SHEET METAL OPERATIONS
• BLANKING OPERATION: PIECE PART (BLANK or COMPONENT)
• PIERCING OPERATION: - HOLE OF ANY PROFILE
• NOTCHING OPERATION: SIDE CUTTING OF ANY PROFILE
• SHAVING OPERATION: MAKING UNIFORM, SMOOTH AND PRECISE OUTER CONTOUR
• TRIMMING OPERATION: MAKING UNIFORM AND SMOOTH OUTER CONTOUR
• SIDE CAM PIERCING: SPECIAL HOLE MAIKKNG OPERATION IN DRAWN CUPS
• DINKING OPERATION: FOR FIBRE MATERIAL
• LOVERING OPERATION: PASSAGE FOR AIR TO ENTER
• LANCING OPERATION: PARTIAL TEARING OPERATION
• BENDING OPERATION: FOR SHAPING OF PRE-CUT BLANKS OR SHEETS IN STRAIGHT AXIS
• FORMING OPERATION: FOR SHAPING IN CURVED AXIS
• CURLING OPERATION: FOR HINGING, PIN GUIDEING PURPOSE
• FLANGING OR EXTRUDING: FOR ORIGINATING THREADS IN SHEET METAL
• DRAW OPERATION: TO SHAPE FLAT BLANK SHEET METAL INTO CUP
• COINING OPERATION: SOLID BLANK IS SQUEEZED TO REQUIRED PROFILE
• STAMPING OPERATION: DEPRESSED LETTERS, SYMBOLS, LOGOS ARE POSSIBLE ON SHEET METALS
• EMBOSSING OPERATION: REQUIRED FOR PLACING SCREWS, FOR RIVETTING ETC ON SHEET METALS
• BULGING: SWELLENING OF THE IRREGULAR PROFILE ON THE TUBE SURFACE
INTRODUCTION TO PRESS TOOLS
Sheet metal components are produced by a device called “Press tool”.
Generally, these tools are Cold working and manufactured to improve the productivity of the components qualitatively and quantitatively.
APPLICATION OF PRESS TOOLS
Press tools are extensively used for the production of sheet metal components in mass.
Examples
Most of the products namely, Television, Tape recorder, Radio, Refrigerator, Automobile Car, Scooter, Motorbike, Watch, Computer etc, consist number of components made of either plastic or sheet metal.
DEFINITION FOR PRESS TOOLS
Press tool as a device used for producing sheet components in large volume by applying an external force with the help of a machine tool called “PRESS”.
Press tools are mainly manufactured for high rate of sheet component production. If the requirement of components is less (less than 1000 numbers), these devices are not economical.
Hence, press tools are categorized according to the requirement, CATEGORIES OF PRESS TOOLS
Simple press tool
Medium production press tool
Large scale production press tool
High speed press tool
Precision press tool
Horological press tool (watch component) SPECIAL PURPOSE PRESS TOOLS
• Cantilever press tool
• Side cam press tool
• Straight cam press tool
• Angular cam press tool
• Curvature cam press tool TYPES OF PRESS OPERATION
• Cutting press tool
• Non - cutting press tool
• Hybrid press tool
(Cutting and Non-Cutting operation)
TYPICAL SKETCH OF A PRESS TOOL WITH BASIC PARTS
Space for Notes:
ACTIVITIES OF SHEET METAL INDUSTRIES
Sheet metal industries have a significant role in the present industrial society.
The production of sheet metal components have increased in many folds due to continuous research and development.
In our country, major activities lies with sheet metal industries only. As per the present survey, it occupies 55% of the industrial supplies.
Sheet metal industries are classified into many categories.
1. Fabrication industries
• House hold products
• Conventional products
• Commercial products
• Non – precision industrial products
• General engineering products 2. Medium precision industries
• Engineering products of second priority 3. High precision industries
• Aero space products
• High end engineering products
• Products with special material
• Products for research and development
For any industry to run efficiently 3 M are very important.
1) M = Money 2) M = Machine 3) M = Men
Money and Machine are supported by many agencies and consultancies, whereas, it is difficult to find skilled man power with good knowledge of both theoretical and practical.
SIGNIFICANT POINTS
• Most Tool and die makers need 4 or 5 years of classroom instruction and on-the-job training to become fully qualified.
• Employment is projected to decline because of strong foreign competition and advancements in automation.
• Despite the decline in employment, excellent job opportunities are expected.
NATURE OF THE TOOL MAKERS
1. Tool and die makers are among the most highly skilled workers in manufacturing.
2. These workers produce and repair tools, dies, and special guiding and holding devices that enable machines to manufacture a variety of products we use daily — from clothing and furniture to heavy equipment and parts for aircraft.
3. Toolmakers produce precision tools.
4. They are capable of handling machines that are used to cut, shape, and form metal and other materials.
5. They also produce jigs and fixtures that hold workpiece while it is bored, stamped or drilled and handle gauges and other measuring devices.
6. Die makers construct metal forms called “DIES”, that are used to cut metal in stamping.
7. Tool & Die makers use computer-aided design (CAD) to develop products and parts.
8. Tool & Die makers set up a test run using the tools or dies they have made to make sure that the manufactured parts meet specifications.
9. If problems occur, they compensate by adjusting the tools or dies.
10. They study metalworking processes, such as heat treating and plating.
11. Classroom training usually consists of tool designing, tool processing, blue print reading.
TRAINING, QUALIFICATIONS AND ADVANCEMENT
1. Even after completing a formal training program, Tool & Die makers still need years of experience to become highly skilled.
2. Most specialize in making certain types of Press tools, Moulds, or Dies.
3. While a State certification is not necessary to work as a Tool & Die maker, it gives workers more flexibility in employment and is required by some employers.
4. Apprentices usually must be at least 18 years old.
5. People entering this occupation also should be mechanically inclined, able to work and solve problems independently
6. They should have strong mathematical skills, and be capable of doing work that requires concentration and physical effort.
ADVANCEMENT
a) There are several ways for skilled workers to advance. Some move into supervisory and administrative positions in their firms or they may start their own workshop.
b) Others may take up computer courses and become computer- controlled machine tool programmers. With a college degree, a Tool &
Die maker can go into engineering or Tool design.
PRESENT GLOBAL STATUS OF TOOL AND DIE MAKERS
• About 75% of Tool & Die makers are in manufacturing industries, such as the fabricated metal products, Machinery and Aerospace products and Spare parts industries.
• Rest is self employed in the related field.
