Machine and method for improving cutting edge

Abstract

A processing machine (40) is described for adjusting the K-factor of a cutting edge of a work tool (60). In one embodiment, the processing machine includes a blast gun (50) that directs a pressurized blast stream of abrasive particles in a blast direction (72) and mounting means for securing the work tool such that an axis of rotation (62) of the work tool is radially offset from the blast direction (72) by an offset distance (80), and control of the offset distance between the blast direction and the axis of rotation adjusts the K-factor of the cutting edge (64, 66).

Description

[Technical Field]

[0001] The present invention relates to a processing machine, and more particularly to a processing machine and method for adjusting the K-factor of a cutting edge. [Background technology]

[0002] The reliability and performance of cutting tools such as drill bits, end mills, slot mills, and thread taps have become better understood and controllable aspects in recent years. The microgeometry of the cutting edge affects tool life, cutting process stability, chip formation, and surface quality, as well as tool head and force loading. It is known that forming a radius on the cutting edge (often referred to as edge honing) can extend edge life. The shape of the honed cross section has also been shown to be important.

[0003] One approach used in WO9735686 demonstrates that wet blasting is superior to brushing for honing the cutting edge of a slender rotary tool. This uses a circular abrasive stream to produce a relatively uniformly honed cutting edge. However, this specification does not describe how to produce a non-uniform honing that is adjustable yet reproducible.

[0004] The shape of the honing cross section can range from a constant diameter to an increasing or decreasing diameter. This symmetry is now known as the K-factor. K is defined as: K=Sγ / Sα where Sγ is the distance from the apex of the chipping face (or rake face) and clearance face (or flank face) to the end of the rounding of the chipping face, and Sa is the distance from the apex to the end of the rounding of the clearance face. Therefore, a symmetric cutting edge microgeometry has a K factor of 1, and a K factor greater than 1 indicates a large rounding of the rake face or chipping face, while a K factor less than 1 indicates a large rounding of the flank or clearance face.

[0005] Various sizes and diameters can be achieved by blasting, brushing, finishing with magnets or chemicals, or by lasers. Turning to blasting, one method of creating edge radius is by wet blasting. In wet blasting, an abrasive blasting material is mixed with a liquid to form a blast slurry, which is passed at high pressure through a nozzle such as a blast gun. The impact of the pressurized slurry or treatment cleans and removes the surface to achieve the desired finish.

[0006] The amount of material removed is controlled by several variables, including the blast pressure of the gas, the angle of the blast stream relative to the cutting edge, and the size, shape and density of the abrasive particles used.

[0007] Controlling the K-factor is more difficult and has traditionally been attempted by adjusting the angle of the blast stream relative to the tool's rotation axis.

[0008] The present invention aims to remedy at least the aforementioned drawbacks by providing a method for more controllably adjusting the K-factor of the cutting edge. Summary of the Invention [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided a processing machine for adjusting the K-factor of a cutting edge of a power tool, the processing machine comprising: a blast gun for directing a pressurized blast flow slurry of abrasive particles in a blast direction; and mounting means for fixing the work tool so that the rotation axis of the power tool is radially offset from the blast direction by an offset distance, and the K-factor of the cutting edge is adjusted by controlling the offset distance between the blast direction and the rotation axis.

[0010] The present invention provides a more controllable mechanism for adjusting the K-factor of the cutting edge. Unlike the prior art, which focuses on adjusting the blast pitch angle relative to the axis of rotation of the power tool, the present invention focuses on the offset distance between the blast stream and the axis of rotation of the power tool.

[0011] It will be appreciated that the blast direction may include a blast axis that may or may not be perpendicular to the longitudinal axis of the work tool. In an embodiment, the blast gun is positioned at a blast distance at a blast angle from the work tool, where the blast direction or blast axis is the direction in which the slurry in the blast stream is incident on the work tool. The center of the blast stream incident on the work tool can be considered to be the origin, and the blast gun can be considered to be positioned at a blast distance r and a blast angle Q, where r and Q are polar coordinates that indicate the position of the blast gun relative to the work tool.

[0012] As an example, a radial offset distance that aligns the blast direction of the blast stream symmetrically with respect to the cutting edge will result in a K-factor of approximately 1. If the blast stream is offset toward the chipping plane, the K-factor can be controlled to be greater than 1. If the offset is away from the chipping plane, the K-factor can be controlled to be less than 1.

[0013] In some embodiments, the blast pattern of the blast stream (which is the broad cross-sectional shape of the blast stream) may be non-circular. In one embodiment, a rectangular blast pattern may be used. This configuration can assist in controlling the offset distance between the blast streams compared to using a circular blast pattern due to the non-linear blast profile presented to the work tool by such a blast pattern.

