Technical Sciences / 8. Metal Treatment in Machine-Building

Doctor of Technical Sciences, Professor Smolentsev V.P.,

Candidate of Technical Sciences, Professor Koptev I.T.,

Doctor of Technical Sciences, Professor Gazizulin K.M.

Voronezh State Technical University, Russia

Kazan State Power Engineering University, Russia

Electroerosive And Dimensional Electrochemical Machining Technological Opportunities And Future Developments

Introduction

It is impossible to create modern technics without wide using of nonconventional methods of processing. It includes electroerosive and dimensional electrochemical machining. The analysis of achievements in this area for last years gives the basis to estimate technological opportunities of nonconventional methods, to predict prospects of their application especially at development of the high technology products of aviation and space technics.

Electroerosive processing

The largest scientific generalizations last years are made in the field of electroerosive geometry generation by the none-form tool at use as the tool of a core or a wire. The researches resulted in [1], [2], show, that for elimination of the basic lack of electrospark process - it is offered to limited productivity to use for strengthening impulses of intensive thermal influence of type of cumulative effect, that on the order and more accelerates speed съема an allowance. In [3] it is reached by application of the tool with a single-layered or multilayered covering of an electrode-tool the metal possessing cumulative effect, for example, by zinc. The problem of improvement of quality of a superficial layer is simultaneously solved at intensive removal of an allowance. In figure 1 the electrode in the form of a brass wire (1) with a zinc covering (2) is shown.

Modern means of automation of electroerosive machine tools allow to change position of a wire so it is always directed by a covering 2 aside zones of processing of a detail. Drop-shaped form of an electrode (figure 1) allows to use more full a covering 2 which in process of deterioration will reduce the size of an electrode from Н₁ up to Н₂, and after calibration of the cut groove by a site (d_пр - L) an electrode without a covering it is possible to lower roughnesses on walls of a groove after intensive erosive process at participation of a covering. The offered technical decision has allowed to accelerate up to 10 times speed of an insertion of apertures of small diameter or reception of narrow grooves, having provided thus roughness Ra=0,63-0,32 a micron (on steel) and an error about 10-20 microns. Continuation of researches on research of new kinds of electrodes and working environments can lead to creation combined electrochemicalerosive process with technological parameters essentially exceeding the reached level. In view of a high degree of universality of an electrospark method it is possible to count on significant expansion of area of use of such process, especially in the high technology branches of mechanical engineering.

It is necessary to consider as the second perspective direction of development of electrospark processing cold restoration of geometry of the worn out details. Essentially new scientific results on multilayered drawing толстослойных coverings from pig-iron or steel with high quality of a superficial layer [3] and reception of coverings from high-temperature alloys (for example, pig-iron) on легкоплавных aluminium materials [4] are received. The problem is solved due to management of properties of a superficial layer of coverings, change of thickness of each layer, by introduction in a cover zone of chemically active environments. On the basis of the received in [3], [4] results researches on drawing qualitative thick coverings with use of titanic alloys that will allow to give to products from not scarce легкообрабатываемых materials the unique operational properties provided by coverings are planned.

Fig. 1. The Electrode-Wire (1) With A Zinc Covering (2)

H₁ - the size of section of an electrode-wire with a covering in a direction

of its submission (it is shown by an arrow); H₂ - the size of a wire

without taking into account a covering in a direction of submission

In [5] the mechanism of process of electrocontact processing in liquid glass that has allowed to pass to use instead of glass of suspension каолина without deterioration of technological parameters of an electrocontact method is opened. Now liquid glass became a scarce product as it, basically, is made in Azerbaijan and is delivered in other countries. Except for that such working environment is toxic and inconvenient in operation. The further researches will allow to specify characteristics of suspension каолина and to begin systematic replacement with this environment of liquid glass.

Electrochemical dimensional processing

In the field of the electrochemical dimensional and combined processing are carried out complex researches on expansion of a scope of these methods at processing internal surfaces [6] and large-sized turbine blades [7]. Positive results are reached due to perfection of a design of the equipment, the tool and application of operated pulsing current of a working environment. In connection with the general slump in production and delay of rates of development of new aviation products interest to the received in [6], [7] results has a little decreased, though it is expedient to continue researches in a direction of research of new working environments (electrolits without water, organic liquids) and in the field of management of process of impulse-cyclic processing [8] under the technological schemes offered by scientists of Tula, Ufa, Saint Petersburg, Voronezh.

In [7] the new way of processing at which the watching system of the machine tool catches speed of braking of a stream is offered and the working current is disconnected, but pressure of electrolit in a backlash is kept. As the stream of a liquid in the end of a cycle has not had time to be braked completely the working environment continues to move along a backlash and bears colloid and gaseous products of processing from interelectrode space.