BASIC WORKSHOP MACHINES
Radial drilling
machine Center lathe Shaping machine
Universal milling machine
Slotting machine Planning machine
Horizontal boring machine
Vertical boring machine
Universal gear hobbing machine
Hydraulic hacksaw
machine
Grinding and Polishing Machines
Universal tool &
cutter grinder Pedestal grinder
Bench grinders / Polishers/Buffers
Abrasive belt grinders
Surface grinder
Roll grinding machine
Cylindrical /
centerless grinder
PRESS MACHINES
Metalforming press is one of the most commonly used manufacturingmachines.
Every day, millions of parts are produced by metalforming ranging from battery caps to automotive body panels. Therefore, even a small improvement may add to significant corporative gain.
Currently, the metal forming presses can be divided into twocategories:
a) MECHANICAL PRESSES b) HYDRAULIC PRESSES
The former is fast(high speed presses may reach up to several thousand shots per minute) and energy efficient (the large flywheel eases theimpulsive force), but lacks flexibility.
On the other hand, the hydraulic presses are flexible (their motions can be programmed) andaccurate, but are expensive to build and to operate. Recently,there are mechanical presses driven by servomotors.
They could perform as flexible as hydraulic presses with high speed.
Nevertheless, theyare even more expensive to build and to operate.
FLY PRESS
Fly presses are simple hand devices used for light work. These are extensively used in small scale industries and need very less space and any unskilled worker can operate with minimum supervision. Fly presses are available in different range of capacity.
Generally, Blanking, Piercing, Notching, V – Bending and L – Bending are performed using single stage press tools.
Bending press is a typical machine applies direct pressure to the material and forcing it to change shape.
PRESS BRAKE
A brake press is a special type of press machine that bends sheet metal into required shape.
Example:
• Backplate of a computer case
• Brackets
• Frame pieces
• Electronic enclosures
Some press brakes have CNC controls and can form parts with accuracy to a fraction of a millimeter. Machine presses are used extensively around the world for shaping all kinds of metals to a desired shape.
SAFETY ASPECTS
Injuries in a press may be permanent, because of the large forces used.
Bimanual controls (controls the use of which requires both hands to be on the buttons to operate) are a very good way to prevent accidents, as are light sensors that keep the machine from working if the operator is in range of the die.
TOOLS FOR POWER PRESSES
Planishing press has a set of plates with a relief, or depth-based design, in them.
The metal is placed between the plates and the plates are pressed up against each other deforming the metal in the desired fashion.
This may be Coining or Embossing or Forming
Punch press is used for forming holes
Capping Presses form caps from rolls of aluminium foil at up to 660 per minute.
Progressive press tool is a manufacturing method that can involve punching, coining, bending and several ways of modifying the metal, combined with an automatic feeding system.
The feeding system pushes or pulls a coil of metal through all of the stations of a progressive stamping die.
Each station performs one or more operations until a finished part is made per the requirements on the print. The final operation is a cut-off operation, which separates the finished part from the parent stock.
The parent stock material that is punched away in previous operations is considered as scrap metal or skeleton.
Power press with a fixed barrier guard
SHEET ROLLING MACHINE SHEARING MACHINE
PRESS BRAKE CNC BENDING MACHINES
CNC PUNCHING MACHINES
Presses & Hammers (for Sheet Metal and Forging applications)
Hand Fly Press and Arbour Press
'C' Frame Power Press
Pillar Type Power
Press Deep Drawing Press
Screw Press / Forging Press
Mechanical Forging Hammers
Friction Drop Hammers
Metal Gathering Machine / Heating
Upsetter
Metal & Sheet Metal Working Machines
Hand Lever Shearing Machines
Foot Operated Mechanical &
Motorized Guillotine Shears
Billet Shearing Machine
Universal Sheet Nibbling
Circle Cutting
Machines Spinning Lathes
Hand Operated and Motorized Swaging
Machines Sheet Folding
Mechanical Press Brakes
Pinch Pyramid Plate Bending Machine,
Hand Operated &
Motorized Bending Rollers & Taper
Rollers Seaming Machines
RO / ROPP Cap Sealing Machine
Machine vice
Section Straightening Machine
Cut to Length Line
Roll Forming Machines
Profile Bending Machine
Tapping - Threading Machines
Form & Thread
Rolling Machines Riveting Machine
Pantograph Milling &
Engraving Machines
MECHANICAL BLANKING & FORMING PRESSES
General view of a blanking and forming press ADVANTAGES
• More parts are produced
• Improved part dimensional accuracy
• Greater material strength
With its blanking and forming presses in this series offers manufacturing systems that permit cost-effective blanking, drawing, coining, piercing, and calibrating for the production of ready-to-install precision parts in a single operating sequence.
A number of fields - proven modules can be assembled to form application - specific, customized manufacturing systems. Press models in these series are mechanical presses with modified knuckle-joint drive.
They are available in nominal press forces of 200T up to 1500T and bed dimensions of 1,500 to 4,000 mm with fixed or adjustable stroke.
ADVANTAGES
• High stroking rates even for complex parts
• Multiple forming operations in a single press pass
• Extreme rigidity of the entire system
• Reduced impact speeds to protect dies
• Optimized slide motion
• Precision, ready - to - install components requiring no subsequent machining
Die space with progressive die MECHANICAL PRESS LINES
Mechanical press line with feeder automation
ADVANTAGES
1. Automated mechanical press lines ensure efficient manufacturing of medium-size and large panels in production of high volumes.
2. Depending on the number of required forming operations, the lines consist of four, five, or six automated mechanical single presses
3. Advanced mechanical presses offer a long slide stroke and thus permit the manufacture of complex part shapes.
4. Fully automated systems solutions for high - volume manufacturing 5. Fast and reliable component transport with advanced technology
6. Parts of the highest quality thanks to perfected press and bed cushion technology
7. The most advanced automation technology increases production rates 8. High levels of uptime for the lines & Process reliability
Mechanical press line with automation
SHEARING AND ITS ACTIONS
DEFINITION
The result of the force imposed on the stock material by the action of the blanking or piercing punch and die is called “Shearing Action”.
These are also related to the effective working and durability of the tool.
The 3 stages of Shearing action are:
1. PLASTIC DEFORMATION 2. PENETRATION
3. FRACTURE
1. PLASTIC DEFORMATION
When the elastic limit of the stock material is exceeded “Plastic deformation”
takes place.
A radius is formed on the top edge of the hole and bottom edge of the slug or blank. The radius is often referred to as “Roll over”.
Load
PUNCH
DIE
MATERIAL EDGE RADIUS
STOCK
2. PENETRATION
Punch is forced to penetrate into the stock material and a piece part is displaced into the die opening by a corresponding amount.
