King Midas mill conversion

[Swarfing]

A good tip here is to also if you are going to use the machine manually is to be able to disconnect the motors from any circuit. Otherwise they will act as little generators sending a nice bit of current back to your circuit boards :whistling:

[Robin Hewitt]

they will act as little generators sending a nice bit of current back to your circuit boards :whistling:

Have you actually had a problem with that?

If you short out a stepper coil you get a definite resistance when you try to turn it.

I don't feel any resistance or cogging when I turn a motor with the driver OFF or FREE so I don't think there is any electrical path for it to push against.

OTOH I could be delusional, it happens at my age.

[Swarfing]

Ezecnc Roger had this issue when he converted his viceroy, he did not suffer any damage luckily but did have a huge issue with resistance. Made it hard work to mill by hand. He was using large steppers but goes to show that the issue is there no matter what size steppers you use. It would be worth whipping out the DTM to check on any back current flow?

[Jonathan]

The back-emf from stepper motors is significant - they're good little generators. The protection diodes in the stepper drivers will rectify the back-emf and if you turn it fast enough power up the driver which is clearly bad news. I found that below a certain speed they manually turn quite easily, but when that threshold is exceeded it gets a lot harder. Clearly it will vary significantly with the size of motor.

Easily solved - just unplug the motors.