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IE 415Introduction to Manufacturing Systems: Design and Analysis

Prof. Darek Ceglarek266E Mechanical Engineering Building

Phone: (608)-265-3457; Fax: (608)-262-8454E-mail: <darek@engr.wisc.edu>

5. Sheet Metal Operations, Forging, Tube Forming

5.1 Sheet Metal Operations

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Sheet Metal Operations

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Sheet Metal Parts

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Types of Metal:• Ductile metals that survive deformation without localized necking or fracture, such as mild and stainless

steels, aluminum, brass, copper, etc.• Some plastics can also be processed with these processes.• Material used in the form of sheets, strips, and coils, depending on the levels of production and automation.

U/D Position

U/D PositionF/A Position

F/A Position

Underbody

Door Outer

Automotive Body

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Types of presses:What's A Stamping Press? Its main function is to provide enough power to open and close the die set. The die set shapes (or cuts) the metal part set. That metal part is then fed into the die block and the ram descends, producing the desired shape. The press uses that energy to construct the part. This is done (ideally) without producing a large amount or possibly no waste (scrap materials) at all. Presses range in size—from small bench top presses that generate as little as five tons to larger presses that can form geometric shapes rated in thousands of tons.Types. Presses are either mechanical or hydraulic. Both have different types of frames, which embrace the moving parts of the press. The Society of Manufacturing Engineers states the two most common types of frames as the "C" frame and "straight side press." The "C" type press is accessible on three sides. It's less costly and takes up less floor space. The straight side press, on the other hand, has vertical columns on each side—a setup that eliminates angular deflection. What's important in the selection process? SME considers the force capacity (or force that can be exerted at a specified point in a stroke) as an important feature take into account. While mechanical presses are still the most common type of press, hydraulic presses have the advantage of delivering "full force" at any point during stroke. It can also be adjusted to facilitate part clearance between cycle, making it possible for press operators to use several different tool and die heights.

Mechanical press: See Figure 16.53 for basic examples. The ram is actuated using a flywheel. Strokemotion is not uniform.Hydraulic press: Have longer strokes than mechanical presses, and develop full force throughout thestroke. Stroke motion is of uniform speed, especially adapted to deep drawing operations.Turret punch press: Has a tool turret much like a turret on a lathe containing punches and dies of variousshapes and sizes. Uses Nibbling techniques to systematically shear the workpiece from a blank. The blankis moved around bed by NC controlled grips.Transfer press: Fully automatic, uses robotic arms to move workpieces from station to station. Similar toprogressive die drawing except this process uses separate tooling for each station.

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Challenges. Stamping Presses, whether mechanical or hydraulic, must be flexible and provide quick running speed and changeover time to compete in today's stamping industry. Manufacturers are constantly striving to enhance the design of stamping presses to provide safe working conditions and improve quality, enabling their presses provide reliable cost efficient parts.

Presses:

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Press 1 Press 2

Material handlingdevice

Die

Endeffector

Part

Press Line

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Press Line

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Press Line

Robotic Material Handling in Press Line

The world’s largest hydraulic press line is installed at Active MetalformingTechnology, Detroit, MI.

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After Parts are Stamped – Part-to-part joining (welding) operations are conducted

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Process Overview:

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PunchingDefinition:+ A shearing operation that separates a scrap slug from the workpiece when the punch enters the die.+ Most economical method of making holes in sheet or strip metal for medium to high production.+ See Figures 1 and 2 for process schematics and Figures 3 and 4 for workpiece geometries.

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Punching

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PunchingTooling:+ Produces various shaped holes.+ Punches and dies typically made of tool steel or carbides.+ See Figures 14.17 and 16.9 for examples.

Punch and Die for Razor Blades

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Punching

Tolerances and surface finish:+ Produces a burnish area and die break on the side wall of

the resulting hole.+ Produces burred and slightly deformed edges (roll over).+ See Figures 16.2 and 16.3.

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Conventional BlankingDefinition:+ Similar process to Punching, except this operation separates the workpiece from parent stock material.

+ See Figures 5,6, and 7 for typical operations.

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Conventional BlankingTooling:+ See Figures 8, 9, and 10 for examples.Tolerances and surface finish:+ Quality controlled by the punch and die clearance.

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ShearingDefinition:+ A process for straight line cutting of flat stock.+ Performed by forcing an upper and a lower blade past each other with a desired offset.+ Used for making blanks of suitable dimensions for further processing.+ See Figures 11 and 12 for process schematics.

Tooling:+ One blade is generally stationary.+ Blades generally mounted at an angle in order to reduce the cutting force required so that the relativelength of the material being cutting at any given instant is very small.

Tolerances and surface finish:+ Produces a burnish area (smooth and shiny) and die break (rough) on the side wall of tile resulting cut.+ Produces burred and slightly deformed edges (roll over). This is controlled by the offset.

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PerforatingDefinition:+ A punching process that cuts a desired pattern of holes into the workpiece by means of multiplepunches and dies.+ See Figure 13 for process schematic, and Figure 14 for workpiece geometries.Tooling:+ Utilizes multiple punches and dies.+ Punches shear waste from the workpiece as they enter dies.Tolerances and surface finish:+ Similar to punching.