[0014] According to one embodiment, the blast pattern may be substantially rectangular with the long edge of the pattern facing the cutting edge. The blast pattern may have an aspect ratio of at least 2:1, and may be 5:2, 3:1, 4:1 or greater.

[0015] In some embodiments, the blast pattern includes sharp edges, which may be incident on the cutting edge.

[0016] In an embodiment, the blast gun of the processing machine comprises a nozzle that ejects a pressurized blast stream of abrasive particles in a blast direction. In a further embodiment, the nozzle comprises a slot with a sharp edge, which provides a counterpart to the sharp edge of the blast pattern. In other words, the long edge of the pattern is the sharp edge.

[0017] Generally, the work tool may be a drill bit, an end mill, a thread tap, or a slot mill. When the work tool is a drill bit, the cutting edge may be the edge of the flutes of the drill bit. The cutting edge may also refer to the edge of the point angle (the end of the cutting edge).

[0018] Although power tools often have round shanks, it will be appreciated that shanks of hexagonal, square, triangular, triangular, or other cross-sections may also be used.

[0019] In embodiments, the abrasive particles include one or more particle types, such as glass beads, metal shot, or aluminum oxide particles. Mixtures or combinations of abrasive particles may be used, and such mixtures are tailored to the desired finish and the materials being used. These blends of different abrasives may have opposing or complementary properties; one example of a blend is glass beads and virgin white aluminum oxide. Virgin aluminum oxide is often used in applications where work tools are prone to rust due to the low iron content of this type of aluminum oxide.

[0020] In a preferred embodiment, the pressurized slurry comprises a wet blasting slurry, which has a mixture of abrasive particles and compressed gas together with a liquid to form a pressurized slurry, lubricating the abrasive particles in a liquid buffer (typically water, although additives may be used to prevent rust, organic buildup, etc.).

[0021] In a second aspect of the present invention, there is provided a method for improving a cutting edge of a work tool, the work tool having an axis of rotation, the method comprising the steps of: fixing the work tool in a blast chamber, the blast chamber comprising a wet blast gun that emits a stream of abrasive particles suspended in a slurry from a nozzle of the blast gun; directing the stream of abrasive particles towards the cutting edge of the work tool; and adjusting a radial distance between the nozzle of the blast stream and the axis of rotation, the blast nozzle being configured to generate a blast stream of a substantially non-circular cross-section, the nozzle being aligned substantially perpendicular to the axis of rotation.

[0022] It will be appreciated that the embodiments and examples described with respect to the first aspect are applicable to the second aspect.

[0023] An example of K-factor control using the present invention allows for adjustment of the K-factor to within an accuracy of 0.02, with a range of K-factor values ​​between 0.4 and 1.9 being achievable, with typical control being accurate to K-factor values ​​between 0.5 and 1.8, which can be achieved to produce diameters of less than 50 microns.

[0024] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. [Brief explanation of the drawings]

[0025] Embodiments of the invention will now be described in detail, by way of example, with reference to the accompanying drawings in which: [Figure 1] Figure 1 shows how to determine the K-factor of the cutting edge. [Figure 2] FIG. 2 shows, in focus on the work tool, a treatment machine equipped with a blast gun according to the invention. [Figure 3] FIG. 3 shows the processing machine of FIG. 2 arranged in a configuration according to the invention, with the work tools aligned perpendicular to the blast flow of the blast gun and with a radial offset. [Figure 4]FIG. 4 shows a semi-stylized illustration of how the blast pattern of the blast stream is directed onto the work tool. [Figure 5a] FIG. 5a shows a nozzle for the blast gun of FIG. 2 according to one embodiment of the present invention. [Figure 5b] FIG. 5b shows an exploded view of FIG. 5a. [Figure 5c] FIG. 5c shows a cross-sectional view of FIG. 5a.

[0026] It should be noted that the figures are schematic and are not drawn to scale. Relative dimensions and proportions in some of the figures have been shown in increased or decreased size for clarity and convenience of the drawings. The same reference numerals are generally used to refer to corresponding or similar features in different modified embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0027] 1 illustrates how the K-factor of a cutting edge of a work tool (or indeed any cutting edge) is determined. As illustrated, cutting edge 10 includes a chipping surface 12, or rake face, and a clearance surface 14, or flank face. As can be seen, edge 16 has an edge diameter that is an approximation of the radius of circle 20. In determining the K-factor of this edge (using the techniques described above), Sy is the distance from the intersection of the chipping surface (or rake face) and the clearance surface (or flank face) to the end of the radius of the chipping surface, i.e., distance 22, and Sa is the distance from said intersection to the end of the radius of the clearance surface, i.e., distance 24.

