2009/6/11 Dave Engvall <dengv...@charter.net> > > On Jun 10, 2009, at 8:39 PM, Neil Macintosh wrote: > > > Gentleman > > I have finished my lathe and now wish to start on the 5-axis mill. > > > > I have been reading all that I can find with regards to dc brushed > > servos vs steppers, I used steppers on the lathe with DIY driver > > boards > > from Oatley Electronics. Results were very satisfactory with the only > > steps being missed when the swarf wrapped around the job. However > > with > > the 5-axis the work will be a lot bigger with much more expensive > > consequences for missed steps. I am hoping to use the DIY UHU servo > > controllers but I have a few questions for the gurus. > > > > Do I need to gear the motors down to increase the holding torque. > > Do I need servos to drive 200kg's+ of gantry and head and attain > > reasonably high feedrates +- 10m/min so that I don't spend to long > > cutting air. > > Can I use rack and pinion drive to cut down costs on the XYAC, Z would > > obviously need to be ballscew with counterbalance of some type. > > > > The machine will be mostly aluminium extrusion for the moving parts > > with > > some type of linear guide, maybe igus polymer bearings. The table > > will > > be fixed and the entire gantry assembly will be attrached to pillars > > either bolted to the floor or roof. I have run a Rambaudi H60 which > > worked in this way but that machine cost A$2 000 000, obviously right > > out of my budget. > > > > I am hoping to first build a prototype using aluminium and acetyl for > > the bearing surfaces,gears etc to test the concept with a working area > > of 1000m x 500mm x 600mm. I know that I can easily drive this with > > steppers but the final build will be an envelope of +- 3000mm x > > 1500mm > > x 1500mm. > > > > All answers would be greatly appreciated. > > > > Regards Neil Macintosh > > > > The difference between theory and practice is a lot smaller in theory > > than in practice. > >
I would advice you to not use Igus style bearings. Many have tried already, and all have failed. They are perfect for narrov rail transport of items, for example between workstations. But none as far as I know has succeeded in using them on a router (or any mill). They have a play you can't get rid of and with an assymetrical force they bind too easy. I run servo's on everything I make. Steppers are for sure enough, but I like to have power, speed and the feedback If you're on a tight budget, go for real linear guides and choose steppers. If you care less about the money, choose servo. I made some small clips on my steel router when I assembled it: http://www.primenta.se/index.php?option=com_content&view=article&id=68 Hiwin 20 mm guides Isel ballscrews 5mm/rev Yaskawa servos belt geared 3:1 (I loose a bit speed, but the force is remarkable) Rutex drivers Gantry weight about 100 kg. Regards, Sven ------------------------------------------------------------------------------ Crystal Reports - New Free Runtime and 30 Day Trial Check out the new simplified licensing option that enables unlimited royalty-free distribution of the report engine for externally facing server and web deployment. http://p.sf.net/sfu/businessobjects _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