Load PUNCH MATERIAL
DIE
BURNISHED PORTION ON STOCK MATERIAL
BURNISHED PORTION ON SLUG OR BLANK
STOCK
This is the actual cutting portion of the cutting cycle. Compression of the slug material against walls of the die opening burnishes a portion of the edge of the blank.
BRIGHT BAND
At the same time the plastic flow pulls the material around the punch, causing a corresponding “Bright band or Burnished area” in the work material.
The sum of the edge radius depth and the burnished depth is referred to as Penetration.
3. FRACTURE
It is clearly shown in the illustration that further continuation of punch pressure causes fracture to start at the cutting edges of punch and the die. Under proper cutting conditions, the cut edge meets exactly at the breaking lines.
PUNCH Load
UNDER TENSION
UNDER COMPRESSION MATERIAL
DIE
BURNISHED PORTION ON STOCK MATERIAL
BURNISHED PORTION ON SLUG OR BLANK STOCK
The edge radius appears more when using soft materials. Highly burnished land is the result of the material being forced against the walls of the punch and die and rubbing during the final stages of plastic deformation.
The remaining cut portion is the Fractured area or Break.
4. BURR
Burr is the projection which appears during fracture.
This burr is not preferable, since the breaking lines of both the cutting lines will not meet each other, resulting in the reduction of the tool life.
BURR
BREAK
PENETRATION EDGE RADIUS
OR CUT BAND BURNISHED LAND
SEPERATED PIECE PART
Space for notes
CUTTING CLEARANCE & ITS EFFECTS
DEFINITION
Cutting clearance is the intentional gap provided between the punch and die for the purpose of separating a piece part from the stock material.
It is expressed in Percentage [%]
NATURE OF CUTTING CLEARANCE
The cutting clearance depends on the type of 1. STOCK MATERIAL
2. SHEAR STRENGTH OF THE MATERIAL 3. SHEET THICKNESS
A visual check of these characteristics tells whether the punch and die have the proper amount of clearance between them.
PLEASE NOTE:
The burr side of a Blank or Slug is always towards the Punch.
The burr side of the Pierced opening is always towards the Die opening
This illustration shows the uniform distribution of Cutting clearance between Punch and Die at each side
OPTIMUM OR NORMAL CUTTING CLEARANCE If the cutting clearance given is sufficient
• Burnished area or cut band will be approximately 1/3 (one third) of the sheet thickness
P IE C E P A R T
(1/3 rd O F S H E ET T H IC K N E S S )
D IE
P U N C H
B U R N IS H ED PO R T IO N O N S L U G O R B L A N K
T E N S IO N A L B U R R
ED G E R A D IU S
B U R N IS H E D L A N D O R C U T B A N D P E N ET R A T IO N B R EA K
P U N C H O U T L IN E
S T O C K M A T E R IA L D IE O U T L IN E
U N D ER T E N S IO N
U N D ER C O M P R E S S IO N O N S T O C K M A T ER IA L B U R N IS H E D P O R T IO N O PT IM U M C U T T IN G
C L E A R A N C E
O P T IM U M C U T T IN G C L EA R A N C E
EXCESSIVE CUTTING CLEARANCE
If the cutting clearance given is Excessive
• Cut band or the burnished area will be less than 1/3 (one third) of the material thickness
• Tensile burr (loose burr) will be more
P I E C E P A R T
D I E
P U N C H
B U R N I S H E D P O R T I O N O N S L U G O R B L A N K
B U R N I S H E D L A N D O R C U T B A N D E X C E S S I V E C U T T I N G
P U N C H O U T L I N E
S T O C K M A T E R I A L
D I E O U T L I N E
U N D E R T E N S I O N
B U R N I S H E D P O R T I O N O N S T O C K M A T E R I A L
U N D E R C O M P R E S S I O N E D G E R A D I U S
P E N E T R A T I O N B R E A K
T E N S I O N A L B U R R
C L E A R A N C E
E X C E S S I V E C U T T I N G C L E A R A N C E
( L E S S T H A N 1 / 3 r d O F T H E S H E E T T H I C K N E S S )
INSUFFICIENT CUTTING CLEARANCE
If the cutting clearance given is Insufficient
• More than one cut band
• Breaking lines will not meet each other
PIE C E PA R T
(M O R E T H A N 1/3 rd O F T H E S H E E T T H IC K N E S S )
BR E A K
U N D E R T E N S IO N
U N D E R C O M PR E S S IO N
D IE
PU N C H
B U R N IS H E D PO R T IO N O N S T O C K M A T E R IA L
B U R N IS H E D PO R TIO N O N S L U G O R B L A N K
T E N S IO N A L B U R R
E D G E R AD IU S
B U R N IS HE D L A N D O R C U T B AN D
P E N E T R A T IO N B R E A K
D IE O U T L IN E S T O C K M AT E R IAL IN S U F FIS C IE N T C U TT IN G
PU N C H O U T L IN E
C L E AR A N C E
IN S U FF IS C IE N T C U T T IN G C L E AR AN C E
MIS-ALIGNMENT OF PUNCH AND DIE
This is the actual shift between the punch and die which affects the proper cutting of the stock material.
Due to this there will be an irregular cut band appearing on the periphery of the component.
CHARACTERISTICS OF CUTTING
Cutting characteristics indicate whether, the Punch and Die are in perfect alignment.
It also enables him to detect and correct misalignment conditions, when they occur during assembling the die.
CLEARANCE INSUFFISCIENT CUTTING
PUNCH OUTLINE
DIE OUT LINE
UNDER TENSION STOCK MATERIAL
DIE
PUNCH
BURNISHED PORTION ON SLUG OR BLANK IRREGULAR
UNDER COMPRESSION BURNISHED PORTION
ON STOCK MATERIAL EXCESSIVE CUTTING CLEARANCE
BREAK
OR CUT BAND BURNISHED LAND EDGE RADIUS
TENSIONAL BURR PIECE PART
Hence, proper alignment should be made between punch and die for maximum tool life.
There are 3 methods commonly used by the tool makers to achieve this.
1. BY USING PRUSSIAN BLUE
When the cutting clearance punch and die is very less i.e., ranging from 0.01 to 0.03 mm per side this method is most appropriate.
P r u s s i a n B l u e
2. BY USING SHIM
Shims are thin foils of soft metal like copper, brass etc, which are inserted in between punch and die to maintain the cutting clearance.
3. FEELER GAUGE
Different thickness and length of checking gauges are available depending on the application. These are used for checking the gap between Punch and Die, after setting them in the die set.
