JP5302941B2 - Roughing ball end mill - Google Patents

Description

  The present invention relates to a ball end mill in which unevenness (roughing) is provided on a side blade for rough machining, and more specifically, the reaction force and resistance (hereinafter referred to as “cutting resistance”) of a member to be cut applied to the cutting edge are reduced. Further, the present invention relates to a ball end mill that eliminates chatter and chipping and improves cutting performance.

  The heat-resistant steel used for turbine nozzles and blades is similar in composition to high-speed steel called high speed steel, and has high high-temperature strength and toughness. Therefore, cutting these parts is not easy. On the other hand, the ball end mill has a spherical tip and is mainly used for cutting a curved surface. Therefore, the ball end mill is suitable for cutting turbine nozzles and turbine blades having many curved surfaces as cutting surfaces. Roughing ball end mills having irregularities (roughing) on the side blades can increase the depth of cut and enable high-speed feed cutting, and are usually used for roughing.

When a turbine nozzle or turbine blade is machined with a tip-changeable ball end mill made of cemented carbide steel, the protruding amount may be large, resulting in large chatter (vibration and resonance), roughened cutting surface, and feed rate. Also did not improve.
For this reason, a solid type cutting tool was used, and the cutting tool was changed into a holder that was shrink-fitted into the holder, and the rigidity of the cutting tool was increased.

  Therefore, I tried using a roughing ball end mill made of sintered high-speed tool steel (powder high speed) whose structure was refined and made high alloy by powder metallurgy, but the resistance of the R part of the tip edge was large. For this reason, a defect occurs in the R portion, the number of tool replacements increases, and the feed rate does not improve much.

  In Patent Document 1 (Japanese Patent Laid-Open No. 7-195221), in a luffing ball end mill, a wave-shaped cutting edge or a nick is provided on a tip edge forming a ball shape to reduce cutting resistance, or chips are removed with a tip edge. The technical matter which enabled the increase of the cutting amount and the high feed rate by dividing | segmenting is disclosed. FIG. 7 shows a configuration of a luffing ball end mill disclosed in FIG.

  In FIG. 7, the luffing ball end mill 100 includes a side blade 102 provided on the outer peripheral surface of the tool body, and a cutting blade 106 having a corrugated uneven section of a tip blade 104 provided on a tip portion having a ball shape. It consists of The corrugated irregularities are continuously formed in a direction intersecting the tool body axis A.

JP-A-7-195221 (FIG. 6)

  Even when a roughing ball end mill is used to cut heat-resistant steel with high high-temperature strength and toughness, such as turbine nozzles and turbine blades, the resistance of the R portion of the tip blade increases, and defects occur in the R portion. And the above-mentioned trouble occurs. This is the same as the roughing ball end mill disclosed in Patent Document 1 in which the corrugated irregularities are formed in the R portion of the tip blade, and cutting is performed by the amount of corrugated irregularities formed in the R portion of the leading edge blade. Although the capability is improved, conversely, the cutting resistance of the member to be cut with respect to the R portion increases, and the possibility that the R portion is missing increases.

  In view of the problems of the prior art, the present invention eliminates chatter when cutting a high-strength and difficult-to-cut member using a luffing ball end mill, and maintains high cutting performance while cutting against a cutting edge with luffing. An object is to reduce the resistance and prevent the R portion of the tip blade from being lost.

In order to achieve such an object, the luffing ball end mill of the present invention includes a plurality of tip blades arranged in a radial direction from the center at a tip portion having a ball shape, and a plurality of concave and convex portions formed on the outer peripheral surface connected to the tip blade. In the luffing ball end mill including the side blades, an elliptical shape (hereinafter referred to as a “laterally-oriented elliptical shape”) in which at least the cross section of the convex portion is oriented in the axial direction of the tool body is provided on the side blades and the tip blades. Concavities and convexities having a difference between successive peaks and valleys formed are formed, and the pitches of the irregularities of the tip blades and the differences of the peaks and valleys are made smaller than the pitches of the irregularities of the side blades and the differences between the peaks and valleys .

  In the device of the present invention, the cutting force applied to the side blade and the tip blade can be reduced by providing the unevenness with reduced protrusion to the member to be cut by making the side blade and the tip blade elliptical. This eliminates chattering of the tool body during cutting, improves cutting performance such as improving the accuracy of the cutting surface and increasing the cutting speed, and can reduce defects in the R portion of the tip edge.

