That looks like a nice build. I hope one day to have the final design of my table looking as nice.
I have a few bits of advice based on my own build and 3D printer experience.
Get rid of steel core belts. The steel core wires inside the belts will break from over flexure when wrapped around 608 bearings- they are too small. You won’t be able to see the breaks, but the belt tension will drop as the polyurethane stretches over the broken wires. You’ll tighten it up and it will be loose again the next day and you’ll think you’re losing your mind. Steel core belts require a lot of force to bend around small pulleys. Your motors will thank you for switching to glass core belts.
Noise: I have spent considerable time and effort trying to quiet my table down- I run it at 500 mm/sec. I have found that if you’re using steppers, they run quietest at high microstepping ratios (I use a Duet board with TMC drivers at 256:1 ustepping) and low rotation speeds. I have the table running pretty quietly by using loop belts and pulleys to step the motor speed up by 4x (use 80 tooth pulleys on the motors and 20 tooth pulleys to run the drive shafts). On my table that lets the mechanism run at 500 mm/sec when the motors are only turning at 1.5 revs per sec. When you step motor speed up, you step the torque down, so I use NEMA-23 motors to drive the table.
This may not be an issue at low speeds, but at anything over 200 mm/sec, the belt teeth will make a zipping noise as they hit the smooth pulleys. I put twists in the belts to ensure that the only pulleys that the belt teeth contact are the drive pulleys. The smooth back sides of the belts contact all other pulleys. I’m finding that even just hitting the drive pulleys makes a zipping noise.
I am now experimenting with iHSV42-40-07-24 servomotors that don’t cog like steppers so they tend to run smoother and quieter. The torque spec on the 75W motors I am using is low (0.186 Nm), but it’s constant all the way up to 3000 rpm. I was a little skeptical that 0.186 Nm would be sufficient to drive the mechanism, but it turned out to be plenty. Here’s a test video of the mechanism set to run with acceleration at an insanely high 10,000 mm/sec^2 and speed set to a ridiculous 2000 mm/sec. It actually hits the 2000 mm/sec speed on some of the longer runs.
It can never run like that when drawing in sand, but I’m looking at other uses such as attaching an air brush to spray paint on paper or a wall. At the “normal” 500 mm/sec I usually run the sand table, the servo motors seem quieter than the steppers. My testing isn’t done yet, but at this point I’m certain that the servomotors will not limit the performance of the table for drawing in sand.
My table uses a corexy mechanism that has 8 pulleys. I’m finding that the pulleys make a clattering noise as they spin, so I’m considering changing the mechanism to something simpler that won’t use as many pulleys and hopefully reduce or eliminate that noise. I’m also going to add some sort of vibration dampers to the motor mounts to keep motor vibrations from being transferred to and amplified by the machine’s frame.