Machine tool, method of estimating force applied to tool, and non-transitory computer-readable medium storing program for estimating force applied to tool

1 . A machine tool capable of cutting a workpiece using a tool, the machine tool comprising:

a first surface that receives a force due to the cutting of the workpiece, the first surface being located in the machine tool;

a second surface that receives a force due to the cutting of the workpiece, the second surface being located in the machine tool, the second surface being not parallel to the first surface;

a first strain sensor coupled to the first surface and the second surface; and

an estimation unit that estimates a force applied to the tool, based on an output value of the first strain sensor during the cutting of the workpiece, wherein

the first strain sensor has a first end in direct contact with the first surface and a second end in direct contact with the second surface, the first strain sensor has a shape not in direct contact with a connection portion constituted of the first surface and the second surface due to a gap located between an inner side surface of the first strain sensor and the connection portion.

2 . The machine tool according to claim 1 , wherein

the first strain sensor includes

a fixing member coupled to the first surface and the second surface, and

a sensing unit attached to a hole provided in the fixing member.

3 . The machine tool according to claim 1 , further comprising:

a spindle that rotates the tool; and

a housing that accommodates the spindle, wherein

the first surface is a surface on the housing and forms a predetermined angle with respect to an axis direction of the spindle, and

the second surface is a surface on the housing and is parallel to the axis direction of the spindle.

4 . The machine tool according to claim 1 , further comprising:

a spindle that rotates the workpiece; and

a cutting tool rest capable of holding the tool that cuts the workpiece, wherein

the first surface is a surface on the cutting tool rest and forms a predetermined angle with respect to an axis direction of the spindle, and

the second surface is a surface on the cutting tool rest or a surface on an installation surface for the cutting tool rest and is parallel to the axis direction of the spindle.

5 . The machine tool according to claim 3 , wherein the predetermined angle is 90°.

6 . The machine tool according to claim 5 , further comprising:

a second strain sensor;

a third strain sensor; and

a fourth strain sensor, wherein

the second strain sensor is coupled to the first surface and a third surface that receives a force due to the cutting of the workpiece, and the third surface is not parallel to the first surface,

the third strain sensor is coupled to the first surface and a fourth surface that receives a force due to the cutting of the workpiece, and the fourth surface is not parallel to the first surface and faces the second surface, and

the fourth strain sensor is coupled to the first surface and a fifth surface that receives a force due to the cutting of the workpiece, and the fifth surface is not parallel to the first surface and faces the third surface.

7 . The machine tool according to claim 5 , further comprising:

a second strain sensor; and

a third strain sensor, wherein

the second strain sensor is coupled to the first surface and a third surface that receives a force due to the cutting of the workpiece, and the third surface is not parallel to the first surface and does not face the second surface, and

the third strain sensor is coupled to the first surface and a fourth surface that receives a force due to the cutting of the workpiece, and the fourth surface is not parallel to the first surface and does not face the second surface and the third surface.

8 . A method of estimating a force applied to a tool when cutting a workpiece in a machine tool,

the machine tool including

a first surface that receives a force due to the cutting of the workpiece, the first surface being located in the machine tool,

a second surface that receives a force due to the cutting of the workpiece, the second surface being located in the machine tool, the second surface being not parallel to the first surface, and

a strain sensor coupled to the first surface and the second surface, wherein the strain sensor has a first end in direct contact with the first surface and a second end in direction contact with the second surface, the strain sensor has a shape not in direct contact with a connection portion constituted of the first surface and the second surface due to a gap located between an inner side surface of the first strain sensor and the connection portion, the method comprising

obtaining an output value of the strain sensor during the cutting of the workpiece; and

estimating a force applied to the tool, based on the output value.

9 . A non-transitory computer-readable medium storing a program for estimating a force applied to a tool when cutting a workpiece in a machine tool,

the machine tool including

a first surface that receives a force due to the cutting of the workpiece, the first surface being located in the machine tool,

a second surface that receives a force due to the cutting of the workpiece, the second surface being located in the machine tool, the second surface being not parallel to the first surface, and

a strain sensor coupled to the first surface and the second surface, wherein the strain sensor has a first end in direct contact with the first surface and a second end in direction contact with the second surface, the strain sensor has a shape not in direct contact with a connection portion constituted of the first surface and the second surface due to a gap located between an inner side surface of the first strain sensor and the connection portion, the program causing

the machine tool to perform:

obtaining an output value of the strain sensor during the cutting of the workpiece; and

estimating a force applied to the tool, based on the output value.