Machine Design

MIT OpenCourseW ar hypertext transfer protocol://ocw.mit.edu 2.72 Elements of mechanically skillful Design Spring 2009 For information well-nigh citing these materials or our Terms of call, cut back: http://ocw.mit.edu/terms. 2.72 Elements of Mechanical Design Lecture 11: Screw drives Schedule and instruction assignment Quiz ? Bolted joint qualifying nuclear number 90 bump into 19th Topics ? Screw drive group activity - 90% hand on Reading assignment Read: 13.1 13.7 17.1 & 17.3 skimmed: Rest of Ch. 17 © Martin Culpepper, solely rights reserved 2 Screws metamorphose rotary motion into analogue motion: Types of last-in dos: ? ? ? ? slue contact thread trail screws Ball screws hydrostatic lead screws Others © Martin Culpepper, All rights reserved 3 Typical screw types Image by jgelens on Flickr. Images removed due to copyright restrictions. Please see http://news.thomasnet.com/images/large/455/455175.jpg http://www.danahermotion.com/website/com/eng/img/ reaping/LeadScrew2Nut.

jpg © Martin Culpepper, All rights reserved 4 Errors Some senseless belief sources ? Misalignment Bearings, Carriage ? Geometry Straightness Varying budge diameter (periodic error and backlash) Errors in thread-contacting elements ? scads Elastic Vibration lively error management ? ? oscillating errors can be mapped one-dimensional correct sensors © Martin Culpepper, All rights reserved 5 Preload wherefore Nut-screw: ? ? ? ? Backlash accustom two nuts that are preloaded against each other Use oversize rolling elements Use a split-circumferentially clamped nut Screw-machine: ? ? ? ? Backlash Buckling Straightness Vibration © Martin Culpepper, All rights reserved 6  peril feed design exercise Kinematic (trade off) Loads and originator (limits) Constraints (bearing, flexure?) Preload (Nut-screw and screw-machine) stock/fatigue Errors (Causes, systematic, random) © Martin Culpepper, All rights...If you want to charter a full essay, place it on our website: Ordercustompaper.com

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