JP6545555B2 - Device and method for estimating remaining life of drill - Google Patents

Description

  The present invention relates to an apparatus and method for estimating the remaining life of a drill while drilling in a machine tool that drills a workpiece while rotating a drill attached to a spindle.

In the process of rotating the drill and making a hole in the work, the damage to the drill causes a processing failure such that the work can not be processed to the desired diameter and depth. In addition, even in situations where the workpiece can not be removed due to drill damage, the feed axis will continue to operate and the drill and workpiece will be in the same situation as a collision, damaging not only the tool or workpiece but also the machine. Therefore, the load of the spindle motor considered to be most representative of the drilling condition is displayed on the monitor of the NC device of the machine tool, the operator judges the quality of the cutting condition, and the machine monitors the load of the spindle motor. It is common practice to stop the feed shaft.
In Patent Document 1, the load current of a spindle motor at the time of drilling by a drill is measured, the variance of the peak value and the bottom value change amount per one rotation of the drill is calculated, and a predetermined threshold value is made three times continuously. A technique is disclosed to stop the processing immediately when an exceeded peak appears. In patent document 2, the temperature rise amount of the drill blade part by processing is calculated from the temperature of the drill blade part during processing or immediately after processing, the reference value for life prediction is compared, and the remaining life of a drill is predicted. Techniques are shown.

JP, 2011-20221, A JP 6-709 A

In Patent Document 1, it is necessary to measure a high frequency component of 10 kHz or more of a load current of a spindle motor with a high frequency current sensor to accurately detect the maximum value and the minimum value. In order to measure such high-frequency signals, not only sensors capable of high sampling, but also a memory for storing a large amount of measured data and a CPU with high-speed computational processing power are required. It costs money.
In patent document 2, the temperature measurement of the drill blade part is performed before and after processing, and the processing time becomes long because of this measurement time. Further, in the drilling process, a high pressure through coolant is often used, and in some cases, the coolant is filled in the form of mist in the processing chamber, and a non-contact temperature measurement can not be performed.

  Then, this invention aims at providing the apparatus and method of estimating the remaining life of a drill in low cost and a short time using the flow volume of through coolant generally used by drilling.

In order to achieve the above object, the invention according to claim 1 is an apparatus for estimating the remaining life of the drill during the drilling, in a machine tool which performs a plurality of drillings by the drill while discharging the through coolant. There,
Flow rate detection means for detecting the flow rate of the through coolant to the drill;
A processing condition determination unit that determines whether the drilling is the same drill and processing conditions;
A storage unit that records the flow rate of the through coolant detected by the flow rate detection unit for each processing hole when the drilling condition is determined by the processing condition determination unit as the same drill and processing condition;
From the flow rate of the through coolant for each of the machined holes recorded in the storage means, using the approximate expression representing the time change of the flow rate of the through coolant in each of the machined holes, the through in the machining time of each machined hole Flow rate estimation means for respectively calculating the minimum value of the coolant flow rate and estimating the relationship between each of the minimum value and the number of holes;
Wherein the relationship of each of said minimum value estimated by the flow rate estimation means and said number of holes, deriving a limit value of the number of holes corresponding to the lower limit of the flow rate of said through coolant previously set in the storage means, the limit value And a remaining life calculating means for calculating the number of holes which can be processed later as the remaining life as the remaining life.
The invention according to claim 2 is characterized in that, in the configuration according to claim 1 , a display means for displaying the limit value for the life and the number of holes for the remaining life is provided.
The invention according to claim 3 is the configuration according to claim 2 , wherein the display means includes the flow rate of the through coolant detected by the flow rate detection means, the flow rate estimated by the flow rate estimation means, and the number of holes. And the lower limit value of the flow rate of the through coolant.
In order to achieve the above object, the invention according to claim 4 is a method for estimating the remaining life of the drill during the drilling, in a machine tool which performs a plurality of drillings by the drill while discharging the through coolant. There,
A flow rate detection step of detecting a flow rate of the through coolant to the drill;
A processing condition determination step of determining whether or not the drilling is the same drill and processing condition;
A recording step of recording the detected flow rate of the through coolant in the storage means for each drilled hole when it is determined that the drilling is the same drill and machining condition;
From the flow rate of the through coolant for each of the machined holes recorded in the storage means, using the approximate expression representing the time change of the flow rate of the through coolant in each of the machined holes, the through in the machining time of each machined hole A flow rate estimation step of calculating the minimum value of the coolant flow rate and estimating the relationship between each of the minimum value and the number of holes;
From the relationship between each estimated minimum value and the number of holes, the limit value of the number of holes corresponding to the lower limit value of the flow rate of the through coolant preset in the storage means is derived, and the limit value is taken as the life thereafter. And a remaining life calculating step of calculating the number of holes that can be machined as the remaining life.

