Sheet-Metal Forming. Introduction Sheet metal forming is a process that materials undergo permanent...
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Transcript of Sheet-Metal Forming. Introduction Sheet metal forming is a process that materials undergo permanent...
Sheet-Metal Forming
Introduction• Sheet metal forming is a process that
materials undergo permanent deformation by cold forming to produce a variety of complex three dimensional shapes.
• The process is carried out in the plane of sheet by tensile forces with high ratio of surface area to thickness.
• Friction conditions at the tool-metal interface are very important and controlled by press conditions, lubrication, tool material and surface condition, and strip surface condition.
Classification of sheet metal parts (based on contour)
1) Singly curved parts2) Contoured flanged parts, i.e.,
parts with stretch flanges and shrink flanges.
3) Curved sections.4) Deep-recessed parts, i.e., cups
and boxes with either vertical or sloping walls.
5) Shallow-recessed parts, i.e., dish-shaped, beaded, embossed and corrugated parts.
Classification of sheet metal forming (based on operations)
1. Shearing2. Blanking3. Punching4. Bending5. Stamping6. Deep drawing7. Embossing8. Spinning9. Roll Forming
Forming machines
PressA press is a machine used for performing most of the cold working operations.1. Rigid Machine Frame2. Press Tools3. Ram4. Power Source and Mechanism5. Die Assy6. Press Accessories
Types of Press
1. Source of Power– Manual Press– Mechanical Press– Hydraulic Press– Pneumatic Press
Mechanical presses• energy stored in a flywheel
is transferred to the movable slide on the down stroke of the press.
• quick - acting , short stroke.
Hydraulic presses• slower - acting, longer
stroke.
2.Actions of presses According to number of slides, which can be operated independently of each other.
1) Single - action press- one slide- vertical direction
2) Double - action press- two slides- the second action is used to operated the hold-down, which prevents wrinkling in deep drawing.
3) Triple - action press- two actions above the die, one action below
3. Method of transmitting power to ram
1. Crank shaft and connecting rod system2. Cam3. Eccentric4. Toggle joint5. Knuckle joint6. Rack and Pinion7. Screw8. Gears
4. Position of the Ram1. Vertical2. Inclined
5. UseBlanking press, embossing press, Drawing press etc.
6. Design of Frame
7. Capacity or Size
Die Assembly
1. Die Block2. Die retainer & Die
shoe3. Stripper4. Punch5. Punch retainer &
Punch pad6. Pressure Plate7. Punch Holder8. Guide Pillars9. Stock Guide
Classification of Die
1. Single Operation Die1. Cutting Die2. Forming Die
2. Multi Operation Die1. Compound Die2. Progressive Die3. Transfer Die
Single Operation Die
Cutting Die
Forming Die
Single Operation Die
Multi Operation Die
Compound Die
Multi Operation Die
Progressive Die– Punches and dies are designed
so that successive stages in the forming of the part are carried out in the same die on each stroke of the press.
– The strip is fed from left to right.– The first punch is to make the
hole of the washer.– The washer is then blanked
from the strip.– The punch A is piercing the hole
for the next washer.
Theory of Shearing the Metal
Theory of Shearing the Metal
Theory of Shearing the Metal
Effect of Clearence
Bending Process
Bending Process
• A process by which a straight length is transformed into a curved length.
• Produce channels, drums, tanks.
Bending Operation
V-Die Bending
Punch Press Bends
Roll Forming
Roll Bending
Bending in sliding die machines
Press Brake Forming
• A single action press with a very long narrow bed.
• Used to form long, straight bends in pieces such as channels and corrugated sheets.
Press Brake Forming
• A single action press with a very long narrow bed.
• Used to form long, straight bends in pieces such as channels and corrugated sheets.
Beading
Method of Bending
(a) Three-roll bender:
(b) Wiper-type bender:
(c) Wrap forming:
Wiper-type bender:
Definition of terms used in bending
Spring Back
• Springback - the elastic recovery of the material after unloading of the tools
• To compensate with the unbending action of the springback, the metal should be slightly overbent.
Rubber Forming
Types of Stretch Forming
Shaving
- finishing operation in which a small amount of metal is sheared away from the edge of an already blanked part
- can be used to produce a smoother edge
Trimming