JP2003323204A - Working method using ball end mill tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dissolve a problem that a surface roughness is not obtained based on theory since a tool is swung owing to a deviation between a center axis and a rotary center axis in a ball end mill tool by attachment precision and a centrifugal force by rotation in the ball end mill tool to be used for a machining center. <P>SOLUTION: Before cutting, a radius R at the distal end of the tool (S1), and the required surface roughness H (S2) are specified, and transmitted from an input part. Then, the machining center 1 is operated by the command of an NC device 4, the ball end mill tool 3 which is attached to a main shaft 2 and stands at an initial position is rotated, and a swing measurement sensor 7 measures an amount of swing of the tool by the number of working rotation. A cutting speed arithmetic apparatus 5 calculates the feeding speed F of the main shaft to obtain the required surface roughness from the inputted tool distal end radius R, the required surface roughness H, and the measured tool swing amount E. Then a cutting method in the public domain is performed by the obtained feeding speed F. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machining method using a three-axis controlled numerically controlled machine tool, which measures a runout amount at a machining speed of a ball end mill tool to obtain a surface roughness required for a finished surface. The present invention relates to a machining method using a ball end mill tool, characterized in that the tool feed speed is calculated and determined from the amount of deflection based on

[0002]

2. Description of the Related Art A ball end mill tool having an arc-shaped cutting edge at its tip is known as a tool used for machining a die or the like in a machining center which is a three-axis control numerically controlled machine tool. This ball end mill tool is a tool in which one or more arc-shaped cutting edges are formed at the tip of a cylindrical body, the rotation locus around the center axis of which is approximately spherical, with two cutting edges among them. Crushed 2-flute ball end mill tools are commonly used. Further, when the ball end mill tool is used, the cutting speed is zero because the cutting edge portion of the ball end mill tool is on the rotation axis, and machining is difficult. Therefore, in the normal machining, the tip portion is avoided. The shape of the end surface of the machined surface at that time is theoretically as shown in the figure, and the theoretical surface roughness H is approximately expressed by Equation 1 where R is the tool tip radius of the ball end mill tool and f is the feed amount per blade. It becomes like.

[0003]

[Equation 1]

Further, Japanese Patent Publication No. 7-067659 discloses a machining information generating system in which the surface roughness is taken into consideration by using the equation (1).

[0005]

However, in reality, due to the mounting accuracy of the ball end mill tool, the centrifugal force due to the rotation, etc., a deviation occurs between the central axis of the ball end mill tool and the central axis of rotation, causing tool runout. Therefore, the finished surface roughness cannot be obtained according to the theory.
It was difficult to obtain the surface roughness required for processing even with the system described in Japanese Patent No. 9 publication.

[0006]

In view of the above problems, the present invention provides a machining method using a ball end mill tool in consideration of tool runout of the ball end mill tool. The structure of the present invention according to claim 1 is a machining method using a three-axis control numerically controlled machine tool, wherein a deflection amount at a machining rotation speed of a ball end mill tool is measured to obtain a surface roughness required for a finished surface. The machining method using the ball end mill tool is characterized in that the tool feed speed is calculated and determined from the deflection amount based on the above. As a result, in the machining method using the ball end mill tool, the most efficient feed speed is calculated and determined to obtain the required surface roughness, and the spindle is moved to perform cutting, so that the desired surface roughness is obtained. I was able to.
In particular, in order to measure the deflection amount at the processing rotation speed of the ball end mill tool, any member that can detect the actual coordinate difference of the ball end mill tool 3 from the main axis coordinates with the center of rotation as a reference may be used, for example, image analysis by a video camera. It is preferable to use a device, a simple distance detecting device, or the like. In addition, the surface roughness required for the finished surface is input by the operator, such as an operation panel that is manually input before or during processing, a computer keyboard, or the work information transmitted by CAD / CAM together with the work information. Input from. Then, it is desirable that the cutting speed calculator connected to the input unit from the outside be input with the tip radius of the attached ball end mill tool and the surface roughness necessary for finishing the work. Further, the step of calculating the tool feed rate from the runout amount based on the surface roughness required for the finished surface is processed by a program stored in the NC device of the machining center or an additional board storing the program. desirable.

