Dave, I did do a quick run on motioneering for you concerning servo gear ratios. Here is a quick rundown of the results:
1) direct drive with 1" diam timing pulley 600 in oz torque 0.4 oz in sec^2 rotor inertia 2) 2:1 reduction drive with 1" diam timing pulley 400 in oz torque 0.4 oz in sec^2 rotor inertia 3) 3:1 reduction drive with 1" diam timing pulley 250 in oz torque 0.1 oz in sec^2 rotor inertia 4) 5:1 reduction drive with 1" diam timing pulley 280 in oz torque 0.1 oz in sec^2 rotor inertia 5) 10:1 reduction drive with 1" diam timing pulley 400 in oz torque 0.1 oz in sec^2 rotor inertia 6) 20:1 reduction drive with 1" diam timing pulley no motor found The numbers are peak torque...continuous required is about a quarter of that figure with the friction I assumed. More details are required to get really good friction numbers though. Se what's happening? At very low reduction the motor has to get pretty big, although not huge. As more reduction is used the motor torque required goes down, but only up to about 5:1 ratio. beyond that the torque requirements rise again, and by 20:1 no practical motor can supply the needed performance. Why does this happen? It's caused by the square term of reflected inertia vs gear ratio. The motor is turning faster and begins to really fight it's own inertia in an attempt to rapidly change speed. So with the numbers I used you can see that there is a sweet spot at about 3:1 to 5:1 where the peak torque required is minimum and a reasonable and typical rotor inertia gives a good impedance match. This is not anywhere near the point where the motor delivers best power or is most efficient. It is simply the point of best economy for your design. 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 -----Original Message----- From: turbulatordude [mailto:[EMAIL PROTECTED] Sent: Tuesday, December 21, 2004 2:21 AM To: [EMAIL PROTECTED] Subject: [CAD_CAM_EDM_DRO] Re: Plasma table gear reduction > The big problem with running servos slow is heat. For the same output > power if you halve the speed you double the torque required. Current is > proportional to torque so the current doubles. Now for the killer - the > heat squares! (heat = I^2 * R). To make matters worse the slower the > armature turns, the less effective the cooling is. > > Les I don't see that as a problem. An external fan would suppliment any low speed heating problem. But then knowing to solve a problem is half the battle ! 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 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/
