JPH05274013A - Method and device for correction of tool length of machine tool - Google Patents

Abstract

PURPOSE:To carry on the highly accurate and stable machining by correcting the change of the tool length caused by a tool pull-in phenomenon that may possibly occur when a machine tool is revolved at a high speed. CONSTITUTION:A correction data input means 3 inputs the tool length correction data to each spindle rotational frequency of each tool. A correction data storage means 5 stores the tool length correction data inputted by the means 3 and also extracts the tool length correction value in response to the prescribed spindle rotational frequency of a prescribed tool. A tool offset value setting means 7 calculates and sets the tool length offset value with addition of the tool length correction value of a prescribed tool given from the means 5 to the static length of the relevant tool. In such a constitution, the shift extent of a feed shaft is calculated based on the tool offset value set by the means 7. Then a machine tool 21 is driven. As a result, the NC machining is carried out in a state where the tool length change caused by the high speed revolution of the tool 21 is corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool length correcting method and device for a machine tool, and more particularly, to a so-called dynamic tool in which the inner diameter of the tool mounting portion of the spindle is expanded by the centrifugal force caused by the rotation of the spindle and the tool is retracted. The present invention relates to a tool length correction method and apparatus for a machine tool that corrects a change in length.

[0002]

2. Description of the Related Art An example of a general spindle structure of a conventional machine tool is shown in FIG. In the figure, a hollow spindle 55 rotatably supported by bearings 52a, 52b, 52c, 52d is coaxially arranged inside a housing 51 incorporated in a spindle headstock 48 of a machine tool (not shown). Has been done.

A tool 61 having a complementary taper shank portion 59 is taper-engaged with a taper hole 57 for attaching a tool at the tip of the main shaft 55, and a so-called pull stud portion 68 at the insertion end of the tool 61. Is gripped by a collet 69 connected to a draw bar 70 that is constantly urged axially rearward by a large number of disc springs 71, whereby the tool 61 and the main shaft 55 are integrally connected at the time of connection.

[0004]

Recently, since the actual rotational speed of the machine tool spindle has reached to several thousands to several tens of thousands rpm, the above-mentioned taper coupling portion, which could not occur conventionally, is involved. The problem has appeared. That is, when the spindle rotates at an extremely high speed, an excessive centrifugal force acts on the tip of the spindle, the taper hole relatively expands, and as a result, the tool is slightly drawn into the spindle, and the tool length relative to the spindle changes. However, for this reason, the static tool length data obtained by measurement when the spindle is stopped before machining is practically meaningless and worthless. Therefore, it is necessary to surely solve or overcome this problem in order to perform more accurate machining.

In view of this, the present invention effectively corrects the adverse effects of the above-described tool retracting phenomenon that may occur during high-speed rotation, and enables stable and high-precision machining to be continued. It is an object to provide a method and a device.

[0006]

In order to solve the above problems, a method for correcting a tool length of a machine tool according to the present invention commands an offset amount of a tool to be used to calculate a moving amount of a feed axis and NC.
In a machine tool for machining, tool length correction data corresponding to the spindle speed is stored in advance, and when the spindle speed is commanded by an NC program, the tool length offset amount of the tool used is stored in the spindle speed. The structural feature is that the correction is performed with the correction data of the tool length corresponding to.

Further, the tool length compensating device for a machine tool according to the present invention is a machine tool for instructing an offset amount of a tool to be used to calculate a moving amount of a feed axis and performing NC machining. Storage means for storing the length correction data in advance, and tool length correction data corresponding to the spindle speed of the tool used instructed by the NC program are extracted from the storage means, and the extracted correction data is used to extract the correction data. The tool length offset amount of the tool used is set, and the tool length offset amount is sent to the feed shaft movement amount calculation means of the NC device.

[0008]

The data of the tool length correction amount corresponding to each spindle rotation speed of each tool is stored, and the tool length correction amount corresponding to the predetermined spindle rotation speed of the predetermined tool is extracted.
By taking into consideration the tool offset amount setting means of the tool offset function provided in the NC device, even when the tool length changes due to the pulling-in phenomenon based on the centrifugal force during actual machining, it is corrected. The tool length offset amount is supplied to the NC device, and the machining accuracy of the machine tool continues stably.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the basic principle of a tool length correction device for a machine tool according to the present invention. The NC program passes through the reading / decoding means 9, information about the feed axis is extracted, and the interpolating means 13 is passed through the feed axis movement amount calculating means 11.
Is interpolated and is amplified by the servo control means 15 to drive each feed motor of the machine tool 21. Then, when the offset amounts of the tool length and the tool diameter are input from the tool offset amount setting means 7 to the feed axis movement calculation means 11, the feed axis movement control is performed in accordance with each offset amount of each tool.
The reading / decoding means 9 is connected to the tool offset amount setting means 7.
Tool length data and tool diameter data input in advance in the NC program sent from the tool, or the tool length from the tool dimension measuring means 17, a manual input device (not shown), a host computer (not shown) of the machining system, etc. Data and tool diameter data are input and output to the feed axis movement amount calculation means 11 as a tool length offset amount and a tool diameter offset amount. Each of these means is provided in the conventional NC device.

The present invention is characterized in that a tool length correction data input means 3, a storage means 5 for the correction data, and a tool offset amount setting means 7 capable of taking in the tool length correction data are further connected, The correction data input means 3, the correction data storage means 5, and the tool offset amount setting means 7 constitute the tool length correction device 1.
The correction data input means 3 can be composed of, for example, a keyboard (not shown), through which a correction data map showing the relationship between the spindle rotational speed for each tool and the tool length correction data is formed. It is input to the storage means 5.

