Shearing, also known as die cutting,[1] is a process that cuts stock without the formation of chips or the use of burning or melting. Strictly speaking, if the cutting blades are straight the process is called shearing; if the cutting blades are curved then they are shearing-type operations.[2] The most commonly sheared materials are in the form of sheet metal or plates. However, rods can also be sheared. Shearing-type operations include blanking, piercing, roll slitting, and trimming. It is used for metal, fabric, paper and plastics.
A punch (or moving blade) is used to push a workpiece against the die (or fixed blade), which is fixed. Usually, the clearance between the two is 5 to 40% of the thickness of the material, but dependent on the material. Clearance is defined as the separation between the blades, measured at the point where the cutting action takes place and perpendicular to the direction of blade movement. It affects the finish of the cut (burr) and the machine's power consumption. This causes the material to experience highly localized shear stresses between the punch and die. The material will then fail when the punch has moved 15 to 60% of the thickness of the material because the shear stresses are greater than the shear strength of the material and the remainder of the material is torn.
Two distinct sections can be seen on a sheared workpiece, the first part being plastic deformation and the second being fractured. Because of normal inhomogeneities in materials and inconsistencies in clearance between the punch and die, the shearing action does not occur in a uniform manner. The fracture will begin at the weakest point and progress to the next weakest point until the entire workpiece has been sheared; this is what causes the rough edge. The rough edge can be reduced if the workpiece is clamped from the top with a die cushion. Above a certain pressure, the fracture zone can be completely eliminated. However, the sheared edge of the workpiece will usually experience work-hardening and cracking. If the workpiece has too much clearance, then it may experience roll-over or heavy burring.
Tool materialsedit
Low alloy steel is used in low production of materials that range up to 0.64 cm (1⁄4 in) thick
High-carbon, high chromium steel is used in high production of materials that also range up to 0.64 cm (1⁄4 in) in thickness
Shock-resistant steel is used in materials that are equal to 0.64 cm (1⁄4 in) thick or more
Tolerances and surface finishedit
When shearing a sheet, the typical tolerance is +0.1 inch or −0.1 inch, but it is feasible to get the tolerance to within +0.005 inch or −0.005 inch. While shearing a bar and angle, the typical tolerance is +0.06 inch or −0.06 inch, but it is possible to get the tolerance to +0.03 inch or −0.03 inches. Surface finishes typically occur within the 250 to 1000 microinches range but can range from 125 to 2000 microinches. A secondary operation is required if one wants better surfaces than this.
Degarmo, E. Paul; Black, J. T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN0-471-65653-4.
Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994), Manufacturing Processes Reference Guide, Industrial Press Inc., ISBN0-8311-3049-0.
Wick, Charles; Veilleux, Raymond F. (1984), Tool and Manufacturing Engineers Handbook: Forming (4th ed.), SME, ISBN978-0-87263-135-9.
External linksedit
February 27, 2024
shearing, manufacturing, shearing, also, known, cutting, process, that, cuts, stock, without, formation, chips, burning, melting, strictly, speaking, cutting, blades, straight, process, called, shearing, cutting, blades, curved, then, they, shearing, type, ope. Shearing also known as die cutting 1 is a process that cuts stock without the formation of chips or the use of burning or melting Strictly speaking if the cutting blades are straight the process is called shearing if the cutting blades are curved then they are shearing type operations 2 The most commonly sheared materials are in the form of sheet metal or plates However rods can also be sheared Shearing type operations include blanking piercing roll slitting and trimming It is used for metal fabric paper and plastics Contents 1 Principle 2 Tool materials 3 Tolerances and surface finish 4 See also 5 References 5 1 Citations 5 2 General sources 6 External linksPrinciple editA punch or moving blade is used to push a workpiece against the die or fixed blade which is fixed Usually the clearance between the two is 5 to 40 of the thickness of the material but dependent on the material Clearance is defined as the separation between the blades measured at the point where the cutting action takes place and perpendicular to the direction of blade movement It affects the finish of the cut burr and the machine s power consumption This causes the material to experience highly localized shear stresses between the punch and die The material will then fail when the punch has moved 15 to 60 of the thickness of the material because the shear stresses are greater than the shear strength of the material and the remainder of the material is torn Two distinct sections can be seen on a sheared workpiece the first part being plastic deformation and the second being fractured Because of normal inhomogeneities in materials and inconsistencies in clearance between the punch and die the shearing action does not occur in a uniform manner The fracture will begin at the weakest point and progress to the next weakest point until the entire workpiece has been sheared this is what causes the rough edge The rough edge can be reduced if the workpiece is clamped from the top with a die cushion Above a certain pressure the fracture zone can be completely eliminated However the sheared edge of the workpiece will usually experience work hardening and cracking If the workpiece has too much clearance then it may experience roll over or heavy burring Tool materials editLow alloy steel is used in low production of materials that range up to 0 64 cm 1 4 in thick High carbon high chromium steel is used in high production of materials that also range up to 0 64 cm 1 4 in in thickness Shock resistant steel is used in materials that are equal to 0 64 cm 1 4 in thick or moreTolerances and surface finish editWhen shearing a sheet the typical tolerance is 0 1 inch or 0 1 inch but it is feasible to get the tolerance to within 0 005 inch or 0 005 inch While shearing a bar and angle the typical tolerance is 0 06 inch or 0 06 inch but it is possible to get the tolerance to 0 03 inch or 0 03 inches Surface finishes typically occur within the 250 to 1000 microinches range but can range from 125 to 2000 microinches A secondary operation is required if one wants better surfaces than this See also editAlligator shear Shear sheet metal Stamping metalworking References editCitations edit Wick amp Veilleux 1984 p 6 20 Degarmo p 424 General sources edit Degarmo E Paul Black J T Kohser Ronald A 2003 Materials and Processes in Manufacturing 9th ed Wiley ISBN 0 471 65653 4 Todd Robert H Allen Dell K Alting Leo 1994 Manufacturing Processes Reference Guide Industrial Press Inc ISBN 0 8311 3049 0 Wick Charles Veilleux Raymond F 1984 Tool and Manufacturing Engineers Handbook Forming 4th ed SME ISBN 978 0 87263 135 9 External links editShearing Capacity Guide Retrieved from https en wikipedia org w index php title Shearing manufacturing amp oldid 1186024785, wikipedia, wiki, book, books, library,
