WO2017204686A1

WO2017204686A1 - Machine tool testing method

Info

Publication number: WO2017204686A1
Application number: PCT/RU2017/000327
Authority: WO
Inventors: Борис Михайлович ДМИТРИЕВ
Original assignee: Борис Михайлович ДМИТРИЕВ
Priority date: 2016-05-24
Filing date: 2017-05-19
Publication date: 2017-11-30
Also published as: RU2634529C1

Abstract

The invention relates to means for testing machine tools for accuracy under thermal influences. The technical result is a more consistently reliable assessment of the thermal state of a batch-produced tool during acceptance testing. The thermal state of a tool is defined by a performance parameter derived from the relationship between the value of each output parameter which defines the accuracy of a tool, expressed in linear or angular units (micrometers/degrees), obtained after the final standard operating cycle of a tool during testing, and the amount of electrical energy consumed at the tool input during said cycle, expressed in kilowatt hours (kWh). In the proposed method, a batch-produced tool is assessed for fitness for use by comparing the numerical value of the performance parameter defining the ability of the structure in question to withstand thermal disturbances against a similar value obtained during testing of the parameters of a test model of the tool. The fitness for use of the test model of the tool is established prior to testing, and its parameters represent the permissible value for batch-produced tools. A batch-produced tool is declared fit for use only if the value of the performance parameter is less in terms of all of the output parameters than the permissible value for the test model.

Description

METHOD FOR TESTING METAL-CUTTING MACHINES

FIELD OF TECHNOLOGY

The invention relates to means for testing the bearing system of metal cutting machines (HSS). In particular, the present invention relates to means for testing the structural properties of metal-cutting machines carried out during research and acceptance tests. Tests are carried out under thermal influences according to the accuracy parameters of the machine.

The invention relates to testing tools for metal cutting machines. The property of the design of the metal cutting machine to withstand the thermal effects that occur during the working process is subject to testing. Tests are carried out in order to assess the suitability of the machine for use after its manufacture and / or repair, as well as modernization.

The design property of the machine to prevent thermal influences is characterized by two indicators. One of them determines the rate of transition of the thermal state of the structure from one equilibrium state to another. This indicator is used by technologists in assessing technological productivity. The faster the structure passes from one state to another, the faster the stable state of the structure in thermal terms occurs, and the faster the accuracy of the machine stabilizes during operation. This indicator is not considered in this application.

Another indicator determines the property of a structure to prevent a change in accuracy. This indicator is formed by the designer of the machine. When assessing the quality of the structure after the manufacture of the machine and / or repair, as well as modernization, produce assessment of the achieved level of quality at a quantitative level by testing.

The design's ability to withstand thermal effects is hidden from an external observer. To evaluate the quantitative value of this property, a measurement transformation is used. The measurement transformation consists in subjecting the structure to external thermal influences of known magnitude and evaluating the reaction of the structure. The quantitative expression of the property is defined as the ratio of the reaction of the structure to the magnitude of the thermal effect [1]. As a reaction of the structure, output parameters are used in the form of geometric accuracy of the structure, which determine the accuracy of the machine. The output parameters are five coordinates according to the degrees of freedom of the NSS, namely, the linear movement of the base under the tool relative to the base under the workpiece along the three coordinate axes, and two angular coordinates that determine the angular positions of the bases (see, for example, FIG. 1).

As a quantitative value of the parameters of thermal effects on the design of the supporting system, various parameters are used. This is either the temperature of the structure, or the parameters of the operating modes characterizing the thermal effect, as well as the influence of the ambient temperature.

In order to make a conclusion on the suitability of the machine for operation based on the test results, a criterion of the truth of such a statement is necessary [2]. The criterion of the truth of the statement, characterizing that the machine is suitable for operation, consists of two signs. The first sign requires a tolerance on the value of the tested parameter and the rules of the conclusion about the suitability of the machine for operation. The tolerances for the output parameters are determined either by regulatory documents, or he is appointed by the developer of the machine. The conclusion about shelf life is as follows. If this value of the property indicator is less than or equal to the permissible value, then the machine is deemed fit for use and not suitable if this value is more than acceptable.

The second feature requires knowledge of the magnitude of the current parameter of the property of counteracting thermal influences of a newly created machine design or retired. The current value of this parameter is obtained as a result of testing the structure under the action of thermal influences according to the developed methodology, which is consistent with the method of forming an acceptable value for each parameter.

