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Effect of the blank-holding load on the drawing force

in the deep-drawing process of cylindrical and square cups

Lucian LAZARESCU 1a, Ioan NICODIM 1b, Dan Sorin COMSA 1c

and Dorel BANABIC 1d *

1CERTETA Research Centre, Technical University of Cluj-Napoca, Cluj-Napoca, Romania

a lucian.lazarescu@, b ioan.nicodim@, c dscomsa@, d [email protected]

Keywords: Deep-drawing, Punch force, Variable blank-holding load, Sheet metals.

Abstract. In this study, the influence of the blank-holding force (BHF) on the drawing force (DF)

in the deep-drawing process of cylindrical and square cups has been investigated experimentally.

For this purpose, different constant and variable BHFs have been applied to AA6016-T4 aluminum

alloy and DC04 steel sheets during the forming process. It has been observed that an increased

constant BHF leads to an increase of DF. On the other hand, the variable BHF approach, in which

the BHF decreases in six steps throughout the punch stroke, reduces the DF.

Introduction

In the deep-drawing process a lower drawing force (DF) is always desirable in order to have

minimum energy consumption. There are many factors that affect DF, such as the friction between

blank and tools, the lubrication conditions, the tool geometry, the punch–die clearance, and the

blank-holding force (BHF). Among these factors, BHF plays a key role. BHF has the role to prevent

the wrinkling. A higher BHF, however, leads to an increase of the friction force between the blank

holder and the blank in the flange area, which implicitly leads to the increase of DF, and, in extreme

cases, it may lead to tearing. On the other hand, a lower BHF will cause wrinkling. Therefore, it is

important to know the effect of BHF on DF as well the conditions in which the DF can be reduced

by adjusting BHF [1]. Studies conducted by other researchers show that BHF can be a temporal

variable [2] or temporal and spatial variable [3], i.e. variable in time as well as along the contour of

the blank [4]. Moreover, the BHF variation can be defined before starting the forming process or it

can be adjusted during the process, depending on the available equipment. Most systems which use

the spatial variable BHF are integrated into the tool and are thus independent of the press: Wei [5]

uses a dual layer blank holder in which a pattern of small pins can be inserted. Yagami [6] presents

a segmented blank holder with 108 individually controllable actuators.

One of the difficulties in the application of variable BHF consists in finding the optimal BHF

evolution. Kitayama [7] classify the strategies for finding the BHF evolution in two categories:

those based on a closed-loop type algorithm and those based on a response surface methodology.

Tommerup [8] presents a die with flexible blank holder which is used for drawing rectangular parts.

Under the influence of a hydraulic pressure applied on the flexible blank holder in four places, this

element is locally deformed and allows the application of a pressure in specific areas of the blank.

BHF is adjusted using a feedback control system [9]. In order to reduce the friction force between

the blank and blank holder, a pulsed force can be superimposed over the BHF. Iwamatsu [10] has

analyzed such effect on the formability of titanium alloys.

In this paper, the effect of constant and time variable BHF is investigated in the deep-drawing

process of cylindrical and square cups. The experiments on AA6016-T4 aluminum alloy and DC04

steel sheets are performed using an Erichsen universal sheet metal testing machine, which allows

setting of constant as well as variable BHFs.

Applied Mechanics and Materials Vol. 760 (2015) pp 379-384 Submitted: 2014-08-10© (2015) Trans Tech Publications, Switzerland Revised: 2014-09-08doi:10.4028/www.scientific.net/AMM.760.379 Accepted: 2014-09-08

Online: 2015-05-18

All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TransTech Publications, www.ttp.net. (ID: 141.211.4.224, University of Michigan Library, Media Union Library, Ann Arbor, USA-19/06/15,09:30:54)

http://dx.doi.org/10.4028/www.scientific.net/AMM.760.379http://www.ttp.net

Tested materials and experimental procedures

Materials. Two sorts of metallic sheets have been chosen to perform the study in this paper: an

AA6016-T4 aluminum alloy, with the nominal thickness 1 mm and a low carbon steel sheet of

grade DC04 with the nominal thickness 0.85 mm. The mechanical parameters of these materials

have been determined by tensile tests using a Zwick/Roell machine, model Z150. Table 1 shows the

mechanical properties obtained from the tensile tests [11].

