 Nd: YAG Q-switched DPSSL available from Powerraise, Crawley, West Sussex, at a fundamental wavelength of 1064 nm. This pulsed laser provides an average power of up to 420 W with a pulse duration of 20-200 ns in the range of repetition rates of 3-50 kHz. The output beam power is changed using an attenuator, and is converted into a parallel beam using Galilean telescopes 16 and 18, and an anoradXYZ operation stage 11 (UK, Basingstoke, Rockwell Automation (Rockwell Automation, Basingstoke, UK) ) (Available from Anorad UK). In this stage, the target is moved in the XY directions, and the condensing head is moved in the Z direction. The Anorad system is rigidly mounted and linearly drives 450 x 450 mm XY movement with an accuracy of +/- 1 μm at the highest possible speed of 2 m / s. The laser beam is collected by various lenses 46 having a focal length of 100 mm to 203 mm. For example, a lens with a focal length of 149 mm produces a 200 μm diameter spot with the best focus. The cutting head 40 allows a coaxial gas jet 48 to be used to assist the cutting process. The gas jet 48 may be compressed air, oxygen or nitrogen and can be supplied to the workpiece at a pressure of up to 10 Bar.

  The cutting technique employed includes reactive melt cutting known as “melt burn and blow”. In reactive melt cutting, the laser beam creates a melt pool and a coaxial gas jet ejects liquid from the bottom of the cut. The gas jet reacts exothermically with the melted material and adds another heat source to the process, facilitating the creation of a melt pool and thus cutting speed. This method provides excellent vertical cutting edge quality using either oxygen or air as the gas jet.

  In practice, it has been found that the cutting operation has two different stages. The drilling stage occurs at the beginning of the cutting line where the percussion drill hole is formed. For most of this work, the hole is a mechla hole, and the debris from the drilling work will rise out of the hole entrance, resulting in a scraped area on the material surface around the hole. After the drilling, a cutting stage follows. The laser cutting head moves over the material at a constant speed, and the material is cut in a single scan. An angled cutting front is formed, which is where the laser beam is absorbed. The laser beam is guided through the thickness of the material.

  The operation of the system is in principle as described above for laser milling, but will be described in more detail below using specific operating parameters, particularly in connection with PCD.

Specifically, the preferred pulse repetition rate is in the range of 10-50 kHz, more preferably 40-50 kHz, and the pulse duration is preferably 30-200 ns, more preferably 100-200 ns. The average laser output is 300 W to 1 kW, more preferably 350 to 400 W. The irradiance is preferably in the range of 10 6 to 10 8 Wcm −2 , more preferably about 100 MWcm −2 , and most preferably 110 MWcm −2 (drilling), 118 MWcm −2 (during cutting). It is. A preferred assist gas pressure is in the range of 1 to 10 bar, more preferably 8 bar. Referring to FIG. 6, the relationship between PCD depth during drilling and test time is shown for a range of repetition rates.

  In terms of the scanning speed of the beam across the material to be cut, it is preferable to operate at high speed. This is because this not only increases the production rate, but also shortens the time for the heat to diffuse laterally and forms a narrower heat affected zone (HAZ). The optimum speed range is 21 to 27 mm / min, and the best cutting edge quality is obtained at about 24 mm / min. The limit of the cutting speed is the point at which the gas jet can no longer release the molten material, at which point the reactive diffusion cutting operation fails.

For a composite PCD / WC material of the type shown in FIG. 2, at 100 MWcm −2 , the PCD removal rate is 7.6 mm 3 / min, while WC is the removal threshold. For cutting purposes, this is above the WC side, near the cutting nozzle and at the best focus, the preferred range of irradiance is 10 8 to 10 9 Wcm −2 , most preferably 120 MWcm −2 , More preferably 100-200 MWcm −2 , repetition rate 40-50 kHz, most preferably 45 Hz, pulse duration 41 ns-200 ns, more preferably 155 ns-200 ns, pulse energy 6 0.7 mJ, meaning that the oxygen gas assist is 8 bar. These values are also preferred when cutting WC directly.

