Machine Design

MIT OpenCourseW ar hypertext transfer protocol://ocw.mit.edu 2.72 Elements of mechanical Design escape 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 2.72 Elements of Mechanical Design Lecture 11: Screw drives Schedule and interpretation appellative Quiz ? Bolted joint qualifying atomic go 90 March 19th Topics ? Screw drive convocation activity - 90% hands on Reading assignment Read: 13.1 13.7 17.1 & 17.3 Skim: Rest of Ch. 17 © Martin Culpepper, solely rights reserved 2 Screws Convert rotary effort into linear motion: Types of lead-in screws: ? ? ? ? Sliding contact thread lead screws stumblebum screws hydrostatic lead screws Others © Martin Culpepper, exclusively rights reserved 3  veritable(prenominal) screw types Image by jgelens on Flickr. Images removed ascribable to copyright restrictions. Please see http://news.thomasnet.c om/images/large/455/455175.jpg http://www.danahermotion.com/website/com/eng/img/product/LeadScrew2Nut.

jpg © Martin Culpepper, all rights reserved 4 Errors Some erroneous belief sources ? Misalignment Bearings, baby carriage ? Geometry candor Varying pitch diameter (periodic error and backlash) Errors in thread-contacting elements ? Loads Elastic Vibration lively error heed ? ? Periodic errors can be mapped Linear correct sensors © Martin Culpepper, All rights reserved 5 Preload why Nut-screw: ? ? ? ? Backlash Use ii nuts that are preloaded against each other Use big rolling elements Use a split-circumferential ly clamped nut Screw-machine: ? ? ? ?! Backlash Buckling Straightness Vibration © Martin Culpepper, All rights reserved 6 Cross lam design exercise Kinematic (trade off) Loads and originator (limits) Constraints (bearing, flexure?) Preload (Nut-screw and screw-machine) distort/fatigue Errors (Causes, systematic, random) © Martin Culpepper, All rights...If you want to get a panoptic essay, order it on our website: OrderEssay.net

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