JPH0696218B2 - Feed variable speed machining method for curved surface cutting of molds etc. - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a curved surface processing method for cutting a mold or the like having a complicated uneven curved surface in a machining center, an NC milling machine or the like.

As shown in FIG. 6, the cutting curved surface processing in the conventional mold etc. is as follows.
For example, it is possible to push the ball end mill vertically while rotating it and to advance it only at a constant speed.

However, with this constant feed rate, it is not possible to sufficiently cope with molds of complicated shape, etc., and if the speed becomes excessive in the inclined part, especially the downward inclined part, the tip of the end mill will be It will be lost and closed.

Therefore, at present, in order to avoid this tip loss, it is the actual situation that the feed speed of the end mill is adjusted to the lowest speed that can avoid the loss, that is, the most inefficient state, which hinders the rationalization of the process. It is one of the biggest causes.

In addition, this low-speed cutting originally requires less wear on the upslope surface when the peripheral speed of the tool is increased, but on the upslope surface, the low speed rather increases wear and shortens the tool life. It has the drawback of

(Problems to be solved by the present invention) Therefore, in the present invention, in cutting of a mold or the like having a complicated curved surface of uneven undulations, a feed rate corresponding to an inclined surface to be processed is calculated in advance, and It aims to develop a machining method that allows variable feed speeds to be optimal for curved surfaces, and aims to improve machining efficiency and extend tool life.

(Means for Solving the Problems) The curved surface cutting method in the mold of the present invention is intended for a machining center equipped with a mechanism capable of numerically controlling the feed speed of a cutting tool, an NC milling machine, etc. Feed rate, F: Feed rate K: Coefficient V: Average peripheral speed of ball end mill a: Radius of ball end mill b: Upper Y coordinate of depth of cut c: Lower Y coordinate of depth of cut Calculate with the formula (see Fig. 2) By inputting a pre-calculated numerical value into the equation, it is configured to perform cutting at the optimum feed rate for the curved surface of the workpiece.

When the cutting tool is a high speed tool, the value of the coefficient K in the feed rate formula F = K · V is calculated as follows: up slope angle: k = 18 ± 4 down slope angle: k = 21 ± 4 is desirable.

If the cutting tool is a cemented carbide tool, the coefficient K in the feed rate formula F = K · V is calculated as follows: k = 26 ± 4 for up-tilt angle: k for down-tilt angle = 30 ± 4 is preferable.

(Operation) When cutting a die etc., the numerical control mechanism of the machining center is Since a variable speed is input in advance based on the equation (3), it works so that the variable speed can be adjusted to an optimum value corresponding to the curved surface (see FIG. 1).

At that time, when the cutting tool is a high speed tool, in the feed rate formula F = K · V, the value of the coefficient K is set to k = 18 ± 4 for up-tilt angle and k for down-tilt angle. = 21 ± 4, it works to make the feed rate suitable for the material of the tool and less worn.

If the cutting tool is a cemented carbide tool, the coefficient K is set to a value of k = 26 ± 4 for an up-tilt angle and k = 30 ± 4 for a down-tilt angle. It acts to avoid tool loss.

(Example) Hereinafter, the case of machining a mold of an automobile using a machining center will be described with reference to the flowchart for numerical control of FIG. 3, in which the uneven shape of the uneven surface of the mold is represented by coordinate axes x, y, and
Copy it on the z-axis and input it as figure data, then determine the tolerance and sculpture height to determine the processing accuracy. And the inclination angle (θ) according to the undulations of the uneven surface
Is calculated, and the average peripheral flux (V) of the ball end mill is calculated. This average peripheral speed (V) is the average cutting radius, Calculate with the formula of and multiply by 2πN / 1000 to calculate. Next, the value of the coefficient K is determined depending on whether the inclination angle (θ) is positive or negative. In the case of a high speed tool, K = 18.6 in the case of an upward inclination and K = 21.6 in the case of a downward inclination. Then, the feed rate for the up or down machining is calculated according to the feed rate formula F = K · V. Next, in order to omit the data to an appropriate length, it is divided into blocks (for example, divided into 5 degrees) according to the value of the tilt angle, and the feed rate for each block is determined. Then, continuous numerical control data is created, output to direct NC or NC tape, and the machining center is operated to perform cutting.