0.1
0.2 0.4
0.5
0.3
3. BY USING SOURCE OF LIGHT
This is one more method of aligning the punch and die, where cutting clearance is ranging from 0.03 to 0.08 mm per side.
NOTE: Clearance is expressed in terms of PERCENTAGE (%) per side or
Clearance is expressed in terms of MILLIMETER (mm) per side
DETERMINING CUTTING CLEARANCE There are 3 important methods in practice
1. By referring the standard Cutting clearance chart 2. By using the Formula
3. By using the Thumb rule
1. By referring the STANDARD CUTTING CLEARANCE CHART Sheet thickness
C/2 = Clearance per side in mm Brass Soft steel Hard rolled
steel
Stainless
steel Aluminum
0.25 0.010 0.015 0.020 0.010 0.020
0.50 0.025 0.030 0.035 0.020 0.050
0.75 0.040 0.045 0.050 0.040 0.070
1.00 0.050 0.060 0.070 0.050 0.100
1.25 0.060 0.075 0.090 0.060 0.120
1.50 0.075 0.090 0.100 0.070 0.150
1.75 0.090 0.100 0.120 0.090 0.170
2.00 0.100 0.120 0.140 0.100 0.200
2.25 0.110 0.140 0.160 0.110 0.220
2.50 0.130 0.150 0.180 0.120 0.250
2.80 0.140 0.170 0.200 0.140 0.280
3.00 0.150 0.180 0.210 0.150 0.300
3.30 0.170 0.200 0.230 0.160 0.330
3.50 0.180 0.210 0.250 0.170 0.350
3.80 0.190 0.230 0.270 0.180 0.380
4.00 0.200 0.240 0.280 0.190 0.400
4.30 0.220 0.260 0.300 0.210 0.430
4.50 0.230 0.270 0.320 0.220 0.450
4.80 0.240 0.290 0.340 0.230 0.480
5.00 0.250 0.300 0.360 0.240 0.500
Space for notes
2. By using the FORMULA
C/2 = 0.01 X t X √ fs
Where, C/2 = Cutting clearance per side t = Sheet thickness in mm
fs = Shear strength of the stock material in kg /mm2 SHEAR STRENGTH CHART
Material Shear strength (fs) in kg/mm2
Soft Hard
Steel with 0.1 % C 24 32
“ 0.2 % C 30 40
“ 0.3 % C 36 48
“ 0.4 % C 45 56
“ 0.6 % C 55 72
“ 0.8 % C 70 90
“ 1.0 % C 80 105
Stainless steel 50 56
Silicon steel 45 55
Steel deep drawing quality 30-35 -
Aluminum A 1 99 & 99.5 7-9 13-16
Aluminum alloy A1 – Cu – Mg 22 38
Bronze rolled 32-40 40-60
Brass 63 & 72 22-30 35-40
Copper 18-22 25-30
Tin 3 4
3. By using the THUMB RULE
Clearance can also be calculated in Percentage [%] of Sheet thickness:
C/2 (CLEARANCE PER SIDE)
Sl. No. Material Percentage of Clearance
1 Brass 5%
2 Soft steel 6%
3 Hard steel 7%
4 Stainless steel 5%
5 Aluminum 8 – 10%
NOTE:
1. Pierced hole is getting the dimension of the PIERCING PUNCH.
Hence, the clearance should be added to the die opening.
2. Blanked component is getting the dimension of the BLANKING OPENING or DIE.
Hence, the clearance should be subtracted on the Blanking punch.
Example: Material: Steel with 0.3% Carbon Shear strength (fs) = 45 kg/mm2 Sheet thickness (t) = 1.75 mm Component: Dimension of the Piercing punch = Ø15.00 mm Dimension of the Die opening =15+ (2 X C/2) (From the table C/2 = 0.10 mm) = 15 + (2 X 0.1)
= 15 + 0.2
= 15.20 mm
Dimension of the Die opening = Ø15.20 mm Dimension of the Blanking punch = 35 – (C/2 X 2) (From the table C/2 = 0.10 mm) = 35 – (0.1 X 2)
= 35 – 0.2
= 34.80 mm
Dimension of the Blanking punch = 34.80 mm x 34.80 mm Dimension of the Blanking die = 35.00 mm x 35.00 mm
SHEAR FORCE & ITS APPLICATIONS
Shear force is the force required to separate a piece part from the stock material with plain punches.
It is expressed in terms of Tonne.
This force is also required to determine the thickness of various plates necessary in the construction of the tool and for selecting the appropriate press.
SHEAR STRENGTH
It is the strength required for producing fracture in the plane of cross section, when acted on by the SHEAR FORCE.
Shear strength is expressed in Kg/mm2 TENSILE STRENGTH
The tensile or ultimate strength is the strength, corresponding to the maximum load reached before rupturing the specimen.
It is also expressed in Kg/mm2
FORMULA USED TO DETERMINE THE SHEAR FORCE K x L x S or (fs) x t
F = --- = …….. Tonne 1000
Where,
F = Shear Force
K = Constant value 1.3
(Because sheet thickness will not be uniform) L = Total length of cut in mm.
S or (fs) = Shear strength in Kg/mm2. T = Thickness of the stock material in mm.
1000 = To convert kg to Ton PRESS SELECTION VALUE
It is the value which is very much helpful in choosing an appropriate press for successful production and efficient working of tool.
PRESS SELECTION VALUE
(Fp) = F + 20% of F, Where, F = Shear Force
METHODS OF REDUCING THE SHEAR FORCE
Sometimes availability of press capacity may be slightly less than the required tonnage. To overcome from this problem there are two effective methods in practice.
1. By providing shear angle on the cutting punches
2. By varying the height of the cutting punches (Staggering the punches) 1. SHEAR ANGLE
It is the angle provided on the cutting face of either punch or die to reduce the shearing force as shown in the illustration.
Advantage of Shear angle: By providing this angle the punch or die will gradually come in contact with the layers of the stock material and cutting or shearing action will be performed layer by layer.
This method is limited to secondary importance components as the cut edge will not be good, compared to normal shearing operation.
1t 1t
1t
1t
1t
1t
not flat Component is at an angle
Cut edge is component
Dished (flat)
component Normal at an angle
Cut edge is
SHEAR ANGLE PROVIDED ON DIE SHEAR ANGLE PROVIDED ON PUNCH
2. STAGGERING
This is one more method of overcoming from the problem of shearing. After assembling the punches with top unit, grind all the cutting punches to one level.
Select a set of punches in such a way that the load required to cut will be equal to the other set of cutting punches. Reduce the height of one of the sets at least by one stock thickness.
