Die Sets
The die set consists of a bottom plate and top plate together with guide pillars and bushes.The guide pillars and bushes align the top and bottom plates.
The advantages of die sets are
- Accuracy of set up.
- improved piece part quality.
- Increased die life.
- Minimum set up time.
- Easy maintenance.
- Alignment of punch and die.
- Easiness of storing.
Die sets can be classified as
- Precision
- Commercial
The difference between them are the accuracy of the fits between the bushes and the pillars.
Precision die sets are used for cutting operation tools.
Commercial die sets are used for operations like bending,forming and other non cutting operations.
Die set materials
Die sets are manufactured by using the following materials:
- Cast iron containing 10 to25% steel.
- Hot rolled steel.
- Semi hardened or hardened tool steels.
Die set components
- Top plate
- Guide bushes
- Guide pillars
- Bottom plate.
Top plate
The upper working member of the die set is called the top plate.The punch holder is clamped to the top plate.
Bottom plate
The bottom plate is the lower working member of the die set.It's shape corresponds with that of the top plate except that it is provided with clamping flanges.The flanges have provision for fastening the die holder to the bolster plate of the press.Usually the bottom plate is made thicker than the top plate.This is to compensate for the weakening effect of slug and blank holes.
Guide pillar
Guide pillars are presicion ground pins which are press fitted into accurately bored holes in the bottom plate.
Guide pillars are assembled into corresponding guide bushes to align punch and die components with a high degree of accuracy.
The commonly used types of pillars are
- small diameter guide pillars which are usually hardened and centreless ground.
- large diameter pillar which are ground between centres after hardening or case hardening.
Removable guide pillars can be easily removed from the die set for resharpening the cutting elements.They are employed for large dies and for dies having more than two pillars.
Guide Bushes
Guide bushes are precision ground bushes which are press fitted into accurately bored holes in the top plate.
Ball cage die set
some die sets are provided with ball cages instead of guide bushes.
Guide pillars are pressed into the bottom plate.They are assembled into linear ball cages whichin turn are guided in hardened sleeves resting in the top plate.
Ball cage die sets are used where high rate of production is required and accurate alignment is necessary.
Types of die set
1. Standard die set.
2. Non standard die set
1.Standard die sets
- used for bending tools.
- secondary operation tools.
Center pillar die set
- used for round working area.
Diagonal pillar die set
- used for progressive tools with rectangular working area.
Four pillar die sets
- used for heavier press working operation.
Non standard die sets
These die sets are made for a particular design when standard die sets are not suitable or not available.These are usually made of mild steel with case hardened pillars and bushes.
Shut height
Shut height is the distance from the bottom plate to the top of the top plate when the tool is in closed position.The height of the pillars must be less than the shut height in order to ensure that the press ram will not strike against the ends of the pillars.If possible, the pillars should be so designed to accommodate the reduction in the shut height which will be due to resharpening of die.