JP6314885B2 - Damage prevention system, grinding wheel - Google Patents

Description

  This invention uses a grindstone having a plurality of sintered abrasive layer chips (hereinafter referred to as a multi-layer grindstone) to detect abnormalities in processing due to breakage or wear of the grindstone when grinding a material having a higher strength than the abrasive layer chips In addition, the present invention relates to a breakage prevention system capable of stopping or correcting machining.

  In grinding, a workpiece is processed using a grindstone. As a measure for preventing large-scale breakage of a workpiece being machined, there is a system that measures a cutting load of a motor current of a spindle and detects a tool abnormality when a threshold value is exceeded (for example, see Patent Document 1).

  Further, since the grindstone wears during processing, there is a grindstone wear correction device that compares the grindstone surface immediately after dressing with the grindstone wear amount for each workpiece processing and performs position correction (see, for example, Patent Document 2).

JP 2003-326438 A Japanese Patent Application Laid-Open No. 51-140294

  However, the multi-layered grindstone used at the time of grinding often breaks all the abrasive layer chips instantaneously when a processing abnormality occurs. At this time, since the strength of the abrasive layer chip is lower than that of the material, no significant change in the cutting load is observed even if it breaks, and the cutting load decreases to the initial value because there is no contact with the material, In the tool abnormality judgment based on the upper limit threshold value, there is a problem that the machining abnormality due to the reduction of the cutting load is not detected. Therefore, the timing at which the machining abnormality is detected is when the base of the multilayer grindstone comes into contact with the workpiece, and there is a problem that the product is damaged.

  In continuous machining for a long time using a multi-layered grinding wheel, the amount of grinding wheel wear increases in a quadratic curve as the cumulative machining volume increases. Is required. In the case of long-time processing, there is a problem that it is difficult to accurately measure the wear amount of the grindstone due to uneven wear or the like.

  This invention is for solving the above-mentioned problems, and as an item for judging a machining abnormality, an increase amount per unit time of a machining reaction force value and a spindle current value during machining and a predicted machining load due to each machining process are set. By doing so, it is aimed to enable detection of processing abnormality before product breakage.

The breakage prevention system according to the present invention includes a current measuring device for measuring a current value flowing in a motor having a grindstone at a tip and rotating a tool for cutting a workpiece about an axis, and the workpiece during cutting. A machining reaction force measuring device for measuring a machining reaction force applied to the cutting force, a cutting simulation for inputting a cutting parameter and calculating a cutting amount per unit time during cutting, a current value output by the current measuring device, a processing reaction force of the processing reaction force measuring device outputs, enter the result of the cutting simulation the cutting simulation output, a damage prevention system comprising a signal processor for detecting the presence or absence of abnormal working of the cutting The grindstone includes an abrasive layer chip for processing a workpiece, and a base metal for fixing the abrasive layer chip, and on the inner surface of the abrasive layer chip at the bottom surface of the base metal. The abrasive grain layer chip than the particle size is small abrasive, or the abrasive grain layer chip than abrasive density is large abrasive grains are attached.

  According to the breakage prevention system according to the present invention, it is possible to detect an abnormality in grinding before the product that is the workpiece is broken, and the breakage of the product can be prevented.

It is a block diagram of the damage prevention system which concerns on Embodiment 1 of this invention. It is a flowchart figure explaining operation | movement of the damage prevention system which concerns on Embodiment 1 of this invention. It is a figure explaining the outline | summary of the cutting simulation which concerns on Embodiment 1 of this invention. (A) It is a figure explaining the fluctuation | variation of the monitoring value at the time of the process abnormality of the damage prevention system which concerns on Embodiment 1 of this invention. (B) It is the figure which showed the time-dependent fluctuation | variation of the processing load by cutting simulation. It is a figure explaining the outline | summary of the grindstone for damage prevention which concerns on Embodiment 2 of this invention. The damage prevention system according to Embodiment 3 of the present invention It is a flowchart figure explaining the grindstone wear automatic correction | amendment of the breakage prevention system which concerns on Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram of a damage prevention system according to the first embodiment. FIG. 2 is a flowchart during system operation. FIG. 4 is a diagram illustrating changes in the spindle motor and the machining reaction force value in the past abnormality.

