[rhysun]

I am in the process of upgrading my CNC router from my faithful old hand-built threaded rod and skateboard bearing jobbie to a CNC'd dream machine with proper leadscrews. I've reused the steppers and the driver board because I was convinced that they had plenty more to give (based on gut feeling rather than maths). The driver is one of those blue TB6560 based boards which I know is hated round these parts but it has never given me any grief in 8 years of service - not even a single missed step!

I have now assembled my new machine and I am currently testing (sans spindle for the time being). I've managed to get it to run quite sweetly at 1800mm/min but it sometimes stalls - which is an alarming thing for someone who've never experienced a stalling stepper before. I've also detected some missed steps.

It is currently running on 24V but I do have a spare 36V supply sitting on a shelf in my garage and I am tempted to give it a go. There are a couple of reasons why I am a bit hesitant about this. Firstly, even though the silk screen print on the board seem to allow a range between 12V and 36V, the TB6560 datasheet has 34V as a maximum value. Secondly, the board has a 12V and a 5V linear regulator built in to power the fan and the logic. I am worried that 36V might be too much for these. I do not have any pocket money left to buy proper equipment so a blown board would mean many months of no CNCing for me.

Anyway, my question is - souldi or shouldn'ti?

[john-100]

I would not increase the motor supply voltage to 36V

from the TB6560 data sheet
Attachment 337758

the data sheet shows the maximum operating voltage as 34V DC

I'd probably go for 30V to maintain a margin for error -
the voltage can increase when an axis is decelerating and dumps power back into the supply

the sales people very often use the absolute maximum ratings that look better on paper even though the devices will fail very quickly !

John

PS

if the 12V regulator is a LM7812 the maximum input voltage is 35V !

[rhysun]

Thanks John.

I can adjust the power supply voltage down to 32V and a bit - which is probably too close to the max for comfort. But I'll probably just go slow for now and save up for some proper drivers in future. The machine seems happy with 1200mm/min, which isn't spectacular but better than my old machine and good enough for my immediate need.

[CitizenOfDreams]

I personally would not raise the voltage above 24V. "Absolute maximum" means just that, the voltage that must never be exceeded - not the recommended operating voltage. 24V gives you a good safety margin; 30V and above, as you said, is too close for comfort. So yes, detuning the motors is the best thing you can do to avoid missed steps.