This application claims priority of Japanese Patent Application No. 2022-096663 filed on Jun. 15, 2022. The contents of this application are incorporated herein by reference in their entirety.
The present invention relates to a machine tool and a method of machining a workpiece.
Japanese Unexamined Patent Application Publications No. 2021-53713 discloses an NC (numerically control) lathe provided with a bar feeder capable of supplying a bar material or a workpiece to a spindle of the lathe. Machining accuracy of the workpiece depends on positioning accuracy of the tip or the end of the workpiece.
Conventionally, the end of every brand new workpiece supplied to the spindle is cut off with a cut-off tool (an operation called “top-cut”) to position the end surface of the workpiece with precision.
When a supply error occurs, cutting off the end of the workpiece will fail, thus deteriorating positioning accuracy of the end surface of the workpiece.
The present invention provides a machine tool capable of solving the problem.
1. A machine tool includes a spindle capable of rotating a bar workpiece around its axis; a cutter capable of cutting the workpiece at a surface perpendicular to the axis; a sensor capable of detecting an object existing in an area where the cutter is located to cut the workpiece; and a controller adapted to execute an abnormality detection process prior to a top cut process of the workpiece. The abnormality detection process includes an abnormality determination process capable of determining that the object does not exist in the area according to a detection value of the sensor and thereby determining that the machine tool is not ready for the top cut process.
The top cut process can be executed only in the event that the workpiece exists in the predetermined area. The controller may determine, prior to the top cut process, whether the workpiece exists in the area in the abnormality detection process according to a detection value of the sensor. If abnormality is detected, the controller may stop the top cut process happening, thus preventing production of a defective product.
The “prior to the top cut process” may include “during the top cut process”.
2. In the machine tool according to 1 as described above, the controller is adapted to execute a retry process in the event that the abnormality detection process reveals occurrence of abnormality. The retry process includes a process of displacing the workpiece in a predetermined direction by a predetermined amount. The predetermined direction is a direction that the workpiece approaches the area where the cutter is located to cut the workpiece. The abnormality detection process further includes another abnormality determination process capable of determining whether the object exists in the area after the retry process according to a detection value of the sensor.
The retry process can modify the position of the workpiece to an appropriate position for the top cut process. Especially during nighttime unmanned continuous operation, the retry process could allow the whole process to continue without suspension.
3. In the machine tool according to 2 as described above, the controller is adapted to execute a number of retries setting process. The number of retries setting process includes a process of receiving a user instruction of the number of retries through an interface. The number of retries is an upper limit of the number of retries of the abnormal detection process and the retry process. The controller is adapted to repeat the retry process within the upper limit until the abnormality detection process reveals no occurrence of abnormality.
The number of retries setting process allows the user to set a desired value for the number of retries.
4. In the machine tool according to 2 or 3 as described above, the controller is adapted to execute a displacement amount setting process. The displacement amount setting process includes a process of receiving a user instruction of a displacement amount of the workpiece through an interface. The retry process includes a process of displacing the workpiece by the displacement amount received in the displacement amount setting process.
The displacement amount setting process allows the user to set a desired value for the displacement amount.
5. In the machine tool according to any of 2 to 4 as described above, the controller is adapted to execute an abnormality measures process in the event that the abnormality detection process reveals occurrence of abnormality after the retry process. The abnormality measures process includes a process of outputting an alarm and shutting off a working machine comprising the cutter and the spindle.
The abnormality measures process after the retry process allows the user to be notified of abnormality and prevents execution of subsequent processes.
6. In the machine tool according to any of 1 to 5 as described above, the cutter includes a cut-off tool and a sensor capable of detecting the object existing in the area where the cut-off tool is located to cut the workpiece. The controller is adapted to execute a cut-off tool breakage detection process after a cut-off process to determine that the cut-off tool is broken in the event that the sensor detects the object exists in the area.
The sensor for use in the cut-off tool breakage detection process is available for the workpiece position abnormality detection process, thus eliminating the need for a separate sensor.
