1、global solutionsinnovationcollaboration 2001 PTCUtilizing Pro/NC High Speed Machining Strategies 2000 PTC2High Speed MachiningOverviewlWhy High Speed Machining?lComponents of High Speed MachininglMisconceptions about High Speed MachininglWhat is High Speed Machining?lThe High Speed MachiningProcessl
2、How to Start?2000 PTC3Why High Speed Machining?lReduces machining timelShortens lead timelReduces,even eliminates,post-machining processeslShortens preparation timelEnhances the quality of the finished part 2000 PTC4HSM:Machining TimeReduces machining timelFor various materiallGraphitelAluminumlCast
3、 ironlMild steellPre-hardened steellTough-to-cut material lHardened steel,Titanium,Inconel,etc.lGreater rate of material removallHigher speed advantages offset disadvantages of greater number of slices 2000 PTC5Why High Speed Machining?lReduces machining timelShortens lead timelReduces,even eliminat
4、es,post-machining processeslShortens preparation timelEnhances the quality of the finished part 2000 PTC6HSM:Lead TimeShortens lead timelEven for hardened steelConventional ProcessPolishingEDMBurningHeat Treat Roughing Making Electrodes High Speed Machining ProcessRough to finish operations in one m
5、achining processHigh Speed Machining 2000 PTC7Why High Speed Machining?lReduces machining timelShortens lead timelReduces,even eliminates,post-machining processeslShortens preparation timelEnhances the quality of the finished part 2000 PTC8HSM:Post-Machining ProcessesReduces,even eliminates,post-mac
6、hining processeslHigh quality machined surfaceslSuperb machining accuracyMirror quality finishlNo need for bench work and polishingLess time spent on adjustments during insert or mold base assembly 2000 PTC9Why High Speed Machining?lReduces machining timelShortens lead timelReduces,even eliminates,p
7、ost-machining processeslShortens preparation timelEnhances the quality of the finished part 2000 PTC10HSM:Preparation TimeShortens preparation timeReduces the requirement for different toolslConventional machining requires 3 tools to make an entry hole and pocketlHSM can make use of one tool onlyCor
8、ners of differing radii can be machined with one toolConventional Machining:High Speed Machining:Spot Drill Drill Mill Ball Nose Endmill Helical Cutting of the hole 2000 PTC11Why High Speed Machining?lReduces machining timelShortens lead timelReduces,even eliminates,post-machining processeslShortens
9、 preparation timelEnhances the quality of the finished part 2000 PTC12HSM:Part QualityEnhances the quality of the finished partlLess tool deflectionlLess warpage on thin wallsEliminates bench worklMaintains accuracy of small detailed geometry lEliminates blending of electrode marginslMaintains accur
10、acy of radiiMore consistent geometrylLess tool wear 2000 PTC13Components of High Speed Cutting 2000 PTC14Components of High Speed CuttingMachine Tool&Controller 2000 PTC15Components of High Speed CuttingSpindles,Holders and Cutting ToolslControlled temperaturelHigh precision bearingslGood concentric
11、itylQuick acceleration and deceleration 2000 PTC16Components of High Speed CuttingMachine StructurelWithstand heavy loadslHigh responsiveness&high feed rateslThe bed,column&table ensure a high structural rigidity 2000 PTC17Components of High Speed CuttingLinear Guide Ways Linear MotorslNo ballscrews
12、lMinimumbacklashlHigh responsiveness 2000 PTC18Components of High Speed CuttingController SystemlGood control software for data handlinglGeometric errors arising from the servo lag can be overcomeServo Lag 2000 PTC19Axis Reversal ErrorslErrors when movement direction is reversedFast Data Processingl
13、At high feed,tool can finish the move before the next move is ready,or vice-versalTool dwells,undershoots or overshootsLook AheadlAnticipate tool path changes,&vary the feed accordinglylGouge AvoidancelSmoother Acceleration&DecelerationComponents of High Speed Cutting 2000 PTC20Speeding in the corne
