CC BY
13
УДК 621
Michai Styp-Rekowski, Dariusz Ozimina
ENLARGEMENT OF PRODUCTION METHODS SET BY
NON-TRADITIONAL HYBRID MACHINING METHODS
The article focuses on possible combinations and reference divisions of metal machining in simple and hybrid methods, as well as in conventional and non-conventional methods of impacting materials. Characteristic features of both method groups are described, with trends of their development shown.
Based on the findings as well as on the nature and mechanism of electric-spark alloying, the machining modes have been developed to make it possible to obtain new properties of surface layers. Those technological methods may be quite progressive in manufacturing various machinery elements such as gas turbine components.
Introduction
Dynamic development of technosphere generates essential progress in production techniques. In this progress one can distinguish two main stream. First of them consist in improvement of well-known technologies, increasing their rate production and accuracy. It is possible first of all thanks to applying greater values of machining parameters (as an result of better tools using), and also constans improvement of machine-tools constructional solution, as well their geometric structure as control.
Second, mentioned main stream of production techniques progress is realized through extensive using of new technologies and hybrid processes, in actual knowledge level admited as non-traditional ones. This trend enable to extend of machined materials set, including materials which are almost unworkable or simply unworkable by means of traditional production methods.
In this paper some hybrid machining methods, in which concentrated energy carriers are applied,
were identified. These ones of them, which can be suitable in progressive technologies of gas turbine elements production are indicated.
Non-traditional hybrid machining methods
As a hybrid process of machining one accept such maching method in which different or different way generated energy forms are simultaneously (in one technologic cut) influence on machined material [6].
In machining process, in which concentrated energy carrier is the tool, onto workpiece acts energy existing in four forms:
— mechanical,
— electric,
— thermal,
— chemical.
Below, in the Table 1 there are compiled different configuration of energy form existing in hybrid machining methods. Presented setting-up is exemplary and it should be accepted as developmental.
Dominant energy forms Assist energy forms
mechanical electric thermal chemical
mechanical USAM, AWJM ECH cutting with point-wise heating explosive methods
electric AMM, BEDMM EDM, ESA ECM, CEPT
thermal EDUM PVD group
chemical ECAFM. ECG ECP, ECM-M SLS, CVD group
Description of used acronyms: USM - Ultrasonic Abrasive Machining, AWJM - Abrasive Water Jet Machining, ECH - Electro Chemical Honing, AMM -Abrasive Mechanical Machining, BEDMM - Brush Electro Discharge Mechanical Machining, EDM - Electro Discharge Machining, ESA - Electro Spark Alloying, ECM - Electro Chemical Machining, CEPT - Combined Electro Physical Treatment, EDUM - Electro Discharge Ultrasonic Machining, PVD - Physical Vapour Deposition group of treatment, ECAFM - Electro Chemical Abrasive Flow Machining, ECG - Electro Chemical Grinding, ECP - Electro Chemical Polishing, ECM-M - Electro Chemical Milling, SLS - Selective Laser Sintering, CVD— Chemical Vapour Deposition group o f treatment.
© Michai Styp-Rekowski, Dariusz Ozimina, 2009
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Table 1. Exemplary hybrid machining methods by means of contcentrated energy carriers for varied association of energy forms
Division on dominant and assist energy forms which act onto workpiece could be subiective and additional it depends on recived measure: quantitative or qualitative. Some of mentioned in Table 1 manufacturing processes will not happen without aid and other-will be very slowly, however all of them there are numbered among hybrid processes.
Moreover, one can see that in number of machining cases cited in Table 1, during processes more than two energy forms can overlap, this way created complex hybrid machining method, e.g. electrochemical milling (ECM-M).
In some metods of machining by concentrated energy carriers also energy in two forms takes advantage, e.g. in laser beam machining (LBM) — electric and thermal or in ion beam machining (IBM) — electric and chemical, however in these methods only one form directly acts onto workpiece so, in above mentioned meaning, they are not include among hybrid machining methods. These methods do not satisfied a condition of simultaneousness acting on machined surface two form of energy. Energy in one form is transformed into other one and then, in changed form acts on workpiece. However, they could be non-traditional methods.
