JPH0319701A - Cutting method for work - Google Patents

Abstract

PURPOSE:To machine a work in a short time with high accuracy and to prolong the service life of a tool by increasing feeding when the sharpness of a cutting tool becomes worse, changing the position of the wear part of a blade for the work, and grinding the work by the new part of the blade. CONSTITUTION:The surface roughness Rmax is restrained less than a required roughness Rg by being worked with a feeding f1 satisfying the required roughness Rg at the beginning of the working start, the apex part 22 of the cutting residual part 21 of a work 2 abuts on the B point of a side cutting edge 13, a boundary wear 34 is formed, the sharpness is worsened by the increase in the number of works and the surface roughness Rmax approaches the required roughness Rg. In the case that the number of pieces N1 found in advance experientially has been machined, the feeding is increased to f2, the apex 22 of the cutting residual part 21 having been abutted on the B point is made to abut on a C point part and the sharpness is restored by using a new edge part C point. The work is continued with the feedings of f3...fn by increasing the feeding whenever the working piece number of the work 2 reaches the specific piece numbers N2, N3...Nn and when the surface roughness Rmax is not restrained less than the required roughness Rg with the number of pieces reaching Nn and becoming too large even if the feeding is increased more than fn, the work is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a workpiece cutting method for processing a workpiece with high precision using a lathe, a boring machine, or the like.

[Conventional technology] Recently, with the development of CBN bits and diamond bits, workpieces made of hardened steel and powder alloys can be manufactured with high precision (fitting tolerance of 7 or more, surface roughness of 68 or less, roundness of 5 μm or less, straightness). Cutting is used instead of grinding (see JP-A-63-1 27801).In this way, if cutting is used instead of grinding, , machining time can be shortened, inexpensive machining equipment can be used, and machining cost per work piece can be kept low.

FIG. 4 shows the condition of the machined surface of a workpiece when precision cutting is performed using a lathe. In the figure, 1 is a byte
Cutting tool〉, 2 is the workpiece, A is the feeding direction, and the opening is the cutting depth. has been done. The size of this uncut portion 21, that is, the surface texture R
max is theoretically determined according to the feed f and the nose radius of the cutting tool 1, and the relationship between these is Rmax - f2
/8 r. Therefore, in theory, in cutting, by appropriately setting the feed f and the nose radius of the cutting tool 1, the surface roughness Rmax can be suppressed to the required roughness Rg or less.

[Problem to be solved by the invention] However, in reality, even if the cutting conditions (feed f, nose radius r) are set so that the surface roughness Rmax is equal to or less than the required roughness Rc+ at the beginning of machining, machining is not continued for a long time. As the process continued, the surface roughness R max increased to exceed the required roughness RG due to the following reasons.

That is, when cutting continues for a long time, as shown in FIG. 3, flank wear 31, rake face wear 32, nose wear 33,
Various types of wear such as boundary wear 34 occur. In addition, in the figure, 13 indicates a side edge, and 14 indicates a front cutting edge.

Among the various types of wear described above, boundary wear 34 occurs at a position corresponding to the apex portion 22 of the uncut portion 21, as shown in FIG. For this reason, if machining continues for a long time and the wear of the tool bit 1 progresses, the influence of the boundary wear 34 will cause the pie 1-
1 becomes dull and the apex portion 22 of the uncut portion 21
is extremely raised, and as a result, the surface roughness R maX
What happens is that .

To solve this problem, conventional methods have been unsuccessful, such as replacing the cutting tool 1 or reducing the feed f once the wear of the piezo 1-1 has progressed to a certain extent. However, these methods each shorten the tool life.
Another disadvantage is that the processing time becomes longer.

In view of the above circumstances, it is an object of the present invention to provide a workpiece cutting method that can process a workpiece with high precision in a short machining time and can extend tool life.

(Means for Solving the Problems) A method for cutting a workpiece according to the present invention is a method for cutting a workpiece by controlling the feed so that the surface roughness of the workpiece is below a predetermined value. The feed is increased sequentially each time the sharpness deteriorates.

[Effect]

According to the above configuration, when the cutting tool becomes dull, increasing the feed changes the position of the worn part of the cutting tool's blade relative to the workpiece, and the workpiece can be cut with the new part of the cutting tool's blade. This will restore the sharpness of the cutting tool. Therefore, there is no need to replace cutting tools.
Machining can be continued with the same tool.

