22.322 Mechanical Design II

1. 22.322 Mechanical Design II Spring 2013

2. Introduction Konstantine A. Fetfatsidis, Ph.D • B.S.M.E. UMass Lowell ‘07 • M.S.M.E. UMass Lowell ’09 • Advanced Composite Materials & Textile Research Laboratory (ACMTRL) • Thesis: Characterization of the Tool/Fabric and Fabric/Fabric Friction for Woven Fabrics: Static and Dynamic • Ph.D (M.E.) UMass Lowell ’12 • Dissertation: Simulation of the Manufacturing Process and Subsequent Structural Stiffness of a Composite Wind Turbine Blade with and without Defects • Composite Structures Research Engineer – Aurora Flight Sciences (Cambridge, MA) • Contact Info: Konstantine_Fetfatsidis@uml.edu • Office hours: email or TA

3. Course Information BAL-214: Monday, Wednesday, Friday • Section 201: 8 AM – 8:50 AM • Section 202: 9 AM – 9:50 AM • Teaching Assistant: Javad BaqersadJavad_Baqersad@student.uml.edu • Textbook: Design of Machinery (Fifth Edition) Robert L. Norton, McGraw Hill, 2012

4. Course Information Course Description • This course is a continuation of 22.321 and concentrates on cam design, gear design, and power train design. • The major term project involves the design, analysis, manufacture, and dynamic testing of a cam having specified characteristics. • The lab uses computer aided design tools (CAD) and computer aided manufacturing (CAM) to generate tool paths. • Numerically controlled milling machines, and dynamic simulation codes are applied. • The lab provides an opportunity for students to work together on their project.

5. Course Information Lecture Topics • Introduction to Cam terminology • SVAJ Diagrams • Single & Double Dwell Cams • Critical Path Motion • Cam Sizing & Manufacture • Design Considerations • Gear Trains • Gear Tooth Nomenclature • Interference & Undercutting • Gear Types (Simple, Compound, and Planetary) • Dynamic Systems • Dynamic Force Analysis • Balancing & Engine Dynamics • First & Second Order Systems • Control of First and Second Order Systems

6. Course Information Program Objectives and Outcomes • This course will support the mission of the undergraduate/graduate Mechanical Engineering program at the University of Massachusetts Lowell by: • Helping the student to comprehend analytical methods and data analysis techniques • Making the student aware of current real world engineering problems • Encouraging cooperative learning and verbal, written, and graphical communication • Providing an understanding of the design of mechanical systems that can be applied to real world problems encountered throughout the career of the future engineer

7. Course Information Course Assessment • Make up teams of 3 or 4 students • All HW assignments and project(s) will be completed by these teams • Homework: 10% (~weekly) • Due at the start of class on assigned date • <1 day late = 25% reduction, <2 days late = 50% reduction, <3 days late = 75% reduction, <4 days late = 100% reduction • Project(s): 20% • Design, build, test, analyze a cam • Written report • 2 Exams: 40% • Closed book • One sheet of notes • Highest exam grade counts 30%; Lowest grade counts 10% • Final Exam: 30% • Comprehensive

8. Course Information Course Assessment • One missed exam without prior permission from the instructor will have the other exam average count as the grade for the missed exam with a 15 point scaled penalty. • Example: • Class average for Exam 1 is 75 • Student scores 95 on Exam 1 (20 points higher) • Student misses Exam 2 • Class average for Exam 2 is 60 • Student receives a grade of 60+20-15=65 • This grading scheme will be strictly enforced! • The approximate overall grading scheme is as follows: • A>93%, A- >90%, B+ >87%, B>83%, B- >80%, C+ >77%, C>73%, C- >70%, D+ >67%, D>63%, D- >60% • The final grade is subject to a scaled curve at the instructor's discretion

9. Course Information Other Course Information • Informed questions are always welcomed. Class discussion is encouraged! • Computer programming assignments will be made. Students are expected to have a knowledge of a programming language and access to some computing platform. MATLAB is strongly recommended! Students are required to produce all drawings using a CAD package of their choice. Additionally, the use of MathCAD, MATLAB, or other general purpose mathematical tools is encouraged for the completion of the homework and design project calculations. • Academic dishonesty will receive a grade of zero and may result in immediate failure in the course and/or dismissal from the university. Homework problems may be discussed with other students but the final product must be your own work. • The use of cell phones, laptops, or text messaging devices is not allowed in the classroom. Attendance to class is strongly encourage but not mandatory.

10. Course Information Academic Honesty • All students admitted to the University of Massachusetts Lowell have signed a statement of academic honesty committing themselves to be honest in all academic work and understanding that failure to comply with this commitment will result in disciplinary action. • This statement is a reminder to uphold your obligation as a student at the University of Massachusetts Lowell and to be honest in all work submitted and exams taken in this class and all others.

11. Course Information Accommodations for Disabilities • Students with disabilities who are requesting classroom accommodation must first register with the Dean of Students Office. • The Dean of Students Office will provide documentation to the student who must then provide this documentation to the Instructor when requesting accommodations.

12. Cam Design • A cam is designed to convert one motion into another form (rotary to linear or vice versa). • A follower is designed to follow the cam profile. • Examples of cam-follower systems: • Valves in car engine are opened by cams. • Machines used in the manufacture of many consumer goods are full of cams. • Compared to linkages: • Easier to design to give a specific output function • More difficult and expensive to make • Cam-follower systems can be classified in several ways: • Follower motion: rotating vs. translating • Type of cam: radial, cylindrical, 3D • Type of joint closure: force- or form-closed • Type of follower: curved, flat, roller

13. Cam Design Crank-rocker fourbar = rotating • For any one instantaneous position of cam and follower, we can substitute an effective linkage that will, for that instantaneous position, have the same motion as the original. • Cam-follower is a fourbar linkage with variable-length (effective) links. Slider-crank fourbar = translating External force required to keep things in contact

14. Cam-Follower Systems No external force needed; Two cam surfaces

15. Common Follower Types • Cam-follower systems are often classified by type of follower. • Roller follower: lower (rolling) friction, but more expensive (essentially ball or roller bearings with customized mounting details) • Grooved or track cams require roller followers. • Flat-faced follower: can package smaller than roller followers for some cam designs; less expensive • Flat-faced or mushroom followers are usually custom designed and manufactured. • Custom designs are warranted for high-volume applications (automobile engines)

16. Cam Design Two common types of commercial roller followers