Experimental investigation of carbon steel in high speed cutting.

Kulenovic, Malik ; Begic, Derzija ; Cekic, Ahmet 等

Abstract: In this paper are presented the experimental results in high speed face milling. Influence of the cutting speed and the feed per tooth on the surface roughness of the carbon G70 steel during high cutting speeds is analyzed. Experimental investigations were conducted in down-cut and up-cut face milling, with the following parameters: cutting speed from 500 m/min to 1500 m/min and feed per tooth from 0.05 mm to 0.15 mm. The results show that, the roughness of machined surfaces decrease with the increase of cutting speed in the domain of variation of cutting speed. Investigations also show that the feed per tooth has great influence on the roughness of machined surface. Surface roughness increases with the increase of feed per tooth.

Key words: high speed milling, surface roughness, cutting speed, feed per tooth.

1. INTRODUCTION

The significance for high speed machining and especially high speed milling in production has increased since new machines and tools enable the possibility to reduce process time on one hand and to improve work piece accuracy and work piece surface on the other hand (Dudzinski et al., 2002).

Manufacturing time, price and quality of made product directly depend of machining parameters such as cutting speed, feed and depth of cut. Due to their higher productivity and throughput, high-speed cutting technologies and especially high-speed milling are commonly use in aerospace industry as well as in die and mold manufacturing for the machining of work pieces with high material removal rates (Brinksmeier et al., 2002)

In the paper are conducted the experimental investigations of the influence of cutting speed and feed per tooth on the roughness of machined surface during high-speed face milling of carbon G70 steel.

2. EXPERIMENTAL DETAILS

The experimental investigations of the influence of machining parameters (cutting speed and feed per tooth) on the surface roughness during ultra high-speed face milling (up-cut and down-cut) of carbon G70 steel conducted on the Faculty of Mechanical Engineering in Sarajevo. Investigations are conducted on the machining VBS system, figure 1.

[FIGURE 1 OMITTED]

Machining VBS system by the adaptation of the stiff universal milling-drilling machine constructed, by building of the modern high-speed components (high speed motor spindle, linear motors and servomotor and so on) that have primary characteristics: flexibility, high productivity and modularity. Problems in the application of high speed machining include issues of tooling, balancing, thermal and dynamic behaviors, and reliability of machine tools (Chi-Wei et al., 2002). The process of the machining VBS system setting up was accompanied by a number of expert and non-standard practices as well as investigations regarding the rigidity and vibration that played an important role in the selection of the mounting (Kulenovic et al., 2005).

During implementation of the experimental investigations the milling tool with exchangeable inserts of hard metal used as the cutting tool, manufacturer SANDVIK Coromant (www.sandvik.com). The cutting tool is balanced for speed up to 27000 rpm. The diameter of the milling tool is 20 mm. The cutting tool is clamped to the motor spindle HSM by a tool interface HSK 40E, and it is produced in Technical office of Sandvik Coromant in Germany by submission of the authors of this paper.

Experimental investigations conducted in down-cut and upcut face milling, with the following parameters: cutting speed from 500 m/min to 3000 m/min and feed per tooth from 0,05 mm to 0,15 mm. Depth of milling and width of milling are 0,30 mm and 12 mm, respectively. The machining process carried out such as always just one tooth of cutting tool was in engagement with work piece. Cutting tests carried out under dry machining conditions. A new cutting edge for each machining experiment is used.

For measuring of surface roughness, the modern device Perthometer Concpet is used. The examined steel was the carbon G70 steel. The mechanical properties and the chemical composite of the examined steel are given in table 1.

3. RESULTS AND DISCUSSION

Graphical presentations the influence of the cutting speed on the roughness of machined surface during high-speed downcut and up-cut face milling of the examined steel are done in: figure 2 for the feed per tooth of 0,05 mm, figure 3 for the feed per tooth of 0,10 mm and figure 4 for the feed per tooth of 0,15mm.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

According to diagrams in figures 2, 3 and 4, the roughness of machined surface decreases with the increase of cutting speed during high-speed face milling. In some cases, the roughness remained constant after reaching a specific cutting speed and further increases had no effect on the roughness.

Figure 5 and figure 6 show that the feed per tooth has great influence on the roughness of machined surface. Surface roughness increases with the increase of feed per tooth. During machining of this steel obtained the lowest roughness in the following machining parameters: the tool diameter 20 mm, upcut milling, the cutting speed of 1500 m/min, the feed per tooth of 0,05 mm, the cut of depth of 0,30 mm and the width of cut of 12 mm. The value of roughness parameters were: Ra=0,157 [micro]m and Rz=0,625 [micro]m.

4. CONCLUSION

According to the reported results it is possible to derive the following conclusions:

* The surface roughness decreases with the increase of cutting speed during high-speed face milling of the examined steel.

* The surface roughness increases with the increase of feed per tooth.

* Furthermore, it is concluded that milling direction (down-cut and up-cut) has no influence on roughness of machined surface for examined material used in the experiment.

5. REFERENCES

Brinksmeier, E.; Mayr, P.; Lubben, T.; Pouteau, P. & Diersen, P. (2002). Influence of material properties on surface integrity and chip formation in high speed turning, In: Metal Cutting and High Speed Machining, Dudzinski, D.; Molinari, A. & Schulz, H., (first), (31-40), Kluwer Academic/Plenum Publishers, New York

Chi-Wei, L.; Jay, F.T. & Kamman, J. (2002) Experimental studies of high speed thermo-mechanical-dynamic behaviors of motorized machine tools spindles, In: Metal Cutting and High Speed Machining, Dudzinski, D.; Molinari, A. & Schulz, H., (first), (455-464), Kluwer Academic/Plenum Publishers, New York.New York

Dudzinski, D.; Molinari, A. & Schulz, H. (2002). Metal Cutting and High Speed Machining, Kluwer Academic/ Plenum Publishers, ISBN 0-306-46725-9, New York

Kulenovic, M.; Goja, Z.; Cekic, A. & Halilagic, D. (2005). Integral access of the machining system development for high speed machining, Proceedings of the 10th International Scientific Conference on Production Engineering, pp 45 -53, Lumbarda, June 2005

Main catalogue Sandvik Coromant, Available from: http://www.sandvik.com, Accessed. 2007-07-16.

Table 1. Mechanical properties and chemical composite of the
carbon G70 steel

 Mechanical properties

Tensile strength Yield strength Hardness
 (N/[mm.sup.2]) (N/[mm.sup.2]) HRc

 734,71 506,13 30

 Chemical composite, %

C Si Mn Cr S P Cu Ni
0,68 0,25 0,78 0,10 0,02 0,02 0,08 0,03