JPS6052901B2 - Cutting abnormality monitoring method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cutting abnormality monitoring method, and in particular, cutting load fluctuations during normal cutting are stored in an internal memory as reference data, and cutting load fluctuations during repeated cutting are compared with stored load fluctuations. The present invention relates to a cutting abnormality monitoring method in which a cutting abnormality is detected when a deviation exceeds an allowable value.

Conventionally, in the above-mentioned cutting abnormality monitoring method, the method of storing reference data over time includes (1) sampling and storing cutting load fluctuations at predetermined time intervals over the entire machining process; (2) Predetermined detection criteria (e.g., predetermined input
A method is used in which the difference or rate of change is memorized at each point in time when the difference or rate of change occurred.

In order to appropriately follow cutting load fluctuations, it is desirable to use method (1), but in this case, the capacity of the internal memory for storing reference data becomes enormous in proportion to the cutting time.

In addition, when method (2) is used, the internal memory capacity can be small, but it is difficult to set detection criteria unless the state of cutting load fluctuations is known, and it is difficult to properly follow cutting load fluctuations. There is a possibility that you will not be able to do so. The main purpose of the present invention is to store reference data based on the idea of combining the advantages of the two methods described above as a method for storing reference data in a first cut abnormality monitoring method in view of the problems of the conventional method. The object of the present invention is to require a small memory capacity for this purpose, to be able to appropriately follow cutting load fluctuations, and to reliably detect cutting abnormalities.

In the present invention, cutting load fluctuations during normal cutting are stored in a temporary memory at system-specific time intervals during a data monitoring period, and the cutting load that should be analyzed to create reference data by analyzing the data stored in the temporary memory. The fluctuation width 1 is determined, and data is read out from the temporary memory for each cutting load fluctuation width Δ1 and stored in the reference data memory as reference data, and the actual cutting load fluctuation is compared with the stored reference data during repeated cutting. , a cutting abnormality monitoring method is provided which determines whether the deviation value has exceeded a tolerance value and detects a cutting abnormality when the deviation value has exceeded a tolerance value. Of course, it is also possible to use a part of the reference data memory as temporary memory. A cutting abnormality monitoring device used in a cutting abnormality monitoring method as an embodiment of the present invention is a first embodiment of the present invention.
As shown in the figure. In FIG. 1, a spindle motor 1, a servo unit 2, an NC device 3, a sampling timer, and a cutting abnormality monitoring device 5 are shown. Cutting abnormality monitoring device 5
includes a first gate circuit 51 and a teaching/monitoring switching device 52.
, temporary memory 53, scan circuit 5, data patterning circuit 55, second gate circuit 56, reference data memory 57
, a comparison circuit 58, a normal operation display circuit 59, and a cutting abnormality display circuit 60 are provided. As data for cutting load fluctuations, the current value of the spindle motor, cutting vibration, etc. can be considered, but in the apparatus shown in FIG. 1, the spindle motor current value is used.

In FIG. 1, a main shaft motor 1 is connected to a servo unit 2, and a current value signal of the main shaft motor 1 is supplied from the servo unit 2 to a gate circuit 51. The gate circuit 51 is also supplied with a monitoring period signal and a sampling time signal from the NC device 3 and the sampling timer 4, respectively. The output of the gate circuit 51 is connected to a teaching/monitoring switching circuit 52.

In the teaching/monitoring switching circuit 52, switching between the teaching mode and the monitoring mode is performed based on a signal supplied from the NC device 3 via the gate circuit 51. In teaching mode. Teach/teach every time a sampling time signal occurs.
The monitoring switching circuit 52 supplies the main shaft motor current value signal and sampling time to the temporary memory 53. In the temporary memory 53, the main shaft motor current value data and the data at the time of sampling are stored in pairs for each sampling time. By the way, N tools are required to process one part.