[0028] 2 shows a blast machine 40 according to this embodiment of the invention. The blast machine generally comprises a blast gun 50 having a first inlet 52 through which passes a slurry of abrasive particles, such as glass beads, sand, metal shot, aluminum oxide, or any suitable blasting media containing a mixture of such abrasive particles; the abrasive is mixed with a fluid, typically water, to form a slurry, which is then mixed with compressed gas from a second inlet 54. This forms a pressurized blast flow directed towards a work tool 60. The work tool is shown as a drill bit having a rotating shaft 62 and having a spiral flute (which may be a cutting edge side) 64 and a cutting edge end 66.

[0029] In one configuration, the blast axis, or blast direction 72, of the blast gun 50 is aligned at a blast angle 76 and a blast distance 74 from the work tool. The intent is to utilize the blast pattern of the blast stream to peen and / or hone the cutting edge side 64 and cutting edge end 66. Previous efforts have focused on adjusting the blast distance 74 and blast angle 76 to create a desired K-factor for the cutting edge.

[0030] FIG. 3 illustrates a blast machine 40 arranged in a configuration according to an embodiment of the present invention. In these embodiments, the blast axis 72 is positioned perpendicular to the rotation axis 62 of the work tool 60. However, in addition to this difference from prior art configurations, the blast axis 72 is offset from the rotation axis 62 by a radial offset distance 80. In this embodiment, when the radial offset is zero, the K-factor is approximately 1. If the blast flow offset is toward the chipping plane, the K-factor can be controlled to be greater than 1. Alternatively, if the offset is away from the chipping plane, the K-factor can be controlled to be less than 1. By way of example, a range of K-factor values ​​between 0.4 and 1.9 is possible, with an accuracy of 0.02. This corresponds to an edge diameter accuracy of less than 50 microns. Thus, by adjusting the offset distance, the K-factor of the cutting edge can be selected with high precision. It will be appreciated that the blast machine may still be arranged at the blast angle 76, but in this embodiment, the offset distance 80 is changed and the K-factor adjusted accordingly.

[0031] Figure 4 shows the work tool 60 when subjected to a directional blast stream from the blast machine of Figure 3. In particular, the effect of the blast stream pattern or shape can be seen. With a circular blast pattern 80, the blast media is difficult to align with the cutting edge of the grooves 64 or cutting edge end 66, making it difficult to control the K-factor of the cutting edge, increasing the likelihood of wasting blast media or an inaccurate finish. It will be appreciated that attempts to adjust the K-factor of the intermediate grooves 64 will likely also affect the lower grooves that have already been processed, resulting in inconsistent results.

[0032] In contrast, embodiments of the present invention utilize non-circular blast patterns 90, such as rectangular blast patterns. The use of such blast patterns allows for greater control and adjustment of the K-factor of the cutting edge, particularly in the configuration described above. A typical non-circular blast pattern is rectangular, although square or elliptical patterns can also be used, depending on the shape of the cutting edge being honed. A typical aspect ratio for such non-circular blast patterns is 2:1, although 5:3, 3:1, and 4:1 can also be used. The use of thin blast patterns in this blast machine configuration allows for finer adjustment of the K-factor than previously possible.

[0033] An exemplary embodiment of a nozzle 100 for generating a non-circular blast pattern 90 is shown in FIGS. 5a-5c. Such a nozzle 100 has a substantially rectangular or square slot or end nozzle 110 through which a slurry of abrasive particles can be ejected. The nozzle 100 includes a base portion 120 having a sloped base surface 122. It will be appreciated that the end nozzle 110 has sharp edges. The sloped base portion extends into a flat base portion 124. The flat base portion 124 extends into the nozzle 100. An air guide 130 is connected to the top of the nozzle base beyond the flat base portion 124. The air guide 130 is a wide, flat surface with a chamfered end face 131 that matches the end of the slot 110 so that the slot opens into a larger slurry chamber. The air guide 130 is secured by a screw 140. The air guide 130 is secured to the base of the nozzle base surface 124 and allows air to pass through a channel 139 via an air inlet 138. In addition to the air guide 130, there is a slurry guide 132. The slurry guide 132 is co-located opposite the air guide, but is positioned within the slot 110 opposite the angled base surface 122 and flat base portion 124. A chamfered edge 133 is also provided. The slurry guide is secured to the nozzle top plate 134 using screws 142.

[0034] The top plate covers the nozzles, leaving rectangular openings exposed to the slots 110. The top plate has slurry inlets or holes 136 through which the slurry can be injected. The top plate secures the air guide 130, slurry guide 132 and top plate 130 to the base 120 using screws 148, washers 146 and nuts 144.

