Microforming is a relatively new realm of manufacturing technology that addresses the issues involved in the fabrication of metallic microparts, i.e., metallic parts that have at least two characteristic dimensions in the sub-millimeter range. The recent trend towards miniaturization of products and technology has produced a strong demand for such metallic microparts with extremely small geometric features and high tolerances. Conventional forming technologies, such as extrusion, have encountered new challenges at the micro-scale due to the influence of ‘size effects’ that tend to be predominant at this length scale. One of the factors that shows a strong influence is friction. This paper focuses on the frictional behavior observed at various sample sizes during micro-extrusion. A novel experimental setup consisting of forming assembly and a loading stage has been developed to obtain the force-displacement response for the extrusion of pins made of brass (Cu/Zn: 70/30). This experimental setup is used to extrude pins with a circular cross-section that have a final extruded diameter ranging from 1.33 mm down to 570 microns. The experimental results are then compared to finite-element simulations and analytical models to quantify the frictional behavior. It was found that the friction condition was non-uniform and showed a dependence on the dimensions (or size) of the micropin. The paper also investigates the validity of using high-strength/ low friction die coatings to improve the tribological characteristics observed in micro-extrusion. Three different extrusion dies coated with diamond-like carbon with silicon (DLC-Si), chromium nitride (CrN) and titanium nitride (TiN) were used in the micro-extrusion experiments. All the coatings worked satisfactorily in reducing the friction and correspondingly, the extrusion force with the DLC-Si coating producing the best results.

1.
Peng
X.
,
Qin
Y.
, and
Balendra
R.
,
2004
, “
Analysis of Laser-heating Methods for Micro-parts Stamping Applications
,”
J. Mater. Process. Technol.
,
150
, pp.
84
91
.
2.
Saotome
Y.
,
Yasuda
K.
, and
Kaga
H.
,
2001
Microdeep Drawability of Very Thin Sheet Steels
,”
J. Mater. Process. Technol.
,
113
, pp.
641
647
.
3.
Saotome
Y.
, and
Okamoto
T.
,
2001
, “
An In-situ Incremental Microforming System for Three-dimensional Shell Structures of Foil Materials
,”
J. Mater. Process. Technol.
,
113
, pp.
636
640
.
4.
Saotome
Y.
, and
Iwazaki
H.
,
2001
, “
Superplastic Backward Microextrusion of Microparts for Micro-Electro-Mechanical Systems
,”
J. Mater. Process. Technol.
,
119
, pp.
307
311
.
5.
Cao
J.
,
Krishnan
N.
,
Wang
Z.
,
Lu
H.
,
Liu
W. K.
, and
Swanson
A.
,
2004
, “
Microforming — Experimental investigation of the extrusion process for micropins and its numerical simulation using RKEM
,”
ASME J. Manuf. Sci. Engng.
,
126
, pp.
642
652
.
6.
Geiger
M.
,
Kleiner
M.
,
Eckstein
R.
,
Tiesler
N.
, and
Engel
U.
,
2001
, “
Microforming
,”
CIRP Ann.
,
50
(
2
), pp.
445
462
.
7.
Engel
U.
, and
Eckstein
R.
,
2002
. “
Microforming — from Basic Research to it’s Realization
,”
J. Mater. Process. Technol.
,
125–126
, pp.
35
44
.
8.
Raulea
L. V.
,
Goijaerts
A. M.
,
Govaert
L. E.
, and
Baaijens
F. P. T.
,
2001
, “
Size effects in the processing of thin metal sheets
,”
J. Mater. Process. Technol.
,
115
, pp.
44
48
.
9.
Hauert
R.
, and
Patscheider
J.
,
2000
, “
From Alloying to Nanocomposites — Improved Performance of Hard Coatings
,”
Adv. Engng. Mat.
,
2
(
5
), pp.
247
259
.
10.
Veprek
S.
, and
Jilek
M.
,
2002
, “
Superhard Nanocomposite Coatings: From Basic Science Toward Industrialization
,”
Pure App. Chem.
