液压夹具设计手册

1、液压夹具设计手册思诚机电1Good Fixture DesignGood fixtures position, clamp and support workpieces in the most effective way possible2Fixture design, workpiece Example 13Fixture design, process4DatumFixture design, workpiece datums5Fixture design, supporting6Fixture design, positioning7Fixture design, clamping8Fi

2、xture design, additional support and clamping9Fixture, positioning, supporting and clamping10Fixture design, workpiece, Example 211Fixture design, process12Fixture design, supporting13Fixture design, clampingXX14Fixture design, clampingDatum15Fixture design, positioning and clamping16Fixture design,

3、 positioning, supporting & clamping17Friction clampingIf clamping using friction only it must be remembered that the coefficient of friction () is normally calculated at 0.1Clamping force FReaction forceTotal clamping force= F x Clamping force FReaction forceTotal clamping force= FClamping force F 2

4、-30 from horizontalPreferable18Friction clampingIf clamping using friction only it must be remembered that the coefficient of friction () is normally calculated at 0.1This can be improved on soft materials (eg. Al) if the clamping piston has enough force to penetrate the workpiece19Fixture designDEF

5、INITION OF A CLAMPING FORCEThe force acting on a workpiece to be clamped, is large enough to hold the workpiece firmly in its given position relative to the cutting tool, against the action of the machining forces20Fixture designCLAMPING FORCESMechanicallow cost, relatively low forcesPneumatichigher

6、 cost, relatively low forces, large componentsHydraulichigher initial cost, high forces, reliable, small components 21Mechanical ForcesMaximum clamping forceusing standard wrenchClamping force (kN)Clamping force with extension piecesas shown, 500N torque, = 0.122Standard clamping strapM20 threadMax.

7、 recommended torque 223NmMax. clamping force 28kN Hydraulic swing clamp 6951F-11-21(page 63, metric catalogue)22 rod, 76mm long armMax. oil pressure 23 MPaClamping force 7.3kN Force comparison23Force comparisonStandard clamping strapM20 threadMax. recommended torque 223NmMax. clamping force 28kN Hyd

8、raulic swing clamp 6951F-11-21(page 63, metric catalogue)22 rod, clamping strapMax. oil pressure 35 MPaClamping force 13.7kN 24Standard clamping strapM24 threadMax. recommended torque 383NmMax. clamping force 40kN Hydraulic swing clamp 6951FN-33-21(page 71, metric catalogue) 38 rod, clamping strapMa

9、x. oil pressure 35 MPaClamping force 35kN Force comparison25Standard clamping strapM24 threadMax. recommended torque 383NmMax. clamping force 40kN Hollow piston cylinder 6921-100 x10(page 26, metric catalogue) M24 threadMax. oil pressure 400 barClamping force 101kN Force comparison26Mechanical or Hy

10、draulic ?27Mechanical or Hydraulic ?50 MPaSequence Valve 47-0440-02 (J-3)Set at 30 MPaCartridge Mount Cylinder (x8)42-1010-04 (page F-12)2.5 kN each 50MPaThreaded Cylinder42-0010-06 (page F-4)3.4 kN 30 MPa5.7 kN 50 MPa28Force diagram30 MPa50 MPaSequence valve opensWorkpiecesMovement of cylinderOil p

11、ressure29Component & Fixture designSENSIBLE USE OF FORCESensible introduction of positioning, clamping and supporting forces will enhance the quality of a workpiece30Oil supply to fixtures2 basic methodsthrough pipesthrough gun drilled channelsMethod depends oncost targetcomplexity of fixtureproduct

12、s being used31Oil supply to fixtures, cost comparisonA:Through pipes using flange type clampsB:Through pipes using threaded type clampsC:Through gun drilled channels & manifold mounted type clampsD:Through gun drilled channels & threaded body type clamps32Oil supply to fixtures, cost comparisonA: Th

