Materials Science Forum
ISSN: 1662-9752, Vols. 704-705, pp 1175-1179
doi:10.4028/www.scientific.net/MSF.704-705.1175
© 2012 Trans Tech Publications, Switzerland
Online: 2011-12-06
Study on Blanking Force of Fine-blanking with Negative Clearance and
Common Blanking for AISI-1045 through Simulation and Experiment
Methods
W.F. Fan1, a, F. Li2, b
1
Department of Electric and Information Engineering, Zhongyuan University of technology,
2
College of Information & Business, Zhongyuan University of technology,
ZhengZhou, 450007, P.R. China
a
[email protected] , b [email protected],
Keywords:Negative clearance, Blanking force, Simulation, Experiment.
Abstract.Fine-blanking with negative clearance is a kind of fine blanking processes. The punch
size of fine-blanking with negative clearance is larger than the die size. The paper does lots of
simulations for the changes of blanking force in fine-blanking with negative clearance and common
blanking by DEFORM software, and the blanking force curves are gained by these experiments.
The changing principle of blanking force and internal material is obtained through the simulation
and experiments. The result shows that simulation blanking force of AISI-1045 is lager than the
actual blanking force. According to the curves derived from experiments, we can see that the
maximum blanking force of fine-blanking with negative clearance is higher than common blanking
force. Compared with fine-blanking with negative clearance, the common blanking force reduces
faster after the blanking force reaches maximum value. The experiment result shows that the force
of fine-blanking with negative clearance under a smaller blanking clearance is a bit bigger than the
force of common blanking force, and the blanking quality of fine-blanking with negative clearance
is much better than that of common blanking. Cracks can be closed effectively by the special
squeeze forming in fine blanking with negative clearance. Then, the crack can not expand
continuously, and the bonding force is enhanced. The squeeze forming can restrain intergranular
deformation and reduce the damage. However, the stretch forming easily leads to the inner crack
and defect of materials. By means of the analysis on experimental curves, the paper further studies
the changing law of fine-blanking with negative clearance blanking force.
Introduction
With the continuous development and application of punching technology, more and more parts are
made by fine-blanking with negative clearance process [1]. This process can not only ensure the
sufficient strength of parts made by punching, but also can improve the quality of the parts cross
section made by punching, enhance labor productivity and reduce production cost. Currently
fine-blanking with negative clearance process has been widely used with obtaining good economic
results.
This paper covers: simulate the fine-blanking with negative clearance and common blanking on
AISI-1045, and obtain the change curve of blanking force in fine-blanking with negative clearance
and common blanking by experiment. Through the simulation and experiment, this paper focuses
on researching the change law of blanking force and internal material.
Common blanking experiment and fine-blanking experiment with negative clearance
The section obtains the punching parameters for different punching force and die stroke through
researching the common blanking experiment and fine-blanking experiment with negative clearance
on AISI-1045. Firstly the sheet is cut into 30 mm × 30 mm and cleaned by alcohol. Then the
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Physical and Numerical Simulation of Material Processing VI
piezoelectric crystal sensor, blanking die, data acquisition instrument about force and stroke are
installed onto hydraulic press machine and bench, and adjusted correctly; put the sheet on the top of
the concave die, punch and run the data acquisition device [2]. After the test, collect and analyze the
punching datas.
Blanking material is AISI-1045 in this experment and the blanking parameters properties are in
the following table 1.
Table 1. The blanking parameters
Blanking
Plate
Punch
Blanking
Allowance
Fillet
Blanking
Material
thickness/mm
diameter/mm
clearance/mm
Value/mm
die/mm
speed/mm/s
AISI-1045
4.0
10.0
-0.2
0.2
0.2
20
AISI-1045
4.0
9.7
+0.1
0.2
0.2
20
Fig4. The blanking force curve of fine-blanking with negative clearance
Fig5. The blanking force curve of common blanking
Fig.4 is the blanking force-punch stroke curve of 4mm thick AISI-1045 steel under -0.2
clearance. From the picture we can easily know that the change of fine-blanking with negative
clearance force could be divided into three stages. Before maximum the blanking force has
experienced two phases of rising. In the first stage, the blanking force is up to 27.4E3N(F1). In the
second stage, the blanking force is up to 37.4E3N(F2) quickly and then reaches maximum
40.0E3N(F) slowly. The third stage the blanking force declines slowly.