7. In the machine tool according to any of 1 to 6 as described above, the controller includes an executing apparatus and a storage apparatus. The controller is adapted to receive a machining program input by a user through an interface. The storage apparatus stores a plurality of code data. The machining program is a selective combination of the code data to instruct the executing apparatus to control a working machine comprising the cutter and the spindle. The code data includes a code for instructing the executing apparatus to execute the abnormality detection process.
Accordingly, the machining program may include the instruction for executing the abnormality detection process.
A plurality of code data may include a code for instructing the executing apparatus to execute the retry process. A plurality of code data may include a code for instructing the executing apparatus to execute the cut-off tool breakage detection process.
8. In the machine tool according to any of 1 to 7 as described above, the sensor includes a detector capable of outputting a signal according to the detection value when the detector is displaced into the area where the cutter is located to cut the workpiece.
It can be determined whether an object exists in the predetermined area according to a detection result by the sensor. In the event that it is determined that an object exists in the predetermined area, it can be then determined that the object exists in the area where the cutter is located to cut the workpiece.
Displacing the detector into the predetermined area can facilitate such determination according to an output signal from the sensor.
The abnormality detection process using the sensor can be executed prior to top-cut. The cutter may include the cut-off tool and the sensor may be provided with the detector. The sensor may output a signal according to existence of the object in the predetermined area by displacing the detector into the predetermined area. The predetermined area may be defined by a component of a first coordinate axis greater than a value of the area where the cut-off tool is located to cut the workpiece, a component of a second coordinate axis containing the value of the component of the second coordinate axis of the workpiece, and a component of a third coordinate axis containing the value of the component of the third coordinate axis of the workpiece. The first coordinate axis includes the axis of the workpiece. The component of the first coordinate axis includes a positive component in a direction that the workpiece approaches the cut-off tool. The second coordinate axis and the third coordinate axis may be perpendicular to each other and perpendicular to the first coordinate axis.
9. In the machine tool according to any of 1 to 7 as described above, the sensor includes a non-contact sensor capable of detecting the object existing in the area where the cutter is located to cut the workpiece.
10. A method of machining a workpiece including executing the processes in the machine tool of according to any of 1 to 9 as described above.
The embodiment is being described referring to the drawings.
A lathe 1 may include a working machine 10 and a machining controller 50. The working machine 10 may include an apparatus capable of cutting a bar material or a workpiece W. The working machine 10 may include a spindle 14 mounted on a bed 12. The spindle 14 may rotate the workpiece W around an own axis as the rotation axis. The spindle 14 may be provided with a chuck 16 capable of holding the workpiece W. The spindle 14 may be displaced in positive and negative directions of a Z-axis shown in
The working machine 10 may have a guide bush 18 capable of supporting the workpiece W on the positive side of the spindle 14 with respect to the Z-axis. The working machine 10 may be provided with a tool post 20. The tool post 20 may have a turning tool capable of machining the workpiece W protruded from the guide bush 18. The tool post 20 may be displaced in directions of a Y-axis and an X-axis shown in
A bar feeder 40 may supply the workpiece W to the working machine 10. The bar feeder 40 may displace the workpiece in the positive direction with respect to Z-axis to thereby insert the workpiece W into the spindle 14. The bar feeder 40 may be provided with an actuator 40a and an end-detection sensor 40b. The actuator 40a may push the workpiece W toward the positive direction. The end-detection sensor 40b may detect a displacement amount of the workpiece W.
A feeder controller 42 may operate the bar feeder 40 to control a supply of the workpiece W to the working machine 10 according to a detection result by the end-detection sensor 40b.
The machining controller 50 may control the working machine 10. The controller 50 may control a Z-axis coordinate of the spindle 14 and X-axis and Y-axis coordinates of the tool post 20. The controller 50 may include a PU (Processing Unit) 52, a ROM (Read Only Memory) 54 and a RAM (Random Access Memory) 56. The PU 52 may include a software processing apparatus such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), and TPU (Tensor Processing Unit). The ROM 54 may include an electrically-non-rewritable memory. The RAM 56 may include an electrically-rewritable non-volatile memory and a storage medium such as a disk.
