sheet metal
26
2.3
Metal Forming
Valery Marinov, Manufacturing Technology
SHEET METALWORKING
Classification of Sheet Metalworking Processes
Basic sheet metalworking operations: (a) bending, (b) drawing, and (c) shearing; (1) as punch first contacts sheet and (2) after cutting. Force and relative motion are indicated by F and v
Cutting Operations
Shearing
Shearing is a sheet metal cutting operation along a straight line between two cut-ting edges by means of a power shear.
Shearing operation
3-m power shear for 6.5-mm steel
Valery Marinov, Manufacturing Technology
Metal Forming
27
Blanking and 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. Both operations are illustrated on the example of producing a washer:
Punch
Starting stock produced by shearing operation from a big metal sheet
Washer
Scrap
Blank
Blanking
Punching
Steps in production of washer
Engineering analysis
Cutting of sheet metal is accomplished by a shearing action between two sharp edges. The shearing action is illustrated in the figure:
28
Metal Forming
Valery Marinov, Manufacturing Technology
Clearance
Clearance c is the distance between the punch and die. The correct clearance depends on sheet-metal type and thickness t: c = at where a is the allowance (a = 0.075 for steels and 0.060 for aluminum alloys).
If the clearance is not set correctly, either an excessive force or an oversized burr can occur:
Effect of clearance: (Left) clearance too small causes less than optimal fracture and excessive forces, and (Right) clearance too large causes oversized burr
The calculated clearance value must be subtracted from the die punch diameter
2.3
Metal Forming
Valery Marinov, Manufacturing Technology
SHEET METALWORKING
Classification of Sheet Metalworking Processes
Basic sheet metalworking operations: (a) bending, (b) drawing, and (c) shearing; (1) as punch first contacts sheet and (2) after cutting. Force and relative motion are indicated by F and v
Cutting Operations
Shearing
Shearing is a sheet metal cutting operation along a straight line between two cut-ting edges by means of a power shear.
Shearing operation
3-m power shear for 6.5-mm steel
Valery Marinov, Manufacturing Technology
Metal Forming
27
Blanking and 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. Both operations are illustrated on the example of producing a washer:
Punch
Starting stock produced by shearing operation from a big metal sheet
Washer
Scrap
Blank
Blanking
Punching
Steps in production of washer
Engineering analysis
Cutting of sheet metal is accomplished by a shearing action between two sharp edges. The shearing action is illustrated in the figure:
28
Metal Forming
Valery Marinov, Manufacturing Technology
Clearance
Clearance c is the distance between the punch and die. The correct clearance depends on sheet-metal type and thickness t: c = at where a is the allowance (a = 0.075 for steels and 0.060 for aluminum alloys).
If the clearance is not set correctly, either an excessive force or an oversized burr can occur:
Effect of clearance: (Left) clearance too small causes less than optimal fracture and excessive forces, and (Right) clearance too large causes oversized burr
The calculated clearance value must be subtracted from the die punch diameter