BACKGROUND

From the prior art it is known, for example, the solution of Jungnickel [3] to conduct testing of a metal cutting machine. This solution considers two property parameters characterizing the thermal state of the machine. One parameter characterizes the thermal stability of the structure. The first parameter is important from the standpoint of the productivity of the production process. It is important that the stabilization time is shorter. This application is not considered.

Another parameter characterizes the reciprocal of the thermal rigidity of the structure, i.e., thermal compliance.

This parameter determines the thermal state of the structure, which is characterized as the thermal rigidity of the structure. It determines the ability of a structure to resist thermal influences. The rule of conclusion about the suitability of the machine for use is as follows: the higher the value of the new machine, the more accurate this machine is, therefore, it is suitable for use. AT quantitatively, this parameter is determined by the following relation:

Sterm = (d (AP) / (d (Axllt _K ))

Where:

- Sterm quantitative value of the indicator of the properties of the machine design to counteract thermal influences, in order to maintain the accuracy of the machine;

- d (ΔΡ) is the differential heat flux ΔΡ, is used as a parameter of the external influence on the structure by heat;

- d (Axlt _K ) - the maximum possible deformation between the bases for the tool and the workpiece during the time t _K , as a result of the reaction of the structure to thermal exposure. This parameter determines the accuracy of the machine.

To determine the truth of the conclusion about the suitability of the machine for use, it is necessary to have a tolerance on the Sterai parameter. As such a value, the author proposes to use the value obtained in relation to the prototype.

The scope of this criterion is to conduct comparative tests of two machines, one of which is a prototype. The choice of test modes is arbitrary, but limited by the test time t _K. Time t _K is the stabilization time of the thermal process. To determine the quantitative value of the parameter, it is required to determine the quantitative value of the "change in heat flux ΔΡ". Methods and means of obtaining this value are unique and require both special training of testers and the presence of complex technical means.

In this offer: 1. He ensures the reliability of the assessment results and their unambiguity regarding the state of the tested machine due to the uncertainty of the procedure for obtaining information about the current state of the machine (the choice of test modes is arbitrary, the problem of obtaining this indicator from the prototype).

2. To create a tolerance for the investigated parameter requires knowledge of the parameter of the prototype. The quantitative value of the requirements for the prototype was formed during its creation under pre-existing conditions. The new machine requires the fulfillment of new requirements that are different from the prototype. The tolerance in this case is a rather uncertain quantity.

3. It is technically difficult to perform a “change in heat flux ΔΡ".

4. There is no effect of ambient temperature on the thermal state of the structure during testing.

The technique has the right to use to assess the state of a newly created machine in the presence of relevant information from the prototype and has limited use.

Existing restrictions relate to the sign of necessity, i.e. the reproduction of thermal effects on the design and the development of tolerance on the test parameter. These conditions do not provide the reliability of the received information about the state of the machine during testing according to the accuracy parameters under the action of thermal influences.

The prior art also known solution POLYAKOVA [4].

This solution aims to reduce time in obtaining information about the thermal state of the machine. Reducing test time is a central issue of any known suggestions. In this solution, the reduction in time is based on the procedure for predicting changes in machine accuracy parameters. The forecast is the time of the onset of a stable value, both temperature and output parameters according to the accuracy parameters of the machine.

Prediction, as a process of predicting the future development of the thermal state of the machine, consists of two parts. The first part is to determine the type of law for predicting temperature changes during thermal action. The second part is to quantify the temperature of the machine structure.

In the proposed method, the law of the development of the parameter of the property of the change in the thermal state is determined using neural networks. The structure of the neural network determines the law of variation of the thermal state of the machine. The process is multi-stage.

The basis is the selection of the architecture of neural networks. After this, the forecast requires information on the quantitative values of the temperature of the structure. However, the temperature of the structure is a continuous value distributed over the structure. To determine the quantitative value of temperature, determine the position of the temperature at one point in the structure. To do this, search for this point on the structure. Such a point uniquely characterizes the thermal state of the structure with its temperature value. After determining such a point, studies are carried out on changes in the thermal state of the machine for a short time. The parameters of the form of the law, as well as temperature readings from certain points of the structure obtained in a short test time, enter the computer. By the developed program processes the received input data. The result is a prediction of the time of onset of the "hot equilibrium state" of the machine. The conclusion rule says: if the stabilization time for a given accuracy value of a machine is less than a given value, then the machine is suitable for operation and vice versa.

