CLAMPING DEVICES

C DCLAMPING DEVICES

Functions of a clamp:Functions of a clamp:Holding the workpieceWithstand forces (Clamping force should not cause any dent/damage)

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PRINCIPLES OF CLAMPING

Position Strength Operator fatigue Productivityy Workpiece variation

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Position:Di h l i f dDirect the clamping force on strong, supported partof the workpiece. (Affects accuracy)Sh ld t b t t th th f th l di g dShould not obstruct the path of the loading andunloading of workpiece.Should not obstruct the path of the cutting toolShould not obstruct the path of the cutting tool.Clamps Should not get machined (i.e. drilled,milled or welded in operation)milled or welded in operation)

Distortion of Distortion of unsupported workpiece

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Strength:Secure clampingSecure clamping.Clamping force should be distributed over widerarea of the workpiece.area of the workpiece.While clamping soft workpieces, clamps should befitted with pads of softer materials, such as nylonor fibre to prevent damage/denting of theworkpiece.

Operator fatigue:Physical effort involved in clamping and de-ys ca e o t vo ved c a p g a d declamping is considered.

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Productivity:yClamping time should be minimized by using hand knobs, tommy bars, knurled Screws, hand wheels, handles etc.

E li f t k iEqualizer for two workpieces

H d t d l i 6Hand operated clamping devices

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Workpiece variation:Spherical washers are used (in pairs) havingmatching male and female parts between clamp

dand nut.Equalizer for 2 workpieces (or even number of

k i ) i lt lworkpieces) simultaneously

Clamping Clamping variable workpieces

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TYPES OF CLAMPS

Th f l h l d i h iThe type of clamp the tool designer chooses isdetermined by the shape and size of the part, thetype of jig or fixture being used and the work to betype of jig or fixture being used and the work to bedone.The clamp used should be the simplest, easiest toThe clamp used should be the simplest, easiest touse and most efficient. Strap clampsp p

spherical nuts and washers Screw clamps Screw clamps Swing clamps Hook clamps

Cam-Action clampsFlat eccentric camsFlat spiral cams Hook clamps

Quick action knobsFlat spiral camsCylindrical cams

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TYPES OF CLAMPS

Wedge clampsFlat edges or flat camsFlat wedges or flat camsConical wedges or mandrels

T l A ti l Toggle-Action clamps Power Clamping

N i l l i Non-conventional clamping

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SCREW CLAMP

Screw clamps arethreaded devices withknurled collar, Handknob or Tommy bar forrotating and tighteningrotating and tighteningthe screw.

The clamping pressurelargely depends on the

k i i i fworkpiece, it varies fromone workpiece to other.It is more time

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It is more timeconsuming and moreefforts are required.

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EQUALISERSEQUALISERS

It is recommended tol lapply equal pressure

on the faces of thework The pressurework. The pressureapplied can be variedby tightening ory g gloosening the screwprovided for thepurpose.

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SPHERICAL WASHERSPHERICAL WASHER

Two-piece washer thatcompensates hene ercompensates whenevera stud and clampingsurface are not exactlysurface are not exactlyperpendicular. The topwasher has a convexspherical radius, whilethe bottom washer has amatching concavematching concavespherical radius.

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SLOTTED (RETRACTABLE) STRAP CLAMP

When clamps fall inthe path of loading orunloading they aremade slotted to permitli ithd llinear withdrawal.

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SWINGING STRAP CLAMP

In this design, the clampi t t d b 90° t lis rotated by 90° to clearthe passage ofloading/unloading theworkpieceworkpiece.

In some cases such asbox jig, the clamp maybe otated b 45° tobe rotated by 45° tomatch with the diagonalof the box to facilitateremoval of theremoval of theworkpiece.

It is used in cases whereheavy clamping

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heavy clampingpressure is not required.

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EDGE STRAP CLAMP A side clamp is also

known as edge clamp.ow as edge c a p.In this case thesurface to bemachined is alwaysclamped above theclamping device Thisclamping device. Thisclamping device isrecommended forfixed lengthworkpiece.

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EDGE JAW CLAMP

Used for clampingp gworkpiece on the edgesduring facingoperations.

Heel slides down as theh l t ihexagonal nut istightened.

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S (S ) SPECIAL STRAP (SPIDER) CLAMP

The clamp shape The clamp shape can be changed to suit the workpiece and the operation.

Circular and symmetrical workpieces can be held very wellheld very well.

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EQUALISEREQUALISER Equaliser principle

can be extended to can be extended to facilitate clamping of many even number of yworkpieces simultaneously by a i l lsingle clamp.

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PIVOTED STRAP CLAMP

Clamps are pivoted at the centre to simplify their simplify their operation.

It is tightened and It is tightened and loosened by knurled head screw.

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PIVOTED EDGE CLAMPSPIVOTED EDGE CLAMPS

Screw shifts from the centre to the end opposite the end opposite the clamping point. This places the pclamp screw well below the path of

f f i cutter for facing workpiece top.

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PIVOTED TWO WAY CLAMPPIVOTED TWO WAY CLAMP

Tightening of the knurled screw knurled screw pushes the workpiece till it t h th touches the locator.

Further tightening Further tightening of the screw pivots the clamp anti-l k i d clockwise and

applies force in two directions

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two directions simultaneously.

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HINGED TWO WAY CLAMP

Workpiece is pushedagainst the location pinsby pivoted edge clamp.

Tightening the knurlednut against the hingedclamp pushes theworkpiece against theworkpiece against thelocation pins.

F h i h i h h l i d Further tightening pushes the clamping padtowards the workpiece which is clampedsimultaneously in 2 directions

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simultaneously in 2 directions.