On actual knowledge level it is not possible to indicate hybrid machining method for all mentioned in the Table 1 associations of energy forms, but it does not mean that such machining methods are not potential possible. On the ground of literature messages one can find only that currently there are not conduct researches over them. In futer, when such needs and possibilities will appear they probably will invent. In initial stage of their existing, they will include into the group of non-traditional hybrid machining processes.
Such formulation of hybrid machining methods classification caused situation that their set is still open. Development of this type of methods one can observe on the ground of numerous literature source. Their authors especially examine following problems of hybrid machining methods:
— designing of improve machine-tools,
— working out and optimization of manufacturing processes,
— maintenance: production with using of above mentioned machines and processes.
Other possible criterion of division of hybrid manufacturing methods by concentrated energy carrier can be erosion source which generates change of workpiece shape, taking also into consideration surrounding of machining. In the Table 2 examples of machining methods, divided using this criterion, are compiled.
Division machining methods into traditional or non-traditional ones (conventional or unconventional, typical or untypical) is decidedly less visible than mentioned above (simply or hybrid). In literature concern this problem, e.g. [4, 6, 9] there are not non-traditional machining univocal definition. In consideration of observed rapid manufacturing techniques development, include particular method as non-traditional has not argumented. Progress of defined machining method causes situation that such method is more and more productive and often and often use in production. This way, it practical disposes its unconventional character.
The representative example of such rapid evolution of machining methods could be electro-erosive machining, especially in plastic moulds and gas turbines (blades) production.
Table 2. Characteristic features of jet-erosive machining methods, acc. to [3]
Machining method Erosion source, main parameters Basic character of machining process Machining surroundings
LBM stream of photons (103...106) W/cm2 thermal (8000.12000) K air
EBM stream of electrons (103.109) W/cm2 thermal (3000.8000) K vacuum
IBM stream of ions (100.5000) eV chemical/physical (373.673) K vacuum
WJM, FJM high-pressure water (fluid) jet mechanical (10.700) MPa air
AWJM, ASJM abrasive and water (suspension) jet mechanical (10.700) MPa air
Description of other used acronyms: LBM - Laser Beam Machining, EBM - Electron Beam Machining, IBM - Ion Beam Machining, FJM - Fluid Jet Machining, ASJM - Abrasive Suspension Jet Machining
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Electro-spark alloying — example of hybrid machining methods
One of example of hybrid method in which machining is realized by concentrated energy carrier is electro-spark alloying (ESA). It is method included to type of partial meltings ones [2]. The most important phase of surface layer (SL) generating is begining stage — process initiation, connected with plasma production, coming into existence of electron and ion currents and other concomitant phenomena.
After supply system switching on, intensification of electric field intensity and contact initiation between electrodes (workpiece [-], tool [+]) following as result of jump of so-called «precursor»,,. It causes gaseous ionization in contact area and in consequence of this — flow of electrons stream. Secondary effect of electro-spark discharges is inertial heat occuring. Existing in this process unbalance plasma and connected with plasma: ions, electrons and photons beams, create area in which transfer of materia (metal atoms and electric charge) is performed [8]. The most essential factors existing in described process of coating creating by ESA are shown in Fig. 1.
Fig. 1. Essence of shaping and modification of SL in ESA process: 1 — material of base (cathode), 2 — working electrode (anode), 3 — created layer with expected operational features, 4 — plasma, 5 — diffusive or reactive-diffusive zone, 6 — nearer surroundings (shielding gas), 7 — further surroundings (air), 8 — electrode holder with channels for supplying gas; IR — infrared radiation, UV — ultraviolet radiation, f — frequency of vibration, a — rotational speed [7]
As result of described above phenomena, transfer of material from electrode (M^) to base material of workpiece (M2) is going on. This way reactive or reaktive-diffusive zone with the structure xM^^cyM^ is created. In volume of created layer exist also admixture components and on its surface oxidated form of this zone: xM1 % yM2 % Ox [8].
Modificated SL in effect of useful introducing atoms (particles) of some metals (or other matters) can be characterized by new properties changed in
expected direction. It is important that features can be changed in precisely limited area. This way, it is possible machining of edge of turbine blade (not all its surface) or places of bearing fitting (not whole shaft).
According to the needs, it is possible to coat one-or (more often) multicomponent covers. It is also possible to coat multilayer covers, in which individual layer assures defined features thanks to them can characterize by features impossible to obtain by other methods [5, 7].
