Superfinishing theory.

Liska, Jan ; Lipa, Zdenko ; Baranek, Ivan 等

1. INTRODUCTION

The superfinishing theory is not a usual connection of terms "theory" and "superfinishing". There exists more general concept of machining theory (Janac, et al., 2007). The connection of concept theory and concepts denoting individual machining methods (turning, milling, drilling, grinding, superfinishing, etc.) is not exerted but possible (Janac et al., 2004). However, it is current in some science. For example, we have theoretical physic, theoretical kinematics, the theory of electromagnetic field etc. Still we remind that the concept theory of machining we would replace with concept theoretical technology of machining.

We will not dispute the idea that the technology of machining does not have its own theory but have only theoretical background that is provided by another sciences. In the history there existed already today overcomed ideas, for example if algebra is the own science or only an instrument. Absolutely we will not disput idea that machining is not the science but art. We could return back to the beginning of the twentieth century when Taylor published his book: On the art of cutting metals (Taylor, 1903).

We can talk about the theory of machining when we want theoretically cover the full area of machining. If we focuse the theory on the individual methods of machining then we can talk about the theory of turning, the theory of grinding (Maslov, 1989) and also about the theory of superfinishing.

The machining consists of different phenomena therefore we can talk about the theory of cutting forces, the theory of chip formation etc. It is natural that if the whole discipline has its own theory then also every part of the discipline has one.

The discipline has the theory when it has its own object of investigation and methods of investigation. This is what the machining technology exactly has.

2. INVESTIGATION SUBJECT OF SUPERFINISHING THEORY

The superfinishing theory exists but till now there was not payed sufficient attention to it (Skocovsky et al., 1978).

The scientific school of machining in Trnava dealed with this problem (Lipa & Janac, 2000; Bonisova & Lipa, 2007). These are contributions from VEGA projects: The theory of finish processes in the machining and The new trends and further development of superfinishing technology.

The superfinishing is characteristical primarily with its moves (Swigert, 1940). Therefore the first part of supefinishing theory is the motion theory (kinematics of superfinishing). It comes from differential equation of harmonic motion

[d.sup.2] y/[dt.sup.2] + [[omega].sup.2] + y = 0 (1)

where y is the oscillating motion variation of the superfinishing tool from its equilibrium position

t is the superfinishing time

[omega] is the angular frequency.

[FIGURE 1 OMITTED]

This equation we use for the calculation of immediate ([v.sub.k]), maximal ([v.sub.kmax]) and middle ([v.sub.kstr]) speed of oscillation motion of superfinishing tool. If we determine peripheral speed of work-piece [v.sub.o] after we can determine tangent of angle foot crossing [beta]

tg[beta] = [v.sub.k]/[v.sub.o] (2)

tg[[beta].sub.max] = [v.sub.kmax]/[v.sub.o] (3)

tg[[beta].sub.str] = [v.sub.kstr]/[v.sub.o] (4)

This angle is important for the material removal from the workpiece by superfinishing. It has to move in certain levels so that removal is adequate. The material removal by superfinishing is not possible to set up such as by turning and must be an object of research. Here we may talk about the theory of removal by superfinishing. We derived a differential equation of Bernoulli model for the removal proportions (Lipa et al., 2008 a).

Dynamical proportions of superfinishing are simplier because the compressive force [F.sub.pr] on the superfinishing tool can be set up at the superfinishing (what is not possible at the turning) and confine to the ingredients determination of cutting force namely tangential [F.sub.c], radial [F.sub.p] and axial [F.sub.f].

The thermie of the superfinishing can be out of interest of superfinishing theory because the superfinishing temperature exceeds the ambient temperature by a couple of degrees celzius and does not influence the superfinishing process.

We do not think of superfinishing optics and atomistics at this moment because superfinishing tool is not a laser jet nor any electron ray.

Acoustic aspects of superfinishing are presented by a case of oscillated tool. The ultrasonic support of superfinishing is until now only in technological research and development. It is not an ordinary technological process.

