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Empower CNC Machine

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CNC Milling, Cimatron, BFW

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Empower CNC Machine

  1. 1. GETTING MOREFROM YOUR CNCMACHINE….. Edsel Vaz
  2. 2. Factors Affecting Your Daily Activity Reliability of your Machine Tool Cutting Tools Machining Techniques 2
  3. 3. TOOL RIGIDITY Use the shortest tool possible. Favor a tool with shorter flute Use Smallest Tool-Out3
  4. 4. Fine Grain CarbideChoose the carbide grade not justfor its hardness (resistance towear).Also for its toughness (resistance toshocks).Compromise between hardness andtoughness comes from carbideswith small grain sizes Fine-grain carbides available todaydeliver improved toughness, withlittle change in hardness comparedto coarser grades. 4
  5. 5. Use Of CoolantHigh speed machining often means drymachiningConsistent high temperature may be betterfor the tool than the widely varyingtemperature that coolant can bring aboutUse it where lubrication is necessary toprotect either the surface finish or the toolCooling effect of coolant may not be well-suited to HSM, but the lubrication effectmay be valuable 5
  6. 6. Speed or RPM & Feed Rate & DOCAt or near maximum spindle rpm for Ball NoseFollow Vc and Trial & ErrorCustomize Params for Different MaterialsCREATE A TOOL LIBSET UP PARAMETERS FOR EACH TOOL INDPENDENTLYDetermining RPM for a particular process can cut maycall for some experimenT 6
  7. 7. Tool LifeTool life and tool performance in HSM aredetermined largely by the consistency of theload on the toolSpeed amplifies the effect of smallfluctuations resulting from factors such astool holding,tool path and controlDetermining how fast a particular processcan cut may call for some experimentationLatest Techniques in Programming todaycan redue your machining time by 50% ormore and increase Tool Life by 100% ormore 7
  8. 8. CNCElectronics can make all the differenceThe right CNC coupled with other elements ofthe control system can let a “slower” machinemill a given form faster than a machine with ahigher top feed rate. The reason is this: In anymilling routine that is relatively complex, thecontrol system will determine how much of theavailable feed rate can be put to use.A control system is only as fast as its slowestcomponentA control system is only as fast as its slowestcomponent 8
  9. 9. ControllerFast CNC processing speed is fundamentalThis is particularly true where the CAMsoftware has defined a complex tool pathas a series of numerous short movesIf the CNC can’t process these blocks fasterthan the machine can move through them,then the machine will stutter as it waits fordata control system is only as fast as itsslowest componentSlow data input to older & Second Handused CNCs can produce a similar effect 9
  10. 10. Input Baud RateWith an older CNC, input baud rate is thebottleneck that can most severely limit feed rateWhen a program must be "drip feed" through aserial port, the CNC cant execute the programcommands any faster than it can receive themacross this connection.Newer CNC’s overcome this bottleneck in either oftwo ways. They provide enough memory for along program to be stored at the control so dripfeeding is no longer necessary, and/or they allowfor network connections (like Ethernet orPCIMCA) that allow much faster program transferthan the serial link. 10
  11. 11. Look AheadIn complex milling, the tool path segments can be soshort that a machining center moving at a high feedrate can’t accelerate or decelerate fast enough to makedirection changes accurately Corners may be rounded off and the work-piecesurface may be in-accurateLook-ahead capability can let the CNC read ahead acertain number of blocks in the program, to anticipatesudden direction changes and slow the feed rateaccordingly.How many blocks a look-ahead feature looks ahead willvary from control to control, and more blocks doesntnecessarily mean better performance.A stiffer, more responsive machine can follow a toolpath11accurately with less advance warning from thecontrol.
  12. 12. CNC Data Flow12
  13. 13. Cutting Tools - LifeEntering or exiting the material at a high feed rate putsa strain on the cutting tool Entering or exiting the material at a high feed rate putsa strain on the cutting toolWhen entering the material, ramp in.Throughout the cut, try Z-level machining. Z-levelmachining strives to keep a steady load on the tool bykeeping the tool continuously engaged The conventional alternative, milling in a zig-zag or“lace” pattern, can shorten tool life at high feed ratesbecause it causes the tool to exit and re-enter thematerial at the end of every passAs a Option always consider Spiral( Climb) instead ofParallel or Die Sinking 13
  14. 14. Rounding CornersAt high feed rates, rounding internal corners can letthe machine cut the corner faster.The material left behind must then be removedthrough re-machining, so there is this tradeoffGains from HSM are likely to be high enough to makethe process more efficientCAM software with a re-machining feature can createtool paths for removing just what stockRest milling (to machine the "rest" of the material) isa term for re-machining. Rest milling generallyemploys multiple passes. When just one pass is usedto let a small tool trace the seam where two surfacesmeet, this is called pencil tracing. 14
  15. 15. Trochoidal MillingThis is an approach to rough milling in whichstraight lines are replaced by “curlicue” circularmoves of constant radius Making the constant circular curve the onlydirection change allows a high feed rate to beconsistently maintainedThe cutting edge is in contact with the materialthrough only about 5% of the cutter’srevolution vs. up to 50% for more conventionalcutting.Chip Evacuation & Cooling of the tool isimproved. 15
  16. 16. Variable Feed ControlA way to keep cutting load more consistent and feedrate as fast as possible is to vary the feed inproportion to the amount of material the toolencounters.Optimization software can perform this functionbased on input from Programmer.The software divides the tool path into segments andsets feed rate according to the profile of the stockremoved With optimization, the tool moves faster throughregions where the depth of cut is light. Anotherpotential benefit is reduced strain on the tool. 16
  17. 17. Smooth Surface FinishFundamental tool path parameters can affect thefinish of the machined surfaceThe smoothest finish tends to result when chip load(mm per tooth) equals the step-over increment (radialdepth of cut)When chip load and step-over are unequal, thisproduces a finish rougher in one direction thananother 17
  18. 18. Get it Right First Time Machine Stability Effective CNC Controls Correct use of Cutting Tools Proper Programming Techniques Use & Record Optimum Params Monitor Sound Levels while Cutting Follow Instructions from M/C Tool & Cutting Tool Mfrs 18
  19. 19. Thank You Edsel Vaz

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