stevem and @fean - this is helpful... I am not entirely convinced of the 30-40% price differential between stepper-based CNC machines and servo-based machines. AND I'm reading that servos require some calibration from time to time - that is something I haven't even read about how to do. I am concerned that I would be buying into a much more expensive system, and getting myself in more trouble than I want to deal with. Also, one article I read quoted a quite low service life on servos. That surprised me, and I don't know if it's really true. Since by far most users of CNCs on my level (not in it for just the money) go for stepper machines, that is likely where the most support would be, and they would be easier/cheaper to maintain. And I'd only have to sell ONE kidney to get a stepper-based machine...
I think you'd be better looking at it from a different perspective. For servos think professional, they actually do regular maintenance and care about accuracy and repeatability over time so yes they check calibration. While for steppers think hobby and "um, the dimensions are close enough" and "oh, I never checked" are common phrases. If you want to hold the same levels over time you should do lots of maintenance and do backlash/tramming checks/adjustments too.
I'm a robotics engineer and I'm not familiar with the need to calibrate servos. I think maybe this is being confused with some finite overall calibration of the equipment as a whole? A servo is not all that functionally different from a stepper - it just has more complex control system with the ability to detect and make up for finite accuracy errors. The rotational distance a servo travels with one pulse is always the same - there's no way to calibrate it that I'm aware of.
Another newbie question - on the Elite models (or Pro+), do you have to set the spindle speed manually, or can you program that into VCarve Pro? That is, tell the software that if you're using a 1/2" end mill, the spindle speed is 18k? It would be great if the spindle speed was controlled by the software - or is it a goofy question?
The spindle speed is set at the machine while you're making the cut. That way you have the ability to make adjustments on the fly. You can adjust the feed rate on the pendant. When you create a project, you can set your feed rate at whatever you want and then make an adjustment whenever you feel you need to.
vintage and stevem - I had been looking at another cnc, which had you input feed rates and spindle speed in the job. The tools could be saved with that info, and adjusted by the job for type of wood and so on as you set up the job, I was assuming that this was the way to go - and it may be. But it’s just another step in the setup of the job... probably not that huge a deal - unless you had an ATC - the. You would want it all preprogrammed by job.
I can see why you'd want that programmed in if you were running a large production run on identical sheets of (consistent quality) stock, but if it's "one or the other", I'll take the pendant based speed & feed any day over having to go back in the file, adjust the speed and/or feed, reload the file, resume the job...rinse & repeat until you get it right, then doing it all again after a bit change. It's a whole different kettle of fish when you're running a file interactively from a computer with a screen that's displaying what's going on in real time, but even the UCCNC approach has these variables adjustable on-screen at run time.
johnb In some systems, I believe you can save the bit profile with speed and feed rate settings. One less thing to think about - BUT, I agree that the interactivity is important and maybe for a non-ATC CNC, that would be preferable. I am sure there would be different settings for different woods or materials. Still trying to get my head around this stuff.
Setting up the feed and speed at the computer is the correct place since you have all the software tools and reference information. Having to manually set the spindle speed is error-prone as it's just another thing to do and check when the G-code already has the information and if you're using Desktop Pro or Aspire you can generate a Job Sheet to help you but the less cognitive load and things an operator has to do the less likely for error. I always use a job sheet to check myself and it has saved me from making mistakes a reasonable amount of time. You're busy thinking about what stock, in what order, the bits, clamping, dust collection... etc.