In figure 2 influence of a impulse -cyclic mode of submission of electrolit on accuracy of processing of channels in length up to 350 mm is shown.

Channel length, mm

imprecision, mm

Fig. 2. The Error Of The Lengthy Channel After Processing At Constant (a curve 1)

And Pulsing (a curve 2) Current Of Electrolit

In figure 2 parameters for channels with a length up to 350 mm are resulted. In case of constant current of electrolit even at an interelectrode backlash 0,6мм (the recommended range of this parameter makes no more 0,4-0,5мм) further there comes "lock-out" of a stream a backlash a gas bubble and коллоидными hydrooxides. The error estimated as a difference of average removing of an allowance (concerning an initial site) on length of the channel, sharply increases and at limiting length than 1 mm reaches more.

Application of a pulsing stream (figure 2, a curve 2) enables to receive an error no more than 0,15-0,25 mm that answers specifications details with accuracy 8, 9 quality level. Especially it is necessary to emphasize, that the increase in length of the channel at pulsing movement of electrolit practically does not affect accuracy of a detail (the error does not exceed 0,25 mm). The results resulted in figure 2, have allowed to specify recommendations at the choice of the bottom limit of speed of submission of electrolit for lengthy channels. It makes from 3 up to 8 km/s (depending on an interelectrode backlash) though speeds up to 60 km/s earlier were recommended, that demanded power-intensive hydraulic units with pressure upon an input more than 2 MPa.

The length of a site of the channel processable by one impulse depends on an interelectrode backlash (figure 3).

Apparently from figure 1, the limiting length of the processed site for one impulse at pulsing movement of electrolit makes from 48-50 mm (at a backlash of 0,2 mm) where the greatest takes place shall eat a material (about 0,12 mm), up to 180-200 mm (a backlash of 0,4 mm). But in the latter case productivity decreases in 2-2,5 times.

In [7] the area of rational use of a pulsing stream (table 1) proves.

Metal removing, mm

Channel length, mm

Fig. 3. Material Removing From A Heat Resisting Alloy For One Impulse At Backlashes: 1 - 0,2 mm; 2 - 0,3 mm; 3 - 0,4 mm.

Table 1

Typical Operations	Schemes Of Processing	The Characteristic Of A Stream	Way Of Regulation Of A Stream
			On Pressure Upon An Input, An Output	On A Cycle Removing An Allowance
1	2	3	4	5
Electrochemical Machining
1. An insertion of apertures	Submission of an electrode	Local uncontrollable pulsation without overlapping of a stream	Рвх=const Рвых=0-0,01 МРа	Is not used
2. Processing of a feather blades greater dimensions

1	2	3	4	5
- An insertion in an integral material	Self regulation, cyclic submission	The Uncontrollable pulsation with variable speed Is not used	Calculation of average speed and Рвх, Рвых	Is not used
-fair processing of a structure	Cyclic, with a variable adjustable interelectrode backlash	For greater blades a pulsing stream with an opportunity of overlapping of current	Calculation Vcp Рвх=const	Under the uniform law of manage-ment of cycles of submission of a current and a working environment
3.Manufacturing of cavities of drop dies, molds with the big area	Cyclic submission	The Pulsing stream with an opportunity of overlapping of current	Calculation Рвх=const	On speed gas-vapor a component also I make
4. Processing of channels of various section of the big length
Without submission of the tool	Motionless electrodes	The Pulsing stream with overlapping current	The Settlement structure on length of the channel Рвх =const	On speed of phases and loop variables of submission of a current
zone processing	With longitudinal submission	Poorly pulsing stream	Calculation of average speed of a stream, pressure on an input (Рвх =const)	Is not used
5.Turning round preparations (disks, turbines etc.)	Submission of the tool on a screw line	Pulsing (depending on position) the tool	Having watered a working liquid	The Dosed out submission of a working environment with a constant cycle
The combined processing
1.With guarantied channels hardening	Longitudinal submission зонного an electrode tool under the law of a constancy of longitudinal force of moving of the tool	Pulsing with the period of pulsations depending on an allowance on processing	Calculation Vcp, Рвх, average speed of submission of an electrode tool	The Dosed out submission of a working environment in a zone of processing with management on speed of submission
2. Deep an electroabrasive grinding	Submission along a surface of preparation with регулируемой in the speed	The Pulsing stream with the cycle defined by the period of submission of a working environment	Having watered of a working liquid	Dosed out submission, changeable by quantity of an electricity, through the processing area

The note: Р_вх - pressure of electrolit upon an input in an interelectrode backlash; Р_вых-противодавление electrolit; V_cp - average speed of current of electrolit (it is estimated under the average charge of a liquid)

Apparently from table 1, the pulsing stream of electrolit is applied not only at electrochemical dimensional processing (ECHO), but also in a combination with electroerosive, mechanical process.

