© 2011 Su-Jin Kim GNU Sheet-Metal Forming Manufacturing Processes Forming ( 성형 ) The sheet is bent or stretched into various shapes by tensile forces in.

© 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 bent or stretched into various shapes by tensile forces in.

Documents

forming sheet metal

circular sheet metal

piece of sheet metal

roll forming

steel sheet

gnu slide

resulting sheet

roll bending slide