In FIG. 1, after the processing tool 4 is attached to a holder 5, it is attached to a spindle 6 that performs cutting. The main shaft 6 is driven and rotated by a main shaft motor 7. A processing reaction force detection table 2 is installed on the processing machine table 1, and a workpiece 3 is installed on the processing reaction force table 2. The processing tool 4 processes the workpiece 3 while rotating.
The breakage prevention system 8 includes a current measuring device 9 that measures a current value flowing through the spindle motor 7, a machining reaction force measuring device 10 that measures a load applied to a product during machining, a current measuring device 9 and a machining reaction force measuring device. Machining is stopped by comparing the output value from 10 with the means of numerical value increase per set unit time or NC (numerically controlled) program that can distinguish between machining and no load (hereinafter referred to as cutting simulation) 12 The signal processing apparatus 11 outputs a signal.
Furthermore, an NC device 13 that receives the machining stop signal and stops the machining tool 4 and the machining table 1 is provided.

  Next, the operation of the damage prevention system will be described using the flowchart of FIG.

  First, a threshold for determining whether or not processing abnormality has occurred is set in the damage prevention system before starting processing. The threshold values are: (1) Upper limit of spindle current value and machining reaction force value (hereinafter referred to as monitoring value) during machining, (2) Increase in monitoring value per unit time, (3) Initial monitoring value during idle operation Value. For the upper limit of (1) and (2) the amount of increase per unit time, an experimental value obtained by a prior machining experiment or a past actual value at the time of machining abnormality is set. Moreover, (3) About the monitoring initial value, the value which carried out the idle driving | running | working before processing and was output is used.

After starting the processing, the values measured by the current measuring device 9 and the processing reaction force measuring device 10 are recorded on the system (S101), and at the same time, compared with the upper limit value of the monitoring value set as the threshold value (S102). .
If the real-time monitoring value (measurement value) is less than the threshold value (upper limit value), the processing is continued (S103).
On the other hand, if the processing is continued and the real-time monitoring value (measurement value) is equal to or greater than the threshold value (upper limit value), it is determined that the processing is abnormal, and the signal processing device 11 outputs a processing stop signal to the NC device 13. The NC device 13 stops the processing operation of the processing tool 4 and the processing machine table 1 (S104).

Further, the amount of increase in the monitoring value per unit time is calculated from the real-time monitoring value on the damage prevention system, and compared with the threshold value set before processing (S105).
If the calculated amount of increase (calculated value) is less than a predetermined threshold, processing is continued (S106).
On the other hand, when the calculated amount of increase (calculated value) is equal to or greater than the threshold value, it is determined that the machining is abnormal, and a machining stop signal is output from the signal processing device 11 to the NC device 13. The processing operation of the processing machine table 1 is stopped (S104).

  Further, the cutting simulation 12 is started simultaneously with the start of machining (S107). The damage prevention system compares the initial value at the start of machining, the monitoring value in real time, and the machining load by the cutting simulation 12 (S108).

FIG. 3 is a diagram illustrating an outline of the cutting simulation 12 according to the first embodiment.
As shown in FIG. 3, the cutting simulation 12 inputs a model to be machined and a machining program that has been created (S201), so that the machining depth can be calculated from the cutting depth, radius cutting depth, and feed rate set in the machining program. The amount of cutting per unit time is calculated and output (S202, S203).