In table 2 the example of processing обтекателя aerials of the flying device from a variable (from 70 up to 180 mm) by width of a structure and submission of a stream in the same direction is resulted.

On specifications on обтекатель the roughness of a surface after processing should be no more Ra=1,25 a micron, an error up to ±0,5 mm. The traditional method of processing with a constant stream of electrolit cannot provide these parameters even at better preparation. The pulsation of a stream with the period of anode dissolution 8-10 with has allowed to provide the parameters set by the technical project on a detail.

Table 2

Way of processing	The Mode of processing	The Roughness, mm		The Error of a structure, mm
		Before processing	After processing	Before processing	Before processing
electrochemical with a constant stream	The Astable stream of a working environment	Rz=60-80	Ra=1-5	±1,0	±0,8
electrochemical with a variable stream	The Pulsing stream combined with impulses of a current	Rz=80-90	Ra=1-1,25	±1,0	±0,4

By scientific personnels of Voronezh and Kazan are carried out researches of processes of electrochemical dimensional processing in a non-stationary mode [9] and at low pressure that allows to simplify and reduce the price of means of technological equipment considerably. In view of the received results it is necessary to adapt the developed methods for typical technological processes, in particular to apply processing at low pressure in combined химикомеханических ways of restoration of tooth gearings.

One of perspective directions in the field of creation of the equipment and equipment for electrochemical dimensional processing is application of drives (including for pulse moving an electrode-tool) with use high (up to 60МПа) pressure of a working environment [10]. It allows to reduce the sizes of drives and to expand a zone of processing, including for large-sized details. Here the decision of some questions on maintenance of tightness and reliability of highways, working capacity of mobile elements of machine tools still is required.

Conclusions

1. The lead analysis of a modern condition in the field of electroerosive and electrochemical dimensional processing shows, that the reserve created earlier in this area of researches allows to receive the new technological results expanding opportunities of mechanical engineering on creation of competitive high technology production.

2. It is shown, that due to management of a stream of electrolit it is possible to expand area of use of electrochemical dimensional processing on lengthy details, having kept thus high technological parameters, earlier achievable only for products with small dimensions.

Cited literature

1. Kodencev S.N. Mechanism Of Course Of Process Of Erosive-Thermal Processing Of Details // Nonconventional methods of processing: collection of scientific papers, Vol. 3. Moscow: Mechanical engineering, 2009. - 130-138 p.

2. Briskly A.F. Effective Technology And The Equipment For An Electroerosive Insertion Of Precision Microapertures // Belgorod:BSTU, 2010.-314 p.

3. Russian patent № 2396153, The Way Of Electroerosive Restoration Of Details From Steel Or Pig-Iron / V.P. Smolentsev, A.V. Bondar, A.N. Nekrasov, G.M. Fatykhova // Bulletin 22, 2010.

4. Russian patent № 2405662 The Way Of Drawing Of A Pig-Iron Covering On Aluminium Alloys / V.P. Smolentsev, A.V. Grebenshchikov, A.V. Perov, B.I. Omigov // Bulletin 34, 2010.

5. Smolentsev V.P. Physical Of A Basis And Technological Application Of Electrocontact Process / V.P. Smolentsev, N.V. Sukhorukov // Voronezh: VPI, 1998. - 148 p.

6. Smolentsev V.P. Technology Of Electrochemical Processing Of Internal Surfaces // Moscow: Mechanical engineering, 1978. - 176 p.

7. Gazizulin K.M. Electrochemical Dimensional Processing Of Large-Sized Details In Pulsing Working Environments // Voronezh: VSU, 2002. - 243 p.

8. Zhitnikov V.P. Pulse Electrochemical Dimensional Processing / V.P. Zhitnikov, A.N. Hare // Moscow: Mechanical engineering, 2008. – 413 p.

9. Smolentsev G.P. Theory Of Electrochemical Processing In A Non-Stationary Mode / G.P. Smolentsev, I.T. Koptev, V.P. Smolentsev // Voronezh: VSTU, 2000. – 103 p.

10. Shipanov M.V. Designing Of Highways Of A High Pressure For Industrial Equipment And The Electrochemical Equipment / M.V. Shipanov, A.V. Kuzovkin // Fundamental and applied problems of technics and technology, 2011, №5. - p.79-83