(Example) Fig. 1<a) shows a case where a plurality of workpieces are machined using a lathe using the workpiece cutting method according to the present invention. The explanation will be based on (b). In these figures, 1 is a cutting tool (cutting tool), 2 is a workpiece, 21 is an uncut portion, A is a feeding direction, and the mesh is a cutting depth.

In this cutting method, at the beginning of machining, as shown in FIG. 1(a), machining is performed with a feed rate of f1. This feed amount f1 is such that the surface roughness Rwax is 30 to 40 lower than the required roughness RQ.
%, the theoretical formula Rmax = f2
/8 Set based on r.

After that, after machining a plurality of workpieces 2, the cutting tool 1 wears out as shown in Fig. 4 and becomes dull, and as shown in Fig. 1 (b), the feed is changed to f1.
Processing is performed by increasing the value f2 to a value larger than .

5 Then, machining is continued at the feed rate of f2, and when a plurality of workpieces 2 have been machined and the cutting tool 1 becomes dull, the feed rate is increased to a value f3, which is even larger than f2, and machining is continued. Below, the value fn is 30% more than the feed f1 at the beginning of machining.
Processing is performed by increasing the feed rate each time the cutting tool 1 becomes dull until the limit is reached. In addition,
During machining, the cutting speed is kept constant.

The cutting quality of the cutting tool 1 is judged by the surface roughness RIllax of the workpiece 2 measured after machining, and if the surface roughness R max approaches the required roughness Rg, it is determined that the cutting tool 1 has deteriorated. do. However, rather than making a judgment by sequentially measuring the surface roughness R max after machining, we empirically determined in advance the number of workpieces 2 to be machined at which the cutting edge of bite 1 becomes dull under each feed condition when machining is performed by sequentially increasing the feed rate. The number of pieces to be machined is determined in advance and the judgment is made based on whether the number of pieces processed has been reached. In other words, when machining is performed by increasing the feed rate from f1 to fn, the surface roughness R is
6 of workpiece 2 when max is close to the required roughness RQ. The number N1 to Nn of workpieces to be machined is determined in advance in advance, and the number of pieces to be machined N1 to Nn corresponding to each feed condition f1 to fn is calculated in advance.
If n is reached, it is determined that the cutting edge of bite 1 has become dull. For example, when machining is performed with a feed rate of f1, if the number of workpieces 2 to be machined reaches N1, it is determined that the cutting tool 1 has become less sharp.

And if you judge that the sharpness of bite 1 has become worse,
Machining is carried out by increasing the feed, but if it is determined that the number of pieces to be machined has reached Nn and the cutting tool 1 has become dull, the machining is stopped only in this case.

According to the above configuration, at the beginning of machining, as shown in FIG. 1(a), machining is performed with a feed of f1 that satisfies the required roughness RQ. Therefore, the surface roughness RIIla× is the required roughness R
It can be kept below Q. If you continue machining with this feed f1,
Since the apex portion 22 of the uncut portion 21 of the workpiece 2 hits the B point portion of the side edge 13 of the cutting tool 1, boundary wear 34 is formed at the B point portion, and as the number of workpieces 2 to be processed increases. The boundary wear 34 gradually develops, the sharpness of the cutting tool 1 deteriorates, and the surface roughness R max gradually decreases to the required roughness RCI.
comes closer to.

When the number of workpieces 2 to be machined reaches N1, it is determined that the cutting tool 1 has become less sharp, and the feed is increased from f1 to f2 as shown in FIG. 1(b). When the feed was increased from f1 to f2, the workpiece 2 that was hitting the point B of the side blade 13 of the cutting tool 1
The apex portion 22 of the uncut portion 21 comes to be closer to the root point C than the point B. That is, the portion corresponding to the apex portion 22 of the uncut portion 21 of the workpiece 2 changes from the B point portion where the boundary wear 34 has developed to the C point portion which has not been used until now. As a result, a new, unworn blade part (point C) of bite 1 is used, the sharpness of bite 1 is restored, and the surface roughness R max, which has once approached the required roughness R (Ill), is used. Become revived.

After that, when machining is continued with a feed of f2, boundary wear 34 is formed at point C, the sharpness of bite 1 deteriorates again, and the surface roughness R max gradually approaches the required roughness Rg. become. When the number of workpieces 2 processed reaches N2, it is determined that the cutting tool 1 has become dull, and the feed is increased from f2 to f3. For this reason, a new blade part at the root part is used rather than the C point part, and the sharpness of bite 1 is restored again, and the surface roughness R
max is revived and maintained below the required roughness R0.

