© Su-Jin Kim GNU

Sheet-Metal Forming

Sheet Metal Forming

판재 성형

Professor Su-Jin Kim

School of Mechanical Engineering

Gyeongsang National University

© Su-Jin Kim GNU

Sheet-Metal Forming

Hyundai Automobile

• The Empty Car Convoy: https://youtu.be/EPTIXldrq3Q

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Sheet-Metal Forming

Hyundai Manufacturing Plant

• Korea : https://youtu.be/mbGukMPPvl0

• Mexico : https://www.youtube.com/watch?v=1U5OPVOkBlI

© Su-Jin Kim GNU

Sheet-Metal Forming

Sheet metal forming (판재성형)

• Sheet metal shearing(전단) deformation(성형) Welding Painting

© Su-Jin Kim GNU

Sheet-Metal Forming

Contents

1. Shearing 전단

2. Forming 성형

3. Press Die 프래스금형

© Su-Jin Kim GNU

Sheet-Metal Forming

Cutting with Shearing (전단) • Sheet metal is separated by applying shearing force

using punch and die.

• Edge fracture & burr. Punch

Sheet metal

Die

F

Clearance

Rollover

Burnish

Fracture

Burr

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Sheet-Metal Forming

Cutting with shear

1. Shearing - Separating material into two parts

2. Blanking - Removing material to use for parts

3. Punching - Removing material as scrap

Blanking

Scrap

Part

Punching

Part

Scrap

Shearing

Part2 Part1

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Sheet-Metal Forming

Shearing

• Shearing cuts straight line to separate a piece of sheet metal into smaller parts.

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Sheet-Metal Forming

Blanking

• Desired part (gears, key) is removed from sheet metal.

• Fine blanking, applying 3 separate forces, produces smooth and flat edges with minimal burrs and tolerances.

Punch

Upper pressure pad

Sheet metal

Die Lower pressure cushion

Stringer

Blanking Fine

blanking

http://ma.gnu.ac.kr/vod/forming/Stainless_Spoon.wmv Spoon

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Sheet-Metal Forming

Punching

Scrap(Hole, slot) is removed from sheet metal.

• Piercing - cylindrical punch

• Slotting - rectangular holes

• Perforating - large number of holes

• Notching - edge of sheet

• Lancing - partial cut to be bent

• Slitting - straight line

• Parting - separating a part

• Cutoff - separating a part

http://www.youtube.com/watch?v=DvONyl-ncMo Punch press machine

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Sheet-Metal Forming

Punch Force

• The punch force is product of shear strength of sheet metal and cross-sectional area being sheared.

• Punch force : F ≈ (0.7σu)tl

σu = ultimate tensile strength

t = thickness

l = total length of the sheared edge

t

l

F

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Sheet-Metal Forming

Estimate the force required in punching a 25 mm diameter hole through a

1.8 mm thick 5052-O aluminium sheet at room temperature. Ultimate tensile

strength of it is 190 MPa.

Solution

F = (0.7 190 Mpa) (1.8 π 25 mm2) = 18.8 kN

Q. Punch force

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Sheet-Metal Forming

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 forming

4. Roll forming

5. Spinning

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Sheet-Metal Forming

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.

134

3

t

R

Et

R

ER

R iyiy

f

i

σy

Ri

Rf

t

θi

θf

ffii tRtR 5.05.0

© Su-Jin Kim GNU

Sheet-Metal Forming

Ex) Springback of bending

A 20-gage (0.0912 cm) steel sheet is bent to a radius of 1.27 cm. Assuming

that its yield stress is 276 MPa, calculate (a) the radius of the part after

it is bent, and (b) the required bend angle to achieve a 1.57 rad bend after

springback has occurred.

Solution

a. The appropriate formula is

and

Hence,

b. Required bend angle is

0192.00912.0000,200

27.1276

Et

Riy

942.010192.030192.043

f

i

R

R

rad 67.15.0

5.0

tR

tR

i

f

fi

cm 35.1942.0

27.1fR

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Sheet-Metal Forming

Bending die

• V-bending die

• Wiping die

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

w

(a) V-die

Punch

Die

w

(b) Wiping die

©갈창우, GNU

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Sheet-Metal Forming

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.