The correction data storage means 5 corrects the tool length corresponding to the predetermined tool information (tool number and spindle rotation speed) sent from the NC program reading / decoding means 9 via the tool offset amount setting means 7. Data is extracted from the correction data map and is used as the tool offset amount setting means 7
To return to. The tool offset amount setting means 7 adds the tool length correction data of the predetermined tool sent from the correction data storage means 5 to the static tool length of the tool,
The corrected tool length (dynamic tool length) data is sent to the feed axis movement amount calculation means 11 as a tool length offset amount. Then, the feed axis movement amount is calculated based on this new tool length offset amount, the machine tool 21 is driven through the interpolation means 13 and the servo control means 15, and the desired NC machining is performed.

The operation and effect of the apparatus 1 of the present embodiment having the above configuration will be described below with reference to the flowchart of FIG. First, tool length correction amount data for each spindle rotation speed of each tool, for example, data showing the relationship between the spindle rotation speed and the tool length correction amount as shown in FIG. 3, is displayed on a keyboard (correction data input means 3) not shown. Input through the correction data storage means 5 (step 20).
1). The tool number is also stored if necessary.

Next, the tool offset number setting means 7 is made to read the tool number and spindle speed of the predetermined tool from the NC program input to the reading / decoding means 9 via a paper tape or mini computer (step 203). .. Then
A tool length correction amount corresponding to the spindle rotational speed of the predetermined tool is called from the correction data map of the tool length correction data storage means 5 (step 205).

Next, in the tool offset amount setting means 7, the obtained tool length correction amount is added to the static tool length of the predetermined tool to calculate the tool length offset amount corresponding to the dynamic tool length. Then, it is obtained and set (step 207).
Then, this new tool length offset amount is sent to the feed axis movement amount calculation means 11 (step 209), and thereafter, this is sent to the machine tool 21 as a machining command,
This subroutine ends.

As described above, in the present embodiment, when the spindle of the machine tool rotates at high speed, the machining accuracy based on the phenomenon that the tool is pulled into the spindle due to the centrifugal force unavoidably generated at the taper joint between the spindle and the tool. Can be effectively overcome (processing error). That is, the tool length offset amount corresponding to the corrected tool length (dynamic tool length) obtained by adding the tool length correction amount corresponding to the rotation speed peculiar to the tool to the static tool length of each tool Since the machining command calculated based on this is sent to the machine tool, even if the tool length changes during high-speed machining with the tool, the desired machining accuracy can be reliably and stably maintained for a long time. Can be achieved.

Needless to say, the relationship between the spindle rotational speed and the tool length correction amount in the correction data storage means 5 may be stored as a function. Further, it is not suitable for use in which a single tool is mounted on the main spindle to perform processing at, for example, 20,000 rpm, and subsequently, at 3000 rpm, such that high speed rotation is performed and then low speed rotation is performed. However, in most cases, with respect to the tool mounted on the spindle, since only a single rotational speed is commanded, there is no practical problem.

Further, although the present invention relates to the offset processing of the tool length, the offset processing of the tool diameter is also performed in the normal NC processing. This tool diameter offset processing is not directly related, so detailed description thereof will be omitted. However, the tool offset amount setting means 7 sets the tool diameter offset amount based on the tool diameter data given from the outside. This tool radius offset amount is input to the feed axis movement amount calculation means 11 and NC machining is performed as in the conventional case.

[0018]

As described above, according to the tool length correcting method and apparatus for a machine tool according to the present invention, it is possible to effectively overcome the adverse effects caused by the tool retracting phenomenon that may occur during high-speed rotation and to achieve high accuracy. It becomes possible to continue machining stably.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic principle of a tool length correction device for a machine tool according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an example of the operation of the tool length correction device of the embodiment.

FIG. 3 is a diagram illustrating a relationship between a spindle rotation speed and a tool length correction amount.

FIG. 4 is a cross-sectional side view of a main part of an example of a spindle structure of a machine tool.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tool length correction device 3 ... Correction data input means 5 ... Correction data storage means 7 ... Tool offset amount setting means 9 ... Reading / decoding means 11 ... Feed axis movement amount calculation means 13 ... Interpolation means 15 ... Servo control means 21 ... Machine Tools

Claims (2)

[Claims] 1. In a machine tool for commanding an offset amount of a tool to be used to calculate a moving amount of a feed axis and performing NC machining, correction data of a tool length corresponding to a spindle rotational speed is stored in advance, and an NC program is used for the spindle. A tool length correction method for a machine tool, wherein when a rotation speed is commanded, a tool length offset amount of a tool to be used is corrected by the stored correction data of the tool length corresponding to the stored spindle rotation speed. 2. A machine tool for instructing an offset amount of a tool to be used to calculate a moving amount of a feed axis and performing NC machining, a storage means for preliminarily storing correction data of a tool length corresponding to a spindle rotational speed, and NC. The correction data of the tool length corresponding to the spindle speed of the tool used by the program is extracted from the storage means,
A tool offset amount setting means for setting a tool length offset amount of the tool to be used by using the extracted correction data, and sending the tool length offset amount to a feed axis movement amount calculation means of the NC device. Tool length correction device for machine tools.