JP-2026075599-A - Methods to reduce residual imbalance in machining spindles

JP2026075599AJP 2026075599 AJP2026075599 AJP 2026075599AJP-2026075599-A

Abstract

[Problem] To reduce spindle imbalance in numerically controlled machine tools. [Solution] A data acquisition step in which, in two measurement operations, the spindle (10) and the tool (20) are positioned at different angles to each other, and in each measurement operation, the vibration experienced by the spindle as it rotates is measured and recorded in a database as a value V0 ,..., Vn representing the intensity, and each value V0 ,..., Vn is associated with an angle value θ0 ,..., θn representing the angle formed by the spindle and the tool during the measurement; a target angle position determination step in which the target angle position of the spindle relative to the tool is determined from a database constructed by measurement, wherein the target angle position has a target angle value θx corresponding to the angle value θ0 ,..., θn associated with the smallest value of V0 ,..., Vn ; and an arrangement step in which the spindle and the tool are positioned to form the target angle value θx . [Selection Diagram] Figure 1a

Inventors

パトリック・ファム
クリストフ・ドンツェ
ジョエル・ロトリスバーガー
ノエ・ジャギ

Assignees

ウーテーアー・エス・アー・マニファクチュール・オロロジェール・スイス

Dates

Publication Date: 20260508
Application Date: 20250925
Priority Date: 20241022

Claims (6)

A method for reducing residual unbalance of a spindle (10) in a numerically controlled machine tool, The spindle (10) is configured to hold a tool (20) that is fixed to the spindle (10) by a tool holder. The aforementioned method, A data acquisition step in which at least two measurement operations are performed, wherein in each of the measurement operations, the spindle (10) and the tool (20) are positioned at different angles to each other, the spindle (10) rotates, the vibration experienced by the spindle (10) is measured and recorded in a database as a value V0 ,..., Vn representing the intensity, and each of the values V0 ,..., Vn is associated with an angle value θ0 ,..., θn representing the angle formed between the spindle (10) and the tool (20) during the measurement, A target angle position determination step in which the target angular position of the spindle (10) relative to the tool (20) is determined from a database constructed by the measurement, wherein the target angular position has a target angular value θx corresponding to the angular value θ0 , ..., θn associated with the smallest value of V0 ,...,Vn, A method comprising the step of positioning the spindle (10) and the tool (20) relative to each other to form the target angular value θx .
During the data acquisition stage, at least three measurement operations are performed. The spindle (10) and the tool (20) are positioned relative to each other such that the angle values θ0 , ..., θn correspond to angles that are evenly distributed over a range of 360°. The method according to claim 1, wherein θ 0 = 0° and θ n ≤ 360°.
During the data acquisition stage, at least three measurement operations are performed. The spindle (10) and the tool (20) are positioned relative to each other such that the angular values θ0 , ..., θn correspond to angles randomly distributed over a range of 360°. The method according to claim 1, wherein θ 0 = 0° and θ n ≤ 360°.
The vibrations experienced by the spindle (10) are measured by an acceleration sensor. The method according to claim 1, wherein the values of V0 , ..., Vn correspond to the displacement, displacement velocity, or acceleration of a point on the tool (20) when the spindle (10) is rotating.
During the data acquisition stage, the spindle (10) is fixed between two consecutive measurements. The tool (20) is removed from the spindle (10) by the manipulator arm. The spindle (10) rotates by an angle corresponding to the difference between two consecutive angular values θ0 , ..., θn . The method according to claim 1, wherein the tool (20) is subsequently engaged with the spindle (10) at the same angular position as when it was removed, according to a reference system linked to the frame of the numerically controlled machine tool.
The method according to claim 1, wherein the data acquisition step and the determination step are performed for a plurality of tools, and for each of these tools, an individual target angle value is recorded in memory.

