Re: [Emc-users] Pivot mill
Yea, being on the other side of the planet from McMaster Carr has got to suck... As for using feedscrews to drive the arms that adds another part to the position calculation as the amount of rotation changes with the angles as well as the amount of force required to do said work. Keep us posted John On 5 Dec 2007 at 9:15, [EMAIL PROTECTED] wrote: Thanks for all the informative replies. I'll pursue the references. Sounds like it's doable, but the time/effort spent on software development will exceed the material savings. Unless of course, a few thousand were to be made. I would not use gears to drive the arms, but feedscrews, forming a triangle, much like a mechanical shovel. I did not draw that all in as it was getting real late. Again, my target is an entry level CNC mill, for milling of plastics, PCB, foam... And it's a pity I'm on the other side of the planet(South Africa), because I'd be happy to supply a prototype to someone who's keen on working on the software, which is not my forte' Thanks for the prices John. I'll look into it. Freight is always a killer. Regards Roland - SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Pivot mill
Hi All Thanks for all the informative replies. I'll pursue the references. Sounds like it's doable, but the time/effort spent on software development will exceed the material savings. Unless of course, a few thousand were to be made. I would not use gears to drive the arms, but feedscrews, forming a triangle, much like a mechanical shovel. I did not draw that all in as it was getting real late. Again, my target is an entry level CNC mill, for milling of plastics, PCB, foam... And it's a pity I'm on the other side of the planet(South Africa), because I'd be happy to supply a prototype to someone who's keen on working on the software, which is not my forte' Thanks for the prices John. I'll look into it. Freight is always a killer. Regards Roland On 05/12/2007, John Thornton [EMAIL PROTECTED] wrote: On 4 Dec 2007 at 16:51, [EMAIL PROTECTED] wrote: This is a very interesting and quite challenging project... The cost to drive each joint of the pivot mill would far exceed the cost of Dremil size slides. While the concept is sound the mechanics of the gears would be the killer. You are designing a robot. The gears would need to be planetary perhaps double reduction to get enough torque to drive the arms. Of course you can't buy them off the shelf they would have to be custom made or purchased from an OEM . I would make the first joint also be the Z axis drop the links to the Z that way your tool position is constant as the Z axis moves. If you do pursue this path please keep us posted as to your progress it is very interesting... and a challenging project... I would look at the options like using 80/20 with their slides and acme threaded rods and nuts if your not needing super tight precision. I'm building a plasma cutter with that as we speed and it is super simple to work with. For a load capacity of 315 lbs each from McMaster Carr you can get slides for $34 each and the rail is $0.09/mm and come in 500mm and 1000mm lengths So for $226 you would have 4 slides and 2 rails with about 16 of travel... Part# 9867K1 and 9867K11 for the rail if you want to look it up. 3/8 acme precision threaded rods are only $28 for 36 and the nuts $22 Part# 95072A124 and 99030A326 So for less than $600 you could have the the mechanics for a 16 x 16 table... And then there is always FleaBay that sometimes has bargains for rails and such... http://cgi.ebay.com/Wafer-Handler-Automation-Robot-21-arm-10- range_W0QQitemZ180186126744QQihZ008QQcategoryZ45044QQssPageNameZ WDVWQQrdZ1QQcmdZViewItem John I believe that the greatest hurdle in constructing a small CNC machine is the cost of the linear slides, - SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users - SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Pivot mill
On Wednesday 05 December 2007, Anders Wallin wrote: John Thornton wrote: Yea, being on the other side of the planet from McMaster Carr has got to suck... It gets worse. McMaster Carr will currently not sell anything to non-US customers. I tried ordering something a while ago and back came a 5-line answer about increasingly complex export rules etc. etc. With the cheap dollar I'd think US companies would export like crazy right now And that, to quote a friend, Joanne Dow, Sucks dead toads through soda straws. Is there not some Finnish importer who can supply this stuff? Or some Euro based company making equ's? -- Cheers, Gene There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order. -Ed Howdershelt (Author) 1 1 was a race-horse, 2 2 was 1 2. When 1 1 1 1 race, 2 2 1 1 2. - SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Pivot mill
I like the idea of rotary joints to eliminate linear bearings. But you are now forced into a complicated drive mechanisim at each rotary joint. It's hard to beat lead screws for simplicity.- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Pivot mill
On Wed, 5 Dec 2007, Roland Jollivet wrote: I would not use gears to drive the arms, but feedscrews, forming a triangle, much like a mechanical shovel. I did not draw that all in as it was getting real late. once you start making triangles out of feedscrews, the madness sets in... http://en.wikipedia.org/wiki/Stewart_platform - SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