According to a second aspect of the present invention, in the machining method using the ball end mill tool according to the first aspect, the step of calculating the tool feed speed from the runout amount based on the surface roughness required for the finished surface, A value obtained by dividing the surface roughness by the shake amount,
2. The ball end mill according to claim 1, wherein the size of the ball end mill is compared with the sine value of the angle of the machining point of the tool, and the feed rate is calculated from the surface roughness and the runout amount in each case. This is a processing method using a tool.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a machining method using a ball end mill tool according to the present invention is carried out by a machining center will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the entire system according to the present invention. A three-axis numerically controlled machining center 1 has a ball end mill tool 3 on a main spindle 2 located inside a cover that prevents scattering of chips.
The NC spindle 4 controls the spindle 2 that rotates the ball end mill tool 3 to process the work placed on the table. In the vicinity of the ball end mill tool 3, a shake measurement sensor 7 is attached to measure the shake of the rotating ball end mill tool 3 in a non-contact manner. The shake measurement sensor 7 is connected to the cutting speed calculator 5 incorporated in the machining center 1 and sends out the detected rotation shake amount of the tool. The shake measuring sensor 7 may be any member that can detect the actual coordinate difference of the ball end mill tool 3 from the main axis coordinate with reference to the center of rotation, and for example, an image analysis device using a video camera, a simple distance detection device, etc. are suitable. is there. The cutting speed calculator 5 calculates the correlation between the rotational speed of the tool and the rotational runout amount from these many detected values. Further, the cutting speed calculator 5 is also connected to an input unit 6 from the outside, and the tip radius of the attached ball end mill tool 3 and the surface roughness necessary for finishing the work are input. The input unit 6 may be an operation panel or a keyboard of an electronic computer that is manually input by a worker before or during processing, or may be input by being transmitted together with work information by CAD / CAM. It may be. Then, the cutting speed calculator 5 calculates the optimum feed speed of the tool in order to obtain the required surface roughness according to the tool deflection amount,
The calculated tool feed speed is transmitted to the NC device 4, and the machining center 1 performs actual cutting under the control of the NC device 4.

FIG. 2 shows a processing flow according to the present invention. The processing flow according to the present invention is performed before the step of actually performing the cutting process, and the cutting process is started by the obtained feed rate of the spindle. First, the tool tip radius R (S1) and the required surface roughness H (S2) are designated and transmitted from the input unit. Next, the machining center 1 is operated according to a command from the NC device 4, the ball end mill tool 3 attached to the spindle 2 standing by at the initial position is rotated, and the shake measurement sensor 7 measures the tool shake amount for each machining rotation speed. Then, from the input tool tip radius R, the required surface roughness H, and the measured tool deflection E, the feed rate F of the spindle for obtaining the required surface roughness.
Is calculated by the cutting speed calculator 5. After that, a known cutting method is performed with the obtained feed speed F. It should be noted that this process is preferably performed immediately after mounting the ball end mill tool 3 or at a stage after machining for a certain period of time to re-detect the correlation, but if the machining condition, especially the surface roughness is low, The combination of the tool number, tool tip radius R, required surface roughness H, and spindle feed rate F stored in is called from the storage medium or storage member to calculate the optimum tool feed rate and reduce the processing time. It is also possible.

Next, the calculation processing for calculating the feed speed of the ball end mill tool 3 according to the finished surface roughness from the tool shake detected by the shake measuring sensor 7 will be described. 3 to 5 show a state in which the ball end mill tool 3 is moved as a feed amount f per blade along a straight line path in a direction parallel to the paper surface. If there is no tool runout,
As shown in FIG. 3, since the cutting depths of the two blades of the ball end mill tool 3 are the same, complete two-blade cutting is continuously performed. On the other hand, if there is tool runout, the depths of the two blades do not match as shown in FIG. 4, so that the finished surface has different valley depths alternately. Then, when the amount of tool runout further increases, as shown in FIG. 5, only the scraped surface of one blade appears on the finished surface. Even if the tool runout is further increased, the finished surface has only one blade scraped off, and the surface roughness does not deteriorate more than that shown in FIG. The relationship between the tool deflection amount E and the surface roughness H will be described with reference to FIG. 6 which is a graph. If there is no tool runout, Equation 1 holds as described above. On the other hand, the surface roughness H when the tool run-out amount increases and only the cutting edge of one blade shown in FIG. 5 appears, as if the feed amount per one blade is doubled, the following formula 2 Can be approximated by