  However, it has been found that when cutting the WC side upwards, streaks are produced by the reactive molten gas cutting process. This problem can be overcome by turning the material upside down so that the PCD side is closest to the cutting nozzle. The best focus position is maintained in this position direction, i.e. halfway through the WC. As a result, the assist gas passes through the PCD layer and reaches the WC, so that the assist gas is hardly deposited on the PCD, and the PCD is kept mostly clean and free from scratches. This method is greatly improved, reduces the PCD line, and forms a sharp cutting edge at the cutting edge. The PCD layer has no scratches, and no cut is formed between the PCD layer and the WC layer. By removing the streak, the linearity of the cutting edge is reduced. The absence of debris ensures that interference in the brazing process of attaching the PCD cutting tool to the cage prior to use is reduced. Otherwise, the brazing joint will be weak. By removing the step or cut at the PCD-WC interface, the weakness of the interface between materials, which can cause initial failure of the cutting tool, is eliminated. It should be noted that some streaks are still present, but the other layers are free of scratches and the streaks assist the brazing process by providing a larger surface area for the brazing process to join.

  The parameter range gives very good operation. This is because the greater the irradiance, the more the laser pulse produces melting and evaporation WC at a high repetition rate for the reacting oxygen. This combustion reaction proceeds outward from the laser focus in all directions, thereby causing streaking until the combustion reaction has moved significantly away from the fuel source (focused laser beam and coaxial gas jet). By this time, the laser cutting head has moved to a new part of the PCD where the combustion process begins again. As the cutting speed increases with respect to the “burning reaction” speed, the formation of streaks decreases.

The pulse irradiance used in a successful cutting test (118 MWcm −2 ) is just above the threshold for WC removal by evaporation, as shown in FIG. The cutting process is believed to be enhanced by this evaporation with the oxygen assist gas reacting directly with the WC vapor rather than melting. This leads to a much greater exothermic reaction, thereby cutting faster.

  In one preferred method, the cutting process is applied in multiple scans, eg, first and second scans. In this case, each scan may use the above settings in the top / nearest PCD layer of the cutting nozzle. In this case, the first scan is used for cutting the PCD, and the second scan is used for improving the quality of the cutting edge of the PCD.

  In a preferred embodiment, dynamic focusing changes between different scans are used to provide improved results. For example, in the first scanning, as described above, the focal position may be located in the WC layer. However, for the second scan, the focus can be raised to the top surface of the PCD. This method has been found to improve the quality of PCD cutting edges, in particular. The focus position for the second scan can also be moved to an alternative position in either the WC layer or the PCD layer.

  In a further refinement, the material cutting edge may be formed with a negative taper so that the leading edge cutting edge protrudes from the lower edge as shown in FIG. In particular, it will be seen that a cutting nozzle, generally designated 70, is provided near the PCD / WC layer composite 76, with the PCD layer 72 on top and closest to the nozzle. The cutting edge 74 at the leading edge of the PCD layer protrudes from the WC layer, thereby forming a negative taper generally indicated by θ. It has been found that changing the focus from the point generally indicated by X and half-passed through the WC layer to the point generally indicated by Y and on the top surface of the PCD layer can help to form a negative taper. . The amount of taper varies depending on the characteristics of the PCD and the material (wood, copper, aluminum, etc.) used for processing the PCD. The taper angle is typically 7 degrees, but usually does not exceed 15 degrees.

  Many advantages are obtained by the method described above. It has been found that hard materials can be processed at higher speeds than the prior art to achieve comparable quality without having to deal with problems such as tool wear and lubrication. This technology allows these materials to be cut and milled simultaneously, thereby providing new flexibility in manufacturing design.

  DPSSL allows for very large energy intensities, and the nanosecond-kilohertz mode of operation greatly improves many difficult laser material processing applications. Short pulses reduce thermal effects and improve machining quality. On the other hand, a large fluence improves material bonding and processing efficiency. DPSSL further provides a combination of good beam quality, high efficiency, robust structure and long diode life. This makes it possible to manufacture on both macro and micro scales. Laser cutting of PCD is possible with a DPSS laser at a much faster cutting speed than alternative techniques.

