Elements of Press Tool
Press tool is divided
into two halves
ü
Fixed half / Stationary half.
ü
Moving half / Floating half.
Bottom plate, Bottom back plate, die plate, fixed stripper plate etc. are mounted on stationary half. & Top plate, thrust plate/ Punch back plate, Punch holding plate, Punch, floating stripper plate etc. are mounted on floating half.
A press tool consists
number of elements
with its type and function, Some basic essential elements
of simple blanking / Piercing tool (cutting
tool) are discussed as follows:-
1. Top Plate:-
Top plate is used for
assembly purpose. The Punch assembly
including the Punch,
Punch holder & Thrust plate is mounted on the top plate with screws and dowels. The
shank is also screwed into the top plate. It
is top portion of the complete tool assembly. Mild steel/ cast iron is generally used to manufacture top plate.
This plate should be of sufficient thickness to prevent bending.
2. Thrust Plate:-
This plate is
also called punch back plate. it is used to absorb shock and avoid digging into
the soft top plate during cutting
operations. Generally 6 mm to 8 mm thickness thrust plate with OHNS material is used. Mild Steel is
also very commonly used to make this plate. But in this case, plate thickness
is increased with respect to cutting force.
3. Punch holding
plate :-
This plate is
used to holding the punch. The punch is usually fixed with a light press fit H7/p6 in the punch holder. It is
generally made up of OHNS.
4. Stripper plate:-
Stripper plate is
used to strip the work piece or strip from the punch. It is used to avoid
sticking between punch and strip.
This plate restrict the up and down movement of strip. It is also support and
guide the punch. Stripper Plate are
usually made up of mild steel. When
high production is required they are made of Medium carbon
steel and hardened to 45-50 HRC.
Types of stripper plate:-
ü
Fixed / close/
box stripper.
ü
Travelling / Floating
stripper.
5. Die plate :-
Die is a female part of the tool.
It gives required shape of opening for Blanking and piercing holes. When this required shape of opening is gives
in single solid metal block, it is called solid die and when it is made in two or more pieces, then it is called split die.
Die blocks are made up of non shrinkable tool steel like HCHCr.
6. Bottom back plate :-
Bottom back plate is generally used to increase
the height of tool and reduce the impact of force on bottom plate. This plate is made up of mild steel.
7. Bottom plate:-
Bottom plate is
used for assembly purpose. All stationary elements i.e. fixed half of tool is
assembled on this plate.
The bottom plate
gives a cushion effect
to the die It provides space for the tool to be clamped to the press bed. Its main function is
to provide a rigid foundation or base to the assembly. The bottom plate is made of mild steel or cast iron.
It should be thick enough to prevent deformation under pressure.
8. Punch:-
Punch is a male member of complete die. It acts in conjunction with the female die to give the desired effect
upon on the strip / work piece.
Punches are classified in three categories:-
a)
Cutting punch
b)
Non- cutting punch
c)
Hybrid punch.
Punches are generally made up of HCHCr / D2 material
with HRC 58-62.
9. Strip:-
Metal strips
are the thin metal sheets which are transformed into desired product after applying the number of press tool operations.
10. Guide Bush:-
Guide bush is a circular flange
made up of case hardened
steel (HRC 56 - 58). These are generally mounted
on top plate to provide smooth sliding contact between
pillars and top plate.
11. Guide pillar:-
Guide pillars
are cylindrical pins also called
guide pins are used to align the
die set. The guide pillar
and guide bush align the
fixed & moving halves of tool in each cycle. A close running fitment H7/g6 is maintained between contact surfaces of guide pillar and guide
bush. The length of pillar should be enough to guide minimum 10
to 15% of pillar length
before touching the punch
to strip / work piece.
12. Fasteners and Dowels:-
The screws are used to hold the
die parts tightly together.
Dowels are the cylindrical rods which are used
to align the tool parts having no relative motion.
13. Shank:-
Shank is used to locate and clamp the tool to the press ram. Diameter
of the shank for a particular tool depends
only on the diameter of the corresponding hole size in the press ram on which
it is to be mounted. Shanks are standardized to suit different presses.
14. Stoppers:-
The stopper
is a plain cylindrical pin. This pin is mounted
on the die block. It is used to arrest
the movement of the strip when strip is fed forward to one pitch length.
15. Strip Guide:-
Strip guider are used to guide
the strip when strip is fed throughout on the die surface.
Strip guider
are two parallel
plates which are mounted
on die surface by screw and dowels and properly aligned with the die parameters.
Elements of Press Tool
1. Top Plate
2. Thrust Plate
3. Punch holding plate / Punch back plate
4. Stripper Plate
5. Die plate
6. Bottom back plate
7. Bottom plate
8. Punch
9. Strip
10. Guide Bush
11. Guide pillar
12. Dowel
13. Fasteners
14. Limit bolt / Stripper bolt
15. Spring
16. Shank.
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| Elements_of_Press _Tool |
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