In this invention apparatus, in addition to the said structure, while making the pitch of the unevenness | corrugation of an end blade into 0.8-1.0mm, making the difference of a mountain valley 0.1-0.15mm, and making the unevenness | corrugation pitch of a side blade into It is good to set it as 1.2-1.5mm and to make the difference of a mountain valley 0.3-0.5mm.
In addition to making the unevenness of the tip blade and the side blade into a laterally elliptical shape, the cutting resistance against these cutting edges can be further reduced by making the unevenness of the tip blade and the side blade fine as in the above numerical range. Here, since the resistance higher than that of the side blade is added to the R portion of the tip blade, the difference between the pitch and the valley of the unevenness of the tip blade is made smaller than that of the side blade.

  Increasing the pitch difference between the top edge and the side edge and the pitch between the upper and lower edges increases the resistance of the member to be cut against these cutting edges, and in particular, the amount of protrusion of the tool body in the case of grooving, etc. When it increases, chattering occurs and cutting performance decreases. On the other hand, if the difference between the unevenness and the pitch of the unevenness of the tip edge or the side edge is less than the lower limit value, the original cutting performance obtained by providing the unevenness is deteriorated.

  In the device according to the present invention, in addition to the above configuration, the twist angle of the twist groove formed between the tip blade and the side blade with respect to the axis of the tool body may be 15 to 30 °. Thus, the core thickness (orthogonal cross-sectional area) of the tool body can be ensured and the rigidity can be improved by setting the twist angle of the twist groove for discharging the chips to be smaller than the conventional one. Therefore, even if the protrusion amount of the tool main body is increased, chattering of the tool main body can be suppressed, and cutting performance (cut surface unevenness reduction, cutting speed increase, etc.) can be improved.

  When the twist angle of the twist groove exceeds the upper limit, the rigidity of the tool body is lowered, and chattering is likely to occur. On the other hand, when the twist angle α is less than the lower limit value, the cutting resistance against the cutting edge increases, chattering occurs, the cutting performance deteriorates, and the chip dischargeability also deteriorates.

  In the apparatus of the present invention, the tool body tip from the blade edge to the holder may be made of solid, and the tool body tip may be fixed to the holder by shrink fitting. As a result, the rigidity of the tool body can be improved, the chatter of the tool body can be eliminated, and the cutting performance can be improved.

  In the device according to the present invention, the plurality of tip blades and side blades may be formed asymmetrically in the circumferential direction with respect to the tool body axis. As described above, it is preferable to dispose a plurality of cutting edges asymmetrically in the circumferential direction of the tool body so that the interval between the cutting edges is randomly and slightly changed. As a result, the timing of vibration caused by the cutting resistance applied to the individual cutting blades can be slightly shifted so that the vibrations cancel each other with the individual cutting blades. Thereby, chattering of the tool body can be suppressed and cutting performance can be improved.

For example, when the tip blade and the side blade are four blades, the angle between the two cutting blades facing each other and the two other cutting blades facing each other is a deflection angle of 2-5 ° further than 90 ° in the circumferential direction of the tool body. It is good to arrange with Accordingly, vibrations are canceled out by two sets of cutting blades, each of which has two cutting blades facing each other, and chattering of the tool body can be suppressed.
If the deflection angle is less than 2 °, the effect of canceling out the vibration is not obtained so much. If the deflection angle exceeds 5 °, the basic configuration of the tip of the tool body is changed, and other cutting performance is affected. Therefore, it is desirable that the deflection angle is in the range of 2 to 5 °.

  According to the device of the present invention, a luffing comprising a plurality of tip blades arranged radially from the center at a tip portion having a ball shape, and a plurality of side blades that are connected to the tip blade and have irregularities formed on the outer peripheral surface thereof. In the ball end mill, since the continuous concavo-convex shape in which at least the cross section of the convex portion forms a laterally elliptical shape is formed on the tip edge and the side edge blade, the cutting resistance applied to the tip edge and the side edge blade can be reduced.

  This eliminates chattering of the tool body and reduces cutting resistance, so cutting performance of the cutting surface (improving cutting surface accuracy, increasing cutting speed, etc.) while maintaining a high cutting speed due to the provision of irregularities. In addition to being able to improve, it is possible to reduce the loss of the R portion of the tip blade and reduce the frequency of tool replacement.

