Solid dies
The required shape of opening for blanking or piercing made on a single metal block is solid die.
Split die
/the die contour built up from two or more pieces.
the following factors influence the design of the die.
1.Pierce part size.
2.stock thickness
3.Intricacy of piece part contour.
4.Type of tool.
5.Machinery available for manufacturing tool.
Material:die blocks are made out of non shrinking tool steels.
Heat treatment
Hardened and tempered to 58 to 62 HRC.Non shinking steel is selected to avoid dimensional instability.To withstand the high cutting pressure and to have wear resistance,the die block is hardened and tempered.
Design requirement:
The die block thickness is influenced by the following factors:
- Severity of the specific operation.
- Expected tool life.
- Properties of the material used in the manufacture.
General Guidlines for die block thickness
for die block length upto 125 mm/125 to 200 mm/200 to 400 mm
Stock material thickness in mm
upto 1mm 16/20/24
1 to 2 mm 20/24/28
2 to 3 mm 24/28/32
3 to 4 mm 28/32/36
4 to 6 mm 32/36/50
6 mm and above 36/40/60
Wall Thickness
For tools(approximately up to a working size of 100*100 mm)1.5 times die block thickness.
For tool having larger working area than 100*100 mm - 2 times die block thickness.
Screw and dowel holes
Screw an dowel holes should not weaken the die.
Screw and dowel hole centres should be away from the edge and opening of die.at least by 1.5d.
Where d=diameter of the screw or the dowel hole.
Deciding factors for solid dies/split dies
1.Size of the die block
for higher size sectional construction.
- Reduces cost of material.
- Easiness of machining.
- Reduces hardening failures.
when die opening is too small for internal working sectional construction is preferred.
- when the component profile is complex,split die construction makes manufacturing easy.
- When die opening consists of many sharp corners split construction avoids cracking of die during hardening.
Perishability
Manufacture and replacement of perishable portions is easier when the die is split.
Profile grinding
When conventional internal grinding is not possible due to the profile feature,split construction facilitates grinding.
Results of spliting
Tilting of splits due to the downward thrust of cutting force.
Lateral displacement due to lateral thrust.
Hence effective fastening of splits is a must.
Methods of fastening
- Only screws and dowels are used when press force is less(this stock materials).
- Nesting is a must hen lateral thrusts are more.
- Nesting does not eliminate the need for use of screws and dowels.
Nesting
Dies sections are nested in two ways:
-dies sections are nested into a pocket milled in the die set.
- Seperate nest blocks.
Pocket milled in the die set
The die sections should fit tightly into the pocket.Too much assembly pressure will distort the die set.
Liners
To facilitate the accurate and easy assembly and dismantling of sectional dies-hardened lines are used.
Liners eliminate the shearing of the walls of pocket.
Discrepancies in the size and position of pockets can be adjusted as the liners are the last to be fitted.
Knoc out are to be provided in the die pocket right under the liners to facilitate removal of liners.
Nest blocks
Separate nest blocks are preferred to direct pocketing for the following resons:
-Pockets weaken the die sets,nest blocks do not.
- Easy to handle.
- Regrinding is possible without dismantling the die.
Die bushes
Hardeneddie bushes in mild steel retainer plates are used in large piercing dies.
Carbide diesTungsten carbide is used as die material for blanking,piercing,trimming,forming and drawing operations.
Carbide dies are used when the production rates are high and the parts have close tolerances.The principles of design are similar to those of steel dies.
The carbide die insert is subjected to high impact load.The inserts should be supported externally by pressing or shrinking the carbide ring into a hardened steel case.