Sheet metal processing Traditional Manufacturing Processes Casting Forming Sheet metal processing Powder- and Ceramics Processing Plastics processing Cutting Joining Surface treatment

Sheet Metal Processes Raw material: sheets of metal, rectangular, large Raw material Processing: Rolling (anisotropic properties) Processes: Shearing Punching Bending Deep drawing Hydroforming

Shearing A large scissors action, cutting the sheet along a straight line Main use: to cut large sheet into smaller sizes for making parts.

Shearing Shearing is a process for cutting sheet metal to size out of a larger stock such as roll stock. Shears are used as the preliminary step in preparing stock for stamping processes. Material thickness ranges from 0.125 mm to 6.35 mm (0.005 to 0.250 in). The dimensional tolerance ranges from ±0.125 mm to ±1.5 mm (±0.005 to ±0.060 in). The shearing process produces a shear edge burr, which can be minimized to less than 10% of the material thickness. The burr is a function of clearance between the punch and the die (which is nominally designed to be the material thickness), and the sharpness of the punch and the die.

Blanking / Punching Blanking and punching are similar sheet metal cutting operations that involve cutting the sheet metal along a closed outline. If the part that is cut out is the desired product, the operation is called blanking and the product is called blank. If the remaining stock is the desired part, the operation is called punching.

Blanking / Punching

Cutting tool is a round/rectangular punch, that goes through a hole, or die of same shape

Main uses: cutting holes in sheets; cutting sheet to required shape Punching Main uses: cutting holes in sheets; cutting sheet to required shape nesting of parts typical punched part Exercise: how to determine optimal nesting?

Body of Olympus E-300 camera Bending Body of Olympus E-300 camera component with multiple bending operations component with punching, bending, drawing operations [image source: dpreview.com]

Typical bending operations and shapes

Sheet metal bending Planning problem: what is the sequence in which we do the bending operations? Avoid: part-tool, part-part, part-machine interference

Bending mechanics Bending Planning  what is the length of blank we must use? Ideal case: k = 0.5 Real cases: k = 0.33 ( R < 2T) ~~ k = 0.5 (R > 2T)

Bending: cracking, anisotropic effects, Poisson effect Bending  plastic deformation Engineering strain in bending = e = 1/( 1 + 2R/T) Bending  disallow failure (cracking)  limits on corner radius: bend radius ≥ 3T effect of anisotropic stock Poisson effect Exercise: how does anisotropic behavior affect planning?

(a) Compensation: the metal is bent by a larger angle Bending: springback Initial Final R i f af ai T How to handle springback: (a) Compensation: the metal is bent by a larger angle (b) Coining the bend: at end of bend cycle, tool exerts large force, dwells coining: press down hard, wait, release

Tooling: similar to punching operation, Deep Drawing Tooling: similar to punching operation, Mechanics: similar to bending operation Common applications: cooking pots, containers, …

Body of Olympus E-300 camera Sheet metal parts with combination of operations Body of Olympus E-300 camera component with multiple bending operations component with punching, bending, drawing operations [image source: dpreview.com]