The behavior output from the cutting simulation 12 is compared with the behavior of the monitoring value in real time (S108).
FIG. 4 is a diagram for explaining the variation of the monitoring value when the breakage prevention system according to the first embodiment is abnormal in machining.
In FIG. 4, the upper graph (a) is an example showing real-time monitoring values of the machining reaction force (machining load) output from the current measuring device 9 and the machining reaction force measuring device 10, and the lower graph ( b) is an example of the result of simulating the variation of the machining load with respect to the machining time by the cutting simulation 12.

As shown in the example of the real-time monitoring value shown in FIG. 4A, the monitoring values obtained by the current measuring device 9 and the processing reaction force measuring device 10 show a substantially constant value after increasing immediately after the start of processing.
After that, when processing is continued and the abrasive layer chip is destroyed, the strength of the abrasive layer chip is lower than that of the material. Since the contact is lost, the cutting load is reduced to the initial value. After that, after a period of no contact with the material for a while, the base of the multilayer grindstone comes into contact with the workpiece, and the monitoring value increases rapidly.

In the breakage prevention system according to the present embodiment, the signal processing device 11 includes a real-time monitoring value by the measuring instrument in FIG. 4A and a variation in machining load with respect to the machining time by the cutting simulation 12 in FIG. And detect the difference. Then, when the difference becomes larger than a predetermined threshold value, that is, when the monitoring value becomes smaller than the cutting simulation value for a predetermined time, it is determined that a mismatch with the cutting simulation has occurred, and it is determined as a machining abnormality. Then, a signal to stop processing is output from the signal processing device 11 to the NC device 13, and the NC device 13 stops the processing operation of the processing tool 4 and the processing machine table 1 (S104).
In the example of FIG. 4 (a), a difference from the simulation is detected, it is determined that the difference is a machining abnormality at the timing indicated by an arrow A for a predetermined time, and a machining stop signal is sent from the signal processing unit 11 to the NC unit 13. The NC device 13 stops the machining operation of the machining tool 4 and the machining machine table 1 (S104).

  In addition, it is possible to stop the machining operation at the moment when the difference becomes larger than a predetermined threshold value, that is, the monitoring value becomes smaller than the value of the cutting simulation. In some cases. For this reason, in the present embodiment, when a time during which the monitoring value is smaller than the value of the cutting simulation continues for a predetermined time, it is determined that a mismatch with the cutting simulation has occurred and it is determined that the machining is abnormal.

  If it is determined that the values match by comparison with the machining load in the simulation (S108), the machining is continued assuming that there is no machining abnormality (S109).

As described above, the breakage prevention system 8 according to the present embodiment includes a current measurement device 9 that measures the value of the current flowing through the spindle motor 7, a machining reaction force measurement device 10 that measures the load applied to the product during machining, A cutting simulation 12 for calculating and outputting a cutting amount per unit time during machining from a shaft cutting amount, a radius cutting amount, and a feed rate set in the machining program by inputting the model to be created and the created machining program; The signal processing device 11 includes a signal processing device 11 that inputs signals from the current measuring device 9, the machining reaction force measuring device 10, and the cutting simulation 12 to determine whether there is a machining abnormality.
The signal processing device 11 compares the real-time monitoring values, that is, the spindle current value at the time of machining output from the current measuring device 9 and the machining reaction force value output from the machining reaction force measuring device 10 with predetermined upper limit threshold values. If it is less than the upper threshold, the machining is continued, and if the upper threshold is exceeded, it is determined that a machining abnormality has occurred, and the machining is stopped.
Further, the signal processing device 11 calculates the real-time monitoring value, that is, the amount of increase per unit time of the spindle current value during machining output from the current measuring device 9 and the machining reaction force value output from the machining reaction force measuring device 10. If any of the calculated amounts of increase is less than a predetermined threshold value, the machining is continued, and if it exceeds the threshold value, it is determined that a machining abnormality has occurred, and the machining is stopped.
Further, the signal processing device 11 outputs a machining load output by the cutting simulation 12 and a real-time monitoring value, that is, a spindle current value during machining output by the current measuring device 9 and a machining reaction force output by the machining reaction force measuring device 10. The value is compared from the machining start time, and a difference from the simulation is detected. Specifically, it is detected whether the monitoring value is smaller than the value of the cutting simulation. Then, the signal processing device 11 determines that a machining abnormality has occurred when a time when the monitoring value is smaller than the value of the cutting simulation continues for a predetermined time, and that a mismatch with the cutting simulation has occurred, the machining is performed. To stop.