Table 1 Mechanical properties of the materials

Material Rp0.2 [MPa] Rm[MPa] E[GPa] r [-] n [-] K[MPa]

AA6016-T4 158.070 264.809 64.880 0,552 0.239 479.714

DC04 196.241 309.210 170.920 1.954 0.209 526.759

Experimental equipment. The deep-drawing of cylindrical and square cups have been carried

out using an Erichsen universal sheet metal testing machine, Model 142-20. The machine is

equipped with various die sets that can be changed to perform different tests. The machine software

called “MES” has been used both for process control and for the acquisition of the following data:

drawing force, blank-holding force and punch stroke. The geometry and dimensions of the tools

used in the deep-drawing experiments are shown in Figures 1 and 2.

Fig. 1. Tool geometry and dimensions for deep-drawing of cylindrical cups

Fig. 2. Tool geometry and dimensions for deep-drawing of square cups

For the deep-drawing of cylindrical cups (Fig. 1) the tool dimensions are the same for both

AA6016-T4 aluminum alloy and DC04 steel sheets except the diameter of the drawing die (Dd),

which is adapted to the thickness of the metallic sheet. For this, two drawing dies have been used.

For the aluminum alloy sheet, with the nominal thickness of 1 mm, a drawing die with the diameter

Dd = 52.82 mm has been used, which provides a clearance of 1.41 mm between punch and die. In

380 Advanced Technologies in Designing and Progressive Development ofManufacturing Systems

the case of the DC04 steel sheet with the nominal thickness of 0.85 mm, the die diameter is Dd =

52.38 mm. As a result the punch-die clearance is 1.19 mm.

In the case of the tools used for the deep-drawing of square cups (Fig. 2), the dimensions are also

the same for the two sorts of metallic sheets, except for the die edge length (Ad) and die corner

radius (rd). By adopting two different die edge lengths, a clearance of 1.45 mm for the AA6016-T4

aluminum alloy and 1.20 mm for the DC04 sheet material are provided between the die and punch.

In order to ensure these punch-die clearance values, two drawing dies with appropriate dimensions

have been used.

Procedure. In order to study the influence of the blank-holding force on the punch force, two

kinds of BHF were considered: constant and time variable (Table 2). Two reference values of the

constant BHF have been used for each material, both for cylindrical and square cups. Table 2 also

lists the initial values of the time variable BHF. Starting from these initial values, BHF is decreased

in six increments throughout the punch stroke, as discussed in the results section for each particular

case. The die and sheet have been lubricated with graphite grease. The testing speed has been set to

30 mm/min in all cases.

Table 2. Experimental plan for studying the effect of the blank-holding force (BHF) on the

drawing force (DF)

Material BHF [kN] - Cylindrical cups BHF [kN] - Square cups

AA6016-T4

10 (constant) 6 (constant)


13 (variable) 9 (variable)

DC04

13(constant) 10 (constant)


13 (variable) 19 (variable)

Experimental results

Cylindrical deep-drawn cups. The results of the deep-drawing experiments of cylindrical cups for

the AA6016-T4 aluminum alloy are shown in Figure 3.

Figure 3.a shows the evolution of DF as a function of punch stroke for two values of constant

BHF: 10 kN and 13 kN. The constant BHFs used in these experiments are superimposed on the

same diagram (Fig. 3.a). From this diagram one may observe that when the BHF increases from 10

to 13 kN, the DF vs. punch stroke curve moves slightly to higher DF values. In this case, the

maximum DF increases from 35.02 to 35.88 kN. This increase in DF can be attributed to the friction

force between the blank and blank holder which increases when BHF increases.