  According to the present invention, the remaining life of the drill can be estimated from the flow rate of the through coolant. Since the flow rate of the through coolant is not a phenomenon that changes relatively rapidly, it is possible to estimate the remaining life of the drill at low cost without the need for high-speed sampling. In addition, the flow rate of through coolant can be measured during processing, and the remaining life can be estimated in a short time. Furthermore, in the case of drilling holes in difficult-to-cut materials where welding of tools is severe, the flow rate is reduced by adhering to the through coolant discharge port as the number of holes increases. In this case, it is possible to prevent the processing failure by judging the remaining life of the drill and replacing the tool before the processing failure occurs because the through coolant does not reach.

It is a block block diagram of a machine tool. It is an explanatory view showing change of pressure, flow volume, and spindle load of through coolant in actual hole processing (processing condition 1). It is an explanatory view showing change of pressure, flow volume, and spindle load of through coolant in actual hole processing (processing condition 2). It is explanatory drawing of the estimation method of the drill remaining life which used the flow volume of through coolant. It is explanatory drawing of the calculation method of the through coolant minimum flow rate in one hole process. It is a flowchart of the estimation method of drill remaining life. It is explanatory drawing of the example program of a drilling cycle. It is explanatory drawing of a drill monitor screen.

Hereinafter, embodiments of the present invention will be described based on the drawings.
FIG. 1 is a block diagram showing an example of a machine tool. The spindle housing 1 of the machine tool is provided with a spindle 6 rotatable by the spindle motor 2, and a drill 3 is attached to the tip of the spindle 6. The work 4 is fixed on the table 5, and by moving the table 5, the drill 3 and the work 4 are relatively moved to process the work 4.
In general drilling, a coolant is discharged from a hole drilled in the drill 3 and a through coolant is used to prevent machining defects by forcibly discharging chips from the hole. In particular, in the case where the material to be cut is a hard-to-cut material, a high pressure type through coolant unit capable of more reliably cutting the chips and discharging them from the holes is used in order to prevent processing problems due to biting of the chips. Here, a high pressure through coolant unit 7 is provided, and the high pressure through coolant unit 7 is connected to the main shaft 6 halfway through a flow rate sensor 8 and a rotary joint. The main shaft 6 and the drill 3 are provided with holes through which the through coolant flows, and high-pressure coolant is discharged from the discharge port at the tip of the drill 3.

An NC apparatus 11 controls the machine tool. The NC apparatus 11 operates the machine with the stored NC program 12 to process the work 4 and functions as a remaining life estimation apparatus of the drill of the present invention. Also have.
In the NC apparatus 11, the NC program 12 is subjected to execution processing by the program interpretation unit 13 to interpret a machine control command, and target position command and feed to the feed axis control unit 15 controlling the feed axis of the spindle 6 and the table 5. While passing the speed command to the function generating unit 14, it outputs a rotation speed command to the spindle control unit 16 that controls the spindle 6.
Reference numeral 17 denotes a flow rate detection unit as a flow rate detection unit, and a detection signal from the flow rate sensor 8 is input to the flow rate detection unit 17 and converted into an instantaneous flow rate.
Reference numeral 18 denotes a processing condition determination unit as processing condition determination means. This processing condition determination unit 18 determines whether or not a drill cycle instruction for a plurality of holes is described in the NC program 12 obtained from the function generation unit 14 When there is a drill cycle command for a plurality of holes, a command is issued to the storage unit 19 as storage means to record the flow rate from the flow rate detection unit 17 and each machined hole in the drill cycle at the time of drilling.

Reference numeral 20 denotes a flow rate estimating unit as a flow rate estimating unit, and the flow rate estimating unit 20 estimates the relationship between the flow rate of the through coolant and the number of holes in the drilling cycle using the recorded flow rate of each drilling hole in the drilling cycle Do.
Reference numeral 21 denotes a remaining life calculating unit as a remaining life calculating unit. In the remaining life calculating unit 21, a lower limit value of a coolant flow rate at which a processing defect set in advance occurs and a flow rate estimated by the flow rate estimating unit 20 From the relationship with the number of holes, the limit value of the number of holes causing a defect (the life of the drill 3) is estimated, and the number of holes that the drill 3 can drill thereafter (remaining life of the drill 3) is calculated. Furthermore, the remaining life calculation unit 21 creates a drill monitor screen that displays the coolant flow rate, the relationship between the estimated number of holes and the flow rate, the lower limit value of the coolant flow rate at which processing problems occur, the drill remaining life, etc. It displays on the display screen 22 for displaying 12 grade | etc.,.

