2. PNEUMATIC HOLE PUNCHING HELPS TO MAKE THE HOLE IN
SHEET METAL BY USING COMPRESSED AIR.
PNEUMATIC ACTUATORS CONTROLLED ENERGY TO THE
PUNCH, SO THE OPERATOR NEEDS TO PROVIDE ONLY MODEST
EFFORT REGARDLESS OF CONDITIONS.
PNEUMATIC PUNCHING MACHINE HELPS TO MAKE HOLE IN
VARIOUS SIZE BY CHANGING TOOL.
AS WELL, PNEUMATIC PUNCH PROVIDES SOME FEEDBACK OF
FORCES ACTING ON THE SHEET AND HOLE CAN MADE IN
SHEET METAL.
3.
4. ABSTRACT
HYDRAULIC PUNCH PRESSES, WHICH POWER THE RAM
WITH A HYDRAULIC CYLINDER RATHER THAN A FLYWHEEL, AND
ARE EITHER VALVE CONTROLLED OR VALVE AND FEEDBACK
CONTROLLED. VALVE CONTROLLED MACHINES USUALLY ALLOW
A ONE STROKE OPERATION ALLOWING THE RAM TO STROKE UP
AND DOWN WHEN COMMANDED. CONTROLLED FEEDBACK
SYSTEMS ALLOW THE RAM TO BE PROPORTIONALLY
CONTROLLED TO WITHIN FIXED POINTS AS COMMANDED. THIS
ALLOWS GREATER CONTROL OVER THE STROKE OF THE RAM,
AND INCREASES PUNCHING RATES AS THE RAM NO LONGER
HAS TO COMPLETE THE TRADITIONAL FULL STROKE UP AND
DOWN BUT CAN OPERATE WITHIN A VERY SHORT WINDOW OF
STROKE
THIS PROJECT WORK DEALS WITH THE DESIGN OF
PNEUMATICALLY CONTROLLED SMALL SCALE PUNCHING
MACHINE TO CARRY OUT PIERCING OPERATION ON THIN
SHEETS (1-2 MM) OF DIFFERENT MATERIAL (ALUMINUM AND
PLASTIC). REDUCTION IN PUNCHING FORCE REQUIREMENT
BEING THE MAIN AIM OF THIS PROJECT WORK IS OBTAINED BY
MODIFICATION IN PUNCH TOOL DESIGN
5. DESCRIPTION OF VARIOUS PARTS
Pneumatic Cylinder.
5/2 Flow control Hand Lever Valve.
Pipe connector and push.
Punch and die.
Air Hoes.
6. IN A DOUBLE ACTING CYLINDER, AIR PRESSURE IS APPLIED ALTERNATELY
TO THE RELATIVE SURFACE OF THE
PISTON, PRODUCING A PROPELLING FORCE AND A RETRACTING FORCE
AS THE EFFECTIVE AREA OF THE
PISTON IS SMALL, THE THRUST PRODUCED DURING RETRACTION IS
RELATIVELY WEAK. THE IMPECCABLE TUBES OF
DOUBLE ACTING CYLINDERS ARE USUALLY MADE OF STEEL. THE
WORKING SURFACES ARE ALSO POLISHED AND
COATED WITH CHROMIUM TO REDUCE FRICTION.
7. THE DIRECTION CONTROL VALVE IS USED TO CONTROL THE
DIRECTION OF FLOW OF COMPRESSED AIR.
USUALLY CLASSIFIED INTO NORMALLY OPEN (NO)AND
NORMALLY CLOSED (NC)VALVES.
THE NORMALLY OPEN VALVES WILL PERMIT FLOW FROM
INLET PORT OF VALVE TO OUTLET PORT NORMALLY THE
FLOW WILL BE CUT BY CHANGING THE POSITION OF THE
VALVE.
THE NORMALLY CLOSED VALVES WILL NOT PERMIT FLOW
FROM INLET PORT OF VALVE TO OUTLET PORT NORMALLY
THE FLOW WILL BE PERMITTED ONLY BY CHANGING THE
POSITION OF THE VALVE.
IN GENERAL VALVES ARE DESIGNATED AS 5/2 DCV ETC.
IN WHICH THE FIRST NUMERICAL INDICATES NUMBER OF
PORTS AND SECOND NUMERICAL INDICATES NUMBER OF
POSITIONS.