Fig.5 is the common blanking force-punch stroke curve of 4mm thick AISI-1045 steel. As shown
in Figure 5 above, the rising process of blanking force could be divided into three stages , too. In the
first stage, the blanking force is up to 23.0E3N, the second stage up to 35.0E3N and then reaches
maximum 37.5E3N(F) slowly. However, the falling stage, which including two periods, is different
from that of fine-blanking with negative clearance. The blanking force declines to 20E3N(F4) , hold
for some time, and then continuely declines .
Table 2. The changes of actual blanking force
AISI-1045
F1[N]
F2[N]
F [N]
F4[N]
Fine-blanking with negative
27.4E3
37.4E3
40.0E3
clearance
Common blanking
23.0E3
35.0E3
37.5E3
20E3
Increasing
19.1%
4%
6.7%
As can be seen from Table 2, the blanking force of fine-blanking with negative clearance is
bigger than the common blanking one. But unfortunately, the multiple-output value is small. The
largest blanking force of fine blanking with negative clearance was improved by about 6.7%
Materials Science Forum Vols. 704-705
1177
compared with the maximum blanking force of ordinary blanking. Fine-blanking with negative
clearance gets better blanking quality by using smaller force under a smaller blanking clearance
compared to that of common blanking. This is one of its advantages.
From Figure 4 and Figure 5, we can see that the blanking force and punch stroke curves of the
AISI-410 stainless steel are rather steep. Both positive and negative clearance blanking, blanking
force increase with punch stroke in the first stage, and punch contacted with materials but not punch
into the material. In the second stage, the blanking punch crashed into the material at inflection
point of curve. Through blanking force bearing area of material reduced, as long as the effect of
work-hardening of the material over the effect of a shear stress area reduced, punching force will
continue to increase. When two effects are equal fine-blanking force with negative clearance
reached the maximum. After blanking force over the maximum value, when the effect of a shear
stress reduction area is more than the effect of material work hardening, blanking force starts
decreasing.
Simulation of fine-blanking with negative clearance and ordinary blanking
Fig6. The blanking force curve of fine-blanking with negative clearance simulation
Fig7. The blanking force curve of common blanking simulation
Figure 6 is the simulation curve of fine blanking force with negative clearance. From Figure 6
we can see that the change of blanking force with negative clearance are divided into three stages.
Blanking force increased to the maximum after it experienced two stages. In the first stage blanking
force (F1) increased to 52.3E3N. In the second stage blanking force increased slowly to the
maximum (F) that is 63.0E3 N.
Figure 7 is a curve of common blanking force and punch stroke. From Figure 6 we can see that
common blanking force increasing are also divided into three stages. Blanking force increased to
48.0E3N in the first stage. In the second stage blanking force increased slowly to the maximum
(63.0E3 N). Then blanking force began to decrease after increasing to maximum. This process was
similar to that of fine blanking force with negative clearance. The blanking force decreasing process
of common blanking was divided into two stages. After blanking force decreasing to F4(38E3N),
blanking force hold for a period and continued to keep decreasing trend, but the descending speed
of blanking force is slower than the common one [4].
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Physical and Numerical Simulation of Material Processing VI
Table 3. The changes of blanking force in Simulation
AISI-1045
F1[N]
F2[N]
F [N]
52.3E3
63.0E3
63.0E3
Common blanking
48.0E3
62.0E3
62.0E3
Increasing
9%
1.6%
1.6%
Fine-blanking with negative clearance
F4[N]
38.0E3
Table 3 shows the changes of blanking force in blanking with negative clearance. From the
contrast with table.1 we can see that the blanking force in blanking with negative is bigger than the
common one, but the improve law are basically the same. F1 has a bigger increase and F2,F has a
less increase. In addition, from the table 3 we can also see the maximum blanking force in blanking
with negative clearance is bigger than the common one.
Fig.8 and Fig.9 show the final displacements of fine-blanking with negative clearance and
common blanking. In common blanking (Fig.8), the sheet metal material near the edge at the punch
is stretched and teared along the blanking direction to the smaller area between the die and concave
die. The sheet metal punch away from the edge of die move around the center of a point of sheet.
