2CONTENTS Introduction Definition of HSM Advantages Application areas Machining systemSome recommended parametersComparisonDisadvantagesConclusion
3DEFINITION OF HSM Carl Salomon assumes that “At a certain cutting speed which is 5-10 times higher than in conventional machining the chip removal temperature at the cutting edge will start to decrease”
4DEFINITIONS High cutting speed machining High rotational speed machiningHigh feed machiningHigh speed and feed machiningHigh productive machiningFinally,“HSM is a powerful machining method that combines high feed rates with high spindle speeds, specific tools and specific tool motion.”
6ADVANTAGES High material removal rate High surface finish Increased productivityPossibility of machining of very thin wallsReduction in lead timesLow cutting forceCutting tool and work piece temperature are kept lowConnection time between the cutting edge and work piece is shortIt eliminates the need of coolantReduction of production process
8FEATURESEFFECTSReduced heat transfer in to the work piecePart accuracyReduction of cutting forcesSurface qualityIncreased cutting speedStability of rotating cutting tool feed rateIncreased material removal
10APPLICATION AREASIndustry which deals with the machining of Al to produce automotive components, small computer parts or medical devicesAircraft industry involves machining of Al often with thin wallsDie mould industry which requires dealing with finishing of hard materials .Used to machine such parts as die casting dies, forging dies, injection moulds and blow moulds, milling of electrodes in graphite and copper, modeling and prototyping of dies and moulds.
11MACHINING SYSTEM MACHINE TOOLS 3-axis horizontal and vertical milling machinesCNC 4-axis milling machine offers the option of tilting the milling cutters to improve the cutting conditions5-axis machine with inter changeable spindle units allow to rough, semi finish and finish with a single set up.
12DEMANDS ON THE MACHINE Spindle speed range <=40000 rpm Spindle power >22 KWProgrammable feed rate m/minRapid travels <90 m/minBlock processing speed 1-20 msHigh thermal stability and rigidity in spindleAir blast/coolant through spindleAdvanced look ahead function in the CNC
15CUTTING TOOLSTiN and TiCN coated Carbide for materials with hardness less than 42 HRCTiALN coated Carbide for materials with hardness 42 HRC and aboveFor special applications like hard turning (HRC 60-65) PCBN is usedCubic boron nitrite (CBN) and ceramic for cast ironPoly crystalline diamonds (PCD) and Cermets are used for aluminum
16RECOMMENDED PARAMETERS 1.True cutting speedAs the speed is dependent on both spindle speed and diameter of tools HSM should be defined as “true cutting speed” above a certain level
172.Material removal rateMaterial removal rate,Q = (ap* ae * vf)/1000 cm3/minwhere ap = vertical dist from tool tip to the reference point mmae = step over distance mmvf = feed speed mm/min
183. Surface finishSurface finish is depends upon cutting tool geometry, coating of the cutting tool, wear status of the cutting tool etc.
19COMPARISONS Conventional machine High speed machine Max speed 600 m/minSpeed starts at 600 m/minMax feed ~40 ipmFeed starts at 100 ipmRequire high levels coolantWith coolant ,feed rate can go more than 2000 ipmNo need for coolant for low feed rateBetween conventional and high speed machines
20Comparison between speeds used in conventional and high speed machining
21The contact time between tool and work is large Contact time is short ConventionalHSMThe contact time between tool and work is largeContact time is shortLess accurate work pieceMore accurate work pieceCutting force is largeCutting force is lowLow surface finishHigh surface finishMaterial removal rate is lowMaterial removal rate is highCutting fluid is requiredCutting fluid is not requiredComparison between convl and HSM process
22Material removal rate high Material removal rate is low HSMEDMMaterial removal rate highMaterial removal rate is lowDimensional tolerance 0.02 mmDim tolerancemmThere is no need of making cutting tool according to the contour to be machinedCutting tool has to be made according to the contour to be machinedComparison between HSM and EDM
23DISADVANTAGESNeed for expensive and special machine tools with advanced spindle and controllersExcessive tool wearGood work and process planning necessaryIt can be difficult to find and recruit advanced staff
24CONCLUSIONSHSM is not simply high cutting speed .It should be regarded as a process where the operations are performed with very specific methods and precision equipmentHSM is not necessarily high spindle speed machining. Many HSM applications are performed with moderate spindle speeds and large sized cuttersHSM is performed in finishing in hardened steel with high speeds and high feeds often with 4-6 times conventional cutting speeds
25HSM is high productive machining in small sized components in roughing to finishing and in finishing to super finishing in components of all sizes.Even though HSM is known for a long time, the research are still being developed for further improvement of quality and optimization of cost.