8. PUNCH TOOLING (PUNCH AND DIE) IS OFTEN MADE OF HARDENED STEEL
OR TUNGSTEN CARBIDE. A DIE IS LOCATED ON THE OPPOSITE SIDE OF THE
WORK PIECE AND SUPPORTS THE MATERIAL AROUND THE PERIMETER OF THE
HOLE AND HELPS TO LOCALIZE THE SHEARING FORCES FOR A CLEANER EDGE.
THERE IS A SMALL AMOUNT OF CLEARANCE BETWEEN THE PUNCH AND THE DIE
TO PREVENT THE PUNCH FROM STICKING IN THE DIE AND SO LESS FORCE IS
NEEDED TO MAKE THE HOLE. THE AMOUNT OF CLEARANCE NEEDED DEPENDS
ON THE THICKNESS, WITH THICKER MATERIALS REQUIRING MORE CLEARANCE,
BUT THE CLEARANCE IS ALWAYS LESS THAN THE THICKNESS OF THE WORK
PIECE. THE CLEARANCE IS ALSO DEPENDENT ON THE HARDNESS OF THE WORK
PIECE. THE PUNCH PRESS FORCES THE PUNCH THROUGH A WORK PIECE,
PRODUCING A HOLE THAT HAS A DIAMETER EQUIVALENT TO THE PUNCH, OR
SLIGHTLY SMALLER AFTER THE PUNCH IS REMOVED. ALL DUCTILE MATERIALS
STRETCH TO SOME EXTENT DURING PUNCHING WHICH OFTEN CAUSES THE
PUNCH TO STICK IN THE WORK PIECE. IN THIS CASE, THE PUNCH MUST BE
PHYSICALLY BACK OUT OF THE HOLE WHILE THE WORK IS SUPPORTED FROM
THE PPULLED UNCH SIDE, AND THIS PROCESS IS KNOWN AS STRIPPING. THE
HOLE WALLS WILL SHOW BURNISHED AREA, ROLLOVER, AND DIE BREAK AND
MUST OFTEN BE FURTHER PROCESSED. THE SLUG FROM THE HOLE FALLS
THROUGH THE DIE INTO SOME SORT OF CONTAINER TO EITHER DISPOSE OF THE
SLUG OR RECYCLE IT.
9. WORKING PRICIPLE
THE COMPRESSED AIR FROM THE COMPRESSOR IN THE
PRESSURE RANGE OF 7-10 BAR IS PASSED THROUGH A PIPE
CONNECTED TO THE SOLENOID VALVE WITH ONE INPUT.
THE SOLENOID VALVE IS ACTUATED BY THE TIMER UNIT.
THE SOLENOID VALVE HAS 2 OUTPUTS AND ONE INPUT.
THE AIR ENTERING THE INPUT GOES OUT THROUGH THE TWO
OUTPUTS WHEN THE TIMING UNIT IS ACTUATED.
AS THE AIR PRESSURE IS HIGH AT THE BOTTOM OF THE
PISTON, THE AIR PRESSURE BELOW THE PISTON IS MORE THAN
ABOVE IT.
THE MATERIAL IS PLACED ON THE DIE, WHICH IS FIXED ON
THE BASE OF THE MACHINE AND THE PUNCH.
AS THE EXHAUST VALVE IS OPENED, THE PRESSURIZED AIR
PUSHES THE PISTON DOWNWARDS WHICH IN TURN IS
CONNECTED TO THE PUNCH.
DUE TO THIS THE PUNCH TRAVELS DOWN ON THE METAL
SHEET KEPT OVER DIE, PUNCHING THE HOLE.
10. SIMPLICITY OF DESIGN AND CONTROL
MACHINES ARE EASILY DESIGNED USING STANDARD
CYLINDERS & OTHER COMPONENTS.
MACHINES OPERATE BY SIMPLE ON - OFF TYPE CONTROL.
PNEUMATIC SYSTEMS TEND TO HAVE LONG OPERATING
LIVES AND REQUIRE VERY LITTLE MAINTENANCE.
BECAUSE GAS IS COMPRESSIBLE, THE EQUIPMENT IS
LESS LIKELY TO BE DAMAGED BY SHOCK. THE GAS IN
PNEUMATICS ABSORBS EXCESSIVE FORCE, WHEREAS THE
FLUID OF HYDRAULICS DIRECTLY TRANSFERS FORCE.
COMPRESSED GAS CAN BE STORED, ALLOWING THE USE OF
MACHINES WHEN ELECTRICAL POWER IS LOST.
VERY LOW CHANCE OF FIRE (COMPARED TO HYDRAULIC
OIL).
MACHINES CAN BE DESIGNED TO BE OVERLOAD SAFE
