Temperature research during processing with ceramic plates in turning.

Salihu, Avdi ; Bunjaku, Avdyl ; Zeqiri, Hakif 等

Abstract: In this paper are introduced research results of the temperature using the thermocouple method during the turning. The research is done in numerical control lathe GILDEMESTER MD 5S on material C 45 (according to DIN) with cutter plates MC2 of the HERTEL Company. The processing is implemented by changing various independent sizes: cutting velocity (v), feed (s), cutting depth (a) and nose radius (r) using the plan with four first row factors (4 2 4 +).

Key words:.temperature, turning, cutting plates, thermocouple

1. INTRODUCTION

During the cutting process, as a result of energetic transformations a large amount of heat is released in the cutting zone. In the cutting process appear three heat sources in the zone of cutting as follows:

--in the plastic deformation zone of the cut layer (on the cutting plane),

--in the meeting surface of chip couple--the front surface and

--in the meeting surface of the couple, the processed surface the back surface.

According to the research results 99,5 % of the spent force for implementing the cutting process (force for plastic deformation, force for defeating the friction force) turns into heat energy.

Regarding to the average temperature during cutting, many scientific studies are published. Researches have been conducted in order to establish the influence of processing parameters in temperature distribution, in the processing part and the cutting edge. In these publications, mathematical models were obtained, that describe the change of the average temperature and the distribution of the temperature on the front surface of the cutting edge (Aleksander 1976).

Former researches for temperature measurement are done by Savin (1909), Brokenberg Mayer (1911), that have measured temperature using the caliometric method during the cutting process. Usachev in 1915 applied the thermocouple which he placed on a tool and measured the temperature directly. At the same time, Shore (1924) in the USA, Getwin (1925) in Germany and Herbert (1925) in England, have developed temperature measurement through natural thermocouple that is made up from the instrument and the processing part.

In this paper are introduced the research and experimental results of temperature measurement through the method of thermocouple.

2. CONDITIONS FOR EXPERIMENT REALIZATION

Material: Steel C 45 is used (according to DIN) product of foundry Ravne from Koroshka's Ravne, Republic of Slovenia. Machine: The experiment for measuring the average temperature is done in numerical control lathe type GILDEMEISTER M5S P= 1.85 - 25 KW number of rotations n=100-4000 [min.sup.-1] and feed s= 0.001-39.99 mm/rot. Metal cutting tool: Ceramic cutting plates MC2 are used 120712-120716-120720 product of HERTEL. It is used the holder IK.KS2NR-064 25x25 mm made by KENNAMETAL Company (original [chi]=85[degrees] turned 10[degrees]) with the following geometry: [chi]=75[degrees], [[chi].sub.1] = 15[degrees], [gamma] = -6[degrees], [lambda] = -6[degrees], [r.sub.[epsilon]] 1.2 - 1.6mm, [[gamma].sub.f] = -20[degrees], [b.sub.f] = 0.2mm, VB=0.00 mm.

Cutting plate holder is adjusted to the conditions for transporting thermo-electrical signal from the cutting plate. fig. 2.1. The equipment for registration of signals from the working material: HOTINGER'S Head (Salihu 2001)

Installation for the calibration of natural thermocouple C45-MC2, based on results, is obtained dependence between temperature and thermo voltage, as a fifth-order polynomial. Research apparatus: In order to set the average temperature during the cutting process, it is used the measuring apparatus.

[FIGURE 2.1 OMITTED]

Rings: They are made of the following dimensions [??] 170 x 80 x 25 mm. The processing was executed by changing the various independent sizes: cutting velocity (v), feed (s), cutting depth (a) and the nose radius (r) as shown on table 2.1, by using the first row four factors plan ([2.sup.4] + 4) (Salihu 2001).

3. ANALYSIS OF THE RESEARCH RESULTS

The obtained results out of the experiment realization are presented on table 3.1 and based on the data processing, the mathematical model 3.1 is obtained (Salihu 2001). The graphical interpretation of the model 3.1. is presented in fig 3.1 By analyzing the mathematical model and the graphic interpretations we can conclude as follows:

--the highest temperature will be at the chip's contact zone with the front surface because the largest amount of heat is concentrated here as a result of deformation and friction

T = 364.194 x [v.sup.0.188] x [s.sup.0.102] x [a.sup.0.0341] x [r.sup.-0.0865] 3.1

--in the cutting temperature influences except the cutting speed, that has a greater influence, also the feed. If the feed increases, the chip pressure on the tool will increase; along with it will increase the work too which is necessary for deformation. But as it is known, the coefficient of chip contraction decreases, and therefore the required work for deforming a 1 mm3 chip decreases. On the other hand, the friction of the back surface with the work piece does not change. Consequently, the cutting temperature increases when the cutting feed is increased but at a slower rate than to the velocity.