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SWINGING STRAP CLAMP

Workpiece is held by knurled head screw as knurled head screw as shown on full line.

For loading and For loading and unloading the clamp is swung aside as shown by dotted lines.

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HINGED CLAMP Hinged clamps provide

rapid clearance of the l di g d l di g loading and unloading passage.

It is generally clamped It is generally clamped with swinging eye bolt.

For loading and For loading andunloading theworkpiece, thehexagonal nut isloosened half-a-turn.

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SWINGING HOOK CLAMP Turning fixtures uses

compact swinging hook bolt clamps.

The clamp is shaped like a short cantilever with turned outside diameter which slides diameter which slides in a housing.

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SWINGING LATCH

For loading and unloading of u oad g o workpiece the clamping screw is loosened slightly and latch is swung aside to the position as shown the position as shown by chain-dotted lines.

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C WASHER

It is a strap clamp with open slot and simple ope s o a s p e and quick in operation.

Slot permits removal of pc washer after a slight loosening of the h l thexagonal nut.

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HAND OPERATED CLAMPING DEVICES

These are manually operated clamping operated clamping devices.

These are very simple These are very simple in structure and quick in operation.

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REPLACING NUT BY CAMREPLACING NUT BY CAM

These are quick in iaction.

Though there is a risk f l tti l of clamp getting loose

due to the vibrations.

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ECCENTRIC CAM CLAMPING

Eccentric cam can replace hexagonal nut replace hexagonal nut in a strap clamp or a heel pin in a strap clamp.

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REPLACING HEEL BY CAM For loading and

unloading of workpiece the clamping screw is loosened slightly

Bayonet clamp is another type of clamp whichuses a cylindrical cam. The motion of theb i id d b h h i l d dbayonet is guided by the spherical-ended screwmating in the groove of the bayonet.

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Toggle clamps are another kind of quick-actionclamps which can be withdrawn by a considerabledista ce fo loadi g/ loadi g of the o k iece 32distance for loading/ unloading of the workpiece.

POWER CLAMPING

Power-activated clamps are an alternative to thell t d l i d imanually operated clamping devices.

Advantages of power clamps:

Better control of clamping pressures.

Less wear on moving parts Less wear on moving parts.

Faster operating cycles.

The main disadvantage is cost, which can easilybe offset by the increased production speeds andy p phigher efficiency.

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POWER CLAMPING

Fluid powerPneumatic clampingPneumatic clampingHydraulic clamping

Vacuum clamping Vacuum clampingMagnetic clamping Electro static clamping: Electro-static clamping:

By changing the workpiece and chuck face withopposite polarities we get the clamping forceopposite polarities, we get the clamping force.Workpiece and chuck face are separated byputting insulating dielectric fluid in between.putting insulating dielectric fluid in between.By discharging they can be unclamped.

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FLUID POWER CLAMPING

These are actuated bycylinderscylinders.

The feeding of pressurized fluid pressurized fluid through the port pressurizes the clamp against the workpiece.

For unclamping, the port is connected to anunpressurised discharge line. The force of the

i d h l h h l d h

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spring under the clamp pushes the clamp and theram upwards.

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MULTIPLE CLAMPING Figure shows a fixture

with four clamps and acylinder which can beactuated by a single

lvalve. The clamping pressure

of all the clamps wouldof all the clamps wouldbe equal.

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RACK AND PINION ACTUATED FLUID POWERCLAMPING

The fluid power The fluid power cylinder is used to move the clamp into move the clamp into the position.

The clamp would stay p yin the position even if the cylinder is d i ddepressurized.

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VACUUM CLAMPINGThis is convenient to clamp thin flat sheetswhich are vulnerable to distortion underclamping loads.It provides light clamping.The holding face is provided with 0.025 mmdeep grooves which serve as vacuum ducts.

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MAGNETIC CLAMPING

Magnetic clamping force can be developed byt g t l t g tpermanent magnets or electro-magnets.

Permanent magnetsThese are mounted on a sliding member whichcan be moved under a non-magnetic material ona table to block magnetic flux. This releases theworkpiece.For clamping workpiece permanent magnets aremoved under the magnetic part of the table.moved under the magnetic part of the table.

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ELECTROMAGNETIC CLAMPING

Electromagnetic tables use solenoid coil astemporary magnetstemporary magnets.DC current is used to create magnetic field.The magnetic clamping force is controlled byvarying the current passing through thesolenoid coil.Magnetic clamping leaves some residualmagnetism in the workpieces. This can beremoved by demagnetizing the workpiece.y g g p

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ELECTROSTATIC CLAMPINGC OS C C G

In this method, the workpiece is charged withp gstatic electricity with polarity opposite to thepolarity on the chuck face.p yThe workpiece and the chuck areseparated/insulated by dielectric fluidseparated/insulated by dielectric fluid.Even non-conducting materials can be coated

ith thi t lli l d d bwith a thin metallic layer and secured byelectrostatic clamping.

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NON-CONVENTIONAL CLAMPING

Adhesive clamping:Used for flat surfaced workpieces subjected toUsed for flat surfaced workpieces subjected tolight loads.It i ti i d i l iIt requires more time curing during clampingand cleaning of the adhesive tode-clamp. It is used only when no proper

alternative is available.

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Fusion clamping:In this method, the workpiece is jacketed withmolten bismuth alloy (low melting point).On coolingand solidification, the alloy secures the workpiecefirmly.Useful for complicated shapes. Sometimes this is theonly method of clamping possible in odd-shapedonly method of clamping possible in odd shapeddifficult workpieces.

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THANK YOUTHANK YOU

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