JPH02100802A - Cutting method by high-pressure coolant - Google Patents

Abstract

PURPOSE: To reduce damage to a tool by discharging liquid coolant with a pressure higher than 690 kPa to the vicinity of an edge point inside a groove in a cutting method for cutting an undercut groove. CONSTITUTION: A tool bit 20 provided with a cuttable arc type cutting edge 32 is installed inside a clamp 30 with a tube 34, through which cutting fluid to be discharged from an outlet 38 is linearly discharged. As the width of a shank part 40 is narrower than that of a cutting edge part 41, an undercut groove 26 can be cut. In this cutting process, coolant is directed in the Y-axis direction of a tool at a high pressure of 690 kPa or more so as to apply direct impact onto chips during plunge cutting. In cutting in the Z-axis direction, chips are shredded by impact due to the shape and volume of the groove and a coolant pressure of 690 kPa or more. Because the coolant is discharged at a high pressure, continuously connected chips are shredded, and congestion of the groove inside due to the chips can be prevented, so that damage such as abrasion to a cutting tool can be greatly reduced and a life of the tool can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to machining, particularly to a cutting method that supplies coolant to the vicinity of a cutting tool. moreover,
The present invention mainly relates to metal cutting using a cutting tool.

[Prior Art] Generally, a cutting tool is used in metal cutting. When using this type of tool, a method is used to supply coolant near the cutting location in order to extend tool life and improve machined surface finish. This coolant has not only cooling properties but also lubricating properties, and a mixture of water-soluble oil and water has been preferably used because of its cost and good heat conduction properties.

Also, mineral oil or other coolants are sometimes used depending on the processing purpose.

According to literature, the mechanical principles of the phenomena that occur at the contact area between the edge of the cutting blade and the workpiece have been extensively studied. This is because significant economic effects can be achieved by improving this cutting tool and cutting method. A major improvement in recent years has been the extension of tool life through the use of sintered metal carbide instead of hardened alloy steel. However, since carbide tools still deteriorate qualitatively due to aging, there is great interest in suppressing this quality deterioration. In other words, if the tool life can be extended, the cost required for tool replacement will be reduced, resulting in a very large economic effect. This effect is
The downtime required to adjust the position of the tool and the resulting costs are avoided, as is the avoidance of damage to the workpiece if the tool is damaged.

In general cutting, chips from a workpiece collide with the rake face of a cutting tool, increasing the temperature of the tool and making it susceptible to mechanical damage. Therefore, if the tool continues to receive impact from chips, it will eventually break during machining unless the tool is replaced. Therefore, cooling of the cutting edge of the tool and the top surface that hits the chips is of paramount importance; for example, as disclosed in U.S. Pat. No. 2,744,451 to Lee, A method of releasing coolant into the cutting edge body was adopted.

Generally, such "flood coolant (rloo
d coolant)" system is still widely used today, and low-pressure pumps provide a
The structure is such that the coolant circulates at a pressure of kPa. This flood coolant system requires pumping of coolant from a coolant reservoir, siphoning some of the coolant above the tool and discharging it near the workpiece and cutting edge. A large amount of coolant that is released to the workpiece or cutting blade is scattered around, so a shielding plate is used to prevent the coolant from scattering from the vicinity of the cutting area.

Furthermore, this splashing of coolant is usually undesirable due to excessive pressure at the point of coolant discharge. Therefore, by using a low pressure pump as the circulation pump used to supply coolant, it has become possible to lower the high coolant discharge nozzle pressure. fact,"
Mist cooling utilizes the flow of air and water droplets, and is usually used when operating conditions are not too severe.

It has been known for about 90 years that damage to workers can be avoided to some extent by supplying coolant near the cutting edge. For example, U.S. Pat. No. 522,588 to Cho Tzu Woo provides for coolant to be discharged along channels in the scoop of a tool bit. More recently, U.S. Pat. No. 2,683,303 to Bigott discloses a method in which coolant is directed from a manifold directly across the rake face of a milling cutter. U.S. Pat. No. 2,534,232, issued to Onsrud, discloses a method in which coolant is released to the cutting face by holes in the cutting face body and channels that release liquid near the front of the cutting face. A method is disclosed. U.S. Pat. No. 3,176,330 to Jenning discloses a carbide insert in place by a chip breaker having channels through which coolant is supplied to the chip breaker and applied to the cutting surface. It is configured to be emitted against.

[Problems to be solved by the invention] According to the above-mentioned techniques, it is possible to obtain a certain degree of effect in terms of tool damage, but these techniques still have many problems, and the cutting edge surface The structure that forms a channel in the cutting tool is not desirable, and it is not easy to supply coolant to the nozzle that is integrated with the cutting tool.There are many inconveniences, so it was not widely used. .