The ROM 54 may store a control program 54a and a code data group 54b. The RAM 56 may store a machining program 56a. The code data group 54b may include plural code data. The code data may include instructions causing the PU 52 to execute each and every process constituting various machining processes for the workpiece W. The machining program 56a may be a program represented by a combination of plural code data of the code data group 54b. The machining program 56a may define the processes to be executed by the PU 52 to have the workpiece W machined as desired by a user. The machining program 56a may be input by the user through an input device 60 and displayed in a display 62. The control program 54a may include an instruction causing the PU 52 to execute the machining program 56a and an instruction for controlling the display 62.
[Detailed Function of the Lathe]
The tool post 20 may be provided with a cut-off tool breakage detection apparatus 30. The breakage detection apparatus 30 may include a detection probe 32, an object 34, a contact sensor 36, and a resilient member 38. The detection probe 32 and the object 34 may be coupled. The resilient member 38 may push the object 34 to the contact sensor 36. The contact sensor 36 may output a signal according to the contact state of the object 34. The contact sensor 36 may include a differential transformer sensor, an optical scale sensor, and a magnet scale sensor.
[Breakage Detection of Cut-Off Tool]
The contact sensor 36 may thereby detect a contact state with respect to the object 34 according to breakage of the cut-off tool 22 (1).
First, the PU 52 may displace the tool post 20 in the positive direction of the Y-axis by a predetermined amount ΔY (S10) to bring the probe 32 of the breakage detection apparatus 30 into a predetermined area A shown in
Then the PU52 may determine whether an object exists in the predetermined area A according to the detection result of the contact sensor 36 (S12).
The PU 52 may finish the
[Top Cut Operation]
The cut-off tool 22 (1) may be also used to cut off the end of a fresh workpiece W just supplied from the bar feeder 40 for positioning purpose. Displacement amount of the workpiece W held by the chuck 16 can be defined with accuracy by that of the spindle 14. It might be, however, difficult to precisely position the end of the fresh workpiece W just supplied from the bar feeder 40 with deteriorated end detection accuracy. Executing the top-cut can define with accuracy the position of the end of the fresh workpiece W. The Z-axis coordinate component of the end of the workpiece W upon completion of top-cut may be equal to a value of the Z-axis coordinate component of the cut surface by the cut-off tool 22 (1).
The top-cut above described could fail if the Z-axis coordinate component of the end of the workpiece W equals the Z-axis coordinate component of the cut-off tool 22 (1) or lower. The embodiment provides a code that determines whether an abnormal condition exists prior to commencing cut-off.
[Workpiece Position Abnormality Detection Code for Top-Cut]
First, the PU 52 may displace the tool post 20 in the positive direction of the Y-axis by a predetermined amount ΔY (S20). Then, the PU 52 may determine whether an object exists in the predetermined area A by receiving a signal from the contact sensor 36 (S22). In the event that there exists no object in the predetermined area A (S22: NO), the PU 52 may determine that the workpiece W is in the abnormal position (S24). In other words, the PU 52 may determine that executing top-cut could end with an abnormal result.
Then the PU 52 may increment a retry counter C by 1 (one) (S26). The retry counter C may be 0 (zero) by default. The PU 52 may then determine whether the retry counter C equals the number of retries Cth or more (S28). In the event that the retry counter C is less than the number of retries Cth (S28: NO), the PU 52 may displace the tool post 20 in the negative direction of the Y-axis by a predetermined amount ΔY (S30) to bring the probe 32 out of the predetermined area A.
The PU 52 may then displace the workpiece W in the positive direction of the Z-axis by a predetermined amount ΔZ (S32) and then resume the process from Step S20. In the event that the retry counter C equals the number of retries Cth or more (S28: YES), the PU 52 may operate the speaker 64 to output an alarm, thereby notifying the user of abnormality (S34). The PU 52 may stop the working machine 10 (S36), thus shutting off power supply to the spindle motor and to the displacement actuator for the spindle 14 and the tool post 20.