For this reason, tool exchange commands are inserted into the NC program data for each of the N tools. And N
When the C device 3 receives a tool change command, it instructs the machine to change the tool. When the tool exchange is completed and a tool exchange complete signal is generated from the machine side, the NC device reads the next NC data from the NC tape or memory based on the tool exchange complete signal, and executes NC processing based on the NC data. do. Therefore, in the teaching mode, the teaching/switching circuit 52 generates a current value signal and samples it from the time when the tool change completion signal of the first tool is generated until the tool change command of the second tool is generated according to the instruction from the NC device 3. The time is output to the temporary memory 53, and the current value signal and sampling time are not output to the temporary memory from the time when the second tool change command is generated until the time when the second tool change completion signal is generated. Then, the contents of the temporary memory 53 are cleared by the second tool change completion signal, and the current value signal and sampling time are similarly temporarily set from the time when the second tool change completion signal is generated until the third tool change command is generated. The data is output to the memory 53, and the same process is repeated thereafter. On the other hand, the data stored in the temporary memory 53 is supplied to the scan circuit 54 from the time when the tool change command is generated until the time when the next tool change completion signal is generated.
analyzes the data in the temporary memory 53 during tool exchange, and calculates the maximum value 1max, minimum value 1min, and fluctuation rate of change ((Imax
-1 min)/ΔT1 (where ΔT is the time from the tool change completion time to the time when the next tool change command is generated) is calculated and the standard data creation method is determined. In addition, the standard data creation method is to import data from temporary memory at predetermined intervals longer than the sampling time, to import data from temporary memory at each predetermined cutting current change width, or to create data by mixing the above two methods. It's up to you to incorporate it. The following description will be made assuming that data is taken in every predetermined width of change in cutting current. Now, the analysis result in the scan circuit 54 is supplied to the data patterning circuit 55.

In the data patterning circuit 55, the scan circuit 5
The cutting load fluctuation range ΔI for which reference data should be created is determined based on the fluctuation change range from 4 and the reference data creation method. The second gate circuit 56 is supplied with the data stored in the temporary memory 53 and the cutting load fluctuation width Δ1 set in the data patterning circuit 55. The gate circuit 56 selects the current value signal 11 if the data (current signal value 11) from the temporary memory 53 is greater than or equal to ΔI than the current signal value L-1 previously stored in the reference data memory 57. , this selected current signal value 11 is supplied as reference data to the reference data memory 57 and stored therein. Thereafter, similar processing is performed, and the load fluctuations during all machining are stored together with the time in the reference data memory 57, and the teaching ends. On the other hand, when the teaching/monitoring switching circuit 52 is in the monitoring mode, the main shaft motor current value signal is supplied from the switching circuit 52 to the comparison circuit 58 .

In the comparison circuit 58, the main shaft motor current value in the monitoring mode is compared with the data stored in the reference data memory 57, and if the deviation value between the two data is within the allowable value range, the normal operation display circuit 59 A signal is generated to activate the . Furthermore, when the deviation value between the two data points exceeds the allowable value, a signal is generated to operate the cutting abnormality display circuit 60, thereby detecting the occurrence of a cutting abnormality. FIG. 2 is an explanatory diagram of temporary memory data and reference data when machining is performed using a predetermined tool in milling-based machining. In FIG. 2 1, the current value of the main shaft motor is determined by the sampling time (T
l, t2...Tk...Tn), and the sampling points Pl, P2,...
・Pbi... Data of sampling time and main shaft motor current value at Pn (Tl, ll), (T2, l2
)...(T,,Ik)...(Tn,In) is
Stored as temporary memory data. In FIG. 2, reference data selected for each cutting load fluctuation width ΔI from the sampling points in FIG. 2 is shown. That is,
Sampling points and maximum current points P1'', P2'', . . . Pk', which have changed by a constant value ΔI determined by the size of the fluctuation range within the sampling time stored in the temporary memory
...P. ″, P..ax″ (t1
″, 11″), (T2″, 12″)・・(T, ″, I
k'')... (TT.ax'', 1..Ax''), load fluctuations can be appropriately tracked.According to the present invention, the memory capacity for storing reference data can be small, and load fluctuations can be appropriately tracked. A cutting abnormality monitoring method that can track and reliably detect cutting abnormalities can be provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a cutting abnormality monitoring device used in a cutting abnormality monitoring system as an embodiment of the present invention, and FIG. 2 is a current waveform diagram showing current changes in the main shaft motor in the device shown in FIG. It is.

Claims (1)

[Claims] 1 Cutting load fluctuation width during normal cutting is stored in a temporary memory together with the detection time at system-specific time intervals during the data monitoring period, and the data stored in the temporary memory is analyzed to create reference data. Find ΔI,
Read data from the temporary memory for each cutting load variation width ΔI, store it in a reference data memory, compare the actual cutting load with the stored reference data during repeated cutting,
A cutting abnormality monitoring method characterized by determining whether the deviation value has exceeded a tolerance value, and detecting a cutting abnormality when the deviation value has exceeded a tolerance value.