Punch stroke [mm]

0 5 10 15 20 25 30 35

Forc

e (D

F o

r B

HF)

[kN

]

0

5

10

15

20

25

30

35

40Circular cupsAA6016-T4

DF for BHF=13 kN

BHF=10 kN

BHF=13 kN

DF for BHF=10 kN

Punch stroke [mm]

0 5 10 15 20 25 30 35

Forc

e (D

F o

r B

HF) [k

N]

0

5

10

15

20

25

30

35

40Circular cupsAA6016-T4

Variable BHF

BHF=10 kN (constant)

DF for variable BHF

DF for constant BHF

(a) – constant BHF (b) – constant and variable BHF

Fig. 3. Drawing force in deep-drawing of cylindrical cups for the AA6016-T4 aluminum alloy

Applied Mechanics and Materials Vol. 760 381

Figure 3.b compares the DF versus punch stroke curve recorded in conditions of a constant a

blank-holding force (BHF=13 kN) with that obtained using a variable BHF. On this diagram are

also shown the trajectories of constant variable BHFs, respectively, used in these experiments. From

this diagram one can observe that the variable BHF has little effect on the DF.

Figure 4 shows the results of deep-drawing experiments of cylindrical cups for the DC04 steel.

Figure 4.a shows the evolution of DF as a function of the punch stroke for constant BHFs: 13 and

19 kN, respectively. From this diagram one may notice that when BHF increases from 13 to 19 kN

the curve moves to higher DF values and the maximum DF increases from 42.57 to 45.32 kN.

Figure 4.b compares the DF vs. punch stroke curve obtained in the case of applying a constant

BHF of 13 kN with that recorded in the conditions of a variable BHF whose initial value is also set

on 13 kN. It can be observed that by adopting a time variable BHF, DF decreases after reaching its

maximum value. At this stage of the deep-drawing process, BHF decreases significantly and this

can explain the decrease in the DF. One may also notice that the maximum DF decreases from

45.32 to 40.24 kN.

Punch stroke [mm]

0 5 10 15 20 25 30 35

Forc

e (D

F o

r B

HF

) [k

N]

0

10

20

30

40

50Circular cupsDC04 DF for BHF=13 kN

DF for BHF=19 kN

BHF=19 kN

BHF=13 kN

Punch stroke [mm]

0 5 10 15 20 25 30 35

Forc

e (D

F o

r B

HF

) [k

N]

0

10

20

30

40

50Circular cupsDC04

BHF=13 kN (constant)

Variable BHF

DF for variable BHF

DF for constant BHF


Fig. 4. Drawing force vs. punch stroke during the deep-drawing process of cylindrical cups made

from DC04 steel

Square deep-drawn cups. Figure 5 shows the results obtained from the deep-drawing

experiments involving AA6016-T4 square cups. Figure 5.a shows the effect of a constant BHF on

DF. As in the previous cases, one may observe that the increase in BHF leads to an increase in DF.

When BHF increases from 13 to 19 kN, the maximum DF increases from 32.87 to 33.90 kN.

Punch stroke [mm]

0 5 10 15 20 25 30 35 40

Dra

win

g f

orc

e [k

N]

0

5

10

15

20

25

30

35

BHF=6kN

BHF=9kN

Square cupsAA6016-T4

Punch stroke [mm]

0 5 10 15 20 25 30 35 40

Forc

e (D

F o

r B

HF

) [k

N]

0

5

10

15

20

25

30

35Square cupsAA6016-T4

DF for variable BHF

DF for constant BHF

Variable BHF

BHF=9 kN (constant)


Fig. 5. Evolution of DF in deep-drawing of AA6016-T4 square cups


Figure 5.b shows the effect of a variable BHF on DF. As can be noticed, in the first stages of the

drawing process (up to 10 mm punch stroke) the variable BHF coincides with the constant BHF of

9kN. As a consequence, the DF is not influenced by the variable BHF. After the first 10 mm of

punch stroke, the variable BHF begins to decrease which leads to a decrease of DF. In this case, by

applying a variable BHF, the maximum DF decreases from 33.90 (constant BHF) to 33.54 kN.