The PU 52 may finish the
First, the PU 52 may determine whether an input device 60 has received a user instruction of the number of retries (S40). In the event that the input device 60 has received a user instruction of the number of retries (S40: YES), the PU 52 may substitute the user instruction for the number of retries Cth (S42). In the event that the input device 60 has received no instruction (S40: NO), the PU 52 may substitute the default Cth0 for the number of retries Cth (S44).
Upon completion of S42 or S44, the PU 52 may determine whether the input device 60 has received a user instruction of the displacement amount ΔZ for the workpiece W (S46). In the event that the input device 60 has received a user instruction of the displacement amount ΔZ (S46: YES), the PU 52 may substitute the user instruction for the displacement amount ΔZ (S48). In the event that the input device 60 has received no instruction (S46: NO), the PU 52 may substitute the default ΔZ for the displacement amount ΔZ (S50).
The PU 52 may finish the
First, the PU 52 may instruct the feeder controller 42 to control the bar feeder 40 to feed the workpiece W to the working machine 10 (S60). The PU 52 may then instruct the chuck 16 to hold the workpiece W (S62) as shown in
The PU 52 may then execute the
The PU 52 may finish the
The PU 52 may execute S60 to S64 and then finish the
The effect of the embodiment is being described. The code data group 54b stored in the ROM 54 of the controller 50 may include the workpiece position abnormality detection code defining the
The elements described in the embodiment correspond to the elements described in the summary as follows: The machine tool may correspond to the lathe 1. The cutting unit may correspond to the cutting tool 22. The sensor may correspond to the cut-off tool breakage detection apparatus 30. The abnormality detection process may correspond to the S20 to S24 steps. The retry process may correspond to the S30 and S32 steps. The predetermined direction may correspond to the positive direction of the Z-axis. Setting the number of retries may correspond to the S40 and S42 steps. Setting the displacement amount may correspond to the S46 and S48 steps. The abnormality measures may correspond to the S34 and S36 steps. The cut-off tool breakage detection process may correspond to the S10 to S14 steps. The executing unit may correspond to the PU52. The storage apparatus may correspond to the ROM 54. The detector may correspond to the probe 32. The sensor may correspond to the non-contact sensor 80.
Modified Embodiments: The invention can be implemented in a modified embodiment. The embodiment and the modified embodiment can be combined as far as they are not technically contradictory to each other.
[Retry Process]
The maximum number of retries Cth may be set by the user but not necessarily. The parameter setting process may be optional.
The displacement amount “+ΔZ” of the workpiece W may be set by the user but not necessarily. The parameter setting process may be optional.
The retry process may be optional.
[Setting Number of Retries]
In the event that no instruction is given by the user (S40:
[Setting Displacement Amount]
In the event that no instruction is given by the user (S46:
[Abnormality Measures]
The abnormality measures taken in the event of workpiece position abnormality may include both of the S34 and S36 steps but not necessarily. One of the steps may be optional.
[Workpiece Position Abnormality Detection Code]
The workpiece position abnormality detection code may contain subsets of the codes; a code for giving instructions for executing the S20 to S24 steps, a code for giving instructions for executing the S26 to S32 steps, and a code for giving instructions for executing the S34 to S36 steps. The user can separately select at least one of the codes; the code for giving instructions for executing the workpiece position abnormality detection, the code for giving instructions for executing the retry process, and the code for giving instructions for executing the abnormality measures. The code for giving instructions for executing the abnormality measures may be common to, for example, a code for giving instructions for executing the abnormality measures taken in the event of cut-off tool breakage as described below.
For example, the code for giving instructions for executing the workpiece position abnormality detection may be included in the code for giving instructions for executing top-cut.