1 is a front view of a luffing ball end mill according to a first embodiment of the present invention. It is a left view of the said luffing ball end mill. (A) is an enlarged view of the unevenness | corrugation of the front-end | tip blade of the said roughing ball end mill, (B) is an enlarged view of the unevenness | corrugation of a side blade similarly. It is explanatory drawing which shows the unevenness | corrugation of the cutting edge of the said luffing ball end mill. It is a perspective view which shows the place which is cutting the turbine blade with the end mill of this invention. It is a left view of the roughing ball end mill which concerns on 2nd Embodiment of this invention. It is a front view of the conventional luffing ball end mill.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(Embodiment 1)
1st Embodiment of this invention apparatus is described based on FIGS. 1 and 2, the roughing ball end mill 10 according to the present embodiment includes a shrink-fitting fit in which a root portion 13 of a cylindrical tool body 12 is drilled at the center in the axial direction of a holder 14 having a large-diameter cylindrical shape. It is inserted into the use hole 14a and fixed by shrink fitting. On the distal end side of the tool body 12, the distal end portion is formed in a hemispherical shape, and four cutting edges are provided radially from the distal end center B. The cutting blade includes a cutting blade 16 provided at the R portion at the tip, and a side blade 18 provided on the outer peripheral surface of the tool body 12 and connected to the cutting blade 16.

  The tip blade 16 and the side blade 18 are helically twisted starting from the tip center B, and a twist groove 20 for discharging chips is formed between the cutting blades. As shown in FIG. 2, the tool body 12 rotates in the direction of the arrow r, cuts the member to be cut with the cutting edges 16, 18, and the chips are discharged upward through the twist groove 20. The tip edge 16 and the side edge 18 are provided with concavities and convexities 22 and 24 continuously in a direction intersecting the axis A of the tool body 12 (a direction substantially orthogonal to the axis A).

  The shape of the irregularities 22 and 24 will be described with reference to FIG. 3A shows the cross-sectional shape of the unevenness 22, and FIG. 3B shows the cross-sectional shape of the unevenness 24. Concavities and convexities 22 and 24 have a laterally elliptical shape in which at least each of the convex portions 22a and 24a has a major axis directed in the direction of the axis A. Each of the recesses 22b and 24b does not need to have an elliptical shape such as a convex portion, but in order to smoothly connect the connecting portion with the convex portion, the concave portion 22b and 24b have a laterally elliptical shape similar to the convex portion or a radius of curvature. It is desirable to have an R shape with a relatively large.

With such a sectional shape, a difference of H ₂ peaks and valleys of the difference H ₁ and irregularities 24 of peaks and valleys of the irregularities 22 of the present embodiment is smaller than the difference between the peaks and valleys of the irregularities of the conventional roughing end mill. Further, P ₂ of the pitch P ₁ and irregularities 24 of the irregularity 22 is formed smaller than the conventional roughing end mill. Thus, the reaction force and resistance which the unevenness | corrugations 22 and 24 receive from a to-be-cut member can be made small by making the difference and pitch of the peaks and valleys of the unevenness | corrugations 22 and 24 smaller than before.

Specifically, the peak-to-valley difference H ₁ of the irregularities 22 is set to 0.1 to 0.15 mm, the pitch P ₁ is set to 0.1 to 0.15 mm, and the peak-to-valley differences H ₂ of the irregularities 24 are set to 0.3 to 0. 0.5 mm and the pitch P ₂ is 1.2 to 1.5 mm. The tip edge 16 receives a greater reaction force and resistance from the workpiece than the side edge 18, but the difference H ₁ and pitch P ₁ between the peaks and valleys 22 of the irregularities 22 are different from the difference H ₂ and pitch P ₂ between the peaks and valleys of the irregularities 24. By making it smaller, the reaction force and resistance received by the unevenness 22 are reduced.

  Moreover, the unevenness | corrugation 22 or 24 of this embodiment is arrange | positioned by shifting the position of an unevenness | corrugation little by little to the axis A within 1 pitch in each cutting edge. Thereby, the unevenness of the cutting surface of the member to be cut can be reduced, and the cutting resistance with respect to each cutting edge can be reduced. This means is conventionally known.

  Next, as shown in FIG. 4, the torsion angle α of the torsion groove 20 with respect to the axis A of the tool body 12 is set to 15 to 30 °, and the torsion angle α of the conventional luffing ball end mill is set to be smaller than the conventional. If the helix angle α is large, the resistance of the member to be cut against the cutting edge can be reduced, the machinability can be improved, and the chip discharge performance is improved, but the core thickness (orthogonal cross-sectional area) is reduced, so the tool body 12 rigidity is reduced. On the other hand, if the twist angle α is small, the reverse phenomenon occurs.

  In the present embodiment, since the difference between the peaks and valleys and the pitch of the irregularities 22 and 24 of the cutting edge is reduced, the cutting resistance to the cutting edge can be reduced, so even if the twist angle α is made smaller than that of the conventional roughing end mill, Cutting performance does not deteriorate. In addition, since the chips become fine, even if the twist angle α is reduced, the chip dischargeability does not deteriorate. Further, by reducing the twist angle α, the core thickness of the tool body 12 can be secured, and the rigidity can be improved.