Other methods of superfinishing that are being researched and developed are:

* highspeed superfinishing (increased productivity of superfinishing),

* highly accurate superfinishing (additional quality increase of superfinished surface),

* integral superfinishing (connects the operations of grinding and superfinishing to one--we don't need gringing as previous operation).

Subjects of research and develpment are also:

* tools for the superfinishing (superfinishing stone or tape),

* fixture for the superfinishing,

* superfinishing machine tools.

[FIGURE 2 OMITTED]

Above mentioned need their own support in the superfinishing theory.

With the friction theory and the wear theory deals the superfinishing tribology as an additional part of superfinishing theory.

Very serious problem dealed by the superfinishing theory is the theory of generation and formation of a chip by the superfinishing. The discussion is if removed material from the work-piece by the superfinishing are chips or shapeless fragments. The question is if we can talk about chips or microchips by superfinishing.

Very important is also problematic of stiffness primarly for the research and development of superfinishing machine tools.

Roughness and precision are basic phenomena of superfinishing. We derived differential equation for the roughness (Lipa et al., 2008 a) and determined also empirical equation of power type (Lipa et al., 2008 b).

It is necessary in the superfinishing theory to deal with:

* the tool life of superfinishing stone and tapes,

* machinability,

* classification analyse of superfinishing.

3. CONCLUSION

The content and the extent of the Superfinishing theory concept is considerable. Many matters are indicated and not much explored. They can however contribute to the general theory of machining even not so much as the turning theory or the grinding theory.

The theory of superfinishing is necessary to build and it is necessary to deal with it systematically.

This work was kindly supported by the project VEGA SR 1/4108/07 "New trends and next development of superfinishing technology".

4. REFERENCES

Bonisova, M. & Lipa, Z. (2007). Moduldrna vystavba parametrov superfinisovania. (Modular construction of superfinishing parameters) In.: Year-book of international scientific conference ROZVOJ TECHNOLOGiE OBRABANIA, pp. 191-194, Kosice 15-16. 11

Bonisova, M. & Janac, A. (2007). Nove trendy v technologii superfinisovania (The new trends in superfinishing technology). Strojarstvo/Strojirenstvi. 2007, 2 pp. 36--37. ISSN 1335-2938

Darmann. (2009). The art of superfinishing. Available from: http://images.google.com/imgres?imgurl=http://www.darm ann.com/assets/images/superabrasive_three.jpg&imgrefurl= http://www.darmann.com/superfinishing.html&usg=_qek1 cnZax- Bq64oHroRRn2gs68A=&h=501&w=250&sz=24&hl=cs&s tart=10&tbnid=GEOo26TqNQQgdM:&tbnh=130&tbnw=6 5&prev=/images%3Fq%3Dsuperfinishing%26gbv%3D2% 26hl%3Dcs%26sa%3DG Accessed: 2009-06-10

Janac, A., et al. (2004). Technologia obrabania. (Machining technology) STU, ISBN 80-227-2032-3, Bratislava

Janac, A., Lipa, Z. & Peterka, J. (2007). Teoria obrabania. (The theory of machining) STU, ISBN 80-227-23-47-9, Bratislava

Lipa, Z. & Janac, A. (2008). Dokoncovacie sposoby obrabania. (Finish methods of machining) STU, ISBN 80-227-1324-4 Bratislava

Lipa, Z., Baranek, I. & Moravcikova, J. (2008/1a). Prispevok k teoretickej problematike superfinisovania. (Contribution to the theory of superfinishing) In. Vedecke prace MTF STU Trnava

Lipa, Z., Baranek, I. & Moravcikova, J. (2008/2b). Superfinisovanie ako kinematicky najzlozitejsi sposob obrabania. (Superfinishing as the kinematic most complicated type of machining) In. Vedecke prace MTF STU Trnava

Maslov, J. N. (1989). Teorie brouseni kovu. (Theory of metal grinding), SNTL, Praha

Swigert, A. M. jr. (1940). The story of superfinish. Lynn Publishing Company, Detroit. Skocovsky, M. et al. (1978). Superfinisovani ploch. (The surface superfinishing) DTCSVTS, Brno