MACHINE TOOL GEAR BOX
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The document discusses multi-speed gearboxes used in machine tools. It explains that gearboxes provide multiple spindle speeds from a single motor speed to accommodate different feeds, workpiece materials and dimensions, and cutting tool materials. It then describes arithmetic, geometric and harmonic progressions used to calculate speed steps and ensures optimal distribution of speeds. Various terms related to gearbox design such as structural formula, ray diagram, speed chart and gearing diagram are also defined.
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MACHINE TOOL GEAR BOX
- 2. 1. Lathe 2. Shaping 3. Milling 4. Drilling Multi‐speed Gear Box of Machine Tool Single input speed (Motor speed) = nem Multi‐Speeds on Spindle shaft (Spindle Speeds) 24/01/2017 2 n1 ,n2 ,n3 ,n4 n5 ,n6 ,n7 , nz The extreme spindle speeds n1 = nmin nZ = nmax
- 3. Why Multi‐Speeds ? 24/01/2017 3 Different : • Feeds • W/P Materials • W/P Dimensions [D] • Cutting tool materials n1 n2 n3 n4 n5 n6 n7 n8 N9= nz nem D.P.Bhaskar, Sanjivani COE Kopargaon 1 1
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- 8. nmax =Maximum spindle speed (rpm)= nz nmin= Minimum spindle speed (rpm)= n1 n ( ) n1 =nmin n2 =n1 + at n3 = n2 + at =n1 + 2at n4 = n3 + at =n1 + 3at nz = n(z‐1) + at =n1 + (z‐1)at Dk = Diameters to be Machined at Specific cutting speed (v) =Upper limit of Diameter ∆ ∆Dk = Diameters Range = (D2‐D1) = (D3‐D2) ……… 24/01/2017 8
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- 11. Remarks @ AP 24/01/2017 11 At high spindle speeds, the diameter range is very narrow and hence some of the speed steps are redundant. At low spindle speeds the diameter range is wide hence needs to add more speed steps between calculated values. D.P.Bhaskar, Sanjivani COE Kopargaon
- 15. Progression ratio/ Speed ratio Progression ratio/ Speed ratio Geometric progression (also inaccurately known as a geometric series) is a sequence of speeds such that the ratio of any two successive speeds of the sequence is a constant called the Geometric progression ratio (speed ratio) of the sequence. Range ratio It ratio of maximum and minimum speed
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- 18. Remarks @ AP 24/01/2017 18 At high spindle speeds, the diameter range is very narrow and hence some of the speed steps are redundant. At low spindle speeds the diameter range is wide hence needs to add more speed steps between calculated values. D.P.Bhaskar, Sanjivani COE Kopargaon
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- 30. 24/01/2017 30 In gearbox design a set of preferred step ratio or preferred numbers is used to obtain the series of output speed of gearbox. The preferred step ratio is mentioned as basic series named as R5, R10,R20,R40 and R80. Each basic series has a specific step ratio. R [Charles Renard] Definition of preferred number/speed series
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- 34. Z =P1(x1)*P2(x2)*....Pu(xu) Structural Formula The maximum number of speed that can be obtained from two shafts is three. Hence its necessary to use intermediate shafts between the input shaft and output shaft. The structural formula helps to arrive the number of stages and required gears to obtain the desired speeds. Structural Formula P : Speed steps/ Pairs in any stage X : Characteristic in stage
- 42. 24/01/2017 42 1) MAX Node addition=7.5 2) P of Stage one should be less BEST RULE
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- 49. 24/01/2017 49 D.P.Bhaskar, Sanjivani COE Kopargaon A ray diagram is a representation of structural formula. It provides information such as speed in each stage, the transmission ratio in each stage, The total number of speeds and its values. Definition
- 52. 24/01/2017 52 Ray Diagram Kinematic/Gearing Layout A kinematic layout is a pictorial representation of a gearbox, describing the arrangement of gears. It provides information like number of stages, number of shafts used, number of gear pairs and its arrangement. Definition
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- 60. Number of Teeth and Speed deviation diagram Write best Structural formula, Draw Structural Diagram, Ray Diagram, Speed Chart, Gearing Diagram, No of teeth, Speed Deviation Diagram D.P.Bhaskar, Sanjivani COE Kopargaon Question
- 61. Sppeds n1 n2 n3 n4 n5 6 Calculated 100 158 252.8 395 632 995.4 Round off 100 160 250 400 630 1000 e Ray Diagram, Speed Chart Gearing Diagram Spindle speeds
- 66. GE=4 GD=1.6 GC=0.635 GE=4 GD=1.631 GC=0.639 ′ ′ ′ 400′ /GD=400/1.635=244.64 ′ 630′ /GD=630/1.635=385.32 ′ ′ ′ 400′ /GC=400/0.639=626 ′ 630′ /GC=630/0.639=986 n(TH) n(PR) 100 100 160 160 250 244.64 400 385.32 630 626 100 986 Deviated Speeds
- 67. Speed Deviation ∆n nth 100 160 250 400 630 1000 nact 100 160 244.64 385.32 4 986 ∆n 0 0 ‐2.144 ‐3.67 ‐0.639 ‐1.40 Limit for speed deviations ∆n < ± 10(ɸ‐1)٪ ∆n < ± 10(1.58‐1)=5.8٪ Speed Deviation Diagram
- 73. SPPU Questions