John You might look at acme 12 foot long screws. One piece would handle the x and y. I assume plasma cutting is only plus or minus about .020 and brass nuts are easily available to make halfnuts. I don't think you need ball screws and they don't get along well with the metal spray and dust. Brass half nuts can be tweaked periodically for back lash of about .005 to .007. Or you can spring load them to minimize this.
If you attach to the halfnuts with a hook type bracket the screws can be protected from the splatter with U channel. Your prime concern is protecting what ever drive system you end up with from splatter. Also, this would allow the x axis motor to be attached to one end of the frame. Less dangling control wires that way. Just use a bigger motor on the x axis. There is a lot of stored mass in an 8 foot long screw when you add that to the weight of the rest of the moving part of the gantry. This is just my opinion. I have not built one any near this big. There are a lot of guys in the different cnc groups that have built this big stuff. I suggest you just look at the pictures in each cnc group on Yahoo. Most guys will be happy to return an email with their experiences. John Ocala Florida ----- Original Message ----- From: "John" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Sunday, November 07, 2004 7:05 AM Subject: [CAD_CAM_EDM_DRO] Gantry Drive Topology > > > Hi! > > I am thinking of making a gantry for plasma cutting. I will > probably use something like Bosch Rexroth modular aluminium frame > for the travelling sections. > > I understand the difference between steppers and servos, and will > most likely be using servos to achieve a more dynamic movement on > thinner materials. However, I would like to ask for your advice on > choosing a motion system however. > > The table will be designed to take standard sheet metal sizes, > which means that a travel of approximately 1.5m by 2.5m is required. > > With the gantry being made from inherently light materials and only > spanning 1.5m, it shouldn't weigh very much at all. > > As I see it, I have a few options available. Lead screws, timing > belts or rack and pinion. > > I imagine lead screws are the first to go, but what would you > recommend I look at for the drive topology? > > Best wishes, > John > > > > > > 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/