14、rsHow Fast?2000 PTC21Arc the CornersBlindly adding arcs on toolpath corners is NOT High Speed MachininglFor this example,a distance between the path of 1 mm became 1.5 mm at the cornersl50%more loadlConsidering the heavier material at the corner,and the load shoots up to more than 100%lMore severe c
15、onditions for sharper corners 2000 PTC22Spline/NURBS dataNURBS or Spline interpolation is NOT High Speed MachininglStraight lines can be represented in NURBSlNURBS is not exact data from the CAD systemlEven if CAD data was in NURBSlCannot offset easily NURBS curve or surfacelToolpath seldom follows
16、UV linesNURBS are controller requirementslUse if the controller behave better with NURBS,rather than linear,circular or helical interpolation 2000 PTC23What is High Speed Machining?Stable Cutting ConditionslMaintain low temperatures at the tool cutting edgelShallow cuts,both in depth and radial dire
17、ctionlSmall cutting loadlAdditional advantages for low rigidity workpieceslMaintain constant cutting loadlConsistent tool deflectionlLess vibration and chatterlLess tool wearlEffectively remove the cut chipslThru-spindle coolant or airlThru-tool coolant or air(deep cavity)2000 PTC24Axial DepthAxial
18、DepthRadial DepthRadial DepthStable Cutting ConditionsMaintain low temperatures at the tool cutting edgelShallow cuts,both in depth and radial directionlSmall cutting loadlAdditional advantages for low rigidity workpieces 2000 PTC25Stable Cutting ConditionsCutting LoadTool Life Cutting LoadTool Life
19、Maintain constant cutting loadlConsistent tool deflectionlLess vibration and chatterlLess tool wearMaximizedTool Life 2000 PTC26Stable Cutting ConditionsEffectively remove the cut chipslThru-spindle coolant or airlThru-tool coolant or air(deep cavity)2000 PTC27High Speed MachiningTOOLSHigh stress 20
20、00 PTC28High Speed MachiningTOOLSMore Constant Material Removal Process 2000 PTC29High Speed RoughinglConstant cutting conditionlConstant chip loadlApproach from outside materiallContinuous tool engagementlMinimization of sudden tool direction changes lReduction of repositioning movesBalancing all t
21、hese sometimes-contradictory requirements 2000 PTC30Roughing:Cutting ConditionConstant Cutting ConditionlClimb CuttinglLess heat is generatedlSmaller forces on toollWork hardening is minimized,even eliminatedlBetter surface finish 2000 PTC31High Speed RoughinglConstant cutting conditionlConstant chi
22、p loadlApproach from outside materiallContinuous tool engagementlMinimization of sudden tool direction changes lReduction of repositioning moves 2000 PTC32Constant Chip LoadlRate of material removal as constant as possiblelMaintains constant chip sizelBetter heat transferlBoth tool and workpiece sta
23、y coollNo need to manipulate feedrates and spindle speedslLonger tool lifelBetter part qualityNever bury in the materialRoughing:Chip Load 2000 PTC33High Speed RoughinglConstant cutting conditionlConstant chip loadlApproach from outside materiallContinuous tool engagementlMinimization of sudden tool
24、 direction changes lReduction of repositioning moves 2000 PTC34Roughing:Approaching the CutsApproach from outside the material,when possiblelFor regions with open wallslReal-time analysis of the cut materialClosed regionslAll regions with no open wallslHelical plunging approachlOpens up an approach
25、location 2000 PTC35High Speed RoughinglConstant cutting conditionlConstant chip loadlApproach from outside materiallContinuous tool engagementlMinimization of sudden tool direction changes lReduction of repositioning moves 2000 PTC36Roughing:Tool EngagementContinuous tool engagementlWhenever possibl
