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学生の研究活動報告−国内学会大会・国際会議参加記 30

国際会議 ICPE 2018 に参加して2.2 Experimental method
A large-size 10-mm-daimaeter tool (Fig. 1) was pre-右川太一郎

Taichiro UKAWA
機械システム工学専攻修士課程

2018 年度修了

pared to investigate the cutting phenomena in detail anddetermine the damage mechanism. A standard righthand tool was also prepared. The same cutting phenomena were expected to see in both tools, so the flute

1. Preface

shape was the same with only a difference in size fromI participated in “17th International Conference on

the small-diameter end mill. The workpiece material

Precision Engineering” held in Kamakura, Kanagawa

was hardened die steel (JIS: SKD61, HRC53). Table 1

Prefecture on November 12 to 16, 2018. I made an oralshows the cutting conditions. A high-precision machin-presentation on the subject “Experimental Investigations

ing center was used for the cutting test and the cuttingon Micro-end-milling of Hardened Die Steel Damage

force with a dynamometer (Fig. 2).

Mechanism of Left −hand Helix Tool−”.

Cutting force Fze(t) which is absolute value was estimated. Time t was set to zero at the moment when the2. Presentation summary

cutting edge contacted the workpiece. Here, the cutting

2.1 Introduction

force was proportional to section area A(t) in the chip

Precision parts are in high demand in the machinery,

before deformation. Specific cutting resistance Kz waselectronic, and medical industries. Precision machining

estimated by dividing cutting force Fz(t) measured intechnologies are used in micromachining to manufac-

the z direction by section area A(t) when the cutting

ture these parts. Meanwhile, the demand for micro-endmilling for products is increasing, leading to further research and development. Therefore, this research focuses on mechanical machining using a micro-end-mill.
Experiments about a variety of cutting phenomena that(a) Left-hand helix tool

occur during actual machining processes were conducted to achieve high machining accuracy, highfinished-surface quality, and long tool life. In the examinations, micromachining using a left-hand helix toolachieved high-accuracy and high-grade machining. Finishing with a left-hand helix tool reduces burrs and increases machining accuracy. However, re-biting ofchips occurred during cutting. In this research, the damage mechanism in the micro-end-milling of hardened
die steels using a left-hand helix tool was investigated.
Cutting experiments were conducted to measure cutting
force and observe the removed chips.

― ４５ ―(b) Right-hand helix toolFig. 1End-mills

Table 1Fig.2 Schematicof cutting test

Cutting condition

Spindle speed Ns min−1

500 (15.7 m/min)Feed rate ftμm/tooth300

Radial depth of cut Rdμm

200

Axial depth of cut Ad mm

10Cutting length L m

0.5Cutting direction

Up-cutCoolant

Dry airforce was constant.
2.3 Results and discussion
Figure 3 shows a comparison of the cutting forces
measured during one tool rotation. Two peaks according to the number of flutes in the end-mill can be confirmed for the both tools. The changes in cutting force
Fx and Fy are almost same. However, the direction of Fzis different. Fz with a negative direction, which is the(a) Left-hand helix tool(b) Right-hand helix toolFig. 3 Comparison of cutting force measured
during one tool rotation.

direction of the tool pushing the workpiece, can bemeasured with the tool with left-helix angle flutes.
However, the positive direction force can be measured
with the tool with right-helix angle flutes. Thus, measurement of the force is governed by the helix angle direction of the flutes. Figure 4 shows a comparison of
cutting force Fz during one flute cutting. Here, the ab-(a) Left-hand helix toolFig. 4solute value of the left-hand helix tool was evaluated in(b) Right-hand helix tool

Evaluation of cutting forces.

the estimation. With the left-hand helix tool, a small
bump was founded in the end of the constant part ofthe section area and a delay in decreasing cutting force.
However, such tendency was not observed with theright-hand helix tool, while the cutting force changed
with the section area was found. The small bump might
be caused by material stock on the cutting flutes andthe delay might be due to tool deformation. Figure 5
shows scanning electron microscope (SEM) images of
the removed chips. The material stock could not be(a) Left-hand helix tool

seen at the bottom part of the chip from the left-handFig. 5helix tool. On the other hand, it was not observed with(b) Right-hand helix tool

SEM images of removed chips.

the right-hand helix tool. These phenomena might pre-phenomenon might prevent removal of chips and cause

vent the need to remove chips and cause tool damage.

tool damage.

The influence of this tendency is more important inmicro-end-milling.

3. Acknowledgement
I would like to express my sincere gratitude to Associate Professor Keiji OGAWA for giving me an oppor-

2.4 Summary
Material stock at the bottom part of the chip was observed with the left-hand helix tool. On the other hand,tunity to participate in the international conference andgiving me useful advices.

it was not observed with the right-hand helix tool. This
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