Sheet Metal Forming Processes

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Sheet Metal Forming Processes Chapt 16

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Sheet Metal Forming Processes. Chapt 16. Shearing. Process that involves cutting sheet metal by subjecting it to shear stresses, usually between a punch and a die. Blank: removed from a large sheet or coil - part made from blank. Shearing terms. - PowerPoint PPT Presentation

Transcript of Sheet Metal Forming Processes

Page 1: Sheet Metal Forming Processes

Sheet Metal Forming Processes

Chapt 16

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Shearing• Process that involves cutting sheet

metal by subjecting it to shear stresses, usually between a punch and a die.

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Blank: removed from a large sheet or coil - part made from blank

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Shearing terms

• Punching (piercing): sheared slug is discarded.

• Blanking: slug is the part, the rest is

discarded.

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Shearing Operations

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1. Die Cutting – consists of:

• Perforating- punching holes.• Parting- shearing sheet into two or more

pieces.• Notching-removing pieces or shapes

from edge.• Lancing- leaving a tab without removing

the material.

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2. Fine Blanking

• v shaped notch locks sheet, less distortion.• Burrs (clearance, ductility, dull tool edges).

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3. Slitting

• Driven• powered blades

• Pull-through• Strip pulled through idling blades

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4. Steel Rules

• thin strip of metal is bent and held on its edge on a flat base.

• die is pressed against the sheet to cut parts (cookie cutter).

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5. Nibbling

• successive punched holes

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Bending

• One of the most common forming operations, used for producing parts and to impart stiffness.

• After bending, outer fibers of the material are under tension while the inner fibers are in compression.

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Bending• Process Variables

• minimum bend radius• Smallest radius allowed before cracks on outer

surface

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Bending Radius

• The bending radius is measured to the inner surface of the bend and it is normally expressed in terms of material thickness. (2T, 3T, etc.)

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Springback: elastic recovery

• Compensation

• Over bending

• Bottoming

• Stretch bending

• Elevated temps

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Bending Operations using press brake

• Beading• edge of sheet metal is bent into die cavity

• Flanging• bending of edges

• Hemming– edge folded over itself

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Roll Forming

– Metal bent by series of rolls

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Tube Bending and Forming

• pack inside of tube with sand to prevent buckling and folding.

• flexible mandrels

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Bulging

• Flexible plug inserted inside part and compressed

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Stretch forming

• Sheet clamped and stretched over die or form block• Aircraft wing skins and auto door panels

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Rubber Forming

• Also called hydroforming• one die is replaced with a rubber or

polyurethane pad.• Pressure supplied by fluid

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Spinning

• axisymmetric parts over a mandrel with tools or rollers.

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Other Methods

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Peen Forming - shot peening – leaves dimples

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Explosive Forming

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Magnetic-Pulse Forming – • energy stored in a capacitor is discharged

rapidly through a magnetic coil which surrounds a tubular work piece which is placed over solid plug

• Opposing magnetic fields forms thin work piece over solid plug

• Used to collapse thin wall tubes over rods, cables, plugs, compression crimp auto oil filter canisters