© 2011 su-jin kim gnu sheet-metal forming manufacturing processes forming ( 성형 ) the sheet is...
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© 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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
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
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© 2011 Su-Jin Kim GNU© 2011 Su-Jin Kim GNU
Sheet-Metal FormingSheet-Metal FormingManufacturing ProcessesManufacturing Processes
Fast prototyping
• Sheet metal fast prototyping : CAD Tool path Model cutting Incremental forming
http://www.youtube.com/watch?v=KuR_fnZ9JvI&hl=ko