Thereafter, the number of workpieces 2 to be processed reaches the predetermined number N3. N4,...
The feed is increased sequentially each time it reaches ・Each time, a new blade part is used, the sharpness of bite 1 is restored, the surface roughness R max is revived, and it is maintained below the required roughness RQ. become. Then, machining is continued at a feed rate of fn, and when the number of workpieces 2 to be machined reaches Nn, the machining is stopped. Note that even if the feed is increased beyond fn, the sharpness of the cutting tool 1 is restored, but the feed becomes too large, making it impossible to suppress the surface roughness R max to the required roughness Rg or less.

FIG. 2 shows the relationship between the number of workpieces 2 processed and the surface roughness R max when the above processing method is used.

9. For comparison, the relationship when machining is performed at a constant feed rate f1 as in the prior art is shown by a two-dot chain line.

In the case of the conventional method, even if the number of pieces to be machined reached N+ fJAk and the cutting edge of bite 1 became dull, the feed was not changed and the machine was processed, so when the number of pieces to be machined exceeded N111, the surface roughness R max was required. The roughness R(] was exceeded.For this reason, one tool bit 1 can only machine N1 pieces of workpiece 2, which means that the tool life is only up to N1 pieces, and only N1 pieces of workpiece 2 can be machined. Then, a new bih
I had to exchange it for 1.

On the other hand, in the case of the method of the present invention, when the number of pieces processed reaches N1 and the sharpness of bite 1 deteriorates, the sharpness of bit 1 is restored by increasing the feed from f1 to f2. Even if processed beyond the surface roughness R
max does not exceed the required roughness Rg, but is maintained below it.

If cutting tool 1 becomes less sharp while machining with a feed of f2, the feed is increased again.From then on, each time cutting tool 1 becomes less sharp, the feed is increased by 10. The sharpness of No. 1 is restored, Nn pieces of workpiece 2 can be machined without exceeding the required roughness Rg, and the tool life can be extended to Nn pieces. Furthermore, since the feed is gradually increased, the machining time can be shortened.

Specific examples of the present invention and comparative examples are shown below.

(Specific example) Work; diameter 1 6+ (0 to 0.008) s, length 3
Iron-based sintered alloy (C: 0.1%.Cu
: 1.0%, work tool made of "e": CBN tool pie 1 ~ shape; 6° (top rake angle), O' (vertical side rake angle), 11° (front relief angle), 5° ( side clearance angle)
, 88° (front cutting edge angle), 58° (side cutting edge angle) 0.4
m (nose radius) Required roughness Rq; RIlla x 3μm Required accuracy: Squareness 6μm, circularity and cylindricity 5μm Cutting speed V: 200m7min 11 Depth of cut d; 0. 2mttr Under the above conditions, feed f is 0.08sn/rev ~0.1
Precision boring was performed on the workpiece by increasing the speed sequentially between 0.5 s/rev.

(Comparative example) Feed f is 0. Precision boring was performed on the workpiece under the same conditions as in the specific example except that the voltage was kept constant at 0.8 m/reV.

For the above-mentioned specific example and comparative example, the number of processed pieces was measured when the surface roughness R max reached the required roughness RQ after continuous processing. As a result, the number was 190 in the case of the comparative example, and 40011B in the case of the specific example. This results in
It can be seen that the method of the invention extends tool life.

Note that the present invention is applied to cutting processes in which a cutting tool is rotated relative to a workpiece, such as turning with a lathe and boring with a boring machine.

〔Effect of the invention〕

In the method for cutting a workpiece according to the present invention, the feed is sequentially increased each time the sharpness of the cutting tool deteriorates. The new part of the workpiece will be able to be cut, and the cutting tool will regain its sharpness and be able to continue machining. Therefore, tool life can be extended. Moreover, by sequentially increasing the feed, the machining time can be shortened.

[Brief explanation of drawings]

Fig. 1<a) and (b) are cross-sectional views showing the machining state of a workpiece when an embodiment of the workpiece cutting method according to the present invention is used, and Fig. 2 is a relationship between the number of processed pieces and surface roughness. Figure 3 is a perspective view showing the state of wear of the cutting tool, Figure 4 is a graph showing
The figure is a cross-sectional view showing the state of workpiece machining using a conventional workpiece cutting method. 1...Bite (cutting tool), 2...Work, f1~
fn...Feed, R max...Surface roughness.

Claims (1)

[Claims] 1. A workpiece cutting method in which the feed is controlled and cut so that the surface roughness of the workpiece is below a predetermined value, the workpiece being characterized in that the feed is sequentially increased each time the sharpness of the cutting tool deteriorates. cutting method.