CNC Mill - demise of another Rotary Tool

Tool Ready for Salvage

Frozen Bearing

In my last post I left off stating that my stepper motors were heating up, squealing and missing steps (what I found was that all this was happening during "Seeking:" movements - fast movements above the surface of the board).

All of this began after I swapped out a few of my stepper motors with ones I purchased for building a 3D Printer (I'll be documenting that build soon).  The newer steppers are also NEMA 17 but are a bit longer - my rational for swapping out the motors was that the new ones should be stronger and better able to handle the weight of the heavier spindle (compared to the weights that a 3D Printer has to deal with - much less).

I approached the issue systematically, looking at possible causes for motor heating, squealing and missed steps:

• initially thought it must be driver failure
  

  • testing the the drivers on other motors as well as swapping drivers between steppers in current setup - all drivers seemed fine.
• poor connections
  

  • between driver board and arduino - couldn't find any
  • between driver board and motor - nothing
  • between drivers and motor power supply - nothing
• amperage to high
  • adjusting the current limiting on driver boards
    • this did decrease noise
    • also decreased stepper motor heat
    • Did Not – prevent steppers from freezing up during movements or missing steps
• step pulse (GRBL firmware settings)
  

  • I put off testing this until I could look closer at the datasheets for the driver
• default speeds (GRBL firmware settings)
  • decreasing seek speed seems to have fixed issue
    • decreased to 300 than increased up to 400 and no problems
  • lower current limit seems to be keeping motors (and driver boards) cool
    • 1/8^th to ¼ turn clockwise for all motors
  • Other possible answers
    • could be max acceleration instead of max speed