> Steppers are cheap and ridiculously easy to interface and get good positional control out of.
This is exactly why 99% of beginners should start with stepper motors.
Building a CNC is an exercise in tradeoffs. It's tempting to want to choose the best option at every juncture, but that's a recipe for blowing your budget. I strongly recommend that beginners start with sufficiently-large stepper motors to get things done, then consider more expensive motors as a later upgrade.
> As long as they don't skip steps. And they always do. So you end up running at 1/10th of the speed your tool could move at to avoid that
They definitely don't always skip steps. I've never skipped steps on my hobby CNC during normal operation. Only crashing the machine causes skipped steps, at which point I have bigger problems to worry about.
It's very easy to measure the maximum force your stepper-based CNC can apply before skipping steps. You can use a common kitchen scale and manually force the CNC axis to compress the scale until it skips.
In my case, the maximum stepper force is about an order of magnitude higher than the calculated cutting forces in aluminum. If someone was trying to push the cutter so hard that it was overwhelming common NEMA 23 steppers, they're going to need an extremely rigid machine. Most hobby-level machines aren't rigid enough to use high cutting forces, and unless you have a 2.2KW water-cooled spindle, you won't have enough power to cut at those speeds anyway.
As long as your steppers are sized appropriately, it's really not a big deal.
> So you end up running at 1/10th of the speed your tool could move at to avoid that
Again, not really an issue in practice. Use sufficiently-sized stepper motors and the movement speed is just fine.
I strongly suggest that anyone building a CNC focus first and foremost on keeping it simple and cheap. Get it built, learn from the process, and improve on your next iteration. Closed-loop stepper motors are a reasonable upgrade path, but the idea that you're going to be skipping steps with regular steppers just isn't true.
EDIT: Here's a video of a common Shapeoko with significant added weight moving at 1000ipm on the tiny stock steppers without issues: https://www.instagram.com/p/B1wSmXfnm6C/ The stock settings are 200ipm, which leaves ample safety margin for normal operation. 200ipm is plenty fast for rapids unless you're trying to reduce cycle times on large-scale manufacturing, in which case you wouldn't be using a hobby CNC machine.
This is exactly why 99% of beginners should start with stepper motors.
Building a CNC is an exercise in tradeoffs. It's tempting to want to choose the best option at every juncture, but that's a recipe for blowing your budget. I strongly recommend that beginners start with sufficiently-large stepper motors to get things done, then consider more expensive motors as a later upgrade.
> As long as they don't skip steps. And they always do. So you end up running at 1/10th of the speed your tool could move at to avoid that
They definitely don't always skip steps. I've never skipped steps on my hobby CNC during normal operation. Only crashing the machine causes skipped steps, at which point I have bigger problems to worry about.
It's very easy to measure the maximum force your stepper-based CNC can apply before skipping steps. You can use a common kitchen scale and manually force the CNC axis to compress the scale until it skips.
In my case, the maximum stepper force is about an order of magnitude higher than the calculated cutting forces in aluminum. If someone was trying to push the cutter so hard that it was overwhelming common NEMA 23 steppers, they're going to need an extremely rigid machine. Most hobby-level machines aren't rigid enough to use high cutting forces, and unless you have a 2.2KW water-cooled spindle, you won't have enough power to cut at those speeds anyway.
As long as your steppers are sized appropriately, it's really not a big deal.
> So you end up running at 1/10th of the speed your tool could move at to avoid that
Again, not really an issue in practice. Use sufficiently-sized stepper motors and the movement speed is just fine.
I strongly suggest that anyone building a CNC focus first and foremost on keeping it simple and cheap. Get it built, learn from the process, and improve on your next iteration. Closed-loop stepper motors are a reasonable upgrade path, but the idea that you're going to be skipping steps with regular steppers just isn't true.
EDIT: Here's a video of a common Shapeoko with significant added weight moving at 1000ipm on the tiny stock steppers without issues: https://www.instagram.com/p/B1wSmXfnm6C/ The stock settings are 200ipm, which leaves ample safety margin for normal operation. 200ipm is plenty fast for rapids unless you're trying to reduce cycle times on large-scale manufacturing, in which case you wouldn't be using a hobby CNC machine.