When the difference between the peaks and valleys and the pitch of the unevenness of the tip edge is increased from the upper limit value, or when the difference and pitches of the unevenness and valleys of the side edge blade are increased from the upper limit value, the resistance of the member to be cut against these cutting edges is increased. It has been found that when the amount of protrusion of the tool body 12 is increased in the case of grooving or the like, chattering occurs and cutting performance decreases.
On the other hand, it has been found that when the difference between the peaks and valleys of the irregularities 22 or 24 and the pitch are less than the lower limit value, the cutting performance obtained by imparting irregularities is slightly lowered.

  In the present embodiment, the twist angle α is changed on the way from the distal end side to the root portion side of the tool main body 12. For example, the torsion angle α is set to 20 °, and the torsion angle α is changed back and forth (20 ° ± 2 to 3 °) around 20 ° in the middle from the tip B toward the root side. Thereby, the frequency of vibration generated in the tool body 12 during cutting can be dispersed to reduce chatter. Such means is suitable for application to groove machining where chatter is likely to occur.

  According to the present embodiment, the cross-sectional shape of the irregularities 22 and 24 provided on the cutting edge is set to be a laterally elliptical shape, and the difference between the peaks and valleys of the irregularities and the pitch is made smaller than before, so that the cutting edge is loaded. Cutting resistance can be reduced, cutting performance can be improved, chipping of the cutting edge can be reduced, and the number of tool changes can be reduced, so that cutting efficiency can be improved. In particular, since the difference in the unevenness and pitch of the unevenness of the leading edge 16 that generates a large resistance and the pitch are reduced, the chipping of the leading edge 16 can be reduced.

  In addition to the above configuration, the twist angle α is set to 15 to 30 °, which is smaller than the conventional luffing ball end mill, so that the cutting resistance to the cutting edge is not increased and the chip dischargeability is not lowered. The rigidity can be improved by increasing the core thickness of the tool body 12. Thereby, in the case of grooving or the like, even if the protruding amount of the tool body 12 increases, chatter does not occur, and the unevenness of the cutting surface can be reduced.

  Moreover, it is good to comprise the tool main body front-end | tip part from a blade edge to a holder with a solid, and fix this tool main body front-end | tip part to a holder by shrink fitting. As a result, the rigidity of the tool body can be improved, the chatter of the tool body can be eliminated, and the cutting performance can be improved.

  Further, since the tool body 12 is made of solid and the root portion 13 of the tool body 12 is fixed by shrink fitting in the hole 14a drilled in the center of the holder 14, the rigidity of the tool body 12 can be improved. The chattering at the time of cutting of the tool body 12 can be suppressed, the unevenness of the cutting surface can be reduced, and the cutting feed rate can be increased.

The present inventors have convex portions 22a of the irregularities 22, 24 of the tip blade 16 and the side blades 18, 24a and recesses 22b, and 24b of the cross-section and lateral elliptical shape, and 0.13mm difference _{H 1} of peaks and valleys of the irregularities 22 The pitch P _{1 is set} to 1.0 mm, the difference H ₂ between the peaks and valleys of the unevenness 24 is set to 0.4 mm, the pitch P _{2 is set} to 1.2 mm, the twist angle α is set to 20 °, and the tool body 12 is made of solid. A luffing ball end mill A was manufactured by shrink fitting to the holder 14.

  Using this luffing ball end mill A, the turbine blade was cut. FIG. 5 shows this cutting process. In FIG. 5, the holder 14 to which the tool body 12 is fixed is mounted on a processing machine (not shown), and the turbine blade TB that is a member to be cut is fixed to the fixing jigs 30 and 30. In this state, the tool blade 12 cuts the turbine blade TB to form a three-dimensional curved surface of the turbine blade TB.

  When this luffing ball end mill was used, there was no chatter of the tool body 12 during cutting, and a rough finish surface with good precision could be formed. Moreover, no chipping of the cutting edge occurred. When the luffing ball end mill formed with the above-mentioned powder high speed was used, it took 2 hours to cut one turbine nozzle, but when using the luffing ball end mill A, cutting could be completed in over 40 minutes. .

