Combination DieCombination Die

Combination DieCombination Die

Progressive DieProgressive Die

Principals of metal Principals of metal cuttingcutting

Improper Clearance

ClearanceClearance

Angular ClarenceAngular Clarence It is usually ¼ to 1½ degree per side It is usually ¼ to 1½ degree per side

but occasionally as high as 2but occasionally as high as 200

Cutting ForcesCutting Forces

Shear strengths of various metalsShear strengths of various metals

Energy CalculationsEnergy Calculations

Effect of Shear on cutting forcesEffect of Shear on cutting forces

Staggering of punchStaggering of punch

Minimum Diameter of PiercingMinimum Diameter of Piercing

If If

Inverted Blanking DieInverted Blanking Die

Factors which will influence the Factors which will influence the stock layoutstock layout

1.Economy of material.1.Economy of material. 2. Direction of material grain or fibre.2. Direction of material grain or fibre. 3. Strip or Coiled stock.3. Strip or Coiled stock.

4. Direction of burr.4. Direction of burr. 5. Press used.5. Press used. 6. Production required.6. Production required. 7. Die cost.7. Die cost.

Economy of materialEconomy of material

Strip LayoutStrip Layout

Contd.Contd.

Distance between the Distance between the blank and edge of strip blank and edge of strip known as back scrap known as back scrap (front scrap), (front scrap), determined by equation.determined by equation.

The distance between The distance between successive blanks and successive blanks and also the scrap bridge ‘b’ also the scrap bridge ‘b’ is given in table.is given in table.

Contd.Contd.

No. of blanks which No. of blanks which can be produced can be produced from one blank from one blank stock.stock.

Scrap remaining at Scrap remaining at the end of one the end of one length of strip.length of strip.

Measure of material utilizationMeasure of material utilization

ήήmm should not be less than 70% for economical should not be less than 70% for economical

working. However, for complicated shapes of working. However, for complicated shapes of blanks blanks ήήmm can be less than 70% can be less than 70%

Simple layout of Die BlockSimple layout of Die Block

Die Block ThicknessDie Block Thickness

Die OpeningDie Opening

The side walls of the die block opening The side walls of the die block opening should be provided with sufficient relief or should be provided with sufficient relief or taper so that the blank drops clear through.taper so that the blank drops clear through.

The nominal size and outline of the die The nominal size and outline of the die cavity is identical with blank dimension. At cavity is identical with blank dimension. At least a distance equal to stock thickness least a distance equal to stock thickness should be provided between blanks and the should be provided between blanks and the edge of strip. edge of strip.

The Die wall thickness from the edge of the The Die wall thickness from the edge of the die opening to the die block border, that is die opening to the die block border, that is the Distance ‘A’the Distance ‘A’

Contd.Contd.

A = 1.5 to 2 times the Die thickness A = 1.5 to 2 times the Die thickness (T) for small dies.(T) for small dies.

A = 2 to 3 times the die thickness for A = 2 to 3 times the die thickness for larger dies.larger dies.

Fastening of die blockFastening of die block

According to empirical ruleAccording to empirical rule

Dowel PinsDowel Pins

Contd.Contd.

Center of PressureCenter of Pressure

When the shape of blank is irregular, the When the shape of blank is irregular, the summation of forces about the center line of summation of forces about the center line of press ram may not be symmetrical.press ram may not be symmetrical.

Due to this, bending moment will be introduced in Due to this, bending moment will be introduced in the press ram, producing misalignment and the press ram, producing misalignment and desirable deflection.desirable deflection.

To avoid this the center of pressure of the To avoid this the center of pressure of the

shearing action of the die must be found.shearing action of the die must be found.

StrippersStrippers

After a blank has been cut by the punch on its After a blank has been cut by the punch on its downward stroke the scrap strip has a tendency downward stroke the scrap strip has a tendency to expand.to expand.

On the return stroke of the punch, the strip has On the return stroke of the punch, the strip has the tendency to adhere to the punch and be the tendency to adhere to the punch and be lifted.lifted.

This action interferes with the feeding of the This action interferes with the feeding of the stock through the die and some device must be stock through the die and some device must be used to strip the scrap material from punch. Such used to strip the scrap material from punch. Such device is called as strippersdevice is called as strippers

Strippers are classified in two types Strippers are classified in two types 1. Fixed or stationary. 2. Spring loaded or 1. Fixed or stationary. 2. Spring loaded or

movablemovable

Fixed stripperFixed stripper

Spring Loaded stripperSpring Loaded stripper

Stock StopStock Stop

Latch StopLatch Stop

Automatic StopAutomatic Stop

Solid stopSolid stop

KNOCKOUTKNOCKOUT

Function of knockout is to eject a Function of knockout is to eject a work piece from a die cavity.work piece from a die cavity.

MOUNTING OF PUNCHESMOUNTING OF PUNCHES

Peened Headed punchPeened Headed punch

Contd.Contd.

Quilled PunchesQuilled Punches

Headless PunchHeadless Punch

Contd.Contd.

Ring Neck PunchRing Neck Punch

PilotsPilots