[0035] In use, as shown in FIG. 5c, air is injected into the nozzle at inlet 138. The air passes along channel 139 before exiting the opposite side of air guide 132. Similarly, a slurry of abrasive particles enters through slurry inlet 136. The slurry is guided by slurry guide 130 down chamfer 131 and strikes air guide chamfer 133. At this point, it mixes with pressurized air from air inlet 136. The pressurized air / slurry mixture is then guided through the air guide toward nozzle end slot 120, from which the pressurized blast flow exits. The sloped base 122 of base 120 and the shape of the slot create a substantially rectangular shaped blast flow. It can be seen that the rectangular (or square, or other non-circular) shaped blast flow formed by the correspondingly shaped nozzle slot end 112 provides a sharp edge to the blast flow, rather than the traditional funnel-shaped blast flow from a conventional circular nozzle.

[0036] Other variations and modifications will be apparent to those skilled in the art from reading the present disclosure, and may involve equivalent and other features which are already known in the field of wet blasting and which may be used instead of or in addition to features already described herein.

[0037] Although the appended claims are directed to particular combinations of features, the scope of the present disclosure should be understood to include any novel feature or any novel combination of features, or generalization thereof, explicitly or implicitly disclosed herein, whether or not it relates to the same invention as the invention currently claimed in any claim, and whether or not it alleviates some or all of the same technical problems as the present invention.

[0038] Features that are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment may also be provided separately or in any suitable subcombination. Applicant hereby notifies that new claims may be formulated to such features and / or combinations of such features during prosecution of this application or any further application derived therefrom.

[0039] For the sake of completeness, it is also stated that the word "comprising" does not exclude other elements or steps, the words "a" or "an" do not exclude a plurality, and reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

1. A processing machine for adjusting the K factor of a cutting edge of a power tool, the processing machine comprising: a blast gun that directs a pressurized blast stream of abrasive particles in a blast direction, the blast pattern of the blast stream being substantially non-circular with edges, the edges of the pattern being directed toward the cutting edge of the work tool; and mounting means for fixing the work tool such that a rotation axis of the work tool is radially offset from the blasting direction by an adjustable offset distance, wherein the K-factor of the cutting edge is determined by the offset distance between the blasting direction and the rotation axis; The K factor is defined as Sγ / Sα, Sγ is the distance from the apex of the chipping surface and clearance surface of the cutting edge to the end of the roundness of the chipping surface, The processing machine, wherein Sα is the distance from the apex to the end of the radius of the clearance surface.

2. The treatment machine of claim 1 , wherein the blast pattern is substantially rectangular.

3. The treatment machine of claim 2 , wherein the blast pattern has an aspect ratio of at least 2:

1.

4. 4. The processing machine according to claim 1, wherein the blast gun has a nozzle from which the blast stream is ejected, the outlet of the nozzle being substantially non-circular.

5. 5. The processing machine according to claim 1, wherein the work tool is a drill bit, an end mill, a thread tap, or a slot mill.

6. 6. A processing machine according to any one of claims 1 to 5, wherein the work tool comprises a round shank.

7. The processing machine of claim 1 , wherein the abrasive particles comprise one or more of glass beads, metal shot, or aluminum oxide particles.

8. A processing machine according to any one of claims 1 to 7, wherein the offset distance is an offset relative to a chipping surface of the work tool.

9. 9. The processing machine of claim 8, wherein the symmetrical offset about the blade edge provides a K factor of approximately 1.

10. 10. A processing machine according to claim 8 or 9, wherein an offset towards the chipping plane achieves a K factor greater than 1 and an offset away from the chipping plane achieves a K factor less than 1.

11. A processing machine described in any one of claims 1 to 10, wherein the range of K factor values ​​adjustable by the processing machine is between 0.4 and 1.

9.

12. 1. A method for adjusting a K-factor of a cutting edge of a power tool, the power tool having an axis of rotation, the method comprising: securing the work tool in a blast chamber, the blast chamber comprising a wet blast gun that emits a blast stream of abrasive particles suspended in a slurry from a blast nozzle of the blast gun; directing the blast stream of abrasive particles toward a cutting edge of the work tool; and adjusting a radial distance between the blast nozzle and the rotation axis of the blast flow, the blast nozzle is configured to generate a blast stream of a substantially non-circular cross section, the blast nozzle being aligned substantially perpendicular to the axis of rotation; The K factor is defined as Sγ / Sα, Sγ is the distance from the apex of the chipping surface and clearance surface of the cutting edge to the end of the roundness of the chipping surface, The method of claim 1, wherein Sα is the distance from the apex to the end of the radius of the clearance surface.

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