sheet metal forming processes
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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 PresentationTRANSCRIPT
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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