[Cut-Off Tool Breakage Detection Code]
The cut-off tool breakage detection code may contain subsets of the codes; a code for giving instructions for executing the S10 to S14 steps and a code for giving instructions for executing the S16 to S18 steps. The user can separately select at least one of the codes; the code for giving instructions for executing the cut-off tool breakage detection and the code for giving instructions for executing the abnormality measures.
For example, the code for giving instructions for executing the cut-off tool breakage detection may be included in the code for giving instructions for the cut-off tool.
[Code Data]
The code data may include both of the cut-off tool breakage detection code or the subsets of the codes and the workpiece position abnormality detection code or the subsets of the codes but not necessarily. For example, the cut-off tool breakage detection code may be optional if a sensor is specially provided to detect workpiece position abnormality as described below.
The controller may execute the machining program written by a combination of the code data but not necessarily. The controller may be a control apparatus specially designed to execute a series of predetermined processes to machine the workpiece W. The workpiece position abnormality detection process may be still available prior to top-cut.
[Detector]
The detector may be the probe 32 shown in
[Sensor]
The sensor capable of detecting an object in the predetermined area A may be the cut-off tool breakage detection apparatus 30 but not necessarily. An apparatus having the same structure as that of the breakage detection apparatus 30 may be provided as an apparatus for use in the workpiece position abnormality detection prior to top-cut.
The sensor capable of detecting an object in the predetermined area A may be the contact sensor bringing the detector into the area to detect contact with the object, but not necessarily. A non-contact sensor 80 in
The non-contact sensor 80 may be provided with a sensor coil. High frequency magnetic flux across the sensor coil would cause an occurrence of overcurrent in the workpiece W. The magnitude of overcurrent depends on the intervals between the sensor coil and the workpiece W. Sensor coil impedance is variable on the magnitude of overcurrent. Detection of impedance could therefore reveal the position of the workpiece W, thus determine whether the workpiece W exists in the predetermined area A. The non-contact sensor 80 may be the sensor as described above but not necessarily. The non-contact sensor may include a laser displacement gauge and a proximity sensor.
The sensor may be mounted on the tool post 20 but not necessarily. The sensor capable of detecting an object in the predetermined area A may include a sensor capable of detecting a load applied to the cut-off tool 22 (1) during top-cut. Such sensor may detect a load applied to the tool post 20 during displacement thereof. The load applied to the tool post 20 may rely on motor current of the motor that controls the displacement speed of the tool post 20. The load applied to the tool post 20 may rely on the displacement speed and the motor current if a predetermined voltage is applied to the motor to displace the tool post 20. The sensor may include a sensor capable of detecting torque transmission between the spindle 14 and a back spindle in contact with the end of the workpiece W to determine that the workpiece W is in the normal position.
[Cutting Unit]
The cutting unit may be the cutting tool 22 but not necessarily. A laser cutter 90 in
[Executing Apparatus]
The executing apparatus may be an apparatus capable of executing software processes but not necessarily. The executing apparatus may be provided with a specially designed hardware circuit such as ASIC (Application Specific Integrated Circuit) capable of executing at least part of the processes. The executing apparatus may necessarily include at least one of the configurations; (a) a processing circuit provided with a processor capable of executing all the processes in accordance with a program and a program storing device such as a memory, (b) a processing circuit provided with a processor capable of executing part of the processes in accordance with a program, a program storing device, and a specially designed hardware circuit capable of executing the other of the processes, and (c) a processing circuit provided with a specially designed hardware circuit capable of executing all the processes.
One or more software executing apparatuses may be provided. One or more specially designed hardware circuits may be provided.
[Controller]
The feeder controller 42 and the machining controller 50 may be separately provided but not necessarily. They may be integrated.
[Others]
The storage apparatus for the control program 54a and the storage apparatus for the code data group 54b may be the same but not necessarily. The storage apparatus for the control program 54a and the code data group 54b and the storage apparatus for the machining program 56a may be separate but not necessarily.
Number | Date | Country | Kind |
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2022-096663 | Jun 2022 | JP | national |