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Wednesday, July 8, 2015

Example of rotary indexer sizing calculation for table plate drive application (3/3)

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Step 4 : Rotary Indexer Model Selection
Minimum Follower Wheel Pitch Diameter (Credit : Sankyo)

  • Recommended Size of Rotary Indexer can be estimated. By calculate Radius of Gyration divide by Follower Wheel Pitch Radius, this value should be less than 5 (this value may vary depend on difference manufacturer)
Recommended Follower Wheel Pitch Radius of Rotary Indexer
  • Minimum Follower Wheel Pitch Radius, [PRmin] = 427/5 = 85.424 ≈ 85.4 mm
  • Then, Minimum Follower Wheel Pitch Diameter, [PDmin] ≈ 85.4 x 2 ≈ 171 mm
  • Recommended Size of Rotary Indexer also can be estimated by another method. By calculate Table Diameter divide by center distance between input & output shaft, this value should be less than 7 (this value may vary depend on difference manufacturer)
Distance Between Input & Output Shaft
Recommended Center Distance between Input & Output Shaft of Rotary Indexer
  • Then, Minimum Distance Between Input & Output Shaft, [CDmin] = 1000/7 = 142.857 ≈ 143 mm
  • Total Output Torque for Indexer Selection, [Tt select] = Tt x SF = 307.271 x 1.2 = 368.726 ≈ 369 N.m @ Input Shaft(camshaft) Speed 60 rpm
Thus, Select Indexer that Dynamic Rated Output Torque [Top] is more than 369 N.m at input shaft speed more than 60 rpm, 8 stops, Indexing Angle 270 degree, MS motion curve, minimum center distance between input & output shaft 143 mm and minimum follower wheel pitch diameter 171 mm
Step 5 : Gear & Motor Selection
Find the maximum torque on gear output shaft at working shaft speed
  • In this case, gear is directly connect to the rotary indexer. Then the maximum torque on gear output shaft is equal to the camshaft torque of rotary indexer
  • The camshaft torque of rotary indexer[Tc] is determined by following formula:
Rotary Indexer Cam Shaft Torque
  • Internal Indexer Inertia Torque, [Toi] = 2.943 N.m (from rotary indexer manufacturer data)
  • Camshaft Friction Torque, [Tx] = 16.677 N.m (from rotary indexer manufacturer data)
  • Maximum Camshaft Torque Coefficient, [Qm] = 0.987 (This is standard value, find the Qm for Modified Sine Cam Curve from Cam Curve Characteristic Table)
  • Then, Camshaft Torque, [Tc] = 87.552 N.m @ camshaft speed 60 rpm (This is the torque at input shaft of rotary indexer which is equal to torque at output shaft of gear)
Next, calculate the equivalent camshaft torque for gear selection [Tce select] by considering of operating condition & safety factor
  • Calculated Operation Factor, [f] = 1.8 (Calculate from type of load(steady or shock load), operating hours per day, frequency of starts/stops, ambient temperature, type of lubrication or others factor. Please check gear manufacturer information. In this case use 1.8)
  • Then, Tce select = Tce x f x SF = 87.552 x 1.8 x 1.2 = 189.113 N.m @ Output Shaft Speed 60 rpm
Calculate Gear Input Shaft Torque
  • Gear Ratio, [ig] = 10.33 (Check from gear manufacturer info.)
  • Gear Input Shaft Speed, [Ng] = Nrpm x i= 60 x 10.33 = 619.8 ≈ 620 rpm
  • Gear Running Efficiency, [Effg] = 92% (Check from gear manufacturer info.)
  • Gear Input Shaft Friction Torque, [Txg] = 0.9 N.m (Check from gear manufacturer info.)
  • The Gear Input Shaft Torque[Tg] is determined by following formula:
Gear Input Shaft Torque
  • Gear Input Shaft Torque, [Tg] = 10.113 N.m @ Input Shaft Speed 620 rpm
Calculate Motor Torque
  • Motor Revolution per Minute, [Nmotor] = 1730 rpm (from motor manufacturer data)
  • Gear Ratio Required, [ireq] = Nmotor / Nrpm = 1730 / 60 = 28.833
  • Pulley Speed Ratio, [ipulley] = Ireq / I= 28.833 / 10.33 = 2.791 ≈ 2.8 (←if very close to 1, motor can be mounted directly to gear, then set Effpulley = 100% & Txp = 0
Table Drive Application with Pulley (Credit : Sankyo)
  • Pulley Running Efficiency, [Effpulley] = 90% (estimated)
  • Pulley Shaft Friction Torque, [Txp] = 2 N.m (estimated)
  • The Motor Torque [Tmotor] is determined by following formula:
Motor Torque
  • Then, Motor Torque, [Tmotor] = 10.003/(2.791 x 0.9) + 2 = 6.026 N.m @ Speed 1730 rpm
Calculate Motor Power
  • The Peak Motor Power [Pmotor peak] is determined by following formula:

  • Then, The Peak Motor Power [Pmotor peak] = 2 x 3.1416 x 1730 x 6.026 / 60 = 1091.617 Watt ≈ 1.092 Kw
Calculate Motor Power for Motor Selection
  • Power for Motor Selection, [Pmotor sel] = Pmotor peak x SF = 1.092 x 1.2 = 1.310 Kw
Then,  select gear that maximum continuous output torque is more than 189 N.m at output shaft speed more than 60 rpm, gear ratio 10.33
Motor power 1.31 Kw at speed 1730 rpm

Ratio of pulley between gear and motor 2.8




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Every care has been taken to ensure the accuracy of the information but no liability can be accepted for any loss or damage whether direct, indirect or consequential arising out of the use of the information or calculation sheets from our blog.