TL;DR: Use what Klipper gave you as a starting point, set your slicer acceleration to 0 to default to whats in your config file.
More detailed answer:
Honestly it’s generally a “trial and error” process.
The accelerations all come down to the basic idea of “how fast can it change direction?”
In that context, Z drives are usually the slowest because they have to lift the gantry and deal with the most weight.
Newtons second law: Force = mass x acceleration
or, solving for acceleration.
Acceleration = Force / mass.
So the more mass for the same given force, the less acceleration. Hence why Z drives tend to have a much lower acceleration
X and Y is dependent on the printer type but they’re usually much higher acceleration since they don’t have to deal with the weight.
Extruder doesn’t really deal with ANY weight (comparatively) so you’d THINK it would be super high acceleration. But in reality if you try to change the direction too fast it can gouge out a chunk of the relatively soft filament.
Edit: I forgot to add on the extruder part.
There can be a difference in acceleration between extrusion and retraction because when you’re extruding you’re forcing molten filament through a smaller space (Nozzle diameter is usually .4mm while filament diameter is 1.75mm).
So there is going to be resistance when extruding, so you need a steady amount of force to shove the filament through the nozzle. Compared to when your extracting when you’re pulling the filament out the way it came in and there is essentially no resistance.
So extruding acceleration will be quite a bit slower than retraction. You can only extrude so fast (based on a ton of factors), but you can retract very quickly.
Physics lesson aside, Now you have a decent idea of what roughly makes sense (at least in general). What does that mean for your printer?
The usual way to go about it is, if everything is printing okay now, you can bump up the acceleration in increments until your stepper motors start skipping steps (you’ll usually hear it).
The only issue with that method is, it doesn’t really give you an idea if your steppers can SUSTAIN that acceleration across all prints.
In other words, you find an acceleration and move your gantry/bed/whatever around a lot and everything seems fine. But then you try to print something that has a lot of short, sharp, zig zag turns that really stress the acceleration and your printer might not be able to keep up.
So usually once you find an “upper limit” where your steppers start skipping, you set your max acceleration to something like 80% of that (Max Acceleration * .8)
Caveat: This is very general advice. As with anything everyone has a different opinion on how to go about it. Others might say “That’s too conservative! You can run at 95% of your acceleration and be fine!” and another person will say “80%??? You’ll tear up your printer. You should run it at 60% of max”
Some people will say start high and then move your acceleration down until it stops skipping steps.
You can ask 10 different people what the acceleration settings are for your printer and get 12 different answers.
Hence why it’s really a “Trial and error” process based on YOUR printer. There is no “right” answer.
Biggest picture: Is your printer printing? Do the prints look good? Are you happy with it? When you get to that point, Don’t fix what isn’t broken, or more aptly, don’t break what works right.