Figure 6 shows the effect of constant and variable BHFs on DF in the deep-drawing process of

DC04 square cups. From Figure 6.a, one may notice that as the BHF increases from 10 to 13 kN,

the maximum DF increases from 39.27 to 39.82 kN. As one may notice from Figure 6.b, up to a 10

mm punch stroke the variable BHF has the same value as the constant BHF and there is no effect on

DF. After the value of 10 mm punch stroke, the variable BHF decreases and this leads to a decrease

of DF. By applying a variable BHF, the maximum DF decreases from 39.82 to 38.44 kN. This

decrease is more significant after the maximum value of DF. The reason for this behavior is that, at

this stage of the deep-drawing process, the variable BHF decreases with higher increments.

Punch stroke [mm]

0 5 10 15 20 25 30 35 40

Dra

win

g f

orc

e [k

N]

0

5

10

15

20

25

30

35

40

45

BHF=10 kN

BHF=13 kN

Square cupsDC04

Punch stroke [mm]

0 5 10 15 20 25 30 35 40

Forc

e (D

F o

r B

HF

) [k

N]

0

5

10

15

20

25

30

35

40

45

DF for variable BHF

DF for constant BHF

Variable BHF

BHF=9 kN (constant)

Square cupsDC04


Fig. 6. Drawing force vs. punch stroke in the deep-drawing process of DC04 square cups

Conclusion

The goal of this work was to investigate the effect of blank-holding force on the drawing force in

the deep-drawing process. Two types of BFH have been adopted in experiments: constant and time

variable. Both cylindrical and square cups made from AA 6016-T4 aluminum alloy and DC04 steel

sheets have been considered to perform the study in this paper. On the basis of the experimental

results, the following conclusions can be drawn. In the case of the AA6016-T4 cylindrical deep-

drawn cups, DF is influenced by the amount of BHF (the DF increases when the BHF increases)

and less influenced by its type, constant or time variable. In the deep-drawing process of the DC04

cylindrical cups, DF is influenced both by the amount and type of BHF. In the case of a time

variable BHF, a decrease in DF occurs after it reaches its maximum value. In the case of square

deep-drawn AA 6016-T4 cups, DF is influenced by the amount and the type of BHF. A decrease in

DF occurs only in the second stage of the drawing process, after it reaches its maximum value. In

the first stage of the drawing process, the variable BHF is equal with the constant BHF. As a

consequence no effect on DF occurs in first stages of the drawing process. In the case of square

deep-drawn DC04 cups, a significant decreasing in DF has been observed in the second stage of the

drawing process, when a variable BHF is used, as compared to the case of a constant BHF.

Applied Mechanics and Materials Vol. 760 383

References

[1] I. Nicodim, Increase of deep-drawing process efficiency by using control systems of blank-

holding force. PhD Thesis (Technical University of Cluj-Napoca, Romania 2013) (in

Romanian).

[2] K. Siegert, S. Wagner, A. Galaiko, Close loop control system for the blank holder forces in

deep drawing, Annals of the CIRP. 44 (1995) 251-254.

[3] K. Siegert, Research and development in sheet metal forming at the Institute for metal forming

technologie of the University of Stuttgart (University of Stuttgart, Germany 2004).

[4] D. Banabic, I. Tapalaga, Review of the criteria for determination of the blank-holding forces in

deep-drawing processes, J. of Plastic Deformation. 1 (1994) 42-47.

[5] Z. Wei, Z. Zhang, X. Dong, Deep drawing of rectangle parts using variable blank holder force.

Int. J. Adv. Manuf. Technol. 29 (2006) 885–889.

[6] T. Yagami, K. Manabe, M. Yang, H. Koyama, Intelligent sheet stamping process using

segment blank holder modules. J. of Materials Proc. Techn. 155-156 (2004) 2099–2105.

[7] S. Kitayama, S. Hamano, K. Yamazaki, T. Kubo , H. Nishikawa, H. Kinoshita, A closed-loop

type algorithm for determination of variable blank holder force trajectory and its application to

square cup deep drawing, Int. J. Adv. Manuf. Technol. 51 (2010) 507–517.

[8] S. Tommerup, B. Endelt, Experimental verification of a deep drawing tool system for adaptive

blank holder pressure distribution, J. of Materials Proc. Techn. 212 (2012) 2529– 2540.