The proposal submitted is characterized by the following provisions:

1. A sophisticated forecasting apparatus: the choice of network architecture (the type of law of the change in the output parameter over time) depends on the skill of the operator.

2. The procedure for finding a certain point on the design of the machine is long and rather complicated, due to the multidimensionality of the temperature field of the structure.

3. The conditions for reproducing the thermal effect on the structure during testing are not defined. The conditions for reproducing thermal effects depend on the degree of versatility of the machine and have a very wide range of operating conditions.

In connection with these conditions, the method does not provide the reliability of the received information about the thermal state of the structure.

Fulfillment of these requirements when applying this approach gives the result in specially organized laboratories, with specially trained specialists, methods and testing tools. The use of this method, when carrying out acceptance work in the factory, requires significant material costs.

The Jacob solution [5] is also known in the art, which discloses a test proposal for two property parameters. One indicator characterizes the property of the design of the machine, another group of indicators relates to issues of test technology. What is not considered in this application.

The method of assessing the design properties involves the assessment of "thermally determined design quality of the machine, which is the quotient of dividing the power losses by the resulting maximum deformation in the selected coordinates at a certain speed".

Cn = p _v / Atah

In this case, the parameter Cn is used as a parameter, which characterizes the design property of counteracting thermal influences as “conditional design quality of the machine”. The quantitative value of this parameter is defined as the ratio of the power loss that occurs during testing to the maximum change in the output parameter of the machine in coordinates for the same time.

Measurement of structural deformation is known by what and how to measure. It remains unclear the concept of the parameter “power loss”, how and how to measure “power loss”, with respect to what initial value of power to measure the loss.

1. In order to take advantage of this proposal during testing, it is necessary to be able to establish the permissible value of “the value of the conditioned design quality of the machine”. When forming the tolerance It is proposed to apply a comparison of this parameter with the prototype (the binding of the spindle speed of the test machine to the prototype is required). At the same time, there is no rule for concluding that the machine is suitable for use;

2. The reproduction of thermal effects on the structures is carried out at a certain number of spindle revolutions. Under the concept of “a certain number of revolutions” of the spindle, different values can be realized, a specific number of revolutions is not assumed, and there is no proposal to formulate the principle of its choice

3. There is no measurement principle (method and tool) how to measure "power loss".

4. There is no effect of ambient temperature on the thermal state of the structure during testing. The combination of these provisions determines the application of the proposal in each limited case. The totality of these conditions does not ensure the reliability of the information received due to the uncertainty of the principle of formation of tolerance and reproduction of thermal effects on the structure during testing. They do not contribute to the unambiguity of conclusions about the thermal state of the machine design due to the following reasons.

The prior art also knows the solution of the method for assessing the quantitative value of the parameter of the property of counteracting thermal influences, disclosed in section 6 of the standard: "Thermal deformation due to spindle rotation", International standard ISO 230-3, second edition on 5.08.2007. Instructions for testing metal cutting machines. Part 3. Determination of thermal effects.

[6, p. 7]. In the prior art, comparability of the obtained information about the current thermal state of machine tools of different models, different dimensions, tested at different periods of the machine life cycle, as a rule, is ensured by reproducing the normalized law of thermal loading of the structure with heat for all tested machines.

To quantify the indicator, the composition of the reaction of the machine in the form of output parameters of the machine in the amount of five parameters is provided. For a quantitative assessment, a reference frame for the parameters of the thermal motion of the structure is provided. It has a rectangular coordinate system, primary transducers for assessing changes in the position of the base under the tool relative to the base under the workpiece, a chronometer for evaluating the temporal parameters of the thermal motion of the machine structure.

As a thermal effect on the design of the machine, the law of reproduction of a set of spindle speeds necessary for thermal exposure is formed. The law contains a provision to take into account the influence of the environment on the thermal state of the structure.

Instead of tolerance on the property indicator during testing, a certain condition is introduced. During testing, a quantitative assessment of the parameter of the property of counteraction to thermal influences is not performed. The result of the tests is the construction of a graphical dependence of the change in the output parameters and the temperature of the structure during the test under the action of the law of heat exposure by means of the spindle.

As a conclusion on the suitability of the machine for operation, the following agreement “When tests required for acceptance work, it is up to the user to choose, by agreement with the supplier or manufacturer, which tests related to the properties of the structural elements of the machine are of interest ”[7, p.2].

In this case, the manufacturer and the consumer, on the basis of a mutual agreement, have the right to establish both a set of output parameters and tolerances on them, as well as a rule for concluding that the machine is suitable for use.