Die

Punch

Blankholder

Blank

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Sheet-Metal Forming

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

t d0

dp

Blank

Cup

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Sheet-Metal Forming

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

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Sheet-Metal Forming

Roll forming

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

• Roll bending: Cylindrical shaped produced from plate.

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

Roll forming Roll bending

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Sheet-Metal Forming

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=9B6D9EAE75875D9D

Stainless: http://ma.gnu.ac.kr/vod/forming/Stainless_Spinning.wmv

Mandrel

Tool

Blank

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Sheet-Metal Forming

Custom manufacturing

1. Laser cutting

2. Press break

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Sheet-Metal Forming

Laser cutting

Laser Cutting

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

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Sheet-Metal Forming

Press brake

Press brake (Bending)

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

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Sheet-Metal Forming

Mass production & Die (금형)

• Single operation

1. Stamping Die

2. Press Machine

• Die is used for multiple station operation of shearing, bending and drawing.

1. Progressive Die

2. Transfer Die

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Sheet-Metal Forming

Stamping Die (프레스 금형)

• Automotive panel forming process: Drawing → Trimming → Hemming → Punching

• Draw die = upper die + lower die + blank holder

Lower die

Blank holder

Upper die

Draw die http://www.youtube.com/watch?v=ydoEJnwMlnk Press

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Sheet-Metal Forming

Stamping Die

• NC machining of die and side panel forming.

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Sheet-Metal Forming

Press Machine (프레스)

Hydraulic press Sheet metal / Stamping Die

http://ma.gnu.ac.kr/vod/forming/stamping.mp4

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Sheet-Metal Forming

Hydroforming (Sheet)

• Hydralic pressure applied on sheet.

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

DRAW RING BLAN

K

FLEXIBLE DIAPHRAGM

1 2 CONTROLLED

FLUID PRESSURE

FORMING CHAMBER

Blank is placed on

Draw Ring with

forming chamber in

raised position.

Forming chamber is

lowered and initial

pressure is applied.

PUNCH

©정하림

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Sheet-Metal Forming

Transfer machine

• The large sheet metal part is transferred to next station after an operation by transfer machine.

http://www.youtube.com/watch?v=MTPQfEwxtf8&hl=ko

Bar feeder Finger

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Sheet-Metal Forming

Frame of automobile

Press Welding Painting

Korea : https://youtu.be/mbGukMPPvl0

Mexico : https://www.youtube.com/watch?v=1U5OPVOkBlI

© Su-Jin Kim GNU

Sheet-Metal Forming

Progressive Die (순차이송 금형)

• Multiple operation such as punching, bending, blanking.

• Ring washer production by progressive die.

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

Ring washer

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Sheet-Metal Forming

Frame of home appliances

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Sheet-Metal Forming

Design Considerations (설계)

• Guidelines for design issues of sheet-metal forming operations:

1. Punching

2. Bending

3. Progressive-die operations

4. Deep drawing

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Sheet-Metal Forming

Economics (경제성)

• Cup-shaped part can be produced by deep drawing, spinning.

• Automotive or aircraft panel can be produced by drawing, stretch forming.

500 1,000 2,000 3,000 4,000 1

Number of parts

Cost p

er

pa

rt

Drawing

Spinning

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Sheet-Metal Forming

Summary

• Process: Shearing Forming Welding Painting

• Shearing: Sharing, Blanking, Punching

• Forming: Bending, Drawing, Stretch, Roll, Spinning

• Laser cut + Press break

• Stamping die, Progressive die

© Su-Jin Kim GNU

Sheet-Metal Forming

References

• SIMPAC: http://www.simpac.co.kr 프레스장비

• SIMPAC: https://youtu.be/-fXvBE4WkoY

• DieTec: www.dietec.co.kr 프레스금형

• Sheet metal : http://posco.co.kr 판재

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Sheet-Metal Forming

Fast prototyping

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

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

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Sheet-Metal Forming

Peen forming

• Produce curvatures on thin sheet metals by short peening.

• Aircraft skin panel.