SU753547A1 - Method for controlling wear of tool cutting edge during cutting - Google Patents

Description

(54) METHOD OF CONTROL OF WEAR OF CUTTING EDGE OF TOOL DURING CUTTING

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The invention relates to metal cutting and can be used in all cases where an electrically driven tool is used.

Optical devices and adaptive systems are known that make it possible to judge the degree of wear of the cutting tool during machining.

The disadvantages of these devices and systems are the complexity and high cost, with the result that a small number of machines, mainly experimental ones, are equipped with means for controlling wear of the relevant edge.

The purpose of the invention is to increase the reliability of control by obtaining an additional signal that responds to abrasive wear.

The goal is achieved by calculating, in two counts, corresponding to the maximum and minimum impedance of the measuring circuit and the resistance of the current collector, the short-circuit current of a natural thermocouple, and the amount of wear is determined from the product of the current by the term, o-emf.

Tsa FIG. 1 dan machine for the implementation of the method; in fig. 2 - volt-ampere characteristic of a natural thermocouple;

in fig. 3 - Ospillogr.ammy current and voltage.

Claims (1)

The workpiece 1 is fixed in the chuck 2 and the rear center 3 of the machine 4, 5, the cutter 5 is fixed using insulating spacers 6. Through the current collector 7 and the measuring circuit, the workpiece is electrically connected to the cutter 5. During cutting, the natural part occurs between the workpiece 1 and the cutter 5 thermocouple, and in the specified circuit - electric current. The resistors of the circuit are chosen so that they are small (ohms shares), and .2 varies from zero to a maximum value (several kΩ). When R2 is equal to the maximum, the readings of a millivoltmeter .nV- are practically the ramp of the EMF of a natural thermocouple, and the maximum current flows through the circuit (/ hh), while the readings of the millivoltmeter mVo are proportional to / max a / 77V, decrease to a certain minimum / min} (Fig. 2). AG is a true volt-ampere characteristic, cutting off on the coordinate axis (for example, 25 1p) a segment equal to the EMF of the thermocouple, and on the abscissa axis (current) - short-circuit amperage. -, -,.). Mz-due to the presence of a current collector with its own resistance RT, experimentally obtained voltamnern The characteristics of the node is greater than the truth (1) (angle to the abscissa axis (). Due to this, the points obtained using the circuit, corresponding to the maximum A and minimum B and the scheme (max and 2 0), are attributed to the direct speaker. to zero the resistance of wires, terminals, etc. when point B is somewhat separated from point C. Consequently, between two readings A and B lies the entire set of experimental points characterizing the current-voltage characteristic of a thermocouple. However, to determine all the parameters of a natural thermocouple as a source of electrical voltage, it is sufficient to have two readings (A and B) and the corresponding values of current and voltage. 11 - -F- t / - l i I / - min - t From FIG. 2 obvious ratios (Ohm's law):. (c. GG p / - Attah (numerically equal to tgp), and the required product: -C / 1п1 | 1 - During the operation of the machine, the tool removal control is carried out as follows. During the turning period of the workpiece 1 (Fig. 3, a), the cutter 5 continuously alternately registers the comfort of the EMF of a natural thermocouple current / max. This corresponds to t. L and 5 volt-ampere characteristic of a natural thermocouple (Fig. 2). The transition from the measurement E to the measurement I, is made by measuring the resistance value of resistor 2 (php. 1), which is conventionally shown by the arrows in fig. 3, b. The vertical lines from the arrows: kami (Fig. 3, b) separate the period of EMF measurement from the period of current measurement. The transition frequency from the EMF measurement IK to the current measurement is determined by the specific processing conditions: length of passage, number of passes, workability of the material of the part, required processing reliability, etc. The continuously recorded values of E and / m ax depending on the passage length L allow according to the above methodology, calculate the product EI ,,,,. At the initial moment, when the wear of the tool is absent, the value of this product is minimal. With cutting (increasing L), the wear increases, which affects the fixed current values of E and / max (and the product - / c.) Depending on the nature of the wear, the type of dependencies (L) and / max 1 (/ -) will be different . In the case of the predominance of adhesive wear of the cutter, the temperature of the contact of the cutter increases — the workpiece is processed and, as a result, the EMF E of the natural thermocouple increases (Fig. 3, b). The current is either slightly increasing or staying at the same level when there is no wear. In the case when abrasive wear prevails, accompanied by an increase in the actual contact area of the tool with the workpiece, the EMF E decreases, while the recorded current increases (Fig. 3, c). However, in either case, the computed product is /? H. appears to be a monotonically increasing function of the wear of the tool. Some value of this product, E / Z, is set, upon reaching which the cutting stops and a command to change the tool is given, i.e., the work is stopped when the specified level of tool wear is reached. The calculation of the product. on the basis of the current values of E and / lax, is carried out by conventional means (for example, by a microprocessor of the machine control system). Claims The method of controlling the wear of the cutting edge and the tools during the cutting process using thermo-emf is also distinguished by the fact that, in order to increase the reliability of control by obtaining an additional signal that responds to abrasive wear, they are calculated using two samples corresponding to to the minimum impedance of the measuring circuit and the resistance of the current collector, the short-circuit current strength of the natural thermocouple and set the amount of wear by simulating the current to the thermal emf. The source of information taken into account in the examination: 1. Balakshin B.S. et al. Adaptive control of machine tools. “Mashipostroyiye, 1973, p. 306-310.