,
74
(
3
), pp.
475
481
.
11.
Navinsek
B.
,
Panjan
P.
, and
Milosev
I.
,
1997
, “
Industrial Applications of CrN Caotings Deposited at High and Low Temperatures
,”
Surf. Coat. Technol.
,
97
(
1–3
), pp.
182
191
.
12.
Dohda, K., Tsutiya, Y., 2005, “Application of Thin Hard Coatings to Forming Tools,” Proc. of 5th Int. Conf. on Indust. Tools, Slovenia, April, pp. 153–158.
13.
Dohda, K., Kubota, H, and Tsutiya, Y., 2005, “Application of DLC Coating to Ironing Die,” Proc. of JSME/ASME Int. Conf. On Materials and Processing, Seattle.
14.
Gee
M. G.
, and
Wicks
M. J.
,
2000
, “
Ball Crater Testing for the Measurement of the Unlubricated Sliding Wear of Wear-resistant Coatings
,”
Surf. Coat. Technol.
,
133–134
, pp.
376
382
.
15.
Reisel
G.
,
Wielage
B.
,
Steinhauser
S.
, and
Hartwig
H.
,
2003
, “
DLC for Tool Protection in Warm Massive Forging
,”
Diamond and Related Materials
,
12
, pp.
1024
1029
.
16.
Podgornik
B.
,
Hogmark
S.
,
Sandberg
O.
, and
Leskovsek
V.
,
2003
, “
Wear Resistance and Anti-sticking Properties of Duplex Treated Forming Tool Steel
,”
Wear
,
254
, pp.
1113
1121
.
17.
Sato
T.
,
Besshi
T.
,
Tsutsui
I.
, and
Morimoto
T.
,
2000
, “
Anti-galling Property of a Diamond-like Carbon Coated Tool in Aluminum Sheet Forming
,”
J. Mater. Process. Technol.
,
104
,
21
24
.
18.
Panjan
P.
,
Cvahte
P.
,
Cekada
M.
,
Navinsek
B.
, and
Urankar
I.
,
2001
, “
PVD CrN Coating for Protection of Extrusion Dies
,”
Vacuum
,
61
, pp.
241
244
.
19.
Hara
K.
,
Ohtake
N.
,
Horita
K.
, and
Yamagata
A.
,
2004
, “
Variable-shape Extrusion of Aluminum Square Pipes Using DLC Coated Dies
,”
New Diamond and Frontier Carbon Technol.
,
14
(
6
),
331
340
.
20.
Avitzur
B.
,
1965
, “
Analysis of Metal Extrusion
,”
J. Engng. Indust.
,
87
(
1
), pp.
57
70
.
21.
Altan, T., Oh, S. and Gegel, L.H. (1983) Metal Forming: Fundamentals and Applications, American Society of Metals.
22.
Chanda
T.
,
Zhou
J.
, and
Duszczyk
J.
,
2001
, “
A Comparative Study on Iso-speed Extrusion and Isothermal Extrusion of 6061 Al Alloy Using 3D FEM Simulation
,”
J. Mater. Process. Technol.
,
114
, pp.
145
153
.
23.
Li
L.
,
Zhou
J.
, and
Duszczyk
J.
,
2004
, “
Prediction of Temperature Evolution During the Extrusion of 7075 Aluminum Alloy at Various Ram Speeds by Means of 3D FEM Simulation
,”
J. Mater. Process. Technol.
,
145
, pp.
360
370
.
24.
Hsu
T-C.
, and
Huang
C-C.
,
2003
, “
The Friction Modeling of Different Tribological Interfaces in Extrusion Process
,”
J. Mater. Process. Technol.
,
140
, pp.
49
53
.
25.
Mori
H.
, and
Tachikawa
H.
,
2002
, “
Increased Adhesion of Diamond-like Carbon-Si Coatings and its Tribological Properties
,”
Surf. Coat. Technol.
,
149
, pp.
225
230
.
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