  As described above, the signal processing device 11 of the breakage prevention system according to the present embodiment processes the above three processes in parallel, and if any of them is out of regulation, it is determined that a processing abnormality has occurred and the processing is performed. Since the operation is stopped, it is possible to more accurately determine in real time whether or not there is a processing abnormality in the apparatus and prevent the workpiece from being damaged.

Embodiment 2. FIG.
In the breakage prevention system according to the first embodiment, a system that can detect the prevention of machining abnormality of the apparatus is constructed, but it is difficult to predict depending on the shape of the material of the workpiece and the machining tool to be used. It can be. Therefore, in this embodiment, a grindstone that can more reliably prevent damage will be described.

FIG. 5 is a diagram for explaining the outline of the breakage preventing grindstone according to the present embodiment.
In FIG. 5, the breakage preventing grindstone 40 includes an abrasive layer chip 401 for processing a workpiece, a base metal 402 for fixing the abrasive layer chip, and an abrasive formed on the bottom surface of the base metal 402. It is composed of grains 403 and a bonding layer 404.

The abrasive grain layer 410 composed of the abrasive grains 403 and the bonding layer 404 is not used for processing a workpiece, but abnormally increases the monitoring value when the abrasive grain tip breaks or the base metal and the workpiece contact each other. Is for the purpose of detecting.
The abrasive grains 403 have a smaller particle diameter than the abrasive grain layer chip 401 or a larger abrasive grain density in the abrasive grain layer 410 to reduce the average abrasive grain spacing and increase the processing stress per abrasive grain. Without increasing the total machining load, the monitoring value is increased from that during normal machining.

Thus, in the breakage prevention system according to Embodiment 2, the breakage prevention grindstone 40 is used as the grindstone.
The breakage preventing grindstone 40 includes an abrasive layer chip 401 for processing a workpiece, a base metal 402 for fixing the abrasive layer chip, and abrasive grains 403 formed on the bottom surface of the base metal 402. The abrasive layer 410 composed of the abrasive grains 403 and the bonding layer 404 is provided on the bottom surface portion of the base metal 402 inside the abrasive layer chip 401, which is composed of the binding layer 404 and provided at the end of the base metal 402.
The abrasive grain 403 has a smaller particle diameter than the abrasive grain layer chip 401 or increases the abrasive grain density in the abrasive grain layer 410 to reduce the average abrasive grain interval. Thereby, only the total processing load can be increased without increasing the processing stress per one abrasive grain.

  By using this breakage prevention grindstone 40, when it is difficult to predict the breakage of the workpiece due to the shape of the workpiece material or the processing tool used, the abrasive grains instantly when a machining abnormality occurs. Even when all of the layer chips 401 are damaged, the abrasive grain layer 410 composed of the abrasive grains 403 and the bonding layer 404 formed on the bottom surface portion of the base metal 402 hits the workpiece, and the processing is continued for a while. Therefore, it is possible to prevent the product that is the workpiece from being damaged as in the prior art.

Embodiment 3 FIG.
In the first and second embodiments, the breakage prevention system for preventing the product as a workpiece from being damaged when all of the abrasive layer chips 401 are damaged has been described. In the third embodiment, the tool is used. A countermeasure for product defects due to wear will be described.

  FIG. 6 is a diagram illustrating signal output timing when the tool is worn in the breakage prevention system according to the third embodiment. FIG. 7 is a flowchart for explaining automatic grinding wheel wear correction of the breakage prevention system according to the third embodiment.

