Hello
I'm new to this forum and pretty new to CNC also actully.
I have a Sajo NC45 milling machine. It's a Swedish 70's NC machine that weighs about 5000 lbs I would guess. I'm going to take all the old DC servos of it and putting AC servos on it. Actually 2 of the 4 are already gone. But for know I'm only going to replace the x, y and z servos leaving the knee non-motorized.
I have measured what torque makes the different axis move. When I apply about 2-2.5 Nm I get a good acceleration on the table, but the spindle is a bit harder to move. I have taken it apart to lube it up, but I still think it needs a bit more torque to work properly.
The measuring were done with the machine all turned off and not during operation. The servos on it is marked 6.7 Nm cont and 21 Nm stall, so they are fairly big.
So no for the questions. How big servos should I choose based on this information? Anyone have a recommendation what to look for? I have been searching Ebay but not all have the specs. We have 240 volts 1ph and 400 3ph over here in Sweden so I guess I need to ger 240 v servos. Or do I? How thoes that work? I have seen servos with all kinds of operational voltages. Do they need to be run with a transformer or does the controllers somehow change the voltage? I have found servos with a great spec but the operational voltage on them is 200vac. Can I make that work?
Next step would be the controllers of course. If you have a good recommendation there please let me know. I have been looking at the Allen Bradley ultra 3000 series, since they seem to be quite easy to find and are able to run 240v.
Sorry for all the newbie questions, but I need to know to make this thing work for me.
Thanks,
Magnus