Detection device and storage medium storing a program

A detection device includes an idling feed threshold acquiring unit configured to acquire, as an idling feed threshold, a threshold of an acceptable load in an idling feed operation; an expected load acquiring unit configured to acquire, as an expected load, an expected increase in load due to execution of an actual machining operation; a calculating unit configured to calculate, based on the idling feed threshold and the expected load, an actual machining threshold which is a threshold of an acceptable load in the actual machining operation; an actual machining load acquiring unit configured to acquire, as an actual machining load, an actual load during an actual machining operation; and a detecting unit configured to detect, based on the operating mode, an excess of the actual machining load relative to the idling feed threshold or the actual machining threshold.

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2019-188034, filed on 11 Oct. 2019, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a detection device and a storage medium storing a program.

Related Art

Conventionally, in removal machining devices that perform removal machining such as cutting using a tool, machining of a workpiece is carried out by bringing the tool into contact with the workpiece. At this time, the tool is moved (fed) by an operation of a worker, or a program set in the removal machining device.

When operating a removal machining tool, the main axis of the moving tool preferably does not contact the workpiece or jig. Such contact may cause damage to the tool (and the removal machining device). Therefore, measures are taken to prevent damage, by detecting a load on the feed axis (main axis). For example, when a load torque equal to or more than a threshold is detected on the feed axis, operation of the removal machining device is stopped. In this way, a device that compares an upper limit of the machining load to an actual load has been proposed as a device for monitoring a load (see, for example, Japanese Unexamined Patent Application, Publication No. H08-19939).

SUMMARY OF THE INVENTION

In Japanese Unexamined Patent Application, Publication No. H08-19939, it is determined whether an actual load exceeds a preset upper limit of the machining load. This allows for monitoring of breakage and wear of the tool.

The threshold for detecting the load is set to a value that includes a margin considering the influence of a load due to removal machining. This makes it possible to prevent stopping due to the load at the time of removal machining. However, detection of the load by the threshold including the margin of the removal machining load is carried out even in cases where no removal machining takes place (idling operation), such as when testing the program with the tool separated from the workpiece. It would therefore be preferable if it were possible to prevent damage to the tool in a more suitable manner according to the operating conditions.

The present disclosure relates to a detection device to detect an abnormality in a removal machining load on a feed axis in a removal machining feed by a removal machining device, the detection device including: an idling feed threshold acquiring unit that acquires, as an idling feed threshold, a threshold of an acceptable load in an idling feed operation where a workpiece is not machined; an expected load acquiring unit that acquires, as an expected load, an expected increase in load due to execution of an actual machining operation in which the workpiece is actually machined; a calculating unit that calculates, based on the idling feed threshold and the expected load, an actual machining threshold which is a threshold of an acceptable load in the actual machining operation; an operating mode acquiring unit that acquires whether the operating mode is an idling feed operation or an actual machining operation; an actual machining load acquiring unit that acquires, as an actual machining load, an actual load during an actual machining operation; a detecting unit that detects, based on the operating mode, an excess of the actual machining load relative to the idling feed threshold or the actual machining threshold; and an output unit that outputs a signal indicating the excess of the actual machining load.

In addition, the present disclosure relates to a storage medium storing a program to cause a computer to operate as a detection device to detect an abnormality in a removal machining load on a feed axis in a removal machining feed by a removal machining device, the program causing the computer to function as: an idling feed threshold acquiring unit that acquires, as an idling feed threshold, a threshold of an acceptable load in an idling feed operation where a workpiece is not machined; an expected load acquiring unit that acquires, as an expected load, an expected increase in load due to execution of an actual machining operation in which the workpiece is actually machined; a calculating unit that calculates, based on the idling feed threshold and the expected load, an actual machining threshold which is a threshold of an acceptable load in the actual machining operation; an operating mode acquiring unit that acquires whether the operating mode is an idling feed operation or an actual machining operation; an actual machining load acquiring unit that acquires, as an actual machining load, an actual load during an actual machining operation; a detecting unit that detects, based on the operating mode, an excess of the actual machining load relative to the idling feed threshold or the actual machining threshold; and an output unit that outputs a signal indicating the excess of the actual machining load.

According to the present disclosure, a detection device and storage medium storing a program that more appropriately prevents damage to a tool according to operating conditions can be provided.

