sheet-metal forming school of mechanical...
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© 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
© Su-Jin Kim GNU
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
© Su-Jin Kim GNU
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
© Su-Jin Kim GNU
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
© Su-Jin Kim GNU
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.