Operational features of coatings covered by ESA can be improve by following treatment by other techniques, e.g. laser treatment. In effect of such machining sequence, one can obtain surfaces with e.g.: greater hardness, more corrosion or/and fatigue resistant and more hermetic [1].
Directions of hybrid methods development
On the ground of conducted analyse, one can identify the two basic directions of development. First of them concern expansion of hybrid machining by concentrated energy carriers on special materials, such e.g.: composites, sandwiches, special alloys. In this group of researches following scientific problems are essential (the most often discussed):
— increasing rate of production and resulting accuracy,
— consideration of surface layers and their surface geometric structure features,
— optimization of manufacturing parameters and conditions.
Second direction of development leads to design new, very interesting production techniques. As an example could be abrasive flow machining (AFM). During this type of machining individual phenomena resulting different energy form (mechanical, chemical and electric) mutually put on what generate synergetic reactions. Improvement of this method consist mainly on optimization of composition and properties of working paste.
References
1. Antoszewski B. Ti and Mo Coatings Covered by means of Electro Spark Alloying / B. Antoszewski, N. Radek . — Welding Review.— N 8-10/2002.
2. Burakowski T. Engineering of Metal Surfaces / T. Burakowski, E.Rolinski. — Wierzchon T. WNT Warszawa (Poland). — 1995 (in Polish).
3. Gol^bczak A. Selected Problems of JET Shaping. Proceedings of VIth Conference EM 2000 (Electromachining) / A. Gol^bczak, J. Kozak . — Academy of Technology and Agriculture Publishers, Bydgoszcz (Poland). — 2000. — P. 43— 64 (in Polish).
4. Groover M.P. Fundamentals of Modern Manufacturing. Materials, Processes and Systems / M. P. Groover. — Prentice-Hall Inc. — New Jersey (USA). — 1996.
5. Musial J. Geometrical Structure of Surface Generated by Erosive Methods. Proceedings of VIIth Conference EM'03 (Electromachining) / J. Musial, M.Styp-Rekowski. — Academy of Technology and Agriculture Publishers. — Bydgoszcz (Poland). — 2003. — P. 253—260 (in Polish).
6. Oczosft K. E. Nature, Importance and Development of Hybrid Metal Removal Processes. Scientific Publications of Academy of Technology and Agiicultuie 225, serie : Mechanics / K. E. Oczos.ft — Bydgoszcz (Poland), 2000. — N 46. — P. 135—144 (in Polish).
7. Ozimina D. Modification of Surface Layer
Features by means of Electro Discharge Machining / D. Ozimina , N. Radek , M. Styp-Rekowski // Archive of Machine Technology and Automatization, Poznan (Poland). — 2004. — N 24 (2). — P. 229—238 (in Polish).
8. Ozimina D. Antiwear Surface Layers Forming by means of Electro-Spark Alloying. In: Styp-Rekowski M.(edit.) : Some Problems of Machining by Concentrated Energy Carrier / D. Ozimina , H. Scholl, M. Styp-Rekowski // Bydgoszcz Scientific Association Publishers. — Bydgoszcz (Poland) 2003. — P. 104—110 (in Polish).
9. Ruszaj A. Non-conventional Methods of Machines and Devices Elements Production / A. Ruszaj. — Institute of Cutting Publishers, Krakyw (Poland) (in Polish).
Поступила в редакцию 21.08.2008
В представленной статье описаны возможные комбинации, образцовые деления механической обработки металлов в простых и гибридных методах, в традиционных и нетрадиционных способах влияния на материал. Описаны характерные черты для групп обоих методов и тенденций их развития.
По результатам анализа природы и механизма обработки электроискровым легированием получены режимы нового качества поверхностных слоев. Эти технологические методы могут быть достаточно прогрессивными в производстве многих элементов машин, например, деталей газовых турбин.
У представленш статтi описано можливi комбшаци, зразковi роздыення мехатчног обробки металiв у простих та гiбридних методах, у традицтних i не традицтних техно-логiчних способах впливу на матерiал. Описано характерт риси для груп обох методiв та тенденци ¡х розвитку.
За результатами аналiзу природи i мехатзму обробки електроккровим легуванням от-римано режими ново1 якостi поверхневих шарiв. Ц технологiчнi методи можуть бути достатньо прогресивними у виробництвi багатьох елементiв машин, наприклад, деталей газових турбш.
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