DETAILED DESCRIPTION OF THE INVENTION

The detection device1and program according to each of the embodiments of the present disclosure are described below with reference toFIGS. 1 to 9. First, the detection device1will be summarized.

The detection device1is, for example, incorporated into a numerical control device200that controls a removal machining device100, as shown inFIG. 1. The detection device1monitors a load on a feed axis (main axis) of the removal machining device100. The detection device1acquires, for example, a load torque or load current on the feed axis caused by a movement of the tool102, in order to detect contact of the tool102against the workpiece101or jig (not shown). The detection device1thus prevents breakage, damage, etc. of the tool102. The detection device1according to each of the embodiments below particularly monitors the load of a removal machining feed of the tool102. Specifically, the detection device1monitors load in an idling feed operation where the workpiece101is not machined, and an actual machining operation where the workpiece101is actually machined. It should be noted that in each of the embodiments, “removal machining” is a general term for a type of machining in which a tool contacts a workpiece, including cutting, grinding, polishing, etc.

First Embodiment

Next, a detection device1according to a first embodiment of the present disclosure will be described with reference toFIGS. 1 to 4. The detection device1is a device for detecting a removal machining load abnormality in a removal machining feed operation of a removal machining device100. As shown inFIG. 2, the detection device1includes an idling feed threshold acquiring unit11, an expected load acquiring unit12, a calculating unit13, an operating mode acquiring unit14, an actual machining load acquiring unit15, a detecting unit16, an output unit17, and a stop control unit18.

The idling feed threshold acquiring unit11is realized, for example, by the operation of a CPU. The idling feed threshold acquiring unit11acquires, as an idling feed threshold, a threshold of an acceptable load in an idling feed operation where the workpiece101is not machined. For example, the idling feed threshold acquiring unit11acquires, as the idling feed threshold, the load on the feed axis in a test operation for testing an operation of the tool102. The idling feed threshold acquiring unit11acquires a smaller load as the idling feed threshold, on the premise that the tool102is not in contact with the workpiece101.

The expected load acquiring unit12is realized, for example, by the operation of a CPU. The expected load acquiring unit12acquires, as an expected load, an expected increase in load due to the execution of an actual machining operation in which the workpiece101is actually machined. For example, the expected load acquiring unit12acquires, as the expected load, a value determined as the increase in load due to actual machining. In other words, the expected load acquiring unit12acquires an acceptable load margin beyond the idling feed threshold as the expected load.

The calculating unit13is realized, for example, by the operation of a CPU. The calculating unit13calculates, based on the idling feed threshold and the expected load, an actual machining threshold, which is a threshold of an acceptable load in the actual machining operation. For example, as shown inFIG. 3, the calculating unit13calculates the sum of the idling feed threshold and the expected load as the actual machining threshold.

The operating mode acquiring unit14is realized, for example, by the operation of a CPU. The operating mode acquiring unit14acquires whether the operating mode is an idling feed operation or an actual machining operation. For example, the operating mode acquiring unit14acquires an operating mode, which is either the idling feed operation or the actual machining operation set by the numerical control device200.

The actual machining load acquiring unit15is realized, for example, by the operation of a CPU. The actual machining load acquiring unit15acquires an actual load during actual machining operation as the actual machining load. For example, the actual machining load acquiring unit15acquires from the numerical control device200the actual load on the tool102, which changes over time as the actual machining load. In other words, the actual machining load acquiring unit15acquires an increased load due to contact of the tool102against the workpiece101as an example of the actual machining load. Conversely, the actual machining load acquiring unit15acquires a reduced load due to separation of the tool102from the workpiece101as an example of the actual machining load.

The detecting unit16is realized, for example, by the operation of a CPU. The detecting unit16detects, based on the operating mode, an excess of the actual machining load relative to the idling feed threshold or the actual machining threshold. In case the operating mode is set to the idling feed operation, the detecting unit16detects an excess of the actual machining load relative to the idling feed threshold. On the other hand, if the operating mode is set to the actual machining operation, the detecting unit16detects an excess of the actual machining load on the tool102relative to the actual machining threshold. In other words, if the operating mode is set to the idling feed operation, the detecting unit16detects an excess of the actual machining load relative to the idling feed threshold, which is the lower threshold. Conversely, in case the operating mode is set to the actual machining operation, the detecting unit16detects an excess of the actual machining load relative to the actual machining threshold, which is the higher threshold.

