Wt4603 unit4 week5
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  • 1. WT4603Wood Processing Safety & PracticeLecture Unit 4 (Week 5)
    • PLANING MACHINES & SETTING PLANER KNIVES
    • 2. Lecturer: Mr. Joseph Lyster
    • 3. joseph.lyster@ul.ie
    • 4. Notes prepared by: Mr. Donal Canty, Mr. Des Kelly and Mr. Joseph Lyster
    • 5. Notes available on www.slideshare.net/WT4603
  • WT4603
    Surface Planer
    Planer Knives
     
    Important factors when selecting a planer knife
     
    Suitability for cutter block
    Material being processed
    Finish required
    Volume being machined
    Clamping and setting mechanisms
    Department of Manufacturing & Operations Engineering
  • 6. Surface Planer
    WT4603
    Planers can have 2,3,4,6……. Cutter knives.
    Most smaller machines such as those found in schools will have 2,3 or 4 knives.
    Department of Manufacturing & Operations Engineering
  • 7. Surface Planer
    WT4603
    Knives can be made from Chrome Vanadium steel alloy.
    This is suitable for machining softwoods and non abrasive hardwoods.
    However with advances in machining technology better materials have been developed to machine wood and wood composites.
    Chrome Vanadium knives dull quickly on harder more dense material.
    This requires more sharpening, setting up and leads to a lot of time wastage.
    Department of Manufacturing & Operations Engineering
  • 8. Surface Planer
    WT4603
    High Speed Steel (HSS) is a cobalt steel alloy with a small percentage of Tungsten added.
    It is more suitable for machining all types of wood than the chrome steel compounds.
    Department of Manufacturing & Operations Engineering
  • 9. Surface Planer
    WT4603
    Abrasive stock should be machined using solid or tipped cutters.
    Tungsten Carbide (TC) is the best tool compound for machining manufactured boards.
    For general work HSS cutters are preferred to TC
    Cutters can be re-sharpened easily.
    A keener edge can be achieved on HSS giving a better finish
    Department of Manufacturing & Operations Engineering
  • 10. Surface Planer
    WT4603
    The reason for this is that steel compounds are smelted and shaped by rolling and forging while the metal is close to melting point.
    The molecules of the compound flow and align themselves in response to this pressure giving the material maximum strength and edge holding capabilities
    Department of Manufacturing & Operations Engineering
  • 11. WT4603
    Surface Planer
    Tungsten carbide is a sintered compound. The fine grain powder from which the cutter will eventually will be made is compressed into a mould ( the ‘blank’ un-edged cutter required) under extremely high temperature (1500C) and pressure to form a solid block.
    Tungsten does not flow – it retains a granular structure and will chip rather than deform if abused.
    Department of Manufacturing & Operations Engineering
  • 12. Surface Planer
    WT4603
    Because if its brittle nature TC cutters require a more obtuse sharpness angle than the HSS cutters (more support for the cutting edge).
    This makes it less satisfactory for cutting softwoods than HSS knives which can be ground to a more acute cutting angle.
    Department of Manufacturing & Operations Engineering
  • 13. WT4603
    Surface Planer
    Department of Manufacturing & Operations Engineering
  • 14. WT4603
    Knife Cutter geometry
    Rake or Cutting angle
    Angle created between the face of the cutting knife and the centre of the cutter block
    Can have a wide range
    Softwoods 27° to 35 °
    Hardwoods 15° to 25 °
    Department of Manufacturing & Operations Engineering
  • 15. WT4603
    Knife Cutter Geometry
    Bevel or Lip Angle
    Angle formed to give the cutting edge
    Minimum of usually 35°
    Greater for tipped cutters
    Department of Manufacturing & Operations Engineering
  • 16. WT4603
    Knife Cutter Geometry
    Clearance Angle
    Angle formed between a line tangential to cutting circle and the bevel angle of the knife
    Must be present
    Has a bearing on the life of the cutting edge
    Usually 10° to 15°
    Department of Manufacturing & Operations Engineering
  • 17. WT4603
    Knife Cutter Geometry
    Peripheral Cutting Speed
    A constant speed in the range of 35-45 m/s will give best results
    Increase in speed may cause loss of dynamic balance due to vibrations
    Poor finish
    Increased noise levels
    Department of Manufacturing & Operations Engineering
  • 18. WT4603
    Pitch distance
    Combination of a rotary cut and a linear feed will leave the surface of the material with a series of arcs on it called Curtate Trochoids
    The pitch and depth of these arcs will determine how smooth the surface finish will be
    Department of Manufacturing & Operations Engineering
  • 19. Department of Materials Science & Technology
    University of Limerick
    WT4603
    Pitch Distance
    2mm to 3mm for non obvious joinery and painted external work.
      
    1mm to 1.5 mm for internal painted work.
    0.5mm to 1mm for hardwood joinery and furniture.
    Department of Manufacturing & Operations Engineering
  • 20. WT4603
    Pitch Distance
    The SI unit of time is the second , but the minute is acceptable.
     