26、elWithout breaking prior ruleslClimb machininglConstant loadlDo not bury the tool 2000 PTC37High Speed RoughinglConstant cutting conditionlConstant chip loadlApproach from outside materiallContinuous tool engagementlMinimization of sudden tool direction changes lReduction of repositioning moves 2000
27、 PTC38Roughing:Minimize Sudden MovesMinimization of sudden tool direction changeslRetrofitted machines will always overshoot or undershootlHSM machines have no overshoot/undershoot problemslAutomatically slow down in cornerslLonger-than-planned cycle timelChip size at the corner goes down lVolume of
28、 chip material too small to carry heat lTool heats up lPremature failuresLook Ahead Functionality Alone is Not Enough!2000 PTC39High Speed RoughinglConstant cutting conditionlConstant chip loadlApproach from outside materiallContinuous tool engagementlMinimization of sudden tool direction changes lR
29、eduction of repositioning moves 2000 PTC40Roughing:Minimize Repositioning MovesReduction of repositioning moveslPrevent retract moveslMinimize non-cutting time lWithout breaking prior ruleslClimb machininglConstant loadlDo not bury the toollHSM rapid at rates around 50 000 MMPM.lHelp the machine rea
30、ch maximum speed on repositioning moveslReduce the need for great accelerations/decelerationslSmooth repositioning moves 2000 PTC41Roughing:Closed Areas BehaviorHelical spline approach to open up the materiallTangent to both the approach move and the cutOnce open,the helical location is now an open
31、wallContinuous spiral cut,until a wall is reachedlConstant loadlConstant cutting conditionlContinuous cuttingRemainder material is treated as open areasOpening 5 2000 PTC45Material boundaryOn approach,tool load goes up greatlyOn outside corners,tool load goes downOn inside corners,tool load goes up
32、greatlyTraditional Cutting ApproachlTool load changes are quite severelGuard against critical tool conditions by artificially lowering cutting expectationslExamplelApproach:load up rapidly from 0 to 2x cutting load lOutside corners:load down to 0 ltool moves outside material when turning the cornerl
33、Inside corners:load up from cutting load to 2x cutting load ltool catches material on the front wall before turning the cornerTool Load Profile 2000 PTC46Tool Load ProfileBalanced-load Cutting ApproachlEliminates load spikes lAllows for a more aggressive roughing strategyHigher performance roughing
34、approachlAnalyzing the material lBuilding tool path based on material rather than resultant geometrylRunning machines at their optimal speed 2000 PTC47Additional Roughing ScanslMaintain CUT_TYPE(Climb/Conventional)lIdeal for pockets with aspect ratio 5lClimb boundaries,maintain cut typelControl of w
35、all profile feeds and speeds lMaintain CUT_DIRECTION lIdeal for pockets with aspect ratio 5lClimb material,maintain cut direction lControl of wall profile feeds and speeds lFollow Hard WallslIdeal for core parts with minimal concave corners(bad for concave corners)lOffset only of hardwallsl“S”-conne
36、ction moves for closed contour transitionsHigh Speed Roughing3421234 2000 PTC48Maintain Cut Type ScanVolume NC sequencesParameters:lROUGH_OPTION=ROUGH_ONLYlSCAN_TYPE=MAINTAIN_CUT_TYPElCUT_TYPE=CLIMBlSTEP_DEPTHlSTEP_OVER lMust be 1/2 of TOOL_DIAMETERlCLEAR_DISTOptional controls:lRAMP_ANGLE lHELICAL_D
37、IAMETERlCORNER_ROUND_RADIUSlTRIM_TO_WP 2000 PTC49Maintain Cut Direction ScanVolume NC sequencesParameters:lROUGH_OPTION=ROUGH_ONLYlSCAN_TYPE=MAINTAIN_CUT_DIRECTIONlCUT_TYPE=CLIMBlSTEP_DEPTHlSTEP_OVER lMust be 1/2 of TOOL_DIAMETERlCLEAR_DISTOptional controls:lRAMP_ANGLE lHELICAL_DIAMETERlCORNER_ROUND
38、_RADIUSlTRIM_TO_WP 2000 PTC50Follow Hardwalls ScanVolume NC sequencesParameters:lROUGH_OPTION=ROUGH_ONLYlSCAN_TYPE=FOLLOW_HARDWALLSlCUT_TYPE=CLIMBlSTEP_DEPTHlSTEP_OVER lMust be 1/2 of TOOL_DIAMETERlCLEAR_DISTOptional controls:lRAMP_ANGLE lHELICAL_DIAMETERlCORNER_ROUND_RADIUSlTRIM_TO_WP 2000 PTC51Hig