--when the cutting feed is increased, the contact of chip with the front face is improved the heating decline.

--it can be stated that the increase of the average temperature is a result of the increase of temperature on the back surface of the tool because of the increased friction between the processed surface and the tool's back surface.

--the cutting depth influences in the cutting temperature and this is seen from mathematical models and their graphical interpretation, because the pressure on the cutting edge length unit does not change. With the increase of the cutting depth the length of the edge that takes part in the cutting process is increased, and thereby the heat removes from the cutting zone.

--the geometry of tool influences on the cutting temperature, with the increase of the cutting angle the cutting forces increase and consequently the quantity of heat that is created at the cutting zone increases - that is the temperature increases.

--tool's material influences on the cutting temperature by starting off from two directions; first--the coefficient of its friction with the work piece and second from thermal conductivity (Aleksander 1976).

4. CONCLUSION

Out of the mathematical models analysis and graphical interpretations we can conclude:

[FIGURE 3.1 OMITTED]

--the change of the average temperature during the cutting process in the function of cutting parameters can be presented through gradual function,

--the largest influence on average temperature has the cutting velocity and cutting feed where during the research the maximal temperature value was 1102.75 0 C.

--the influence of cutting depth is lower in temperature during the cutting process.

--when the nose radius of the top cutting plate is increased, the temperature is decreased.

5. REFERENCES

Salihu, A. (2001), Research of machinability of cutting material with increased speed (Hulumtimi i peerpunueshmerise se materialit me prerje me shpejtesi te rritura), doctoral dissertation, Faculty of mechanical Engineering, Prishtine.

Stankov, J. (1982),Measurement technical basic, methods and experiments planification (Osnove merne tehnike,metode planiranja eksperimenata), Faculty of mechanical Engineering, Novi Sad..

Miltton C.Shav, (2005), Metal cutting principles, Arizona State University, Oxford New York.

Aleksander B,. (1976), Mechanical technology, volume I (Teknologjia mekanike, volumi I), Faculty of mechanical Engineering, Tirane.

Table 2.1. Factors levels during the investigation

 CHARACTERISTICS OF INDEPENDENT VARIOUS SIZES

 Level
Nr Note Code Maximal 1 Average 0 Minimal -1

1 v (m/min) X1 700,000 458,258 300,000
2 s (mm/rrot) X2 0.320 0,226 0,160
3 a (mm) X3 1,600 0,894 0,500
4 r (mm) X4 2,000 1,549 1.2

Table 3.1. Results of the investigation

 REAL PLAN OF MATRICA REZULTS

 v s a r T
Nr (m/min) (mm/rrot) (mm) (mm) ([degrees]C)

1 300.000 0.160 0.500 1.200 850.600
2 700.000 0.160 0.500 1.200 1020.700
3 300.000 0.320 0.500 1.200 905.600
4 700.000 0.320 0.500 1.200 1050.900
5 300.000 0.160 1.600 1.200 890.600
6 700.000 0.160 1.600 1.200 1070.800
7 300.000 0.320 1.600 1.200 942.300
8 700.000 0.320 1.600 1.200 1102.750
9 300.000 0.160 0.500 2.000 805.600
10 700.000 0.160 0.500 2.000 940.010
11 300.000 0.320 0.500 2.000 890.600
12 700.000 0.320 0.500 2.000 1050.400
13 300.000 0.160 1.600 2.000 840.700
14 700.000 0.160 1.600 2.000 980.400
15 300.000 0.320 1.600 2.000 930.010
16 700.000 0.320 1.600 2.000 1058.600
17 458.258 0.226 0.894 1.549 940.800
18 458,258 0.226 0.894 1.549 930.300
19 458.258 0.226 0.894 1.549 945.700
20 458.258 0.226 0.894 1.549 927.200