This condition provides ample opportunity for uncontrolled actions, entailing various interpretations of the reliability of information about the thermal state of the structure.

The above solution was chosen by the applicant as the closest analogue to the proposed method for testing metal cutting machines, as containing a list of components of the evaluation criterion for the suitability of the machine for use. Moreover, it is important, in relation to reliability, to evaluate the thermal state of the machine, in the closest analogue to the proposed method for testing metal cutting machines, the following approach:

1. A change in the output parameters during the tests is considered as the movement of the structure under the action of heat. What is the reference system used for, as an indispensable need for the study of motion parameters.

2. The parameter of thermal influence on the structure in the form of the law of alternating spindle speeds and pauses is uniquely determined.

3. A requirement has been formed to take into account changes in ambient temperature during testing. The disadvantages of this solution is that it does not solve the problem of quantifying the parameter of the property of the thermal state of the machine, only a qualitative solution to the problem is proposed. This situation does not create grounds for unity in assessing the thermal state of the tested machines. This decision does not imply the possibility of comparing the build quality of not only machines of the same type, but even two machines of the same design, since this depends only on the agreement of the contracting parties, namely, the manufacturer and the consumer. Therefore, the application of the known solution leads to a lack of reliability of the received information about the thermal state of the machine.

SUMMARY OF THE INVENTION

The objective of the present invention is to eliminate the above disadvantages known from the existing level of technology. The technical result of the claimed invention is to increase the reliability of the assessment of the state of the machine during testing. This is done by obtaining a quantitative assessment of the property indicator and comparing it with the basic requirement of a usable machine, a prototype model of a future series of machines.

The specified technical result is ensured due to the fact that the method proposed in the present invention allows to automatically evaluate the technical condition of the structure of each new machine after assembly, after repair or modernization during a work shift with a normalized level of reliability, ensured by the reproduction of a given law of exposure to thermal disturbance for each test machine individually, as well as by setting tolerances on the output parameters, which are three linear and two angular geometric accuracy parameter of the machine. The tolerance for these output parameters is formed once during research tests of the experimental machine of this model, which is recognized as fit for use (after all standard checks). The value of the change in the geometric accuracy of the experimental machine under the action of thermal influences, when testing by this method, are recognized as tolerances. Further, they are used as tolerances for testing serial machines of this model during test acceptance tests.

In the inventive method, the suitability of a serial machine for operation is determined by comparing the parameter of its structural property, obtained as the ratio of the value of each output parameter, expressed in micrometers (μm), obtained after the final cycle with respect to the amount of electrical energy consumed at the input of the machine for the same time cycle, expressed in kilowatt hours (kWh), and comparing this value with the same value obtained in the study of the parameters of the prototype of the machine tested using of the proposed method, which is an acceptable value for serial machines, previously recognized as serviceable, and also the fact that a serial machine is considered suitable for use if and only if the value of the specified parameter for all output parameters is less than the value of the specified acceptable value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 - a general view of the machine with the layout of the primary converters on the machine bases to determine changes in the output parameters that determine the accuracy of the machine.

DETAILED DESCRIPTION OF THE INVENTION The essence of the claimed method of testing metal cutting machines is as follows.

During the tests, the external influence on the design of the machine is reproduced according to a law that is constant for all tested machines (see ISO 230-3).

At the same time, the power consumption is measured at the entrance to the machine’s energy system using standard power meters.

The reaction of the machine tool system is evaluated by the displacements of the base under the tool relative to the base under the workpiece according to five degrees of freedom (see Fig. 1.), using primary transducers based on any principles for measuring linear displacements. In particular, mechanical devices are used: lever, with gears, with spring gears, with gears, or optomechanical devices: optimometers, spring-optic heads, as well as primary transducers based on electro-magnetic principles with digital output for automatic processing data and test results.

In parallel with the steps to measure the reaction of the structure obtained by the action of thermal influences according to the law of reproduction of the spindle speed, the effect of the ambient temperature is evaluated. The temperature change during the test is taken into account when determining the index of the design property of counteraction to thermal influences, making adjustments to the magnitude of the changes in the geometric accuracy of the machine.