  For example, compared to EDM, a laser cutting speed of 24 mm / min is achieved, which is four times faster than the corresponding speed using EDM. Furthermore, if a laser and a scanner stage are used, cutting can be performed in all directions.

  Laminated structures can be cut using techniques such that PCD and WC discs achieve the same quality as EDM or better cutting quality than FPSS. Such laminated structures include Syndite (R) available from deBeers or a single layer or composite structure, preferably having a thickness in the range of 0.5 mm to 3.2 mm, such as 0.8 on a WC substrate. Composite structures with a thickness of 1.6, 2.0 or 3.2 mm with a PCD of 5 mm are included.

  It is understood that the techniques described herein can be extended to any suitable rigid material and can be extended to achieve the specific parameters presented herein using any laser. Like. Use any material processing application to form 3D shapes by drawing dies or 3D milling using fine holes, for example, in addition to cutting and milling such as permanent marking and drilling of PCD material be able to.

It is a schematic block diagram which shows a laser milling apparatus. It is a cross-sectional perspective view of a PCD composite material. 6 is a graph of removal rate versus laser beam pulse irradiance for PCD over a range of pulse repetition rates. It is a graph of the removal rate with respect to the pulse irradiance of tungsten carbide in a certain range of repetition rate. It is a schematic block diagram which shows a laser cutting device. FIG. 6 is a diagram of PCD cutting depth versus test time for a range of pulse repetition rates. It is a perspective view of the use of a laser milling process. It is a side view of a PCD / WC composite material and a cutting nozzle.

Claims (32)

