Steppers sometimes lose steps

[RsX]

I tought it would never happen to me, but it did, the steppers lost some steps during a rapid movement on X and Y even with a generous power supply. Fortunately nothing broke.
I think this is because I power the drivers with a single switching power supply and no capacitor.

My setup is:
3x DM542T
3x Nema 23 1.9Nm 2.8A
1x Switching PSU 48V 600W 12.5A

I'd like to add a capacitor to help the PSU with current surges and absorb the spikes from the deceleration of the steppers.
What would be a good value for it? 63V 20.000uF? 80V 40.000uF?

[sebba]

you should pay attention also for the acceleration values. could be too big. try with lower values and see what happen

[RsX]

I found a 63V 22mF capacitor and tested the motors with and without it.
Also connected an oscilloscope to the 48V and found that the voltage is really stable and the capacitor doesn't make a significant difference.
The easy explanation is: It's cold.
I setup the acceleration in summer and everything was ok. Now that the temperature dropped, the grease is more viscous and the motors run on the very edge of failure. So I lowered the acceleration as suggested by sebba (from 1500 to 1000mm/s^2) and everything seems to run fine.

[cncdrive]

Capacitor with 1000uF per motor Amper (or greater) should work fine.
And at least +20% rated Voltage of the capacitor is nessessary.
For 48V powersupply use 63Volts capacitors.
You can also parallel smaller capacitors if required.
And you can place one diode (it can be a diode of a power bridge rectifier) from the output of the PSU pointing forward to the capacitor + terminal.
This is called a "one-way rectification" and is great to block the back-emf voltage coming from the motors when they rapidly deccelerating, so the diode can protect the powersupply from overvoltages and damage as the diode blocks the overvoltage.
Like on the attached image.

[Battwell]

Capacitor with 1000uF per motor Amper (or greater) should work fine.
And at least +20% rated Voltage of the capacitor is nessessary.
For 48V powersupply use 63Volts capacitors.
You can also parallel smaller capacitors if required.
And you can place one diode (it can be a diode of a power bridge rectifier) from the output of the PSU pointing forward to the capacitor + terminal.
This is called a "one-way rectification" and is great to block the back-emf voltage coming from the motors when they rapidly deccelerating, so the diode can protect the powersupply from overvoltages and damage as the diode blocks the overvoltage.
Like on the attached image.

i wouldnt trust any stepper above 1000 /s acceleration. unless there was very low inertia in the system

[RsX]

Thank you all, you've given me a lot of good information
I'll definitely try the One-way rectification in case I have further issues.
For now the 22mF (22.000uF) capacitor should be more than enough.