  In the following, the operation of the breakage prevention system will be described by taking as an example the processing when the tool advances in the vertical direction as described in FIGS. 6 and 7 in the configuration of the breakage prevention system of FIG.

  First, as shown in FIG. 6A, the machining tool 4 starts machining the workpiece 3 from a predetermined position separated by a distance X from the machining surface in accordance with an instruction from the NC device 13. At this time, a real-time monitoring value is measured, and the amount of increase from the initial value is calculated (S301 in FIG. 7). Then, a signal is output from the signal processing device 11 to the NC device 13 as the moment when the machining tool 4 and the workpiece 3 come into contact with each other when the rising amount reaches a certain value (S302).

The NC device 13 records the cutting amount from the surface of the workpiece 3 at the time when the signal from the signal processing device 11 is received. When there is no tool wear, the depth of cut at the time of receiving the signal is zero, but when wear has occurred, the work tool 4 is processed at the start of machining as shown in FIG. 6B. 3 away from 3 by a distance X ′.
Therefore, when the processing tool 4 and the workpiece 3 come into contact with each other, the cutting has already been performed by (X′−X). The amount of cut (X′−X) recorded here is the amount that could not be targeted by grinding wheel wear, and is equal to the wear amount of the grinding wheel. In this way, the cutting amount (wear amount) at the time of receiving the signal can be calculated by the NC device (S303).

  Note that the cutting depth can be calculated from the contact timing on the program recorded in the NC device 13 and the machining time and feed speed until the signal is output by the actual contact.

  After the completion of the previous process (S304), before the machining tool 4 cuts into the workpiece 3 in the next process, the tool length and the tool diameter are corrected for the wear amount calculated on the NC processing unit 13. By carrying out and processing, it becomes possible to prevent the occurrence of significant dimensional defects (S305).

  Thus, according to the damage prevention system according to the present embodiment, the wear amount of the grindstone can be accurately calculated, and the tool length and the tool diameter can be corrected with respect to the calculated wear amount. Occurrence of dimensional defects after processing can be suppressed.

1 processing machine table, 2 processing reaction force table, 3 work piece, 4 processing tool, 5 holder, 6 spindle, 7 spindle motor, 8 product defect prevention system, 9 current measuring device, 10 processing reaction force measuring device, 11 signal Processing device, 12 Cutting simulation (means capable of distinguishing between NC program processing and no load), 13 NC device, 40 Grinding stone for preventing damage, 401 Abrasive layer chip, 402 Base metal, 403 Abrasive, 404 Bonded layer 410 Abrasive layer

Claims (2)

A current measuring device for measuring a current value flowing in a motor having a grindstone at a tip and rotating a tool for cutting a workpiece around an axis;
A machining reaction force measuring device for measuring a machining reaction force applied to the workpiece during cutting;
Cutting simulation that inputs cutting parameters and calculates the amount of cutting per unit time during cutting,
The current value output by the current measuring device, the processing reaction force output by the processing reaction force measuring device,
A signal processing device that inputs a result of a cutting simulation output by the cutting simulation and detects the presence or absence of a processing abnormality in the cutting process;
A damage prevention system comprising :
The grindstone includes an abrasive layer chip for processing a workpiece, and a base metal for fixing the abrasive layer chip,
Abrasive grains having a grain size smaller than that of the abrasive grain layer chip or abrasive grains having a grain density larger than that of the abrasive grain layer chip are attached to the inside of the abrasive grain layer chip at the bottom surface of the base metal. Damage prevention system characterized by. A grindstone chip composed of an abrasive layer chip for processing a workpiece and a base metal for fixing the abrasive layer chip,
Abrasive grains having a grain size smaller than that of the abrasive grain layer chip or abrasive grains having a grain density larger than that of the abrasive grain layer chip are attached to the inside of the abrasive grain layer chip at the bottom surface of the base metal. A whetstone characterized by

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