MIT2_72s09_lec06

MIT2_72s09_lec06 - MIT OpenCourseWare http:/ocw.mit.edu...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
MIT OpenCourseWare http://ocw.mit.edu 2.72 Elements of Mechanical Design Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2.72 Elements of Mechanical Design Lecture 06: Constraints
Background image of page 2
Schedule and reading assignment Quiz ± Quiz – HTMs Topics ± Principles of exact constraint ± Bearing layout exercises ± Spindle shaft constraint/bearing layout Reading assignment ± Chapter 11 in Shigley and Mischke Read sections 11.1 – 11.6, 11.9 Skim sections 11.7 – 11.8, 11.10 – 11.12 ± This is 40ish pages, but most of it is pictures/graphs/examples © Martin Culpepper, All rights reserved 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Principles of exact constraint
Background image of page 4
Under, exact and over constraint Constraints are fundamental to mechanical design ± A mechanical designers goal is to control, i.e. to constrain, parts so that they are where they are supposed to be. Exact constraint: ± There should be one constraint for each degree-of-freedom that is constrained. Under constraint ± Too few constraints, part is not held in all the directions it needs to be Over constraint ± Too many constraints, some constraints may fight each other when trying to do the same job. © Martin Culpepper, All rights reserved 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Mechanical constraints We want to learn how to model and design each We first need to know: ± How they should be used ± What their functional requirements are How they should be used and their FRs depend upon: ± How they are laid out ± Dos and don’ts Learn to lay them out right ± Use this to obtain their Functional Requirements ± Then do the detailed design of each © Martin Culpepper, All rights reserved 5
Background image of page 6
Constraints and Degrees-of-freedom Rigid components have 6 degrees-of-freedom We will represent an ideal constraint as a line 6 – C = R C = # of Non-Redundant Constraints R = # of Independent Degrees of Freedom Example: 6 - 2 constraints = 4 DoFs R z Courtesy John Hopkins, MIT © Martin Culpepper, All rights reserved 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Constraints, compliance and motion Exact constraint: Achieve desired motion ± By applying minimum number of constraints
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 36

MIT2_72s09_lec06 - MIT OpenCourseWare http:/ocw.mit.edu...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online