design of a tensile load frame for a scanning electron microscope senior design project 04004

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


Agenda

• Project Overview• Objectives and Specifications• Final Design• Manufacturing and Assembly• Production Report• Recommendations


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


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


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


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


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


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


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.


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


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


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


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


Controls• Control through

LabView• End user definable• USB Minilab 1008• Stock or freeware

libraries • Hard emergency stop


Vacuum InterfaceAvailable

port

2 ¾ “ Flange

Vacuum chamber

Pro/E Model


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


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


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


Manufacturing and Assembly• Manufacturing Plan

– Machine sequence– Tolerances– Quality checks– Total hours– Pro/E drawings– Cutting speed and

feed rates– Machine tools


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


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


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


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


Questions and Discussion

design of a tensile load frame for a scanning electron microscope senior design project 04004

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