Apparatus for and method of automatically controlling consition of tol cutting edges

The subject of the invention is a method of automatic active control of the state of a cutting tool blade with a specified value of the average reference factor R, "during machining operations, including the measurement of the torque M, and the feed rate F of the tool relative to the workpiece during machining by this tool , and calculating the amount of tool tip wear on this basis.

Automatic control called CNC numerical control is used to control the cutting path of the milling cutter when machining the workpiece with a machine tool. As the workpieces are machined and the milling cutter wears out, when the adaptive control system at least cutter feedrate is not used relative to the workpiece, the CNC control program always gradually increases the cutter torque.

The automatic active control of the state of the machine tool milling cutter is known, for example, from US Patent Nos. US 4,208,718 and US Pat. No. 4,802,095. In the US Patent No. 4,208,718 method of controlling the tool blade condition, the state this is determined as a percentage as the ratio of cutting time as a function of the head power increase to the total time of machining operation.

The method of automatic active control of the milling cutter known from US Patent No. US 4 802 095 consists in measuring the tangential component FT of the lateral force FRES applied to the workpiece, mathematical determination of the radial component FR of this force, and determining on the basis of both components of this degree force cutter blade wear.

U.S. Patent No. 4,544,847 describes a tool for controlling the condition of a tool blade which is equipped with an adaptive control system with the TLMNTR control subprogram (FIG. 13H. From row 64 of column 35 to row 49 of column 38). This subroutine assumes a linear process of blunting the tool, and it is necessary to enter a number of parameters into the main control program, such as the speed of the tool blade feed, the spindle speed, and the depth of the cutting path constant. The feed rate of the tool blade is linearly adjusted.

Using the subroutine of this device, it is possible to determine the dulling time of the tool blade only for simple operations of cutting the workpiece, with the need to enter a large number of input parameters.

An adaptive control system is presented, for example, by the applicant in International Patent Application Publication Number WO 94/14569. The adaptive control system is used at least to control the feed rate of the milling cutter in response to a change in the machine tool shaft torque according to the relationship: M = AF^s pY where M is the measured torque of the machine tool driving the cutter, F is the instantaneous cutter feed speed, p is the cross-section of the workpiece at a given moment, and A, y and y are factors depending on the milling cutter and the material of the workpiece.

The object of the invention is to develop such a method of automatic active control of the state of the cutting edge of the cutting tool that will allow effective control of the state of the tool for any complex machining operation only on the basis of a small number of input parameters, and thus eliminate the drawbacks of previously known similar methods.

The object of the invention was realized in a method of automatic active control of the cutting tool blade condition, which is characterized in that the signal corresponding to the measured torque M₀₎, and the signal of the corresponding variable instantaneous feed speed of the tool Λα, as well as the signal corresponding to the previously determined coefficients Aq, which depends on the material and the workpiece material processed, is fed to the first processor, which calculates the coefficients r₀₎ temporary wear of the tool blade according to the empirical relationship: M_in = A ^ Fj) r_(]) \ Signal corresponding to the determined values ​​of these coefficients r₀₎ is fed to the second window processor^andheavy wed^andn^ret al^sLaterny of the Middle Ages^ęp^atAI^ec^aboutivzrtn^sziśrz^ssnow mountains^kazrżiż R, with ^^ is running! corresponding co-worker^dic:^pirdikocⁿon the rise of Rⁿⁿepłowzdzani^from to mobile^srra^Lnna,^rd^fromequalizer of the signatory signature ^Frommobrżb^rhe^aboutm^and- this thing! - ^ excuse it ^aboutpy^gizrómżłsⁿ I am at the monastery.

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In order to better understand the method of automatic active control of the cutting edge of the cutting tool, the machine control system in which the method according to the invention can be implemented will be described first.

The machine control system shown in Fig. 1 is equipped with an AMSl system for automatic control of the state of the tool blade according to the invention, which makes it possible to determine the instantaneous state of the blade of the milling cutter 2, rotationally driven by the machine tool 3. The machine tool 3 is controlled by means of a CNC control unit connected to it 4 (i.e. the control computer), and adaptive control system (ACS) 5, which aims to modify the control using the CNC control unit 4. The CNC control unit 4 and the adaptive control system 5 allow control of at least the feed rate of the milling cutter in response to a change in the torque of the machine tool 3, which is measured in the tracking system 7, connected via its output to the input of the adaptive control system 5. The CNC control unit 4 is connected via its output to the input of the adaptive control system 5, by means of which connection the F signal of the instantaneous feedrate of cutter 2 is transmitted, and preferably by means of the connection through which the signal S of the rotational speed of the machine tool spindle 3 is transmitted. The adaptive control system 5 is in turn connected at the output to the input of the machine tool 3 by means of connections via which the signals F 'and S' are transmitted to modify the feed rate of the milling cutter and the rotational speed of the machine 1.

The AMS 1 system is connected at its input with the output of adaptive control system 5, tracking system 7 and interface 9, and at the output with monitor 8.

During the tests, it was found that the condition of the milling cutter removing the material allowance during a given machining depends on a large number of factors, such as the type of machine, type of workpiece, cutting path, milling feed rate, rotational speed of the mandrel, and the type of cooling lubricant, which can be determined by the empirical relationship: M = A₀F^IX R^p, where M is the measured torque of the machine tool. F is the instantaneous cutter feed rate relative to the workpiece, and A ^, a and β are factors depending on the type of cutter material and workpiece material. The coefficients A <,, a and β are determined by the ratio R ^ / Ro, where R_(and) is the factor for the average milling wear for the i-workpiece, and R ^ is the average reference factor for the new milling cutter in the same machining operation, which is equal to the upper critical value of ε_ι;. corresponding to the dullness of the cutter.