In addition, the difference H ₁ and the pitch P ₁ of the peaks and valleys of the unevenness 22 of the tip edge 16 are increased from the upper limit, or the difference H ₂ and the pitch P ₂ of the peaks and valleys of the unevenness 24 of the side edge 18 are increased from the upper limit. As a result, the cutting resistance against these cutting edges increased, and it was found that when the amount of protrusion of the tool body 12 is increased in the case of grooving or the like, some chattering occurs.
On the other hand, it was found that the cutting performance was slightly lowered when the difference between the peaks and valleys of the irregularities 22 or 24 and the pitch were lower than the lower limit.

  Moreover, when the twist angle (alpha) of the twist groove 20 exceeded the said upper limit, the rigidity of the tool main body 12 fell and it turned out that a chattering generate | occur | produces a little. Further, it was found that when the twist angle α is less than the lower limit, the resistance to the cutting edge increases, the cutting surface becomes slightly rough, and the cutting accuracy of the cutting surface slightly decreases.

(Embodiment 2)
Next, a second embodiment of the device of the present invention will be described with reference to FIG. 6, among the four tip blades 16a-d, the tip blades 16a and 16c, similarly to FIG. 2, are arranged facing on transverse centerline _{C 1.} In contrast, the tip blades 16b and 16d are arranged at positions rotated by respective deflection angle β to the longitudinal center line C ₂ around the center B. The deflection angle β is in the range of 2 to 5 ° (for example, 4 °). Other configurations are the same as those of the first embodiment.

  According to the present embodiment, since the four tip blades 16a to 16d are not arranged at equal intervals in the circumferential direction of the tool main body 12, the timing when each cutting blade hits the member to be cut is set to each cutting blade. Can be different between. The frequency of vibration generated during cutting is determined by the cutting timing of each cutting edge. As in the present embodiment, by changing the cutting interval between the cutting edges, the generated vibration can be canceled out, thereby suppressing an increase in chatter and ensuring cutting performance.

According to experiments of the present inventors, and the angle β is less than 2 ° relative to the longitudinal centerline C ₂ of the tip blade 16b and 16d, the vibration suppression effect hardly occurs, is greater than the inverse of the angle β is 5 ° The basic configuration of the tip of the tool body 12 is changed, which affects other cutting performance. For this reason, it has been found that it is desirable to set the angle β in the range of 2 to 5 °.

  The luffing ball end mill of the present invention provides cutting resistance against cutting edges even for members made of difficult-to-cut materials used in blades, turbine nozzles, plastic molding dies, etc. used in aircraft and power generation turbines. By reducing it, chatter and chipping of the cutting edge can be reduced, and cutting performance can be maintained high.

10 Roughing ball end mill 12 holes for fit the tool body 13 root portion 14 holder 14a baked 16,16a~d tip blade 18 side edge 20 twisted grooves 22, 24 irregularities 30 fixing jig A axis B end center C ₁ transverse centerline C ₂ longitudinal center line TB Turbine blade (member to be cut)
r Direction of rotation α Torsion angle β Deflection angle

Claims (6)

In a luffing ball end mill comprising a plurality of tip blades arranged in a radial direction from the center at a tip portion that forms a ball shape, and a plurality of side blades that are connected to the tip blade and have irregularities formed on the outer peripheral surface thereof,
Concavities and convexities having a difference between continuous peaks and valleys forming an ellipse in which the long axis is directed in the axial direction of the tool body are formed on the tip blade and the side blade ,
The roughing ball end mill characterized in that the difference between the pitch of the unevenness of the tip edge and the difference between the peaks and valleys is smaller than the difference between the unevenness pitch of the side edge and the difference between the peaks and valleys .   The pitch of the leading edge irregularities is set to 0.8 to 1.0 mm, the difference between the peaks and valleys is set to 0.1 to 0.15 mm, and the pitch of the irregularities on the side blades is set to 1.2 to 1.5 mm. The luffing ball end mill according to claim 1, wherein the thickness is 0.3 to 0.5 mm.   The roughing ball end mill according to claim 1 or 2, wherein a twist angle of a twist groove formed between the tip blade and the side blade with respect to the tool body axis is set to 15 to 30 °.   The luffing ball end mill according to any one of claims 1 to 3, wherein the tool body from the blade tip to the holder is made of solid, and the tip of the tool body is fixed to the shank by shrink fitting.   The roughing ball end mill according to any one of claims 1 to 4, wherein a plurality of tip blades and side blades are formed asymmetrically in the circumferential direction with respect to the axis of the tool body.   The tip blades and side blades are four blades, and the angle between the two cutting blades facing each other and the two other cutting blades facing each other is set to a deflection angle of 2 to 5 ° further than 90 ° in the circumferential direction of the tool body. The luffing ball end mill according to claim 5, wherein the luffing ball end mill is arranged.

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