© 2011 Su-Jin Kim GNU Sheet-Metal Forming Manufacturing Processes Forming ( 성형 ) The sheet is...

© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU

Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes

Forming ( 성형 )The sheet is bent or stretched into various shapes by tensile forces in the plane of the sheet.

1.Bending 2.Deep Drawing 3.Stretch forming4.Roll forming 5.Spinning



Bending ( 굽힘 ) of Sheet and Plate

• A force is applied to a piece of sheet metal, causing it to bend at an angle and form the desired shape.

• In bending, recovery is called springback.

1343

t

R

Et

R

ER

R iyiy

f

i

σy

Ri

Rf

t

θi

θf

ffii tRtR 5.05.0



Ex) Springback of bending

A 20-gage (0.0912 cm) steel sheet is bent to a radius of 1.27 cm. Assumingthat its yield stress is 276 MPa, calculate (a) the radius of the part afterit is bent, and (b) the required bend angle to achieve a 1.57 rad bend afterspringback has occurred.

Solutiona. The appropriate formula is

andHence, b. Required bend angle is

0192.0

0912.0000,200

27.1276

Et

Riy

942.010192.030192.04 3 f

i

R

R

rad 67.15.0

5.0

tR

tR

i

ffi

cm 35.1942.0

27.1fR



Bending die

• V-bending die• Wiping die

• Acute angle die; Gooseneck die; Offset die; Rotary bending die

http://www.youtube.com/watch?v=qTUMbVNf1Xc&hl=ko

w

(a) V-die

Punch

Die

w

(b) Wiping die

© 갈창우 , GNU



Press brake

• Laser Cutting

• Press brake (Bending)

Laser Cutting: http://ma.gnu.ac.kr/vod/forming/Sheet_Laser_Cutting.AVI Press brake: http://ma.gnu.ac.kr/vod/forming/Sheet_Bending.AVI



Deep Drawing

• Flat sheet-metal blank is pressed, using punch, into the die cavity.

• Bank is held in place with a blankholder under a certain force.

http://www.youtube.com/watch?v=nA8y__BMl-o&hl=ko

Die

Punch

Blankholder

Blank



Drawing ration & Punch Force

• LDR(limiting drawing ratio) = is the max ratio of blank diameter d0 / to punch diameter dp that can be drawn without failure. 2.7(steel) 2.4(Brass, Aluminum)

• Maximum punch force ≈ f (strength, thickness, blank diameter - punch diameter) pu ddtF 7.000

Die

Punch

Blankholder

Blank

F

td0

dp

Blank

Cup



Stretch forming ( 신장 성형 )

• Sheet metal is clamped and stretched over a die to make double curved aircraft skin panels.

http://www.youtube.com/watch?v=Kh4MBHyHAtg

Die

Hydraulic force

Sheet metal

σy



Roll forming

• Roll forming: Metal strip is bent as it pass through series of rolls.

• Roll bending: Cylindrical shaped produced from plate.

SME: http://www.youtube.com/watch?v=xGLHjyPdDBICom: http://www.youtube.com/watch?v=44XD5mZoM_0&hl=ko

Roll forming Roll bending



Spinning

• A circular sheet metal is held against a rotating mandrel where the tool deforms and shapes it over the mandrel.

• The resulting sheet will have a diameter smaller than the blank.

Al : http://www.youtube.com/watch?v=0RY0cjSUPGg&p=9B6D9EAE75875D9DStainless: http://ma.gnu.ac.kr/vod/forming/Stainless_Spinning.wmv

Mandrel

Tool

Blank



Hydroforming (Sheet)

• Hydralic pressure applied on sheet.

http://www.youtube.com/watch?v=XUMs3cWBlks

DRAW RING BLANK

FLEXIBLE DIAPHRAGM

1 2CONTROLLED

FLUID PRESSUREFORMING CHAMBER

Blank is placed on Draw Ring with forming chamber in raised position.

Forming chamber is lowered and initial pressure is applied.

PUNCH

©정하림



Fast prototyping

• Sheet metal fast prototyping : CAD Tool path Model cutting Incremental forming

http://www.youtube.com/watch?v=KuR_fnZ9JvI&hl=ko



Peen forming

• Produce curvatures on thin sheet metals by short peening.

• Aircraft skin panel.

© 2011 Su-Jin Kim GNU Sheet-Metal Forming Manufacturing Processes Forming ( 성형 ) The sheet is...

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