During machining, the torque M is the torque of the machine tool driving the cutter, and in turning operations the torque of the machine tool driving the workpiece. For the instant determination of the cutting edge condition, the relationship M = A₀Fa R^p, can be converted to another form: M = A ^ with R^pwhere F_from is the feed rate of one blade of a multi-edge cutter.

The temporary marking of the cutting tool's cutting edge is displayed on monitor 8 as its percentage of wear, which allows the machine tool operator to decide whether to change the cutter. The tool blade status marking can also be displayed on monitor 8 in the form of the word "working" or "non-working" when the cutter is worn or cracked. In the latter case, the AMS1 system sends to the CNC control unit 4 the TC interrupt signal, which stops the machine 3.

The AMS1 system is connected to interface 9, which is used for coding the type of MC cutter, type of workpiece material WM and type of machining MO.

The AMS1 system shown in Fig. 2 is equipped with a memory 10 that stores three coefficients A ^, a, β for various combinations of cutter material and workpiece material, selected on the basis of 9 parameters entered in the interface: type of Mc cutter, type of workpiece material WM, and MO machining type. The average reference factors Ro of the tool tip wear for various machining operations are also stored in memory.

Typical coefficients Ao, a, β for four-edge milling cutters are as follows: Ao = 148, a = 0.75, β = 0.83 for mild steel milling cutters, A_about = 116, a = 0.68, β = 0.75 for cast iron milling cutters, and A ,, = 79, a = 0.72, β = 0.8 for aluminum milling cutters.

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Coefficients A_about, a, β for various combinations of cutter material and workpiece material are determined experimentally with a large number of machining operations.

The new reference factor R * of tool nose wear for a new machining operation is determined in a test operation with a new milling cutter by means of a calibration unit 11 connected to memory 10, using the measured torque M_ffl and cutter feed speed F, and coefficients A ^, a, β for various combinations of cutter material and workpiece material selected by the machine tool operator

The AMS 1 is equipped with the first processor 13, connected at the input with the adaptive control system 5, with the torque tracking system 7 and with memory. 10. The first processor 13 is used to calculate the instantaneous r factors, wear of the tool blade, according to the empirical relationship: Mo = AoFj r_Q)^pwhere F_ZXj) is the instantaneous feed speed of cutter 2 at different positions along the cutting path during machining of the ith workpiece. If the instantaneous feed rate F ^,) of the cutter blade 2 is not known, it is calculated from the following relationship: ί '_ζω = F '_ABOUTj / (S '(j) xz), where F' is the feed rate of milling cutter 2 relative to the workpiece, S 'is the instantaneous rotational speed of the shank, and az is the number of cutting edges of the milling cutter 2.

The first processor 13 is connected at the output to the input of the second processor 14, to calculate the average factor R₍₁₎ wear of cutter blade 2 for the next ith workpiece, according to the relationship:

R (.) = -Συ.) N

The second processor 14 is connected with its output to the input of the comparator 15, also connected to the memory 10. The comparator 15 is used to compare the average factor R_(and)tool tip wear and average reference factor Ro. The result of this comparison is displayed on the monitor 8 in the form of information on the status of the milling cutter, and is optionally sent to the CNC unit 4 as a TC interrupt signal.

The method of automatic active control of the cutting tool blade condition, implemented using the AMS1 system, is shown in Fig. 3. After determining the unknown value of the average reference factor Ro for a new milling cutter in a new machining operation, for subsequent workpieces, a signal corresponding to the measured torque M "and a signal of the corresponding instantaneous feed rate F are fed to the first processor 13₀₎ tools, as well as the signal corresponding to the previously determined coefficients Ao a, β depending on the type of tool material and workpiece material, which calculates the coefficients r, instantaneous wear of the tool blade according to the empirical relationship: M₀) = AoF₀"₀)^!at a sampling rate of 10 per second. Then, the signal corresponding to the determined values ​​of these coefficients r is fed to the second processor 14 determining the unweighted average consumption coefficient R ,. The signal corresponding to the value of this coefficient R ;, and the signal corresponding to the reference coefficient R0 are fed to comparator 15, which compares both these signals after each processed i-th object, and the result of this comparison, e.g. in the form of the RR ratio, is displayed on the monitor 8.

The milling cutter is replaced when the ratio of R ^ R coefficients exceeds the upper critical value ε "or is smaller than the lower critical value 81, which means the cutter breaks. For simplicity, the critical values ​​of ε 'and ε 1 are invariant with respect to the type of machining operations and are 1.6 and 0.9, respectively. Choosing a lower critical value of 0.9 instead of 1 means that the milling cutter actually failed, and not, for example, that the workpiece has broken.

The ratio of R / R wear of the cutter blade is in the range of 0.9 to 1.6, while the percentage of wear of the cutter blade is:

16-R (,) R0 0.6 x100%.

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The ratio of R coefficients expressed as a percentage₍₁/ R0 equal to 100% means for the machine tool operator that the cutter is new, and 0% means that the cutter is worn and needs to be replaced.

As shown in Fig. 4, as the cutter blade wears for the next ith workpiece, the R / Ro ratio increases asymptotically to an upper threshold of 1.6, which means that the cutter is blunt and needs to be replaced. The tested milling cutter was worn after processing about 45 items.

If the ratio of R, / Ro coefficients drops below the lower threshold value of 0.6, then it means that the milling cutter has worn out or has cracked, as a result of which the AMSl system is sent to the CNC control unit 4 the TC interrupt signal, automatically stopping machine tool work.

The AMS1 system by which the method according to the invention is carried out can be installed as an OEM version (i.e. together with a machine tool, and not as a separate system), and the CNC unit - modified accordingly.

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FIG.2

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FIG.3

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<img file="PL182940B1_D0003.tif" />

FIG.4

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FIG. 1

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