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Chapter 11

Chapter 11. Mechanical and Other Methods of Change of Form. Forming . This is another way to get metal to flow into a desired shape. Not a gentle process Sometimes described as a “bulk deformation process”, which involves a lot of force. Can be performed with hot or cold metals.

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Chapter 11

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  1. Chapter 11 Mechanical and Other Methods of Change of Form

  2. Forming • This is another way to get metal to flow into a desired shape. • Not a gentle process • Sometimes described as a “bulk deformation process”, which involves a lot of force. • Can be performed with hot or cold metals

  3. Some terms associated with Mechanical forming • Billetthe piece being formed. • Ram orPunchis the moving part that delivers the blow. • Dieis the tool with the cavity through which the billet is formed. • Reference figures 11-2, 3, & 4.

  4. Forging Extrusion Rolling Bending Drawing Spin Forming High-energy-rate forming.Explosive and Magneforming There are 7 processes of Forming

  5. First recorded use of forging was around 5000 B.C. Several methods are common Hand Black Smith Drop Mechanized Black Smith Open Press between flat plates Cogging Reduces size of billet Closed Use of dies Coining Different patterns on each side Heading Upset to form nail or screw heads Swaging Tubing size reduction Forging

  6. Hand Forging • This is what the Blacksmiths did. • Still around • Some horse shoes are hand forged.

  7. Drop Forging • Simplest form. • Raise a massive weight and let it fall. • Mechanized form of a Blacksmith’s hammer. • Reference figure 11-6

  8. Two basic forging machines • Presses • Hammer

  9. Aluminum Magnesium Beryllium Alloys Bronzes Brass Exert forces up to 75,000 tons (670 meganewtons. Slow enough to let metal flow Metals used in a Press Machine

  10. Hammer machines • Raise a massive weight and let it drop. • Power hammers add to gravity with pneumatics or hydraulics. • Can be vertical or horizontal. • Horizontal uses two opposed hammers (counterblow hammers) that work together. • Produce much less vibration.

  11. Metals used in Hammer Machines • Copper • Alloys • Steel • Titanium • Refractory Alloys

  12. Open Forging, pressing the billet between two flat plates to reduce thickness Cogging, reduces thickness with small increments by hydraulic pneumatic, or mechanical means. Closed forging, uses dies to form or fill die, makes flashing. Coining, used in making coins. Heading, used in making nails. Swaging, reduces tubular billets uses 2 to 4 dies Presses and Hammers can be used in many ways

  13. Lubricants for Forging • Lubricants improve the flow of the materials in to the die. • Also help it flow out of the die. • Cold forging lubes are mineral oils, soap, silicones, and low friction lubes like polytetrafluorethene. Teflon. • Hot forging lubes are graphite, molybdenum disulfide, or powdered glass

  14. Pressures involved in forging • Depends on metal • Area of metal • Temperature being forged • amount of deformation being exerted for each stroke

  15. Hydroforming • Has one die • Top is covered with a rubber sheet. • Oil or water fills the dam that has the rubber cover. • An even pressure of the fluid is pumped into the dam and forms the piece. • Reference figure 11-12

  16. Extrusion • Developed in the late 18th century. • Compared to squeezing tooth pastes from a tube. • This also can be done hot or cold. • Involves the use of a ram or piston as well as a cylinder extrusion die.

  17. Direct, cold metal being forced through a die, done vertically. Indirect, used in smaller batches where the ram is part of the die. Hydrostatic, like direct but liquid fills between ram and part. Impact, impact for making hollow containers. Hollow, some obstacle is part of the die design, aluminum is hollow extruded to make tubes. Extrusion is divided into five major parts

  18. Rolling • Developed in the late 16th century • One of the most used process in today’s industry.

  19. Bend rods or sheets into curved surfaces. Change the grain structure of cast bars or sheets Form billets into structural shapes such as flanges, funnels channels, or railroad rails Produce tapers or threads on rods Straighten bent sheets, rods or tubing. Rolling uses

  20. More rolling uses • Threads • Gears • Ball bearings • Straightening • Bending • Tubing • I beams

  21. Rolling • Hot versus Cold • Hot leads to softer product • Cold leads to harder products

  22. Factors affecting Rolling • Material being rolled • Material of the roller • The shape being rolled • Size of the stock being rolled • Size of the rollers • Power Requirements

  23. Bending • On of the most basic processes available. • Mostly used on flat sheets, plate, extrusions, rods, and tubing stock.

  24. Punch and dies Wiping Hinged braking Press braking Air bending Beading Flanging Dimpling Hemming and seaming Tube flaring Tube bending Roll forming Bending

  25. Continuous roll bending, three rollers curving sheet metal distance of the bottom rollers sets curvature. Punch and dies, similar to forging. Wiping die, slides a moveable die across an extended piece of Metal bending around a mandrel. Hinged braking, used for one of a kind bends, uses fingers to support the bend. Press braking, extension of the punch and die for complex shapes Bending methods used

  26. Air bending, no defined cavity or die. Free hand operation. Bicycle handle bars are made this way. Beading, forming a rolled edge. Flanging, piece of an object that protrudes at 90 degrees Dimpling, formation of a cylindrical flange at a location other than the end. Hemming and Seaming, folding sheet metal and pressing it back. Seaming, joining two edges. Contin…

  27. Tube flaring, bend is less than 90 degrees. Tube bending, uses two ways to prevent collapse inner core substance or outer constraint to keep sides of the tubing from spreading apart. Roll forming, used to form seamless gutters. Still more...

  28. Drawing • Primary process in forming wire and metallic thread. • In drawing the billet is pulled through the die. • Pressure is used on the output side rather then the input side. • Most used lubricant is soap.

  29. Spin forming • A process that deforms a disk of metal material around a mandrel. • Used for making cymbals. • Has some limitations • Not very practical. • Used for simple low production parts • Reference figures 11-53 & 54

  30. High energy rate methods • Explosion forming is the use of explosives that range from a .38 caliber blank to sticks of dynamite. • Metal is placed in a sealed container and the air pressure of the explosion forces the metal into the die forming the piece. • Underwater explosions are also used, in this case the water pressure forms the metal.

  31. Die materials for explosion forming • Do not have to be extremely high strength. • Aluminum alloys, Steel, Zinc alloys, reinforced concrete, wood, or even plastics can be used.

  32. High-energy-rate methods • Magneforming based on the principles that poles repel each other. • High energy capacitor flows energy through a coil and forms the a magnetic field, since the the poles are the same they repel each other. • The coil is mounted to the frame so the metal is the only thing that moves and forms to the die.

  33. Magneforming • Some metals may be painted before magneforming. • Used in making toys and aircraft. • Reference figures 11-62 & 63

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