In completing this invention, we first attempted a special method of discharging low-pressure coolant onto the cutting edge of the tool, with reference to the method disclosed in the Jenning patent. However, this type of method does not provide the tool life necessary for machining cutting grooves on the outer circumference of a cylinder made of titanium and nickel alloy, resulting in significant damage and permanent damage. Ta.

Therefore, the present invention aims to improve the cutting of members having difficult-to-cut materials and shapes, reduce damage to tool bits, and prevent special damage to tool bits when cutting undercut grooves. .

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a cutting tool that has an undercut shank (and a metal member that forms a cutting edge at the intersection line between the undercut shank and the flank surface). In the cutting method of cutting an undercut groove by relative movement with the tool bit, the tool bit is substantially parallel to the rake face of the tool bit, and
Cutting with high-pressure coolant that releases a liquid coolant with a pressure greater than 690 kPa (100 psig) near the cutting edge in the groove, breaks the cutting chips, and then expels the chips from the groove to prevent chip clogging. A method is provided.

[For production] The means for solving the problem described in L operates as follows.

High pressure liquid coolant is discharged from the nozzle against the rake face of the operator bit. The cutting blade is subjected to a large force by this coolant, and chips are produced by cutting the workpiece.

Particularly when cutting undercut grooves, this method reduces the likelihood of ductile chips clogging in the grooves, which can cause tool breakage.

Coolant pressure and flow rate are important factors and must be somewhat high to achieve the desired results. When cutting undercut grooves in titanium alloy, approximately 690 kP is required, exceeding the pressure normally used for flood cooling.
Damage decreases when the temperature rises to a. However, chip clogging of continuous chips still occurs within the groove, causing damage to the tool bit. pressure is 1400k
When the temperature rises to Pa and exceeds it, chips break continuously and tool breakage decreases. When cutting high-pressure nickel alloy, a high pressure of approximately 2200 kPa is required.
The coolant is preferably water-soluble in terms of mass, low viscosity, and practicality.

[Example] Hereinafter, the present invention will be described in detail based on the accompanying drawings.

In particular, AMS4928 (weight percent 6: AL,
The following describes cutting of an industrial titanium alloy known as 4:V, remainder: Ti, and an undercap type circumferential groove cut into the outer periphery of a cylindrical body such as a compressor rotor of a gas turbine engine. As described below, there are many problems with cutting this type of shape, but the present invention can be fully applied to members other than the shapes and materials described below.

FIG. 1 shows a tool bit 20 attached to a holder 28.
2 shows a method of cutting a groove 26 formed on the outer periphery of a cylinder 24 (shown in partial cross-section) having a radius R using this tool bit. In the figure, the tool bit is shown within an undercut groove. This tool bit is held in a holder 28 and mounted in a cross feed table 29 of a vertical turret lathe (not shown) with a mechanism for rotating a workpiece in the direction of arrow 27. FIG. 4 is another embodiment of the present invention, showing a general tool bit 50 used for circumferential cutting of a cylindrical body 66.

In Figure 1, C-4 grade carbide tool bit 20
is held to the tool holder 28 by a clamp 30 (-details regarding marine attachment not shown). This holder has a holding part 33 extending below the tool bit, and an arc-shaped cutting edge 32 that can cut on 72 planes is formed at the intersection of the flank face 42 and the scoop 36. There is. This tool bit has a zero rake angle and a clearance angle of about 7 degrees. The tube 34, which has a substantially rectangular cross-sectional shape, is arranged along the top or rake face so that the cutting fluid discharged from the outlet 38 is partially discharged to the cutting blade 32 provided linearly along the Z axis. Clamp 30
installed inside.

In other words, this tool bit is capable of cutting an undercut groove because the width of the shank portion 40 (in the Z-axis direction) is substantially narrower than the cutting blade portion 41 constituting the cutting blade.

Next, FIGS. 2 and 3 will be explained.

The circumferential groove 26 initially has a diameter of 0.0 mm with respect to the rotating cylinder.
It is formed on the outer periphery of the cylindrical body by making a plunge cut that moves in the X direction, that is, in the radial direction, at 05xx/rotation. The cutting surface speed of the tool bit in all the cuts described herein is approximately 2.8 i/s, which is the economical optimum cutting speed found empirically. When the desired depth of cut in the X-axis direction is reached, the tool holder and tool bit are moved toward the top of the load at a relatively low speed of 0.013xx/rev in the Z-direction until the desired dimension is obtained. The tool is then moved in two directions at the same speed to form a groove of the desired width. Further, the tool returns to the basic two-wheel cutting position and is withdrawn in the X-axis direction.

