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Kate Gleason College of EngineeringR·I·T
Design of a Tensile Load Frame for a Scanning Electron Microscope
Senior Design Project 04004
Project Manager - Robert RinefierdFaculty Mentor - Dr. Elizabeth Debartolo
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Team Members• Project Manager – Robert Rinefierd• Lead Engineer – Evan Kastner• Mechanical Engineers
– Nicholas Currier, Evan Kastner, Robert Rinefierd, Blaine Stuart
• Industrial Engineer– Kennedy Mogwai
• Computer Engineer– Evan Brunner
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Agenda
• Project Overview• Objectives and Specifications• Final Design• Manufacturing and Assembly• Production Report• Recommendations
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Project Overview• Design and construct a load frame to apply tensile
loads to specimens inside the Scanning Electron Microscope (SEM) in the CIMS Materials Science Lab
• The load frame should be lightweight, modular, and easy to carry between buildings
• Developed for Mechanical Engineering Department faculty and students performing metallographic research
• Funded by the Mechanical Engineering department
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Objectives and Specifications• Performance
– 200 lbs Compression, 2000 lbs Tension – Position and Load Control– Live Displays
• Implementation– Cylindrical Threaded Specimen– Remove Part of Position Frame
• Evaluation – Pass Fatigue and Stress Calculations
• Safety– Vacuum– Electrical Grounding
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Design Constraints• Spatial constraints• Vacuum compatibility• CIMS Materials Lab owns the SEM; Mechanical
Engineering department will own the load frame– Load frame to mount to existing position fixture– Limited to existing ports for vacuum feedthrough
• Budget - $7,500
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Existing SEM Load Frames• Lehigh University concept
– Tension, bending, compression
– Spur gears and worm gears• US Patent
– Temperature controlled• Southwest Research
Institute (Dr. Davidson)– Fatigue testing capability
• Custom designs for individual applications
• Provided general ideas
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Final Design
Six basic Modules• Motor and Gear Box• Drivetrain• Gripping• Base and frame• Control system• Vacuum interface
Motor and gearbox Specimen
Lead screw Fixed end and base
Grip and collarFree end
Gears Load cell
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Motor and Gearbox Selection
• Motor Specifications:– Vacuum Rating – 10-7 torr– Maximum torque of 2 in·lb, driven at ~1 in·lb
• Gearbox Specifications:– Vacuum Rating – 10-7 torr– Reduction Ratio – 700:1– Maximum torque output of 1040 in·lb
• Cost is high, but parts are necessary
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Drivetrain - Gears
• Consists of two 2.5” diameter spur gears and a 1” diameter pinion gear.
• Gearing reduction of 2.5• Case hardened 8620 steel• Spur gears transmit torque to the power
screws though keys.
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Drivetrain - Power Screws• ACME 1-10 2G
threaded rods with end machining - self locking capability
• Gray iron ACME nuts inserted in free end
Keyway
Gear shaft
Bearing shaft
ACME thread
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Drivetrain – Bearings and Nuts• Fixed end – bearing
bores for shafts• Bearings and
washers to reduce friction and add stability
• Free end – ACME nuts instead of taps
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Grip Design• 3/8 – 24 threaded grip• Load cell acts as
opposite grip• Easy to change
samples• Standard ASTM
threaded samples• Test Area
– Gage length of 1 inch– Diameter of ¼ inch
Collar Grip Load Cell
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Base and Frame
• Purpose– Interface between load frame and SEM– Mounting surface for stage– Hold SEM position resolution device
• Function– Matched bolt holes– Designed to withstand 100 lb external force
(leaning) while it sits on a table.
Kate Gleason College of EngineeringR·I·T
Control System- Physical Layout
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Controls• Control through
LabView• End user definable• USB Minilab 1008• Stock or freeware
libraries • Hard emergency stop
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Vacuum InterfaceAvailable
port
2 ¾ “ Flange
Vacuum chamber
Pro/E Model
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Stress Analysis
Selected hand calculations for major components
Part Section of Part a FS
Free End Vertical Section Through CTR 10.61 30 2.83
Free End Bolt Individual Thread 6.94 30 4.32
Cylindrical Fastener Cross Section at Thread 2.96 30 10.14
Cast Iron Nut Cross Section 4 43.5 10.88
ACME Shaft Thread 4.5 30 6.67
ACME Shaft Radial Load Bearing 15.77 30 1.90
ACME Shaft 5/8" to 1/2" Step 17.35 30 1.73
ACME Shaft Keyway 15.64 30 1.92
Fixed End Vertical Section Through CTR 8 30 3.75
Pinion Gear Tooth 64.86 180 2.78
Spur Gear Tooth 25.95 180 6.94
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Stress Analysis• Verified preliminary
calculations done for major parts
• Shear stress, Von Mises stress, and displacement in gears, free end, and ACME shafts
• Load conditions were maximum possible
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Design for Manufacture and Assembly
• Assembly sequence• DFA Index – 6.23%• Minimum Number of
Parts - 15• Theoretical number of
parts -61 • Estimated cost -
$7223.50
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Manufacturing and Assembly• Manufacturing Plan
– Machine sequence– Tolerances– Quality checks– Total hours– Pro/E drawings– Cutting speed and
feed rates– Machine tools
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Cost AnalysisMotor + Gearbox $4,105.00 Drive Train $461.48 Load cell $900.00 Material stock $147.81 User Interface/Controls $31.00 Vaccum Interface $709.65 Miscellaneous $152.10 Fasteners $33.72 Subtotal $6,540.76 Shipping $73.32Total $6,614.08
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Production Report• Early March:
– Completed of all aspects of mechanical design– Submitted purchase order for components
• Mid-March: – Completion of detailed design including FEA analysis– Design for assembly analysis
• April:– Fabrication of steel components– Development of control system with LabView– Submit order for all additional standard components
• May: – Assembly and troubleshooting
• Early June:– Motor and gearbox expected to arrive for assembly– Electromechanical integration and system troubleshooting
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Recommendations
• Weight of load frame may be an issue • Alignment – threads are general fit rather
than precision fit• Position resolution - encoder• Optimize control system after motor
arrives
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Acknowledgements
• Dr. DeBartolo – Faculty Mentor• Dave Hathaway and Steve Kosciol• Dave Fister, Mike Haselkorn, Newton
Green – NCR³• Charlie Clark and Frank Rheaume –
Gleason Works• Ron Foster – Empire Magnetics
Kate Gleason College of EngineeringR·I·T – Senior Design 04-004
Questions and Discussion