All actions during testing are synchronized in time, using standard timers. The received data from all converters is converted to the result. As a result, a parameter of the design property is obtained to counteract thermal disturbances in quantitative terms. For linear values, this is μm / kWh and for angular degrees / kWh. This property is determined for each output parameter of the machine as the ratio of the amount of movement to the moment of the end of the next cycle of thermal exposure to the amount of energy consumed at this time. The measurement of power consumption at the input of the machine is carried out according to the operating instructions of the power meters, synchronously with the inclusion of spindle rotation. This action is performed for each elementary cycle of thermal exposure. At the end of the full test cycle, three quantitative values of the design property are set, which are set as reference points. For each complete test cycle, the structure of the quantitative value of the parameter of the property of resistance to thermal disturbances, which is expressed in three values, is compiled.

In order to get rid of the dependence on the prototype, it is proposed as an admission to set the output parameters obtained from the prototype of the machine. The prototype machine was initially tested according to all regulatory documents (hereinafter - the prototype). It meets the requirements of all standards for products approved for use in the state. At the end of the test procedure of the prototype and recognized as fit for use. A prototype of the machine is tested for thermal effects using the proposed method. Data on the quantitative values of the output parameters of the prototype according to thermal influences represent the regulatory tolerance in they are subsequently used as mandatory values when bringing test acceptance tests of serial machines of this model.

The output parameters are the linear coordinates of the movement of the spindle axis along the coordinate axes. To do this, use two primary transducers located at the same level. They generate information about the change in the position of the spindle axis in the horizontal plane along the corresponding coordinate axes. At a distance of 100 mm. two more transducers are located, which, together with the previous ones, form information about the angular changes in the spindle axis and the angular displacements of the spindle axis relative to the base under the workpiece.

In the proposed method, the serviceability of a serial machine or out of repair is determined by comparing the design property parameter with the values obtained from the prototype of the machine. In the claimed method, a serial machine is recognized as serviceable if and only if the value of the specified property parameter for all output parameters is less than the value of the specified allowable value.

List of cited sources:

1. Novitsky P.V. Fundamentals of the information theory of measuring devices. L .; Energy, 1968 .-- 248s.

2. Mathematics in terms, definitions and terms. / Ed. L.V. Sabinina. M .: Education, In 2 parts, 4.1- 319 s, Ch2-351s. h. Jungnickel G. Warmeubertragung durch freie onvektion an

Maschinenbauteilen. Maschintnbautechnik. / 1979 / vol.28 / N.72 / pp. 568-573] 4. Poles AH, Dyakonov P.I. The study of the thermal state of machines using neural networks. / STIN, 2006, C 10-13. 5. Jacob K. Beurteilungskriterien fur das termische Verhalten von Werkzeugmaschinen. Maschinenbautechnik. 1981.v.30. N ° 12. P. 540-544]

6. International standard ISO 230-3, second edition on 5.08.2007. Instructions for testing metal cutting machines. Part 3. Determination of thermal effects.

Claims

CLAIM

A test method for metal-cutting machines to assess the serviceability of a newly assembled and / or left after repair or modernization of the machine, which determines the set of output parameters of the machine, determining the accuracy of the relative position of the machine tool and the workpiece, using a reference system that includes a coordinate system, a set of converters, chronometer, set of design temperature parameters, study time, where the specified output parameters characterize the change in the thermal state of the structure during testing, a system for assessing the environmental effect on the output parameters of the machine, where the assessment is an assessment of the properties of the structural elements of the machine of user interest, the law of reproduction of the thermal regime of the machine during testing, consisting of alternating the work of the machine spindle at rotational speeds as a percentage of the maximum spindle frequency, in such a sequence as, first, the operation of the machine every 15 minutes with an alternating spindle frequency of 25, 100, 75, 25 units as a percentage of the maximum frequency, then providing a spindle operation interruption for 10 minutes, then providing the next cycle with an alternating spindle frequency of 25, 50, 25, 50, 75, 25 units as a percentage of the maximum, then ensuring a spindle operation interruption for 10 minutes, then ensuring the final cycle with a variable spindle frequency of 25, 50, 75, 100, 25, 50 units as a percentage of the maximum frequency, characterized in that the suitability of a serial machine for operation is determined by comparing the parameter of its design property obtained as the ratio of the magnitude of each output parameter, expressed in micrometers (μm), obtained after the final cycle with respect to the amount of electric energy consumed at the input of the machine during the same time of this cycle, expressed in kilowatt hours (kWh), and comparing this value with the same value obtained by studying the parameters of the prototype of the machine, which is an acceptable value for serial machines, previously recognized as serviceable, and also the fact that a serial machine is recognized as serviceable if and only if the value of the specified property for all output parameters is less it values specified permissible value.