Therefore, the tool bit cuts against a force in a direction opposite to the cutting direction. Therefore, firstly, the time during which the cutting blade is in contact with the workpiece during cutting is relatively long, and secondly, there is a bending moment due to the undercut while cutting the side surface. If the tool bit were to break in the groove, it would be undesirable because there is a risk of damaging the groove during cutting. This requires a very detailed inspection to determine the extent of the damage.

Prior to the completion of this invention, tool bits were prone to breakage during the operations described above, and despite adequate maintenance management, 8 out of 11 tool bits were damaged during the two-axis movement described above.
There was damage to the size of a book.

It was difficult to determine the cause of this damage because the blade was only slightly fed, and furthermore, because coolant was being used, it was not easy to confirm the cause of the damage. However, small compacted lumps could be found in the cutting chips.

It was also assumed that the chips would accumulate in the undercut groove at the portion 46 during grinding of the portion 44. If these chips become clogged, there is a high risk that the tool bit will break. Most attempts have been made to solve these interlayer problems by changing cutting conditions, etc., but in the case of the ductile titanium alloy AMS4928, the chips become continuous (this means that the chips do not break off). teeth,
Continuously moving away from the workpiece and sliding across the rake face. The length of the chips at this time is 1~
(There are some that exceed 311, but they end up getting entangled with the processing machine around the cutting part and breaking.) Under such circumstances, it is common to use a chip breaker on the tool bit, but the tool The shape is not suitable for mounting a chip breaker, and we considered wrapping the grinding section 46 with rubber, wax, etc., but we were not able to obtain very good results.

Until Moe completed this invention, cutting was performed using a conventional method using a coolant. As this coolant, water-soluble oil or Hocut 3210 (E,
F, Houghton Co.) was used, and a method was adopted in which the material was released into the air through a nozzle installed toward the cutting location. For the purpose of increasing the cooling effect, coolant was discharged in the longitudinal direction of the rake face of the tool equipped with a coolant nozzle having a cross-sectional area of approximately 15III'' using the method shown in Figures 1 and 4. Approximately 690 kPa
A pressure source of relatively high pressure was used in common usage (where the total pressure is the gauge pressure measured on the supply line 34 between the hydraulic pump and the tool bit; the pressure actually emitted from the nozzle Pressure will be somewhat lower than indicated). Even when coolants began to be used in machining, the problems associated with chip clogging (backing) described above remained unsolved. Regarding coolant, U.S. Patent No. 3,176 described in the prior art
．． Improvements were made as disclosed in No. 330, with approximately 1
It has been confirmed that damage to the tool bit can be prevented by using a high pressure of 400 KPa or more. Continuous chip breakage was due to the coolant volume and its pressure, and the extent of damage was substantially reduced. Although there were not enough experiments to obtain accurate data on liquid volume. , it was proved to be very effective from the experimental results.

Damage to the tool bit was first confirmed by a decrease in the sharpness of the cutting edge, and a slight dent on the rake face was discovered.

FIG. 5 shows the formation of a long chamfer at the intersection of the cutting edge, that is, the flank face and the rake face. This dimension was measured with an unbroken and chip-free tool bit.

Figures 6 and 7 show relative experimental results.

Figure 6 shows how the degree of damage to the tool bit decreases as the coolant pressure (combined pressure) increases. For example, when cutting a groove, the dimension varies from 0.1111 to shoulder to 0.0511. decreased to

This is due to a predictable phenomenon, as disclosed in the Zienik patent and others, which shows that cooling and thereby lubrication of tool bits, especially in titanium alloys, increases tool life.

However, at the pressure of the above result in Fig. 7,
The unusability rate still shows a high value. (This unusable condition can be detected by damage and is caused by the now well-known chip jam.) However, Figure 7 also shows that the pressure required to prevent damage is When the tool is substantially exceeded, the tool unusable rate is decreasing.

I actually tried grinding 27 workpieces under the above conditions.

For titanium, it has been confirmed that a pressure of about 1400 kPa is sufficient, and even if a higher pressure is used, no effect can be expected.

Additionally, data regarding industrial IN-100 nickel heat-resistant alloy is also shown. This alloy also produces continuous chips, which indicates that it has a certain degree of strength. (AMS4928 is approximately 1000 at room temperature.
With a maximum tension of MPa and an elongation of 13% to 15%, the modified IN100 has a tension of about 1400 MPa and an elongation of 12%
It has an elongation of 15% from However, lN-10
0 is a heat-resistant alloy for high temperatures, and AM94928 is not a heat-resistant alloy, so it has relatively low heat-resistant strength. Although the actual temperature of the chips is unknown, it is probably around 600°C, and the actual temperature at the cutting point is estimated to be around 1000°C). When cutting an undercut groove of the same shape (
A high pressure of approximately 2250 kPa (cutting using C-9 carbide on the bottom surface at a cutting speed of approximately 1.3x/S) is required for chip breakage and Chip clogging can be prevented.