39、h Speed Re-roughingNC sequences:Local/Prev SequenceParameters:lSCAN_TYPE=CONST_LOADlCUT_TYPE=CLIMBlSTEP_DEPTHlSTEP_OVER lMust be 1/2 of TOOL_DIAMETERlCLEAR_DISTOptional controls:lRAMP_ANGLE lHELICAL_DIAMETERlCORNER_ROUND_RADIUSlTRIM_TO_WP 2000 PTC52High Speed FinishinglTool contact point determines
40、finishing strategylClassification of sections of surfaces lShallow lSteep lFlatlFor a given RPM and feed,higher surface footage on steep wallslMinimize sharp moveslMinimum arc value(1.5 x tool radius)lLeave sharp concave corners for post-finishing operationslCorner clean-uplStay in cut when possible
41、Slope Angle 2000 PTC53High Speed FinishingTrue Scallop Heightl2D Scallop Height Computationl3D Scallop Height Computation 2000 PTC54Classify surfaces for finishing based on slopeCreate 2 Mill Surfaces(Steep and Shallow)Mill Surface Type:Advanced/SlopedlDirection PlanelSlope AnglelSelect whether to k
42、eep the shallow or steep portionUse the mill surface for machining strategyFlat horizontal planeslSequence type=VolumelROUGH_OPTION=FACES_ONLYFinishing:Surface Classification 2000 PTC55Finishing:Steep AreasContinuous profile finishing lMaintain the tool in cut ltransitions between slices or cuts wit
43、h 2D or a 3D“S”move for closed connections lSmooth and continuous finishing toolpathHigh Speed friendly approaches and exits lTangent SplinelHelical or Tangent arclAny approach/exit that yields little direction change 2000 PTC56Steep Areas Finishing:SettingsVolume NC sequencesParameters:lROUGH_OPTIO
44、N=PROFILE_ONLYlSCAN_TYPE=CONST_LOADlSTEP_DEPTHlCLEAR_DISTOptional controls:lNUM_PROF_PASSESlPROF_INCREMENTlCORNER_ROUND_RADIUS 2000 PTC57High Speed Machining:Corner ConditionFor both roughing and profile finishingGuards against undesirable corner conditionslMinimum Corner RoundslKeeps the tool from
45、getting into dead-stop state in corners 2000 PTC58Finishing:Shallow AreasProjected type methodologylStraight machininglFlowline cut machininglProjected spiralMinimize directional changeslArc connectionslLoop connectionsSmooth approaches and exitslTangent SplinelHelicallTangent arclAny approach/exit
46、that yields little direction changeAdvantages for machines with rotary axes 2000 PTC59Shallow Areas Finishing:SettingsSurface Mill NC sequencesSequence Setup/Define Cut/Cut typelStraight CutlCutlineParameters:lSCAN_TYPE=TYPE_3lLACE_OPTION=ARC_CONNECTor LOOP_CONNECTlSTEP_OVER 2000 PTC60Shallow Areas
47、Finishing:SettingsLoop Connections for Closed CutlineslCutlinelSCAN_TYPE=TYPE_3lLACE_OPTION=LOOP_CONNECTContinuous Helical CutlineslCutlinelSCAN_TYPE=TYPE_HELICAL 2000 PTC61Flat Areas Finishing:SettingsVolume sequence for Flat surfacesParameterslROUGH_OPTION=FACES_ONLYlSCAN_TYPE=MAINTAIN_CUT_DIRECTI
48、ONor TYPE_SPIRALlCUT_TYPE=CLIMBlSTEP_OVER lMust be 1/2 of TOOL_DIAMETERlCLEAR_DISTOptional controls:lRAMP_ANGLE lCORNER_ROUND_RADIUS 2000 PTC62Rest MillingNC sequences:Local/Prev ToolParameterslSCAN_TYPE=TYPE_1lCUT_TYPE=CLIMBlMACHINING_ORDER=CORNERS_FIRSTlSURFACE_CLEANUP=SINGLE_PASSlCORNER_CLEANUP=Z
49、_PLANE_CUTSlRETRACT_OPTION=SMARTlSLOPE_ANGLE=30lSTEP_DEPTH lSTEP_OVER lRAMP_ANGLE lCUT_ENTRY_EXT=HELIXlCUT_EXIT_EXT=NONElINITIAL_ENTRY_EXT=HELIXlFINAL_EXIT_EXT=NONELeftover materialPrevious ToolCurrent ToolPart 2000 PTC63Pencil Tracing 2000 PTC64HSM ProcessRoughingRe-roughing(sometimes)Surface Machi
50、ning based on the slope of the surfacelSemi-finishing(sometimes)lSteep Surface AreaslShallow Surface Areas(including flats)lFinishinglSteep Surface AreaslShallow Surface Areas lFlat surfaces(sometimes)Cleanup of Corners(sometimes)lRest Milling orlPencil tracing 2000 PTC65How to Start with HSMTesting