Here, the pressure and flow rate of the through coolant and spindle load generated in actual drilling will be described using FIGS. 2 and 3. FIG. 2 shows a waveform when drills of 3 holes are performed with a high-speed drill (processing condition 1) and FIG. 3 with a cemented carbide drill (processing condition 2). In FIGS. 2 and 3, since the feed amount per one rotation is the same and the spindle rotational speed of the cemented carbide drill is set to three times that of high-speed drill, the machining time is 1/3.
The life of the drill is considered to be correlated with the number of holes opened, and in order to estimate the life, information correlated with the number of holes is required. The pressure of the through coolant does not change even if the number of holes increases, but the spindle load, in the case of a carbide drill, may have a high rotational speed, and as the number of holes increases, the spindle load increases. On the other hand, in the case of a high-speed drill, no change in spindle load is observed.
The flow rate of the through coolant decreases as the number of holes increases regardless of the processing conditions. The reason is considered to be that the work material is welded to the coolant discharge hole of the drill and the discharge is hindered. If the flow rate of the through coolant is not sufficient, even if there is no damage to the cutting edge, the possibility of processing failure is increased, so it can be regarded as a substantial drill life.

  In the graph of FIG. 4, the vertical axis represents the flow rate of the through coolant, and the horizontal axis represents the number of holes in the drilling cycle. The method of determining the remaining drill life of the remaining life calculation unit 21 of FIG. 1 will be described using FIG. 4. First, how to obtain the relationship between the flow rate of through coolant and the number of holes (C in FIG. 4) will be described. Although the through coolant flow rate (A in FIG. 4) decreases as the hole becomes deeper, the value (B in FIG. 4) at which the flow rate is the smallest in one hole machining is adopted. Then, from B in the figure, the relationship between the flow rate and the number of holes (C in FIG. 4) is calculated using, for example, the least squares method. Determine the number of holes (limit value) at which the straight line indicating the relationship between the flow rate of through coolant and the number of holes found and the flow rate lower limit (D in FIG. 4) causing machining defects intersect, and set this limit value as the drill life . In FIG. 4, the drill life is 7 holes, and the remaining life in the case where 3 holes are already drilled is 4 holes.

  Here, FIG. 5 is a graph showing the flow rate of one hole processing. When the flow rate instantaneously decreases due to chipping as shown by E in FIG. 5 or fluctuation of the flow rate by step feeding of the drilling cycle as shown by F in FIG. It is difficult to simply select the selection of (B in FIG. 4) as the minimum value in one hole machining. Therefore, the flow rate at the time of one hole machining is represented by an approximation formula (here, an approximation curve, G in FIG. 5), and the minimum value (B in FIG. 5) of this approximation formula is adopted as the minimum value.

Next, FIG. 6 is a flowchart summarizing the drill residual life estimation method described so far.
First, in S11, it is determined whether it is a drilling cycle (processing condition determination step). Here, a program example of the drilling cycle is shown in FIG. The program is composed of a line beginning with a code indicating drilling cycle such as G81, in which a feed rate and a hole depth are described, and two lines beginning with BHC etc., which indicate a regular hole position in the next line. In this program example, an 8-point hole is drilled on a circle under the same processing conditions. The NC device 11 can recognize from the code indicating the drilling cycle whether drilling is being performed. Moreover, it can be regarded as the same processing conditions during the drilling cycle.
If it is determined in step S11 that the drilling cycle is performed, in the next step S12, the flow rate during drilling of one hole in the drilling cycle is measured (flow rate detection step). This will measure the flow rate of drilling under the same conditions.

Then, in S13, the measurement result is recorded to obtain an approximate curve of the flow rate change during one hole processing as shown in G of FIG. 5, and the minimum value is recorded in the storage unit 19 (recording step).
Next, in S14, when the result recorded in S13 is 2 points or more, the relationship between the flow rate and the number of holes as shown in C of FIG. 4 using the method of the least squares method from the data of the flow rate and the number of holes. Calculate an approximate straight line indicating the (flow rate estimation step).
Next, in S15, the life of the drill is calculated from the point of intersection of the approximate straight line obtained in S14 and the lower limit value of the flow rate set in advance, and the number of holes that can be machined thereafter is the remaining life for the calculated life. Calculated as (remaining life calculation step).
Then, at S16, the drill remaining life is displayed on the display screen 22. The above-described S11 to S16 are repeated until it is determined in S17 that the drilling cycle is completed.

  An example of the drill monitor screen displayed on the display screen 22 is shown in FIG. Here, in addition to the drill life "7 holes" and the remaining (remaining life) "4 holes", the flow rate for each drilled hole in the drilling cycle, the approximate straight line of the relationship between the flow rate and the number of holes, and the flow rate lower limit are displayed graphically It is done.