    Feed rate on wood working machines is expressed in metres per minute. (m/min)
     
    The formula for the pitch of the cutter marks is given by:
     
    f
    p = -------
    nR
     
    where p = pitch of cutter mark
    f = feed rate
     
    n = number of effective cutters
     
    R = revolutions per minute of block
    Department of Manufacturing & Operations Engineering
  • 21. Pitch Distance
    WT4603
    The unit for “p” will be metres (m)
     
     
    f m/min m min
    p = ---- = --------- = ----- x ------ = m
    nR 1/min min 1
    Department of Manufacturing & Operations Engineering
  • 22. WT4603
    Pitch Distance
    Problem 1
    Calculate the cutter pitch of a 4 cutter block revolving at 4200 rev/min with a feed speed of 24m/min.
     
     
    F 24 24
    p = ------- = ------------ = --------- = 0.0014m = 1.4mm
    nR 4 x 4200 16800
    (Internal painted work)
    Department of Manufacturing & Operations Engineering
  • 23. Pitch Distance
    WT4603
    If a graded surface is specified and the machine has a multi-speed feed gearbox, the same formula is used but “f” is expressed in terms of n ,p, and R.
     
     
    f
    p = -------  f = nRp
    nR
    Department of Manufacturing & Operations Engineering
  • 24. Pitch Distance
    Problem 2
     
    From a cutter block which rotates at 4200 rev/min and has two cutting knives, a surface finish of a 4mm pitch is required. At what speed should the feed gearbox be set.
     
    f = nRp = 2 x 0.004 x 4200 = 33.6 m/min
     
    WT4603
    Department of Manufacturing & Operations Engineering
  • 25. WT4603
    Chip formation
    Department of Manufacturing & Operations Engineering
  • 26. WT4603
    Riving
    Department of Manufacturing & Operations Engineering
  • 27. Riving
    WT4603
    Cracking occurs below the cut depth
    Department of Manufacturing & Operations Engineering
  • 28. WT4603
    A
    On the surface planer the in-feed table (A) acts as chip breaker and the downward pressure exerted by the operator also makes it act as the pressure bar.
    Department of Manufacturing & Operations Engineering
  • 29. WT4603
    Chip formation
    Department of Manufacturing & Operations Engineering
  • 30. WT4603
    Chip formation
    Chip breaking aid and pressure bar prevent riving and splintering
    Department of Manufacturing & Operations Engineering
  • 31. WT4603
    Square cutter blocks
    Department of Manufacturing & Operations Engineering
  • 32. WT4603
    Square cutter blocks
    • Clamping bolts are in tension
    • 33. Tension force increases with rotational speed
    • 34. Will be ejected at failure
    Department of Manufacturing & Operations Engineering
  • 35. WT4603
    Square cutter blocks
    Clamping bolts are in tension
    Department of Manufacturing & Operations Engineering
  • 36. WT4603
    Circular cutter block
    Clamping bolts are in tension
    Department of Manufacturing & Operations Engineering
  • 37. WT4603
    Circular cutter block
    • Reduced noise levels
    • 38. Better balance
    • 39. Safer clamping mechanism
    • 40. Can run head at higher speeds (RPM)
    • 41. Can produce better finish
    • 42. Easier and quicker maintenance
    Department of Manufacturing & Operations Engineering
  • 43. WT4603
    Knife clamping mechanism
    Department of Manufacturing & Operations Engineering
  • 44. WT4603
    Knife clamping mechanism
    Department of Manufacturing & Operations Engineering
  • 45. WT4603
    Knife clamping mechanism
    Department of Manufacturing & Operations Engineering
  • 46. Cutter projection
    WT4603
    Round form tool with limited cutter projection
    Department of Manufacturing & Operations Engineering
  • 47. Cutter projection
    WT4603
    Use of a limiter to achieve limited cutter projection
    Department of Manufacturing & Operations Engineering
  • 48. Cutter design
    WT4603
    Cutters should preferably be designed to be used in dimensionally similar pairs, formed to the same profile.
    Pairs should be mounted directly opposite one another. The manufacturer should ensure that instructions on balancing the pairs of cutters after grinding are given to the user.
    Department of Manufacturing & Operations Engineering
  • 49. Cutter projection
    WT4603
    The design of cutter blocks should, as far as is practicable, be such as to prevent excessive cutter projection.
    Where the mounting arrangement permits projection which could subject the cutter to unsafe stresses, the maximum permissible projection for given cutter types should be specified in the user’s instructions.
    Department of Manufacturing & Operations Engineering
  • 50. Hand-fed machines
    WT4603
    For machines designed for hand-fed operations, where cutters are necessarily exposed, the use of chip limiting cutters should be recommended
    For other hand and semi-mechanical feed operations, cutter blocks should have as little cutter projection as is practicable.
    Department of Manufacturing & Operations Engineering
  • 51. WT4603
    Surface Planer
    Cutter and Machine Maintenance
     
    Involves:
     
    Grinding and setting of knives
     
    Roller and pressure bar setting
     
    Prevention of resin build up on table and rollers.
     
