On Thu, 2009-06-11 at 13:39 +1000, Neil Macintosh wrote: ... snip > 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.
I believe the UHU driver is a step/direction driver, with its own PID loop. I prefer to use a PWM input amp, to better integrate with EMC2's PID, Halscope, etcetera. The UHU micro-controller chip outputs PWM, so theoretically, you could leave the chip out and feed PWM into the socket. It seems to me that the UHU is not being updated or enthusiastically supported. I think for the power levels you are looking at, their isn't allot for the DIYer because you can't just scale up a simple low power amp. I'm not an expert, but it seems the big amps like to burn themselves up if the design doesn't keep a tight control on how much and when. You might want to check Sam Sokolik's amp: http://www.electronicsam.com/images/KandT/servostart/schem/latestcurrentlimit/ A search on CNCzone.com might help to find threads on DIY amps. > 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. In my opinion, if you want speed, servos are what you need, and a hardware signal generator/encoder counter. > 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. I don't have any gantry router experience, but my guess is that what would work on the X and Y will depend on what you are machining and how accurate it needs to be. > 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 don't like aluminum for anything structural on a machine tool, but someone with an aluminum router may prove me wrong. I'm planning on welded steel. ... snip -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ 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