13、rough pipes usingflange type clampsRelatively easy to manufactureFittings weakest part of systemChip trapsControl fixtureCOST 100%33Oil supply to fixtures, cost comparisonB: Through pipes usingthreaded type clampsLess swarf traps Reduces machining areaFittings weakest part of systemCOST ?%against co

14、ntrol fixture34Oil supply to fixtures, cost comparisonC: Through gun drilled channels & manifold mounted type clampsMaximum component density Minimum swarf trapsCOST ?%against control fixture35Oil supply to fixtures, cost comparisonD: Through gun drilled channels & threaded body type clampsMaximum c

15、omponent density Minimum swarf trapsCOST ?%against control fixture36Oil supply to fixtures, cost comparisonC: Through gun drilled channels & manifold mounted type clamps98%B:130%D:104%A:100%37Hydraulic circuit design38Circuit design39Cam Cover fixture example40Circuit design4142Barrel fixture exampl

16、e43Circuit design4445Getting the oil to the fixture46Rotary & Rotary Valve Couplings47Rotary CouplingsUsed when free passage of oil is required to be distributed on rotary table arrangementsStandard versions of single, twin, four and six passages with/without leakage portMaximum operating pressure 2

17、50/500 barWhen specifying include data on rotation speed, pressure, temperature, media and cycle timeSpecial designs available on request48Twin passage rotary couplingUse on rotary table with two single acting cylinders49Four passage rotary couplingUse on rotary table with 4 single acting or 2 doubl

18、e acting cylinders50Six passage rotary couplingUse on rotary tables with combination of up to 6 oil feeds ie. 6 s/a, 3 d/a, 2 d/a & 2 s/a cylinders51Rotary Coupling circuitSingle acting circuitDouble acting circuit52Application example53Rotary Valve CouplingsUsed on rotary table arrangements when lo

19、ading/unloading of stations is required whilst maintaining clamping pressure on remaining stationsVersions include 5,6,7,8,9 &10 stations.Applications requiring 2, 3 or 4 stations use 6 & 8 stations with unused ports plugged.Special designs availableUp to 200 bar an accumulator is recommended, above

20、 200 bar it is essential due to internal leakage within the oil return cavity of the unit54Rotary valve coupling functionLoad stationUnload stationRotary couplingWork stationClamping cylinder55Rotary Valve Coupling circuitSingleactingDoubleacting56Application example57Coupling unitsQuick disconnect

21、couplingsOne-hand operation quick disconnectCoupling unitsAutomatic coupling systemsThreaded coupling elements 58Quick DisconnectCouplingsMax operating pressure 500 barOne hand operationAlways use dustcapsCoupling units59Coupling UnitsSingle or double actingIntegral accumulator and pressure gaugeMul

22、ti-coupler units availableCoupling units & accumulators60Coupling SystemsAlways use accumulators on static systems10 temperature difference relates to 10 bar pressure differenceCoupling units & accumulators61Threaded coupling elements62Breathing63What is breathing?Breathing is the action of single a

23、cting cylinders during the spring return part of the component cycle64Why breathing has to be madeExcess pressure or vacuum in the spring area changes the spring forces which leads to malfunctionFormation of condensation water promotes rust formation and can lead to a complete failure of the element

24、sLeakage of hydraulic seals must drain off to exterior without pressure otherwise there will be malfunctionsDust and chips are retained by sintered metal air filtersLiquids can be drawn through the sintered metal filter, thus the breathing spring area is reduced, a higher excess pressure or vacuum i

25、s caused and the function is impaired65What is breathing?What happens during breathing66PrecautionsCoverClamping elements without breather ports can be covered.Due to high coolant pressure and flow this is not always successfulConsider using double acting elements wherever possible67PrecautionsBreat

26、her hoseConnection of a breather hose is approved if the outlet is sited at a point where no liquid can penetrateEnsure no fluid traps in hose68PrecautionsClosed breather systemSpring area is increased by connection of additional closed area.Electrical die cast boxes are idealVolume of additional area should be 10 times the stroke volume