    Attention to: bearing wear
    feed complex adjustments
    rise and fall table
    Department of Manufacturing & Operations Engineering
  • 52. Surface Planer
    WT4603
    The grinding angle of a cutter can vary between 30 to 35
    This is increased to 40 for hardwoods (cutting edge lasts longer)
    Department of Manufacturing & Operations Engineering
  • 53. WT4603
    Surface Planer
    Overheating
     
    May produce micro cracks in the cutting edge which can run into gaps when the cutter is used.
    May cause the cutter to bow due to expansion.
    Department of Manufacturing & Operations Engineering
  • 54. WT4603
    Surface Planer
    Overheating can be avoided
    By taking light cuts.
    By ensuring that the grind wheel is ‘dressed’ when required to ensure that the face is open and not glazed when grinding the knives.
    By using a ‘soft’ grinding wheel on HSS cutters – the soft structure of the wheel allows its grains to break away as soon as they are blunt revealing sharper ones.
    By wet grinding – this is the grinding of cutters while partially submerged in a mixture of water and soluble oil. The water is a coolant to prevent frictional heat developing and to disperse it should it occur. The oil prevents rust in the cutters and it provides a degree of cutting lubrication.
    Department of Manufacturing & Operations Engineering
  • 55. WT4603
    Surface Planer
    Setting Cutters in Block 
    Before setting the following points should be checked.
     
    The out feed table and cutter block must be clean and free from dust resin.
     
    Method of adjusting cutters.
    Area where setting device is used from should be free from resin and damage.
    Straightness of cutters.
    Cutters correctly balanced both in weight and end for end.
    Department of Manufacturing & Operations Engineering
  • 56. WT4603
    Surface Planer
    Setting devices
    There are a number of cutter setting devices.
    This device and procedure will often be supplied with the machine.
    They can be loosely placed into the following four categories:
     
    Bridge device
     
    Precision cutter setter device
     
    Pin locater device
     
    Wooden straight edge device
     
    Cutters require accurate setting in the block because if the knives are not revolving in the same cutting circle a poor finish will be produced.
    Department of Manufacturing & Operations Engineering
  • 57. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 58. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 59. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 60. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 61. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 62. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 63. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 64. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 65. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 66. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 67. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 68. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 69. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 70. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 71. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 72. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 73. WT4603
    Surface Planing
    Department of Manufacturing & Operations Engineering
  • 74. WT4603
    Setting Planer Knives
    When planing wooden material a number of factors combine to generate the flat surface.
    Number of cutting knives in the block
    Speed of the revolving block
    Feed speed of the material
    Knife cutter design
    Chip breaking aids
    Nature and species of the material
    Department of Manufacturing & Operations Engineering
  • 75. Knife cutter design & Chip breaking aids
    These factors combine to produce an acceptable surface finish
    Tip of the cutter splits away the chip
    The chip is forced away from the stock and up along the face of the cutter which is exerting a tearing effect on the grain fibre
    As the knife exits the stock the chip is either cut or will “rive” or tear deeply along the grain line and lift as a long heavy splinter
    WT4603
    Department of Manufacturing & Operations Engineering
  • 76. Knife cutter design & Chip breaking aids
    The cutter projection and the shape of the block face cause the severed chip to bend back causing a crack across its width
    This makes long grain riving less likely
    (Chip breaker not shown)
    WT4603
    Department of Manufacturing & Operations Engineering
  • 77. WT4603
    Knife cutter design & Chip breaking aids
    Sharp tooling (a) will aid in the chip bending back and cracking across its width
    Blunt tooling (b) will aid riving
    Department of Manufacturing & Operations Engineering
  • 78. WT4603
    Chip Formation
    Before knife makes its cut
    Department of Manufacturing & Operations Engineering
  • 79. WT4603
    Chip Formation
    Chip to be formed
    Department of Manufacturing & Operations Engineering
  • 80. WT4603
    Chip Formation
    a
    Chip breaker will help prevent riving (a)
    Department of Manufacturing & Operations Engineering
  • 81. WT4603
    Knife cutter design & Chip breaking aids
    Large cutting angle which gives the knife a lifting action which will cause riving
    Grinding a face bevel reduces the risk of riving as it changes the cutting angle
    Department of Manufacturing & Operations Engineering
  • 82. WT4603
    Face bevel on cutter knife (B)
    Department of Manufacturing & Operations Engineering
  • 83. WT4603
    Setting Cutter Knives
    Setting of knives will greatly depend on the type of cutter block
    Knife cutter projection
    Chip breaker
    Knife parallel to table
    All knives in the same peripheral cutting circle
    (Refer to machine manual for setting)
    Department of Manufacturing & Operations Engineering
  • 84. WT4603
    Process Sheet Example:Double Mortise and Tenon
    Department of Manufacturing & Operations Engineering
  • 85. Marking Out
    WT4603
    Department of Manufacturing & Operations Engineering
  • 86. Marking out:
    WT4603
    Department of Manufacturing & Operations Engineering
  • 87. Cutting 1
    WT4603
    Department of Manufacturing & Operations Engineering
  • 88. Cutting 2
    WT4603
    Department of Manufacturing & Operations Engineering
  • 89. Completed Joint
    WT4603
    Department of Manufacturing & Operations Engineering