Staggering Punches fixed
in punch holder
By this method one set of punches will start shearing the material and other set will come in contact with the stock material only after the completion of the operation performed by the previous set of punches.
Hence, whenever this method is adopted in the tool, there will be two IMPACT CUTTING SOUND, which can be heard very clearly. This method of varying the punch height is called as “Staggering”.
Space for Notes
CUTTING OPERATION
IDENTIFICATION OF OPERATIONS
BLANKING: Cutting the outer contour of a piece part. After completing all the remaining operation, it is called as “COMPONENT”.
PIERCING: Hole originated within the piece part. Any geometrical profile of hole can be pierced.
NOTCHING: Partial cutting is done at the side of the stock strip. Usually, notching operations are done to simplify the blanking profiles.
SIDE NOTCHING
CUT-OFF: Single line cutting without Scrap Bridge. Produced components are of secondary importance. Usually, used to produce commercial components with maximum economy on tool cost
PART-OFF: Double line cutting producing scrap normally equal to the value of one scrap bridge.
TRIMMING: Secondary operation carried to redefine the contour of the component.
Usually Drawn cups and Die cast components are trimmed to remove the excess material appeared during the production.
SHAVING: Secondary operation performed on pre blanked components to resize the dimensions and achieve higher accuracy.
This operation produces smooth surface on the periphery of the component through its thickness
SIDE PIERCING: Usually, this is a secondary operation performed on drawn cups.
Cups of required shape and size are drawn followed by cam piercing.
DINKING: Components from fiber material like Nylon, Plastics, Rubber, Fiber glass, Printed circuit boards (PCB) etc, are produced with this operation.
Blanking punch is the only member which is employed for cutting the contour.
Piercing is done as usual with punch and dies. The cutting face of the piercing punch is made as concave profile.
NON – CUTTING OPERATION
IDENTIFICATION OF OPERATIONS
BENDING: Bending is performed on pre-cut sheets or blanks to obtain a required angle. It is done in straight axis. General bending profiles are L – Bending, U – Bending, V – Bending and Z-Bending.
Usually, Bending has to overcome both “Tensile stresses” as well as
“Compressive stresses”. When Bending is done, the residual stresses make it re-bend or spring back towards its original position, so we have to over bend the sheet metal keeping in mind the residual stresses.
FORMING: Any profile with curves can be formed with proper study of material behavior. Materials must posses’ good ductility and deep draw quality.
Forming takes place in a curved axis.
CURLING: More than 3/4th forming in a continuous curvature is referred to as Curling.
This operation is divided into a) Pre curling.
b) Final curling
Material must be soft enough to accept the severity of the forming.
Hence, deep draw and extra deep draw quality materials are preferred.
Usually, this is employed for the production of hinges for links, to the components which need fulcrum points etc.
FLANGING: Sometimes it is also referred to as “Extruding”. Many methods are used in this operation.
1. Flanging without pre pierced hole 2. Flanging with pre pierced hole
3. Flanging with pre pierced hole located by the punch pilot
The height of the flange depends on the diameter of the pre-pierced hole.
DRAWING: Cylindrical or Rectangular or Square cups are produced with this operation.
Material undergoes severe strain and flow into the die from all the directions. Hence, it must have maximum tensile strength and yielding capability.
COINING: The material will experience maximum strain, because of squeezing. The die halves are pressed against the material, which is sandwiched and forced to accept the inner profile of the die.
Coining requires higher tonnage than any other press operation.
STAMPING: Punch profiles are directly transferred on to the work piece.
Depressed profiles to a certain depth are possible with this operation.
EMBOSSING: Sheet metal surfaces can be depressed to a depth till it tears. Hence, before the material selection “CUPPING TEST” has to be conducted.
In this operation thinning does not take place.
MATERIALS AND THEIR PROCESS
Different materials are very essential to construct the tool and production of components.
Materials are divided into two main groups.
1) Steel material for the construction of the tool 2) Sheet material for the production of component 1) STEEL MATERIAL FOR THE CONSTRUCTION OF THE TOOL
The construction of tool involves various types of steel material. It depends on the function of the part in the tool.
Usually, HCHCr, OHNS, St-42, Mild steel (MS) and 17Mn1Cr95 materials are used.
TOOL MATERIAL AND ITS IS: CODIFICATION
Sl. No. Material IS: Codification
1. HCHCr: High Carbon High Chromium steel T215 Cr12 W90
2. OHNS Oil Hardened Non – Shrinkable steel T110 Cr1 W2
3. St–42 Steel with 0.42% Carbon
4. MS Mild steel
5. LCS Low carbon steel or Case hardening steel 17Mn1Cr95:
The below chart may be referred for appropriate temperature required to heat treat different materials commonly used in tool making. Quench Media Water Oil or Air Oil Air Air Oil
HRc 62 – 40 62 - 56 62 - 60 62 - 60 52 – 42 62 - 56
Tempering temp o C 120 - 350 200 - 350 550 550 550 - 590 150 - 300
Hardening temp o C 750 - 780 920 - 970 1250 -1300 1100 - 1175 950 – 1000 820 – 840
Annealing temp o C 750 - 780 820 - 850 820 820 850 - 875 750
Type of steel High Carbon Steel (2.15%) HCHCr (2.15%) T215Cr12W90 HSS(W) (0.6%) HSS (Mo) HDS (0.4%) OHNS (1.1%) T110 Cr1 W2
Sl. No. 1 2 3 4 5 6
A brief description is given below about the material and the tool element.
1. Die and Punch
for cutting operation --- HCHCr (T215 Cr12 W90) 2. Die and Punch
for Non-Cutting operation --- OHNS (T110 W2 Cr1) 3. Punch Back plate --- OHNS or 17MN1CR95 4. Die Back plate --- OHNS or 17MN1CR95 5. Punch plate --- Mild steel (MS)
6. Stripper plate --- Mild steel (MS) 7. Stripper insert --- OHNS
8. Guide plate --- Mild steel (MS) 9. Strip support plate--- Mild steel (MS)
10. Top plate --- Mild steel (MS) or Cast iron 11. Bottom plate --- Mild steel (MS) or Cast iron 12. Shank --- Mild steel (MS)
13. Guide Bush and Pillar --- OHNS
14. Tie bar --- Mild steel (MS) 1. HIGH CARBON HIGH CHROMIUM STEEL (HCHCr)
These are specifically used for cold working press tools and oil hardened up to 60-62 HRc.
The chemical composition:
a) 2.15% Carbon, b) 0.9% Tungsten c) 12% Chromium
d) Small percentage of Silicon and Manganese.