When the results of this cutting process were tested on the relationship between the number of times of cutting and the tool wear width, in Fig. 4 (A) showing the case of a 45-degree upslope with a high speed tool, F = 400 is the most wear. With a small optimum value, the wear is very large below that and slightly above that. Further, in FIG. 4 (B) showing the case of the downward inclination of 45 degrees, F = 250 is the optimum value with the least friction, and if it is more than that, the wear is large, and if it is less than that, it slightly increases.

On the other hand, in FIG. 5 (A) showing the case where the cemented carbide tool has an upward inclination of 45 degrees, F = 900 is the optimum value with the least wear, and below that, the wear is large. Further, in FIG. 5 (B) showing the case of the downward inclination of 30 degrees, F = 350 is the optimum value with the least wear, and the wear becomes greater above and below.

In any case, it was shown that the optimum feed rate depends on the tilt angle and the material of the tool, and it was found that if it deviates from this, wear and fracture are likely to occur.

(Effects of the Invention) The present invention is as described above, and the feed rate of a cutting tool such as a machining center is Since it can be calculated based on the formula, and the variable speed can be used, the feed speed is set low for downward cutting, where chipping is likely to occur, and conversely set relatively high for upward cutting. It is possible to reduce the work time. Therefore, it is possible to meet today's request for streamlining of the process, which is demanded to shorten the delivery time.

Further, at that time, by making the downward inclination low and the upward inclination high, it is possible to solve the problems of chipping in the downward and wear on the upward, and to extend the life of the tool by about 5 times.

Since the value of coefficient K is set on the plate according to the material of the tool, the characteristics of the tool can be utilized. Especially, in the case of a cemented carbide tool, it is not possible to use it for curved surface machining due to the fact that it is liable to chip. Since what has been described above can be used by the method of the present invention, the characteristics of a cemented carbide tool that is resistant to high-speed cutting can be utilized for curved surface processing by a machining center, NC milling machine, or the like.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a schematic view showing a method of the present invention in which a ball end mill is fed along a mold at an optimum feed speed, and FIG. 2 shows a ball end mill and a mold inclined surface. The front view in which the relationship is positioned on the coordinate axes, FIG. 3 is a flowchart, FIG. 4 (A)-(B) is a graph showing the relationship between cutting length and flank wear when cutting is performed using a HSS tool, 5A and 5B are graphs showing the relationship between cutting length and flank wear when cutting is performed using a cemented carbide tool, and FIG. 6 is a schematic diagram showing conventional die cutting.

Claims (3)

[Claims] 1. In a machine tool such as a machining center having a mechanism capable of numerically controlling the feed rate of a cutting tool, the feed rate of a cutting blade to a curved surface is F: Feed rate K: Coefficient V: Average peripheral speed of ball end mill a: Radius of ball end mill b: Upper Y coordinate of depth of cut c: Lower Y coordinate of depth of cut Calculate with the formula A variable feed method for curved surface cutting of dies, etc., which is characterized by inputting the numerical value and performing cutting processing on the curved surface at the optimum value. 2. When the cutting tool is a high speed tool, the coefficient K in the feed rate formula F = K · V is set to k = 18 ± 4 when the ascending inclination angle is k. = 21 ± 4. The variable feed machining method for curved surface cutting of a mold or the like according to claim 1. 3. When the cutting tool is a cemented carbide tool, in the feed rate formula F = K · V, the value of the coefficient K is as follows: in the case of an upward inclination angle: k = 26 ± 4 in the case of a downward inclination angle: The variable feed machining method in curved surface cutting of a mold or the like according to claim 1, wherein k = 30 ± 4.