Dave, Right...large diameter rotors, pulleys, etc tend to have higher moments of inertia. Many (not all) low inertia servos are long and skinny as a result of this.
If we are optimising for COST we don't go for the very lowest motor inertia though. We approximately match reflected motor inertia and the load inertia. Motioneering takes care of all that. You can google inertia matching if you want more info. By the way I should mention that the numbers I used will give a VERY high performance machine. It can ramp from a dead stop to 240 ipm in 42 milliseconds. It can traverse a corner at full speed with a 0.16 in radius. If you're gonna make one why not make it good? I should also mention that this is for a low friction plasma with essentially no cutting forces. For a different machine like a mill or router the results would be completely different. Leslie M.Watts L M Watts Furniture Tiger Georgia (706) 212-0242 Main page: http://www.lmwatts.com Engineering: http://www.lmwatts.com/shop.html Cnc surplus for sale: http://www.lmwatts.com/forsale.html Carved signs: http://www.lmwatts.com/signwp.html But, it seems one of your earlier posts mentioned flat and large diameter motors are bad and long skinny ones are good. That makes sense as the flywheel effect from the large motor would get in the way of quick response. Ditto cast iron timing pullies vs. plastic ones. I do have the idea that a DC motor is rated on a somewhat linear curve. and that generally speaking, a 100 volt, 10hp 4,000 RPM motor is also a 50volt, 5hp 2,000 RPM or 25 volt, 2.5hp 1,000 RPM motor. so, generally speaking, I can make a prototype axis a few feet long and test the motors I have with different gear ratios to see the acceleration. Dave Dave Addresses: FAQ: http://www.ktmarketing.com/faq.html FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/ Post Messages: [EMAIL PROTECTED] Subscribe: [EMAIL PROTECTED] Unsubscribe: [EMAIL PROTECTED] List owner: [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED] Moderator: [EMAIL PROTECTED] [EMAIL PROTECTED] [EMAIL PROTECTED] [Moderators] URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO OFF Topic POSTS: General Machining If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble. http://www.metalworking.com/news_servers.html http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list. NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........ bill List Mom List Owner Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