The output unit17is realized, for example, by the operation of a CPU. The output unit17outputs a signal indicating an excess of the actual machining load. For example, the output unit17displays a screen showing the excess on a display device (not shown). In addition, the output unit17causes an audio playback device (not shown) such as, for example, a speaker, etc. to play a sound indicating the excess.

The stop control unit18is realized, for example, by the operation of a CPU. Based on a detection of the excess of the actual machining load, the stop control unit18stops operation of the removal machining device100. For example, the stop control unit18stops operation of the removal machining device100by outputting a trip signal to the removal machining device100.

Next, an operation of the detection device1will be described with reference to the flowchart inFIG. 4. First, the idling feed threshold acquiring unit11acquires an idling feed threshold (Step S1). The idling feed threshold acquiring unit11acquires, for example, a threshold of a load on the tool102in an idling feed operation set in the removal machining device100. The idling feed threshold acquiring unit11sends the acquired idling feed threshold to the calculating unit13and the detecting unit16.

Next, the expected load acquiring unit12acquires an expected load (Step S2). The expected load acquiring unit12acquires a different expected load according to, for example, the type of tool102or the type of removal machining. The expected load acquiring unit12sends the acquired expected load to the calculating unit13.

Next, the operating mode acquiring unit14acquires an operating mode (Step S4). For example, the operating mode acquiring unit acquires whether the operating mode is an idling feed operation or an actual machining operation. The operating mode acquiring unit14sends the acquired operating mode to the detecting unit16.

Next, the actual machining load acquiring unit15acquires an actual machining load (Step S5). The actual machining load acquiring unit15sends the acquired actual machining load to the detecting unit16.

Next, the detecting unit16determines which operating mode the device is operating in (Step S6). If the operating mode is determined to be the idling feed operation (Step S6: YES), the process flow advances to Step S7. On the other hand, if the operating mode is determined to be the actual machining operation (Step S6: NO), the process flow advances to Step S10.

At Step S7, the detecting unit16determines whether the actual machining load exceeds the idling feed threshold. The detecting unit16detects, for example, an excess of the actual machining load relative to the idling feed threshold, as shown inFIG. 3. If the actual machining load exceeds the idling feed threshold (Step S7: YES), the process flow advances to Step S8. On the other hand, if the actual machining load does not exceed the idling feed threshold (Step S7: NO), the process flow advances to Step S11.

At Step S8, the output unit17outputs a signal indicating the excess of the actual machining load to the outside. For example, the output unit17causes a display device to display an indication of the excess of the actual machining load.

At Step S9, the stop control unit18stops operation of the removal machining device100. This concludes the processing according to the present process flow.

At Step S10, the detecting unit16determines whether the actual machining load exceeds the actual machining threshold. The detecting unit16detects, for example, an excess of the actual machining load relative to the actual machining threshold, as shown inFIG. 3. If the actual machining load exceeds the actual machining threshold (Step S10: YES), the process flow advances to Step S8. On the other hand, if the actual machining load does not exceed the actual machining threshold (Step S10: NO), the process flow advances to Step S11.

At Step S11, it is determined whether or not to continue monitoring by the detection device1. For example, if removal machining feed by the removal machining device100is performed continuously, monitoring by the detection device1is continued. If monitoring is to be continued (Step S11: YES), the process flow returns to Step S5. On the other hand, if monitoring is to be ended (Step S11: NO), processing according to the present process flow ends.

Next, the program will be described. Each of the configurations included in the detection device1may be realized by hardware, software, or a combination thereof. The expression “realized by software” as used here means to be realized by a computer reading and executing a program.

The program may be stored using a variety of non-transitory computer readable media and provided to the computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable storage media include magnetic storage media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical storage media (e.g., magneto-optical discs), CD-ROM (Read Only Memory), CD-R, CD-R/W, and semiconductor memories (e.g., mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)). Alternatively, the display program may be provided to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to the computer via a wired communication path such as electric wires and optical fibers, etc., or via a wireless communication path.

The detection device1and program according to the first embodiment described above exhibit the following effects.