The final displacements of AISI-1045 sheet due to the stretching and tearing of die, which leading
to the sheet warp. Figure 9 is the final displacement of sheet metal when the punch reaches the
allowence value. From the figure we can see that the sheet metal material near the edge at the punch
is squeezed under oblique and the sheet metal material distant from the edge at the punch is
squeezed away from the die. Apparently, fine-blanking with negative clearance is extrusion forming,
while common blanking is stretch forming.
The blanking resistance of punch find expression in the maximum of blanking force, which is
related to total blanking area. The maximum blanking force include the work hardening force and
fracture force principally[4]. Cracks can be closed effectively by the special squeeze forming. The
crack can not be expanded continuously and the bonding force enhanced. The squeeze forming can
restrain intergranular deformation and reduce the damage. However, the stretch forming easily lead
to the cracks and defects of materials. In consequence, the blanking force of fine-blanking with
negative clearance is bigger than the common blanking one.
Fig8. Each node displacement of common blanking simulation
Fig9. Each node displacement of fine-blanking with negative clearance simulation
Materials Science Forum Vols. 704-705
1179
Table 4. The blanking force contrast between actual and simulation
F1[N]
F2[N]
F [N]
F4[N]
AISI-1045
Simulation
Actual
Increasing
Simulation
Actual
Increasing
Simulation
Actual
Increasing
52.3E3
27.4E3
91%
63.0E3
37.4E3
70%
63.0E3
40.0E3
58%
48.0E3
23.0E3
109%
62.0E3
35.0E3
77%
62.0E3
37.5E3
65%
Simulation
Actual
Increasing
38.0E3
20E3
90%
Fine-blanking with negative
clearance
Common blanking
Increasing 81.3% on average
100%
73.5%
61.5%
90%
The simulated and experimental results are different in the table. First of all, the rising blanking
force simulated is divided into two phases, while the actual curve is divided into three phases, added
a stage from F2 to F(the max). This is mainly because the intervolving of material internal
organization makes work-hardening. When the effect of work hardening is higher than the effect of
shear area reduced, the mechanical properties has undergone tremendous changes and the plasticity
decreased, hardness increased, the physical properties of materials changed, so that the blanking
force can not be rised on the original trend continuously and cause a sudden increase. The
simulation software considered the changes of blanking force and shear area reduced only, without
other properties changes. In addition, from the contrast we can see that the changes of actual
blanking force is less stable than the changes of simulated blanking force, which is also due to the
changes of mechanical properties. Second, the reduction velocity of blanking force simulated is
faster than the actual one. This is mainly because the material friction coefficient in simulation is set
smaller (in this simulation is 0.2)[5]. Besides, have other relations with the internal impurities in
materials, temperature, sheet metal mesh, etc. Third, the simulated blanking force is bigger than the
actual blanking force. As can be seen from the table 4, the simulation increased by 81.3% on
average than the actual, the biggest is 61.5%.
Conclusions
An AISI-1045 simulation and experiment comparative analysis of fine-blanking with negative
clearance and common blanking are adopted in this paper. The results obtained are summarized as
follows.
The blanking force simulated by DEFORM is bigger than the actual one, increases by an average
of 81.3%.
The maximum blanking force in fine-blanking with negative clearance adopted by experiment is
bigger than the common blanking one, improves 6.7%.
The descending rate after maximumin in common blanking is faster than fine-blanking with
negative clearance.
Reference
[1] Qin Siji, Peng Jiageng:Metal Forming Technology(2002):P.4-7.
[2] F.Robert. Fine Blanking Process for Thick Plate(China Machine Press,Beijing1991).
[3] Wu Shidun. Blanking Technology(Northwestern Polytechnical University Press, Xi An 1987).
[4] Hu Shiguang, Chen Hezheng. Cold Forming Sheet Metal Engineering Analysis (Beijing
University of Aeronautics and Astronautics Press, Beijing 2004).
[5] Xiu Feng, Li Qingxiang. Design of Precision Machinery(Tsinghua University Press, Beijing
2005).
Physical and Numerical Simulation of Material Processing VI
10.4028/www.scientific.net/MSF.704-705
Study on Blanking Force of Fine-Blanking with Negative Clearance and Common Blanking for AISI1045 through Simulation and Experiment Methods
10.4028/www.scientific.net/MSF.704-705.1175