  As described above, according to the apparatus and method for estimating remaining drill life of the above embodiment, it is possible to estimate the remaining life of the drill 3 from the flow rate of the through coolant. Since the flow rate of the through coolant is not a phenomenon that changes relatively rapidly, it is possible to estimate the remaining life of the drill 3 at low cost without the need for high-speed sampling. In addition, the flow rate of through coolant can be measured during processing, and the remaining life can be estimated in a short time. Furthermore, in the case of drilling holes in difficult-to-cut materials where welding of tools is severe, the flow rate is reduced by adhering to the through coolant discharge port as the number of holes increases. In this case, it is possible to prevent the processing failure by judging the remaining life of the drill 3 and replacing the tool before the processing failure occurs because the through coolant does not reach.

In addition, the drill remaining life estimation apparatus and method which concern on this invention are not limited at all to the aspect of the said embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably as needed. For example, instead of judging whether it is the same machining condition by the same drill or not with the tool number and the drilling cycle, the operator judges that the machining condition is the same and passes through at the timing when the “measurement” button on the screen of FIG. The coolant flow rate may be recorded to indicate the remaining life.
Further, the relationship between the through coolant flow rate and the number of holes for predicting the remaining life of the drill may be approximated not by a straight line but by a curve. Furthermore, not only the flow rate of the through coolant but also the pressure and the spindle load of the through coolant may be displayed together on the drill monitor screen shown in FIG. 8.

  1 · · Spindle housing · 2 · · Spindle motor · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · high pressure through coolant unit, 8 · · · Flow sensor, 11 · · NC Device 12, NC program 13, Program interpretation unit 14, Function generation unit 15, Feed axis control unit 16, Spindle control unit 17, Flow rate detection unit 18, Determination of processing conditions The unit 19 storage unit 20 flow rate estimation unit 21 remaining life calculation unit 22 display screen.

Claims (4)

A machine tool for performing a plurality of drillings by a drill while discharging a through coolant, wherein the remaining life of the drilling is estimated during the drilling,
Flow rate detection means for detecting the flow rate of the through coolant to the drill;
A processing condition determination unit that determines whether the drilling is the same drill and processing conditions;
A storage unit that records the flow rate of the through coolant detected by the flow rate detection unit for each processing hole when the drilling condition is determined by the processing condition determination unit as the same drill and processing condition;
From the flow rate of the through coolant for each of the machined holes recorded in the storage means, using the approximate expression representing the time change of the flow rate of the through coolant in each of the machined holes, the through in the machining time of each machined hole Flow rate estimation means for respectively calculating the minimum value of the coolant flow rate and estimating the relationship between each of the minimum value and the number of holes;
Wherein the relationship of each of said minimum value estimated by the flow rate estimation means and said number of holes, deriving a limit value of the number of holes corresponding to the lower limit of the flow rate of said through coolant previously set in the storage means, the limit value Residual life calculating means for calculating the number of holes which can be processed later as the residual life,
An apparatus for estimating the remaining life of a drill comprising: The apparatus for estimating the remaining life of a drill according to claim 1 , further comprising display means for displaying the limit value for the life and the number of holes for the remaining life. The display means further displays the flow rate of the through coolant detected by the flow rate detecting means, the relationship between the flow rate and the number of holes estimated by the flow rate estimating means, and the lower limit value of the flow rate of the through coolant The remaining life estimating device of the drill according to claim 2 characterized by doing. A method for estimating the remaining life of the drill during the drilling, in a machine tool that performs a plurality of drillings with a drill while discharging the through coolant,
A flow rate detection step of detecting a flow rate of the through coolant to the drill;
A processing condition determination step of determining whether or not the drilling is the same drill and processing condition;
A recording step of recording the detected flow rate of the through coolant in the storage means for each drilled hole when it is determined that the drilling is the same drill and machining condition;
From the flow rate of the through coolant for each of the machined holes recorded in the storage means, using the approximate expression representing the time change of the flow rate of the through coolant in each of the machined holes, the through in the machining time of each machined hole A flow rate estimation step of calculating the minimum value of the coolant flow rate and estimating the relationship between each of the minimum value and the number of holes;
From the relationship between each estimated minimum value and the number of holes, the limit value of the number of holes corresponding to the lower limit value of the flow rate of the through coolant preset in the storage means is derived, and the limit value is taken as the life thereafter. Remaining life calculation step of calculating the number of holes that can be machined as the remaining life;
A method for estimating the remaining life of a drill characterized by performing.

Images