JP-7857017-B2 - Maintenance methods for machine tools

JP7857017B2JP 7857017 B2JP7857017 B2JP 7857017B2JP-7857017-B2

Inventors

溝口春機

Assignees

株式会社ＭＳＴコーポレーション

Dates

Publication Date: 20260512
Application Date: 20220926

Claims (2)

A spindle (2) to which a tool can be detachably attached, a spindle bearing (7) that rotatably supports the spindle (2), a spindle motor (8) that rotationally drives the spindle (2) , a table (3) to which a workpiece to be machined by the tool is attached, an X-axis feed device (10) that moves the spindle head (9), composed of the spindle (2), the spindle bearing (7), and the spindle motor (8), relative to the table (3) in the left-right direction, and moves the table (3) and the spindle head (9) relative to each other in the front-back direction. The machine has a Y-axis feed device (20), a Z-axis feed device (30) that moves the table (3) and the spindle head (9) relative to each other in the vertical direction, a cooling pump (41) that circulates cooling oil to the spindle head (9), an automatic tool changer (40) that exchanges tools between a tool magazine (42) that houses multiple types of tools and the spindle (2), a splash guard (4) that surrounds the machining space of the workpiece, and a front door (6) that opens and closes the front opening (5) of the splash guard (4). The X-axis feed device (10) consists of an X-axis linear guide (11), an X-axis ball screw (12), and an X-axis motor (13). The Y-axis feed device (20) consists of a Y-axis linear guide (21), a Y-axis ball screw (22), and a Y-axis motor (23). In a maintenance method for a machine tool that is a machining center, the Z-axis feed device (30) is composed of a Z-axis linear guide (31), a Z-axis ball screw (32), and a Z-axis motor (33) . A method for maintaining a machine tool, characterized by periodically measuring the runout accuracy of the spindle (2), and when the runout accuracy of the spindle (2) obtained from the measurement exceeds a preset threshold, inspecting all of the movable parts of the machine tool, namely the spindle bearing (7), the spindle motor (8), the X-axis linear guide (11), the X-axis ball screw (12), the X-axis motor (13), the Y-axis linear guide (21), the Y-axis ball screw (22), the Y-axis motor (23), the Z-axis linear guide (31), the Z-axis ball screw (32), the Z-axis motor (33), the cooling pump (41), the automatic tool changer (40), and the front door (6) .
A method for maintaining a machine tool according to claim 1, comprising using a rod-shaped inspection jig (50) having a cylindrical outer surface with a circumferential runout of 1 μm or less , or a rod-shaped portion (53) having a cylindrical outer surface with a circumferential runout of 1 μm or more and 3 μm or less, wherein the rod-shaped inspection jig (50) has markings on its outer surface indicating the phase , which is the angular position where the runout is maximum when the circumferential runout of the rod-shaped portion (53) is measured, and a measured value of 1 μm or more and 3 μm or less obtained by measuring the circumferential runout of the rod-shaped portion (53) in advance, and attaching the inspection jig (50) to the spindle (2), and measuring the runout of the outer surface of the inspection jig (50) with a dial gauge (54) when the spindle (2) is rotated, thereby measuring the runout accuracy of the spindle ( 2 ).

Description

This invention relates to a method for maintaining machine tools such as machining centers. When machining a workpiece, machine tools such as machining centers are used. Machine tools generally have many moving parts. For example, a machining center has, as its movable parts, a spindle to which a tool can be detachably attached, a spindle bearing that rotatably supports the spindle, and a spindle motor that rotates the spindle. The spindle, spindle bearing, and spindle motor constitute the spindle head. Furthermore, the machining center has, as movable parts, an X-axis feed device that moves the table on which the workpiece is mounted and the spindle head relative to each other in the left-right direction, a Y-axis feed device that moves the table and the spindle head relative to each other in the front-back direction, and a Z-axis feed device that moves the table and the spindle head relative to each other in the up-down direction. The X-axis feed device has an X-axis linear guide, an X-axis ball screw, and an X-axis motor; the Y-axis feed device has a Y-axis linear guide, a Y-axis ball screw, and a Y-axis motor; and the Z-axis feed device has a Z-axis linear guide, a Z-axis ball screw, and a Z-axis motor. In addition to the above, machining centers also have movable parts such as a cooling pump for circulating cooling oil to the spindle head, an automatic tool changer (ATC) that automatically changes tools between the tool magazine, which holds multiple types of tools, and the spindle, and a front door that opens and closes the front opening of the splash guard surrounding the workpiece machining space. The moving parts of machine tools, such as the spindle bearings, spindle motor, X-axis linear guide, X-axis ball screw, X-axis motor, Y-axis linear guide, Y-axis ball screw, Y-axis motor, Z-axis linear guide, Z-axis ball screw, Z-axis motor, cooling pump, automatic tool changer, front door, etc., gradually deteriorate due to wear and tear with repeated use. Conventionally, among the moving parts of machine tools, the spindle bearings have been inspected for deterioration by periodically measuring the runout accuracy of the spindle (for example, Patent Document 1). On the other hand, moving parts other than the main shaft bearings were not regularly inspected; repairs or parts replacements were generally carried out only when a malfunction occurred. However, if a malfunction occurs in a moving part and repairs or parts replacement is carried out, there is a risk of significant losses, such as defective workpieces being processed, or delays in delivery due to the machine tool being shut down while the repair or replacement of the moving part is completed. Therefore, the inventor of this application considered a maintenance method to prevent malfunctions in the moving parts of machine tools by conducting a complete inspection of the machine tool at regular intervals (for example, every three years). However, if machine tools are inspected at regular intervals, there is a risk that moving parts may fail before the inspection period arrives, especially if the machine tools are used frequently or under harsh conditions. Conversely, if machine tools are used infrequently or under mild conditions, the moving parts may not have experienced significant wear or deterioration by the time the inspection period arrives, resulting in unnecessary time and cost for the inspection. Japanese Patent Publication No. 2001-347440 Front view showing a machining center implementing a machine tool maintenance method according to an embodiment of this invention.Figure 1 is a schematic front view showing the internal structure of the splash guard of the machining center.Figure 2 is a partial cross-sectional view seen from the right side.Enlarged cross-sectional view of the vicinity of the inspection jig in Figure 2. Figure 1 shows a machine tool implementing a maintenance method for machine tools according to an embodiment of this invention. This machine tool is a machining center 1 that processes a workpiece (not shown) fixed to a table 3 using a tool (not shown) attached to a spindle 2. The machining center 1 has a splash guard 4 that surrounds the workpiece machining space, and a front door 6 that opens and closes the front opening 5 of the splash guard 4. The splash guard 4 is an enclosure designed to prevent chips generated during workpiece machining and cutting fluid sprayed towards the machining point of the workpiece from scattering to the outside. The front door 6 is slidable from side to side between a closed position that closes the front opening 5 of the splash guard 4 and an open position that opens the front opening 5 of the splash guard 4. As shown in Figure 2, the machining center 1 has a spindle 2 to which a tool (not shown) can be detachably attached, a spindle bearing 7 that rotatably supports the spindle 2, and a spindle motor 8 that rotationally drives the spindle 2. The spindle 2, spindle bearing 7, and spindle