As a result of inspection of chip fragments, under conditions where the unusability rate decreased due to pressure, continuous chips increased from 31 pieces to 12 pieces.
It was found that a discontinuous cut of about M was formed. As can be seen from the reduction in the number of chamfered portions 48 and craters, chip clogging no longer occurred, and the degree of damage was also reduced.

As shown in FIG. 1, the coolant is directed in the y-axis direction of the tool. Therefore, when a chip is formed and slides across the rake face during plunge cutting, the chip is directly impacted. However, when cutting in the direction of the tool axis, the chips are not directly affected by the impact of the coolant, but due to the groove shape, volume, and coolant pressure, the chips can be broken by a second impact. It is necessary to change the conditions regarding coolant. Therefore, when cutting the outer periphery using a cutting tool with a simple shape as shown in FIG. 4, even if the pressure and method are somewhat lower, continuous chips 64 can be effectively turned into discontinuous broken chips 64. can do. Under these conditions, chip clogging is not a problem, but there are practical benefits in terms of reducing craters, chip control, and cutting edge damage.

The shape of the boat shown in FIG. 1 is not limited to a rectangle, and various shapes are possible. Furthermore, it is possible to use a plurality of boats, and the cutting conditions are not limited, and it is suitable even when cutting a width greater than the blade width of the cutting blade.

The coolant flow rate at the working pressure stated here is approximately 0.
．． 6 to 0. ”lQ/s, and the typical size of an undercut tool bit is that the cutting edge portion 41 is approximately 7.3*
z and the shank portion 40 has a Z-axis width of approximately 2.
It has a width of 5xx. Also, water-soluble coolant is used. This water-soluble coolant is suitable because it has a unique specific gravity and low viscosity compared to oil and the like. The momentum of the coolant is a factor that causes chip breakage, and its value is determined by the flow rate and the coolant flow rate, and therefore depends on the coolant concentration (the flow rate is determined by the discharge pressure). Therefore, if a high-concentration coolant is used, the pressure can be lowered as long as the conditions according to the present invention are met. Therefore, a nozzle having a shape that lowers the supply pressure can also be used. Also, because the cutting materials described herein are ductile, they tend to form continuous chips in grinding applications where the present invention is useful. When grinding a material with low ductility, it is naturally possible to use a low supply pressure. In other words, if more ductile materials are used or more feed types (resulting in thinner chips) are used, higher pressures are required. Finally, although this embodiment has been described with respect to turning, the principles of the present invention can also be applied to cutting of other metals.

Although the invention has been described with reference to preferred embodiments, it will be apparent to those skilled in the art that the invention can be practiced with various modifications and changes without departing from the concept thereof.

[Effects of the Invention] A unique effect of this invention is that by releasing coolant at a predetermined pressure along the rake face of the cutting tool near the tip of the cutting edge during cutting, the undercut groove can be cut continuously. This is because the chips are torn apart and there is no clogging in the groove during cutting, and damage such as abrasion of the cutting tool due to this is significantly reduced, extending the tool life.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the shape of a tool based on the present invention. FIG. 2 is a diagram showing a method of cutting an undercut groove on the outer circumferential surface of a cylindrical body. FIG. 3 is a partial detail view of FIG. 2 showing the tool bit in the cut undercap groove; FIG. 4 is an end view showing a method of cutting the outer circumferential surface of a cylindrical body using a cutting tool according to the present invention. . FIG. 5 is an explanatory diagram showing the damaged surface of the cutting blade. FIG. 6 is a diagram showing the degree of relative improvement in damage to the cutting edge of the tool bit by increasing the coolant pressure and flow rate. FIG. 7 is a diagram illustrating the degree to which the damage rate of the tool due to backing of chips in the groove is reduced by a sufficient increase in pressure.

Claims (4)

[Claims] (1) In a cutting method in which an undercut groove is cut by relative movement between a metal member and a cutting tool that has an undercut shank and forms a cutting edge at an intersection line between a rake face and a flank face, the rake face of the tool bit A liquid coolant that is approximately parallel to the groove and has a pressure greater than 690 kPa (100 psig) is discharged near the cutting edge in the groove to break up the cutting chips and expel the chips from the groove to prevent chip clogging. A cutting method using high pressure coolant. (2) The cutting method using a high-pressure coolant according to claim 1, wherein the metal member is a nickel heat-resistant alloy. (3) The cutting method using a high-pressure coolant according to claim 1, wherein the coolant is a water-soluble coolant. (4) The cutting method using a high-pressure coolant according to claim 1, wherein the tool bit has an arcuate shape.