These materials are best suited for cutting dies and punches, as they retain the cutting edges for a longer period.
2. OIL HARDENED NON-SHRINKING STEEL (OHNS) These steels consists
a) 1%-2% Carbon b) 4%-12% Chromium
Oil hardened upto 60-62 HRc. But for non-cutting operations 56-58 HRc is quite sufficient.
3. MILD STEEL (MS) and St-42
These are used for most of the parts in press tool, mould box, jigs and fixtures.
Mild steel contains
a) 0.3% Carbon
b) 0.1% - 0.8% Manganese.
Example: Steel En2. This steel can also be case carburized and hardened upto 54-56 HRc.
Free cutting Steel like “En” contains less than 0.15% carbon and cannot be hardened.
4. CAST IRON (C.I)
Cast iron contains 2.25 - 2.75% carbon and can absorb vibrations well and suitable for bases, machine beds and bodies of fixtures. These have self lubricating properties, hence also suitable for machine slides and guide ways.
5. 17Mn1Cr95
These are case hardening steels have good toughness and cost saving. Used where there is no movement of parts and needs good support for the other tool elements.
As the percentage of carbon in the material is not sufficient for hardening process the case must be enriched with carbon by carburizing process.
A case depth of 0.5 to 0.7mm is achieved by a prolonged period of 4 to 5 hours.
2) SHEET MATERIAL FOR THE PRODUCTION OF COMPONENT
Many types of sheet materials are used for the production of components.
Namely,
Non – Conventional materials
a) Plastic coated paper b) Thin plastics
c) Poly-fibres
d) Corrugated sheets
e) Printed circuit boards (PCB) f) Tablet strips
Conventional materials
1. Steel – CRCA (Cold Rolled Close annealed) D – Quality (Draw quality)
DD – Quality (Deep Draw Quality)
EDD – Quality (Extra Deep Draw Quality) 2. Brass – 1/4th hard, Half hard, 3/4th hard and Full hard 3. Copper - 1/4th hard, Half hard, 3/4th hard and Full hard 4. Phosphor bronze -1/4th hard, Half hard, 3/4th hard and Full hard 5. Aluminum – 1/4th hard, Half hard, 3/4th hard and Full hard
2A) FINISHING OPERATION OF COMPONENTS
a) VIBRATORY FINISHING GUIDE
In vibratory finishing, energy in the form of vibratory forces is transformed by the machine's drive system into a mass of loose media and then into the parts.
The entire load is in motion at same time so that the media act against the parts throughout the complete mass.
Producing good surface finishes using barrel finishing depends on the right selection and use of tumblers, abrasives, lubricating agents, carrying agents and polishing agents.
Barrel finishing, also known as “Barrel tumbling”, is a surface improving operation in which a mixture of parts, media and compounds are placed in a six- or eight-sided barrel and rotated at a predetermined speed for the purpose of rounding corners, de-burring, grinding, de-scaling, de-flashing, improving surface finish, burnishing, polishing and radiusing parts in bulk.
It works by tumbling parts in a rotating barrel, thus creating friction by tumbling parts against each other and against other materials, such as media and compounds.
Tumbling Highlights
• Parts can be finished less expensively than by hand.
• Many parts can be processed at one time.
• Requires very little handling.
• Parts are tougher and stronger after tumbling
• Tumbling provides a certain amount of stress relief
• Forgings and castings can be blended
• Machine parts and stampings can be deburred and burnished to a high finish
• On long runs, the systems can run overnight
• Careful and proper machining of your parts will save tumbling time
MATERIAL WEIGHT CALCULATION
DEFINITION 1. WEIGHT
It is the sum of the volume and the specific gravity of the material. Weight is expressed in Kgs. Value of Specific gravity for each material varies depending on the density of molecules in it.
CALCULATION:
Volume X Specific Gravity
Weight =--- =--- Kg 1000000
V X Sp. Gr.
W =---=--- Kg 1000000
Where, W = Weight of the material in Kg
V = Total volume of the material in mm3 Sp. Gr. = Specific gravity in Kg/mm2
Volume of the Flat material =L X B X t
Where, L = Length of the material in mm B = Width of the material in mm T = Thickness of the material in mm
∏ X D2 Volume of the Round material = --- X t
4 Where, ∏ = 3.1416
D = Diameter of the material in mm t = Thickness of the material in mm
SPECIFIC GRAVITY CHART
Material Specific gravity gm/Cm3
Steel 7.85
Cast steel 7.85
Grey cast iron 7.2
High speed Steel 9.0
Hard metal H1 14.75
Invar (36% Ni) 8.7
Brass (Ms 60) 8.5
Al bronze 8.4
Al cast bronze 7.6
Tin bronze 8.6
Lead bronze (Pb Bz 25) 9.5
Al cast bronze 2.8
BASIC CONSTRUCTION OF THE TOOL 1. Die and Punch for cutting operation --- HCHCr
2. Die and Punch for Non-Cutting operation --- OHNS
3. Punch Back plate --- OHNS or 17Mn1Cr95
PUNCH BACK PLATE Material = OHNS
A A
4. Die Back plate --- OHNS or 17Mn1Cr95
Material = OHNS
A A
DIE BACK PLATE
5. Punch plate ---Mild steel (MS)
6. Stripper plate --- Mild steel (MS)
SECTION-AA
A A
7. Stripper insert --- OHNS
SECTION-AA
A A
8. Guide plate --- Mild steel (MS)
9. Strip support plate--- Mild steel (MS)
SECTION-AA
10. Top plate --- Mild steel (MS) or Cast iron
Material = St-42 TOP PLATE
SECTION-AA
A
A
11. Bottom plate --- Mild steel (MS) or Cast iron
Material = St-42 BOTTOM PLATE
SECTION-AA
A
A
12. Shank --- Mild steel (MS)
13. Guide Bush and Pillar --- OHNS
14. Tie bar --- Mild steel (MS)
SECTION-AA
15. Die set and its types
1. Diagonal pillar dies set
2. Rear pillar or Back pillar die set 3. Center pillar die set
4. Four pillar die set
Thread for fixing the Shank
Guide pillar plate
Top
Bottom plate
Guide bush H7/j5
H7/h6
SHUT HEIGHT OF THE TOOL
H7/p6
SECTIONAL VIEW OF A STANDARD DIE SET
PROGRESSIVE STAMPING DIE
Progressive die with strip and punching
A progressive stamping die is one of the types of press tools, designed and built to convert a flat strip of metal into parts that conform to component specifications.
FUNCTION OF PROGESSIVE TOOL
The die is mounted on a suitable press. As the ram moves up, the punch unit opens and closes when the press moves down.