  1. A hard material processing apparatus comprising a laser configured to output a pulsed beam having an irradiance in the range of 10 6 to 10 9 Wcm -2 and a repetition rate in the range of 10 to 50 kHz.
  2.   The apparatus of claim 1, wherein the laser pulse has a pulse duration in the range of 30 to 200 ns, more preferably 100 to 200 ns.
  3. The hard material milling apparatus provided with the apparatus according to claim 1 or 2, wherein the irradiance is in the range of 10 7 to 10 9 Wcm -2 and the repetition rate is in the range of 10 to 50 kHz.
  4. The PCD milling apparatus comprising the apparatus according to claim 3, wherein the irradiance is in a range of 100 to 200 MWcm −2 and the repetition rate is in a range of 40 to 50 kHz.
  5. The irradiance is in the range of 10 8 to 10 9 Wcm −2 , more preferably in the range of 500 to 700 MWcm −2 , and the repetition rate is in the range of 10 to 50 kHz, more preferably 10 to 30 kHz, more preferably 10 to 20 kHz. A WC milling apparatus comprising the apparatus according to claim 3.
  6. The hard material cutting device including the device according to claim 1 or 2, wherein the irradiance is in a range of 10 6 to 10 8 Wcm -2 , and the repetition rate is in a range of 10 to 50 kHz.
  7. The irradiance is in the range of 10 6 to 10 8 Wcm −2 , more preferably 100 to 120 MWcm −2 , or more preferably 110 MWcm −2 (during drilling) or 118 MWcm −2 (during cutting), and the repetition rate is The PCD cutting device according to claim 6, which is in a range of 40 to 50 kHz or more.
  8. The WC cutting apparatus comprising the apparatus according to claim 6, wherein the irradiance is in the range of 10 8 to 10 9 Wcm −2 , more preferably in the range of 100 to 200 MWcm −2 , and the repetition rate is in the range of 40 to 50 kHz. .
  9. A method of milling a hard material, comprising irradiating the material with a pulsed laser beam having an irradiance of 10 7 to 10 9 Wcm −2 and a repetition rate of 10 to 50 kHz.
  10. A hard material cutting method comprising irradiating the material with a pulsed laser beam having an irradiance in the range of 10 6 to 10 8 W and a repetition rate in the range of 10 to 50 kHz.
  11.   The method of claim 10, wherein the material comprises a PCD layer on a WC substrate.
  12.   The method according to claim 11, wherein the surface of the PCD is irradiated with the pulsed laser beam.
  13.   The method of claim 12, wherein the beam is focused at a point in the WC substrate.
  14.   The method of claim 13, wherein the focal point passes through the WC substrate approximately half way.
  15.   The method according to claim 12, wherein the pulsed laser beam is irradiated in a plurality of scans.
  16.   16. The method of claim 15, wherein in a first scan, the laser beam is focused at a point in the WC layer, and in a second scan, the beam is focused at the surface of the PCD layer.
  17.   16. The method of claim 15, wherein in a first scan, the laser beam is focused at a point in the WC layer, and in a second scan, the beam is focused at a point in the PCD layer.
  18. In a first scan, the laser beam is focused at a first point in the WC layer, and in a second scan, the beam is focused at a second point in the WC layer;
    The method of claim 15, wherein the first and second points are different.
  19.   The method according to claim 10, wherein a negative taper is formed on the material.
  20. A hard material processing method comprising irradiating the material with a pulse laser beam having an irradiance in a range of 10 6 to 10 9 Wcm −2 and a repetition rate in a range of 10 to 50 kHz.
  21. Processing hard materials comprising a laser configured to output a pulsed beam with an irradiance in the range of 10 6 to 10 9 Wcm −2 and a pulse duration of 30 to 200 ns, more preferably in the range of 100 to 200 ns. apparatus.
  22. 21. A hard material milling apparatus comprising the apparatus of claim 19, wherein the irradiance is in the range of 10 < 7 > to 10 < 9 > Wcm <-2 > and the pulse duration is in the range of 47 ns to 160 ns.
  23. The hard material cutting device comprising the device according to claim 19, wherein the irradiance is in a range of 10 6 to 10 8 Wcm −2 and the pulse duration is in a range of 100 to 200 ns.
  24.   The apparatus according to claim 1, wherein the hard material comprises a composite material.
  25.   23. The apparatus of claim 22, wherein the composite material comprises a PCD WC composite.
  26.   Output a pulsed laser beam of a predetermined spot diameter and scan the beam over the workpiece so that adjacent pulses overlap in space to the extent that the material is evaporated but does not form a molten pool. And a method for processing a hard material.
  27.   A method of cutting a hard material comprising a PCD layer on a WC substrate, comprising irradiating a surface of the PCD with a cutting laser beam.
  28.   A method of cutting a hard material, comprising irradiating the material with a laser beam in a plurality of scans.
  29.   27. The method of claim 26, further comprising changing the focus of the beam between each scan.
  30.   28. The method of claim 27, wherein the beam is focused on a point in the material for a first scan and on the surface of the material for a second scan.
  31.   29. The method of claim 27 or 28, further comprising forming a negative taper in the material.
  32.   25. Apparatus according to any one of claims 1 to 8 or claims 19 to 24 substantially as herein described with reference to the figures.
JP2007535239A 2004-10-07 2005-10-07 Hard material processing apparatus and processing method using laser having irradiance in the range of 106 to 109 Wcm-2 and repetition rate in the range of 10 to 50 kHz Pending JP2008515643A (en)

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GB0422318A GB0422318D0 (en) 2004-10-07 2004-10-07 An apparatus for processing hard material
GB0511966A GB0511966D0 (en) 2005-06-13 2005-06-13 An apparatus for processing hard material
PCT/GB2005/003855 WO2006038017A2 (en) 2004-10-07 2005-10-07 An apparatus and a method for processing hard material using a laser having an irradiance in the range 10 '6 to 10 '9 w/cm'2 and a repetition rate in the range 10 to 50 khz

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JP2011079300A (en) * 2009-08-26 2011-04-21 Hueck Rheinische Gmbh Method for producing surface structure for metallic press plate, endless belt or embossing roller
JP2011098390A (en) * 2009-10-22 2011-05-19 Ewag Ag Laser machining apparatus and method, for forming surface of half-finished product
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