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NibblingDefinition:+ A shearing process that utilizes a series of overlapping

cuts to make complex shapes.+ Produces complex shapes from sheet metal that is

generally no thicker than 0.25 inches.+ See Figures 15 and 16 for process schematics, and

Figures 17 for workpiece geometries.

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NibblingTooling:+ Generally standard tooling, that remove rectangular or oval slugs.+ Machines usually operate at 300 to 900 strokes/minute+ See Figure 18 for typical tooling.Tolerances and surface finish:+ Low tolerances, gives stepwise "approximations" of curved surfaces.+ Similar surface finishes to punching.

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Brake FormingDefinition:+ A process for the straight line forming and bending of flat stock.+ Is suitable for the production of small parts.+ Used for low to medium production.+ See Figure 19 and 20 for process schematics, and Figures 2 1 and 22 workpiece geometries.

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Brake Forming

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Brake FormingTooling:+ Performed by using a 'U', 'V', or channel-shaped punch and die set.+ May use special application dies, interchangeable press brake dies and numerical controlled machines.+ See Figure 23 and 24 for typical tooling.Tolerances and surface finish:+ Dependent on tooling and preprocessing material surface finishes.

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Plate Roll BendingDefinition:+ A cold forming process that utilizes a combination of 3 rolls,

arrange in a pyramid shape, to form plate or sheet metal into cylindrical shapes.

+ Is used for the production of curved workpieces made from heavysheet or plate material.

+ Materials are typically at least 1/16 inch thick and 15 inch wide, upto 6 inch thick and 20 feet wide.

+ Production on any material capable of cold working.+ Primarily used in forming large cylindrical sections requiring the

seam to be welded.+ See Figures 25, 26, and 13.22 for process schematics, and

Figures 27 for workpiece geometries.

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Plate Roll BendingTooling:+ 2 rolls are power driven, in a fixed position, the 3d is adjustable to suit the desired bend radius and workpiece

thickness.+ See Figure 28 for typical tooling.Tolerances and surface finish:+ Dependent on tooling and preprocessing material surface finishes.

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Stretch Draw FormingDefinition:+ The cold forming of sheet stock over a forming block with a mating die of the desired shape, while the workpiece

is held in tension.+ The workpiece material is extended beyond the yield point of the material to retain the desired shape.+ Reduces material thickness 5-7%, and increases yield stress up to 10'%0.+ Low or high production rates, manually or automatically operated.+ See Figures 29, 30, 16.31, 13.10, 3 1, and 32 for process schematics, and Figure 33 for workpiece geometries.

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Stretch Draw Forming

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Stretch Draw Forming

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Stretch Draw FormingTooling:+ Produces large parts at reduced weight.+ In many cases thickness reduction, and yield stress dependent

on draw-beads.+ Little or no lubrication required.+ See Figures 34, and 16.38 for typical tooling.Tolerances and surface finish:+ Very dependent on tooling capabilities, and preprocessing

material surface finish.+ Edges of draw generally need to be trimmed.

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Deep DrawingDefinition:+ The cold forming process in which a flat blank is shaped by the action of a punch forcing the metalinto a die cavity.+ Very similar to a Stretch draw, except the depth of the drawn part is greater than the diameter.+ Various geometric shapes can be made.+ Low or high production rates, manually or automatically operated.+ See Figures 35,36 for process schematics, and Figures 37, and 38 for workpiece geometries.

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Deep Drawing

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Deep DrawingTooling:+ Lubrication generally required, lowering forces and tooling wear.+ In many cases thickness reduction, and yield stress dependent on draw-beads.+ See Figure 39 for typical tooling.Tolerances and surface finish:+ Very dependent on tooling capabilities and maintenance.+ Edges of draw generally need to be trimmed.+ See Figure 40.

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LancingDefinition:+ A process that is a combination of shearing and bending.+ A portion of the periphery of a hole is cut into the workpiece, while the remainder is bent to a desired shape

matching that of the tool.+ No material is removed from the workpiece.+ See Figures 41 and 42 for process schematics and Figures 43 and 14.16 for typical geometries.

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Lancing

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LancingTooling:+ Single cut used to facilitate the making of special features. See Figure 44.Tolerances and surface finish:+ Similar to Punching.

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Progressive Die DrawingDefinition:+ A cold forming process that utilizes a series of stations to perform 2 or more simultaneous operations.+ Each press stroke develops a final workpiece as the strip stock moves through the die using acombination of shearing and forming processes.+ Various geometric shapes can be made including cutting and forming operations.High production rates that are automatically operated.+ See Figures 45 and 46 for process schematics, and Figure 47 for workpiece geometries.

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ProgressiveDie Drawing

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Progressive Die DrawingTooling:+ Lubrication may be required, lowering forces and tooling wear.+ Tooling may contain many stations depending on the complexity of a workpiece.+ Generally very expensive die sets, capable of producing small parts very rapidly, saving time andmoney by combining operations into a single piece of tooling.+ See Figure 48 for typical tooling.Tolerances and surface finish:+ Very dependent on tooling capabilities and maintenance.+ See Figure 49.

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NestingDefinition:Position parts on a blank to minimize scrap. See Figure 50.

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Typical machine specifications+ Machines rated by press capacity, such as length of stroke, strokes/minute, shut height, and tonnage ratings.+ Also rated by control systems and die changing features (SMED etc.).

Stamping Processes