[0011]

[Formula 2]

The tool deflection amount E at this time is given by the following equation 3 where θ is the angle formed by the rotation axis of the tool and the straight line connecting the center of the tool tip radius and the machining point as shown in FIG. .

[0013]

[Formula 3]

When the tool runout amount is between 0 and E, that is, when the two blades shown in FIG. 4 have finished surfaces in which the depths of the cut valleys are alternately different, the tool runout amount and the surface The relationship of roughness is shown by the shaded area on the left side of the graph in Fig. 6,
This can be approximated by a linear function as shown in Equation 4. The tool shake amount e is set as.

[0015]

[Formula 4]

Therefore, f can be obtained by the following formula 5 by modifying the formula 4.

[0017]

[Formula 5]

On the other hand, when the amount of tool deflection exceeds E, as shown in FIG. 5, only one blade remains, and the surface roughness does not deteriorate further. Therefore, in the graph of FIG. In this case, f can be obtained by the following formula 6 by changing the formula 2.

[0019]

[Formula 6]

Therefore, it can be understood that there are two kinds of calculation methods depending on whether or not the shake amount e exceeds E in the equation (3).

From the above, conversely, when the required surface roughness and tool runout amount are given, the feed amount f per blade can be obtained from equations 5 and 6. That is, the calculation is performed by selecting either of the equations 5 and 6 in which the required surface roughness and the tool shake amount satisfy the conditional equations in parentheses in the equations 5 and 6, respectively.

In order to obtain the feed speed F from the feed amount f per blade, if the number of revolutions of the tool is N, the following formula 7
Is obtained as.

[0023]

[Formula 7]

Thus, in the machining method using the ball end mill tool, the most efficient feed speed is calculated and determined in order to obtain the required surface roughness, and the spindle is moved to perform cutting, so that the desired surface roughness is obtained. I was able to get it.

[0025]

According to the processing method using the ball end mill tool of the present invention, the most efficient feed rate can be calculated and determined in order to obtain the required surface roughness.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a system according to a processing method of the present invention.

FIG. 2 is a flowchart showing a processing method of the present invention.

FIG. 3 is an explanatory diagram showing a shape of a finished surface in a state where a tool is not shaken.

FIG. 4 is an explanatory diagram showing a shape of a finished surface in which two blades cut at different depths.

FIG. 5 is an explanatory view showing the shape of a finished surface when only one cut is visible.

FIG. 6 is a graph showing the relationship between surface roughness and tool shake amount.

FIG. 7 is an explanatory diagram showing a state of tool deflection.

[Explanation of symbols]

1 ・ ・ Machining center, 2 ・ ・ Spindle, 3 ・ ・ Ball end mill tool, 4 ・ ・ NC device, 5 ・ ・ Cutting speed calculator, 6 ・ ・ Input unit, 7 ・ ・ Runout measurement sensor

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Claims (2)

[Claims] 1. A machining method using a three-axis controlled numerically controlled machine tool, wherein a deflection amount at a machining rotation speed of a ball end mill tool is measured, and the deflection amount is calculated based on the surface roughness required for a finished surface. A machining method using a ball end mill tool characterized by calculating and determining a tool feed speed. 2. The step of calculating the tool feed speed from the runout amount based on the surface roughness required for the finished surface, the value obtained by dividing the surface roughness by the runout amount is the angle of the machining point of the ball end mill tool. 2. The machining method using a ball end mill tool according to claim 1, wherein the size is discriminated by comparing with the sine value of and the feed speed is calculated from the surface roughness and the amount of runout in each case.