Description

This invention relates to the field of machine tools, and more particularly to the field of numerically controlled machine tools. More specifically, the present invention relates to a method for reducing residual unbalance in a machining spindle. In particular, for milling parts, spindles are used in numerically controlled machine tools (NCMTs). A spindle is a shaft that rotates relative to the frame using bearings, and is configured to house a tool holder to which the tool is fixed. When the spindle rotates, it transmits rotational motion to the tool, thereby machining the part. Machining and forming a complete part typically requires multiple tools with different shapes and/or dimensional configurations. Therefore, numerically controlled machine tools can be equipped with a tool magazine that stores all the tools and tool holders necessary to produce the complete part. Tools are retrieved from the tool magazine and mounted on the spindle by a manipulator arm. This manipulator arm can also remove tools from the spindle and place them back into the tool magazine. In practice, tools are manually attached to the tool holder by an operator located outside the machine, such as at a workbench. Once the tool is secured in the tool holder, the operator manually inserts the tool holder into a groove in the tool magazine on the numerically controlled machine tool. These manual operations performed by the operator can introduce imbalances into the assembly, resulting in spindle imbalance during rotation. Furthermore, the assembly of the spindle components and bearings can introduce uncertainties regarding the rotational balance of the tool, tool holder, and spindle assembly. These bearings allow the spindle to be mounted to the frame of the numerically controlled machine tool. Similarly, the balance between the tool and tool holder may be disrupted. Furthermore, using tools with asymmetrical shapes is particularly difficult due to their design. This is because the asymmetry of these tools causes the center of inertia to be off the axis of rotation, resulting in imbalance. In summary, there are many factors that cause imbalance during spindle rotation, which effectively leads to a systematic residual imbalance. Figures 1a to 1f schematically show cross-sectional views of a spindle into which a tool is engaged, in order to perform the data acquisition step in a method for reducing residual spindle unbalance in a numerically controlled machine tool, where in each figure the spindle and the tool are positioned to form different angles with respect to each other.This table shows the data measured during the data acquisition phase.Figure 2 shows a radar chart of the data in the table. The drawings are not necessarily drawn to scale for the sake of clarity. This invention relates to a method for reducing residual unbalance in a spindle 10 of a numerically controlled machine tool, also referred to hereafter as "NCMT". As is well known, the spindle 10 is configured to hold a tool 20 fixed to the spindle 10 by a tool holder (not shown) for, for example, machining operations. Such a tool 20 extends along a longitudinal axis and is formed, for example, by a milling cutter. For the sake of brevity in this document, the assembly formed by the tool 20 and the tool holder will also be simply referred to as the "tool". The method according to the present invention includes a plurality of steps, including a first data acquisition step in which at least two measurement operations are performed. In an exemplary embodiment of the present invention shown in the drawings, six measurement operations are performed. In each measurement operation, the angles formed by the spindle 10 and the tool 20 relative to each other are different. The origin of this angle of interest lies on the longitudinal axis of the tool 20, and it is clear that this angle lies in a plane perpendicular to this longitudinal axis. That is, as schematically shown in Figures 1a to 1f, a fixed point 21 is provided on the tool 20 and a fixed point 11 is provided on the spindle 10, so that in each measurement operation, the angles formed by these points on the tool 20 and the points on the spindle 10 relative to each other are different. In each measurement operation, the spindle 10 rotates at a speed preferably greater than 10 krpm, or at speeds of 30 krpm or 60 krpm, and the vibrations experienced by the spindle 10 are measured and recorded in a database. These vibrations characterize the unbalance of the spindle 10. Specifically, as shown in the table in Figure 2, the vibrations are recorded as values V0 ,..., Vn representing their intensity, and each of these values V0 ,..., Vn is associated with an angle value θ0 ,..., θn representing the angle formed between the spindle 10 and the tool 20 during the measurement operation in which the intensity of the vibrations is recorded. The data from Figure 2 is shown in the radar chart in Figure 3. In the method according to the p