[9] B. Endelt, S. Tommerup, J. Danckert, A novel feedback control system - Controlling the

material flow in deep drawing using distributed blank-holder force, J. of Materials Proc. Techn.

213 (2013) 36–50.

[10] G. Iwamatsu, Y. Okude, S. Yoshihara, T. Ishii, Formability of TP 340 pure titanium sheet in

deep drawing superimposed ultrasonic vibration, in: P. Hora (Ed.), Proc. of IDDRG 2013

Conference, Zurich, Switzerland. (2013) 467-472.

[11] L. Lazarescu, D.S. Comsa, I. Nicodim, I. Ciobanu, D. Banabic, Characterization of plastic

behaviour of sheet metals by using the hydraulic bulge test, Trans. Nonferrous Met. Soc. China.

22 (2012) 275-279.


Advanced Technologies in Designing and Progressive Development of Manufacturing Systems 10.4028/www.scientific.net/AMM.760 Effect of the Blank-Holding Load on the Drawing Force in the Deep-Drawing Process of Cylindricaland Square Cups 10.4028/www.scientific.net/AMM.760.379 DOI References[2] K. Siegert, S. Wagner, A. Galaiko, Close loop control system for the blank holder forces in deep drawing,Annals of the CIRP. 44 (1995) 251-254.http://dx.doi.org/10.1016/S0007-8506(07)62319-1 [5] Z. Wei, Z. Zhang, X. Dong, Deep drawing of rectangle parts using variable blank holder force. Int. J. Adv.Manuf. Technol. 29 (2006) 885-889.http://dx.doi.org/10.1007/s00170-005-2578-0 [6] T. Yagami, K. Manabe, M. Yang, H. Koyama, Intelligent sheet stamping process using segment blankholder modules. J. of Materials Proc. Techn. 155-156 (2004) 2099-2105.http://dx.doi.org/10.1016/j.jmatprotec.2004.04.144 [7] S. Kitayama, S. Hamano, K. Yamazaki, T. Kubo , H. Nishikawa, H. Kinoshita, A closed-loop typealgorithm for determination of variable blank holder force trajectory and its application to square cup deepdrawing, Int. J. Adv. Manuf. Technol. 51 (2010).http://dx.doi.org/10.1007/s00170-010-2656-9 [8] S. Tommerup, B. Endelt, Experimental verification of a deep drawing tool system for adaptive blankholder pressure distribution, J. of Materials Proc. Techn. 212 (2012) 2529- 2540.http://dx.doi.org/10.1016/j.jmatprotec.2012.06.015 [9] B. Endelt, S. Tommerup, J. Danckert, A novel feedback control system - Controlling the material flow indeep drawing using distributed blank-holder force, J. of Materials Proc. Techn. 213 (2013) 36-50.http://dx.doi.org/10.1016/j.jmatprotec.2012.08.003 [11] L. Lazarescu, D.S. Comsa, I. Nicodim, I. Ciobanu, D. Banabic, Characterization of plastic behaviour ofsheet metals by using the hydraulic bulge test, Trans. Nonferrous Met. Soc. China. 22 (2012) 275-279.http://dx.doi.org/10.1016/S1003-6326(12)61719-1
http://dx.doi.org/www.scientific.net/AMM.760http://dx.doi.org/www.scientific.net/AMM.760.379http://dx.doi.org/http://dx.doi.org/10.1016/S0007-8506(07)62319-1http://dx.doi.org/http://dx.doi.org/10.1007/s00170-005-2578-0http://dx.doi.org/http://dx.doi.org/10.1016/j.jmatprotec.2004.04.144http://dx.doi.org/http://dx.doi.org/10.1007/s00170-010-2656-9http://dx.doi.org/http://dx.doi.org/10.1016/j.jmatprotec.2012.06.015http://dx.doi.org/http://dx.doi.org/10.1016/j.jmatprotec.2012.08.003http://dx.doi.org/http://dx.doi.org/10.1016/S1003-6326(12)61719-1

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