The stock material is fed through the die while the die is open to a precise amount with each stroke of the press.
When the punch unit is brought down, the tool performs its work on the sheet metal. Due to this action one or more completed piece parts will fall down through the opening in the bottom plate.
These dies can modify the stock metal into different shapes like Bending, Embossing, Drawing, Forming, Horning, Extruding, Coining, and Punching. Different hole profiles is possible to cut in the stock metal.
Since additional work is done in each stage of the die, it is important that the strip be advanced very precisely, so that it aligns within accurately as it moves from station to station.
ROLE OF PILOTS DEFINITION
Pilots are non-cutting male members, mounted usually in the punch holder for re- registering the pre-pierced hole for consecutive stations especially in progressive tools.
These are made with good tool steel material that is OHNS (T110 W2 Cr1) and hardened up to 56-58 HRc. These pilots are also available readily (material used is HSS) in the market with standard diameter and length.
Function of a Pilot:
The function of a pilot is to position the stock strip accurately and bring it into proper register for successive stations.
Bullet shaped or conical "pilots" enter previously pierced round holes in the strip to assure this alignment, since the feeding mechanism usually cannot provide the necessary precision in feeding.
VARIOUS OTHER TYPES OF PILOT NOSE PROFILES
TYPES OF PILOTS
BULLET NOSE PILOT
FLAT ACCORN PILOT
RECTANGULAR PILOT
CUT-OFF PILOT
CONICAL STUB NOSE PILOT
PILOT NOSE CORNER RADIUS
ROLE OF STOPPERS DEFINITION
Stoppers are stopping agents, fixed or engaged on the die to arrest the feeding movement of the stock strip. This is the location of the actual stopping point or stage against which the stock is halted.
TYPES OF STOPPER
Sl. No. Name of the stopper Sketch
1 Solid stopper or Solid stop block
Butting surface
Solid Stop block
2
Pin stopper a) Plain pin b) Headed pin
3 Side or stage stopper
4 Trigger stopper
Heeled punches
Specially, the illustrated punch is a notching punch. However, principles relating to the heel function will be much the same for other punches as well.
Here, the heel is made in a manner commonly used in progressive dies. The nature of the notching operation is such that, cutting force at the front of the punch is unopposed and thus tends to displace the punch away from the front cutting edge.
Partial notching will tend to displace the punch in a direction parallel to the feeding. The purpose of a heel is to support the punch by resisting displacement. This type of heel is an integral boss extending beyond the working face of the punch.
Partial cutting punch with Heel
HEEL
SCRAP
Primary strip width Secondary strip width
The heeled portion is made a sliding fit in the die opening on three sides.
Therefore, the heel affords lateral thrust resistance along any displacement included within the three directions.
Pitch punch
Pitch punches are cutting punches used in the progressive tools for accurate feeding of the strip. These are made of good Tool steel material i.e. (T215W90Cr12) HCHCr and hardened up to 60-62 HRc and ground to the exact size equal to PITCH.
These punches are suitable for sheet thickness less than 2 mm. Pitch punches are placed in the very first stage of the operation.
These are also called as “Partial cutting punches” for the reason that they cut only a portion of the side of the stock strip which is exactly equal to ONE PITCH.
Since pitch punches cut only a portion of the side of the stock material. Due to this cutting action is imbalanced which deflects the punch resulting in punch breakage.
Hence, heels are provided behind the cutting edge to support the pitch punch.
thickness 0.5xSheet
R2(TYP) M5 0r M6
x 20mm deep 2xscrap+2mm
5to6mm 45.0°
a f
b
Pitch punch with HEEL
Secondary strip width
Primary strip width
SCRAP
HEEL
VALUES FOR SIDE SCRAP AND SCRAP BRIDGE Sheet thickness in
mm
Component horizontal width in Millimeters
Upto 10 10 – 50 50 -100 100 -150 150 - 250
0.5 1.5 2.0 3.0 3.5 4.0
1.0 1.0 1.75 2.0 2.5 3.0
1.5 1.5 2.0 2.5 3.0 3.5
2.0 2.0 2.5 3.0 3.5 4.0
2.5 2.0 3.0 3.5 4.0 4.5
3.0 2.0 3.5 4.0 4.5 5.0
4.0 2.5 4.0 4.5 5.0 5.5
5.0 3.0 4.5 5.0 5.5 6.0
6.0 3.5 5.0 5.5 6.0 6.5
7.0 4.0 5.5 6.0 6.5 7.0
8.0 5.0 6.0 6.5 7.0 8.0
9.0 6.0 7.0 7.5 8.0 9.0
10.0 7.0 8.0 8.5 9.0 10.0
Out side Inside
step headed
stop pin step headed
stop pin
Outside step headed stop pin
Die plate Stripper
NON – CUTTING OPERATION IN DETAIL
INTRODUCTION
Present day calls for lots of innovative products which essentially require good knowledge of tooling.
Mechanical, Electrical, Electronic and Automobile industries need products having verities of profiles for different applications.
Non - cutting operations are those which shape the flat blank to the required profile.
In these operations material undergoes severe strain and needs very good knowledge about the material property, behavior, strength and its limitations.
In many tools these operations are integrated depending on the size of the component.
Examples of products for Non – Cutting operations 1. Pressure cooker 2. Pressure pan 3. Utensils
4. Contacts and Relays 5. Heating elements 6. Computer hardware
TYPES OF NON - CUTTING PRESS TOOL OPERATIONS
NON – CUTTING 1. FORMING 9. COINING 2. BENDING 10. STAMPING 3. DRAWING 11. IRONING 4. CURLING 12. PLANISHING 5. FLANGING 13. SWAGING 6. DIMPLING 14. EXTRUDING 7. EMBOSSING 15. BULGING 8. HORNING
HYBRID
1. LANCING 2. LOVRING
7. Electrical appliances 8. Gear box cover
9. Automobile parts – Doors, Bonnet, Wheel drums Clutch plates etc.,
10. Aviation and Space components
It is the basic behavior of material. Whenever a sheet metal deformed and an external loading is unloaded, it will be restored to its initial state i.e., after unloading nothing in the state of structure remains of the previous condition.
CHARACTERISTICS OF MATERIAL
This unique character of the material is most useful in sheet metal fabrication because most products of sheet metal press work are not flat components that can be produced by die cutting operations alone.
They generally have a third dimension obtained by a shaping operation, which can be performed in the same die as of the cutting operation or in a separate die.
Shaping operations are generally divided into three groups.
