Senior Design: Tachometer Calibration Device Team 4: Jennifer Egolf, Matthew Hagon, Michael Lee, Christopher Pawson Sponsor: DuPont Advisor: Dr. Glancey

Mission Statement Design and manufacture a portable device for the relative calibration of multiple surface tachometers.

Surface Tachometers Shaft Encoder WheelBracket

Surface Tachometers V1V2V3V4 Surface tachometers measure surface velocity  Detect small differences in speed across a system  Calibrated tachometers used as diagnostic tools Reduce downtime of continuous processes V1=V2=V3=V4

Desired Features with Metrics Constant Speed % Variation in Speed PortableSize / Weight Ease of UseSet up time Adaptable# of tachometers mounted Adjustable# of attainable speeds Durable# of cycles until failure InexpensiveCost WantsMetrics

Benchmarks High inertia devices  Lathe Current method used + Low variation in speed - Only accommodates one tachometer at a time - Cannot calibrate tachometers relative to one another - Not portable  Drum Previous method employed for calibration + Low variation in speed - Large and not portable Hand-held calibration devices + Portable - Cannot calibrate tachometers relative to one another

Initial System Concept Tachometers User interface Motor Controller Motor Tachometer mounting brackets

Subsystem Configuration Three concepts for the critical subsystem were developed through benchmarking and brainstorming Conveyor Belt Rotating Disc Rotating Drum

Metrics and Target Values

Concept Selection Advantages Easy to mount multiple tachometers Disadvantages Vibrations associated with belt and linkage joints Difficult assembly High cost Advantages Ease of assembly Consistent performance Low cost Disadvantages Machining accuracy of disc crucial Advantages Ease of assembly Consistent performance Easy to mount multiple tachometers Disadvantages Large / Heavy Machining accuracy of drum crucial ConveyorDiscDrum

Choosing the Best Solution The disc was chosen as the best concept because:  Easy to assemble  Consistent performance throughout life  Low Cost  Smallest / Least material

Chosen Concept of Subsystem Tachometers Motor & Gearbox Tach mounts Disk and Shaft

System Component Considerations Tachometer mounts  Positioning Must be able to accommodate tachometers of circumference: 6” 12” 30” Disc  Dimensional variability Motor and Controller Selection  Speed Must be able to achieve specified surface velocities 16 fpm 110 fpm 240 fpm  Torque  Inertia  Ripple

Motor and Controller SGDH Servo Drive Yaskawa SGMPH Servo Motor Power requirements  Start-up torque = 0.66 N-m Inertia requirements  System Inertia = 0.03 kg-m2 Speed requirements  Three speed options 12 rpm 84 rpm 183 rpm Velocity Ripple

Fluctuations around the steady state velocity Exact relationship between motor speed and % velocity ripple unknown  100 rpm: ± 5%  Above 1000 rpm: <1% Need to maintain high motor speeds but output relatively low disc speed  Solution Gearbox

Gearbox Selection Allows motor to run at optimal speeds  rpm CGI, Inc. Planetary Gearbox 22:1 ratio Motor speed of 2000 rpm = Disc speed of 91 rpm Motor speed of 4000 rpm = Disc speed of 182 rpm

Design of Subsystem Components Disc  5” diameter  2” thickness  Machined in house Tachometer mounts  Purchase framing materials from Bosch  Machine mounting blocks in house

Eccentricity Testing Results:  ” < variations <0.001”  Create variations in speed < 0.02%

Positioning Testing

Prototype Locking handle Gearbox Motor Tachometer Disc and shaft Slider Carriages * Controller and user interface not pictured

Testing Method Mount tachometer to rotating disc Record speed variations over time Peaks on graphs indicate  Amplitude of recurring speed variations  Frequency of speed harmonics Time Speed Amplitude Frequency Speed in Time Domain Speed in Frequency Domain

Full System Testing Testing of the system revealed  Large variations in speed  Many frequencies Need to determine cause of variations Speed Amplitude Speed Tachometer speed variations from disc:

Testing of Motor and Gearbox Remove disc and shaft Mount tachometer  Directly to shaft of gearbox  Directly to shaft of motor Record speed variations for each case Tachometer speed variations with gearbox: Tachometer speed variations without gearbox (just motor effect):

Direct Drive System Testing Objective:  Confirm that the gearbox is the problem source (not bearings or coupling) Procedure:  Mount tachometer to directly driven shaft  Record variation in speed Results:  0.2 – 0.6% speed variation  Located at a distinct frequency Speed Speed Amplitude Tachometer speed variations with directly driven shaft:  Similar variations to motor testing

Observations The purchased gearbox is inappropriate for the application  Creates many and large speed variations (2.5%)  Multi-stage construction creates problems The purchased motor exhibits acceptable performance  Speed variations few and small (0.2%)

Recommendations for Further Development Eliminate multiple stage gearbox  Test system using worm gearbox  Consult custom gearbox manufacturers Rino GAM Andantex

Expense Summary to Date ItemQuantityCost Motor and Drive System1$3100 Bearings-NTN pillow block2$70 Coupling1$100 Gearbox1$540 Aluminum Bosch profile3800 mm$190 Bosch AccessoriesMany$690 Total Cost1 ~ $4700 * $1500 under budget – use toward carrying out recommendations for further development

Questions?