(1) A detection device1to detect an abnormality in a removal machining load on a feed axis in a removal machining feed by a removal machining device100, the detection device including: an idling feed threshold acquiring unit11that acquires, as an idling feed threshold, a threshold of an acceptable load in an idling feed operation where a workpiece101is not machined; an expected load acquiring unit12that acquires, as an expected load, an expected increase in load due to execution of an actual machining operation in which the workpiece101is actually machined; a calculating unit13that calculates, based on the idling feed threshold and the expected load, an actual machining threshold which is a threshold of an acceptable load in the actual machining operation; an operating mode acquiring unit14that acquires whether the operating mode is an idling feed operation or an actual machining operation; an actual machining load acquiring unit15that acquires, as an actual machining load, an actual load during an actual machining operation; a detecting unit16that detects, based on the operating mode, an excess of the actual machining load relative to the idling feed threshold or the actual machining threshold; and an output unit17that outputs a signal indicating the excess of the actual machining load. The threshold for detecting an abnormality can be changed between the idling feed operation where no removal machining load occurs and the actual machining operation. In other words, the threshold to be used can be changed according to the operating conditions. This makes it possible to prevent damage to the tool102in a more suitable manner according to the operating conditions.
(2) The calculating unit13calculates the sum of the idling feed threshold and the expected load as the actual machining threshold. This allows the detecting unit16to detect unintended contact of the tool102based on the actual machining threshold in which the load is increased compared to the idling feed threshold. It is thus possible to detect unintended contact of the tool102while preventing erroneous detection during actual removal machining by the removal machining device100.

Second Embodiment

Next, a detection device1and a program according to a second embodiment of the present disclosure is described with reference toFIGS. 5 to 9. In the description of the second embodiment, elements that are the same as in the embodiment described above are given the same reference numerals, and their descriptions will be omitted or simplified. The detection device1according to the second embodiment differs from the first embodiment in that it further includes a load determining unit19, as shown inFIG. 5. The detection device1according to the second embodiment also differs from the first embodiment in that the expected load acquiring unit12acquires an expected load determined by the load determining unit19.

The load determining unit19is realized, for example, by the operation of a CPU. The load determining unit19determines the expected load according to the type of tool102or type of removal machining. As shown inFIG. 6, the load determining unit19changes the expected load according to, for example, hardness of the workpiece101, tensile strength of the workpiece101, the feed rate, the depth of cut and removal machining width in the machining conditions, cutting speed, and shape of the tool102. The load determining unit19changes the expected load using each of these elements as described below.

(Material of the Workpiece101)

The load determining unit19increases the expected load if the hardness of the material of the workpiece101is high. In addition, the load determining unit19increases the expected load if the tensile strength of the material of the workpiece101is high.

The load determining unit19increases the expected load the higher the feed rate. This is because the higher the feed rate, the greater the removal machining amount with each blade strike.

The load determining unit19increases the expected load the greater the depth of cut shown inFIG. 7. In addition, the load determining unit19increases the expected load the greater the removal machining width shown inFIG. 7. This is because the greater the depth of cut or removal machining width, the greater the removal machining amount and greater the load.

The load determining unit19increases the expected load the slower the cutting speed. This is because as the cutting speed becomes slower, the removal machining amount with each blade strike increases, and the load becomes greater.

(Shape of the Tool102)

If the tool102is a milling cutter, the load determining unit19, as shown inFIGS. 8 and 9, increases the expected load the smaller the entering angle. This is because the smaller the entering angle, the greater the removal machining amount with each blade strike and the greater the load.

The detection device1and program according to the second embodiment described above exhibit the following effects.

(3) The detection device further includes a load determining unit19that determines an expected load according to the type of tool102or type of removal machining, and the expected load acquiring unit12acquires the expected load determined by the load determining unit19. This makes it possible to set a different expected load according to the type of tool102or type of removal machining, allowing for more flexible setting of the detection precision.

Preferred embodiments of the detection device and program according to the present disclosure have been described above, but the present disclosure is not limited to the above embodiments and may be modified as required. For example, in the above embodiments, the calculating unit13calculates the actual machining threshold even in a case of an idling feed operation, but the invention is not so limited. For example, the calculating unit13does not have to calculate the actual machining threshold. This may reduce the processing load of the detection device1.

In the above embodiments, the stop control unit18stops the removal machining device100, but the invention is not so limited. The stop control unit18may be omitted from the detection device1. In this case, the detecting unit16only executes signal output by the output unit17.

EXPLANATION OF REFERENCE NUMERALS