GROUPS OF NON – CUTTING
DIES
BENDING FORMING DRAWING
TYPES OF OPERATIONS IN NON- CUTTING DIE GROUPS
BENDING
1. WIPING 2. AIR-BEDING
3. OBTUSE ANGLE BENDING
4. ACUTE ANGLE BENDING
5. L-BENDING 6. U- BENDING 7. V- BENDING 8. Z-BENDING
FORMING
1. FLANGING 2. COINING 3. SWAGING 4. BULGING 5. NECKING 6. CURLING 7. HORNING 8. EMBOSSING 9. FLARING 10. STAMPING 11. EXTRUDING 12. NIBBLING
DRAWING
1. SQUARE CUP 2. RECTANGLE CUP 3. TRIANGLE CUP 4. CONE CUP 5. SHALLOW CUP 6. DEEP DRAW CUP 7. FLANGED CUP
1. BENDING
Bending is shaping the material around a STRAIGHT AXIS, which extends completely across the material. One or more bends may be involved in the bending dies.
These dies are important class of press tools.
The sheet material flow in these tools is always uniform and its thickness remains unchanged.
TYPES OF BENDING
a) L – Bending b) U - Bending c) V – Bending d) Z – Bending
V - B E N D I N G
U - B E N D I N G L - B E N D IN G
Z - B E N D I N G
NEUTRAL PLANE AND ITS IMPORTANCE
(SQUEEZED)
(STRETCHED)
DIE of bend
Outside Inside of bend FORCE
Neutral plane
Neutral plane is an imaginary plane exists between the area under tension and the area under compression.
The neutral plane always moves towards the inner surface at a distance of one- third (1/3) to one-half (1/2) the thickness of the material.
EFFECT OF GRAIN DIRECTION DURING BENDING DEFINITION
The particle chain in the sheet material is called “Fiber” and these fibers are arranged parallel to each other and called as “Grain direction”.
In bending operation the grain direction should be considered for effective bending of the component.
CONDITION OF GRAIN DIRECTION IN BENDING
The Grain direction should always be perpendicular to the bend axis.
Bending will not be effective and bent portion will not be strong, when the axis of bend is parallel to the grain direction.
DETERMINING THE FLAT LENGTH BY BEND ALLOWANCE METHOD
Where,
B. A = Bend allowance [Arc length of neutral axis] in mm Θ = Bend angle in degrees
IR = Inside radius of bend in mm t = Sheet metal thickness in mm K = Constant for neutral axis location K = 0.33 when IR is less than 2t K = 0.50 when IR is more than 2t DEFECTS IN BENDING
1. SPRING BACK
After bending operation if the pressure is released, elastic stresses remaining in the bend area will cause a slight increase in the bend angle.
Material movement of this type is known as “SPRING BACK”.
Θ x Π (IR + Kt) B A = ---
180
SPRING BACK UNDER LOAD
SPRING BACK BENDING RETAINED
2. THINNING
This defect occurs when there is misalignment and axial deflection between the punch and die.
If the clearance between punch and die is less than the sheet thickness, results in the elongation of side wall of the component.
THINNED AREA
METHODS OF PREVENTING SPRING BACK
A) Over Bending in V-bending and Air-bending dies
B) Corner setting or Coining in V–bending and U - Bending A) OVER BENDING
In this method the blank is bent to a lesser angle than required and the blank is spring back to the required angle.
DIFFERENT METHODS OF OVER-BENDING
CASES SKETCH
1. Over bending in a V-bending die is accomplished by under sizing the punch to 880.
90.0°
90.0°
Punch 88°
Die
Component
2. In a single L or U-bending die clearance between punch and die must be slightly less than the sheet metal thickness and punch must be
under sized to 880. pad
90.0°
88.0°
Die
Punch
Pressure
Component
3. In this case the punch is made to 900 but the bending die is under sized to 880 and clearance provided between punch and die is less than the sheet thickness.
Punch Die
88 .0 °
Pressure pad
4. In this case both punches are under sized to 880 to allow the component to achieve 900
88.0° Punch 88.0°
Pressure pad Movable
side punch
B) CORNER SETTING
In this method the metal is squeezed slightly in the corner in order to relieve elastic stresses. This method is also known as ‘Coining or Squeezing’.
The punch nose is modified for corner setting operation. When the punch is bottomed pressure builds up rapidly.
REMEDIES SKETCH
1. Squeeze the intersection points to retain the bent angle permanently.
2. Bottoming is done by squeezing the bent area to retain the bend after
releasing the load. Die
Punch
90.0°
Punch Detail-A A
88°
BENDING FORCE
It is the amount of force required to bend and give a desired shape to the piece part. It depends on the sheet thickness, die opening factor, length of bend and the amount of bottoming or ironing used.
FORMULA TO DETERMINE BENDING FORCE K X SU X W X t2 FB = ---
L Where,
K = Die opening factor (0.33) L = Length of bend (rd + rp + C) rd = Die radius
rp= Punch radius C= Die clearance
Su= Ultimate tensile strength in kgs/mm2 t = Sheet thickness
W = Width of the component or stock material
Where, K is 0.33, when the die opening is less than [<] 5 times the thickness, 0.667 when the die opening is 5-10 times the thickness and 1.20 when the die opening is 10-16 times the thickness.
Pressure pad force FP = 0.5 x FB
Total force required = FP x FB
2. FORMING
The operation of forming is similar to bending except that the line of bend is along CURVED AXIS instead of a straight one. The metal flow is not uniform. Forming dies transfers more complex forms to sheet metal components.
3. DRAWING
In draw tools, flat blank is transformed into a cup or shell. The parent material is subject to severe plastic deformation.
4. HORNING
Horn dies are provided with an arbor or extended horn over which the parts are placed for secondary operations such as Seaming.
Horn dies may also be used for piercing holes in the sides of shell.
5. CURLING
It is an operation of rolling the edges of the sheet metal into a curl or roll. The purpose is to strengthen and provide a protective edge.
Example: A hinge in which both members are curled to provide a hole for inserting the hinge pin.
Pre-curling
Component with
Pre-curling Uniform curve
Good quality component
Deformed
component Inferior
quality component Component
without
Final radius
2
1
4
3 5
6 6
5
3
4 2
1
6. BULGING
Bulging is an internal forming operation used to expand portions of a drawn shell or tube. The bulging force is applied from inside the tubular structure which transmits through a medium that will flow, but does not compress.
Most common Medias are rubber, urethane, bulging oil or water. This presses and expands the walls of a cup, shell or tube with an internal expanding segmental punch or compressed air or liquids or semi liquids, such as waxes or tallow of rubber and other elastic materials.
