[CEStanley]

Hi,

I am almost done with CNC-ing a Grizzly G8689 Mini Mill. I have X, Y and Z Steppers running, I added a belt drive and replaced the bearings on top and bottom of the spindle. I removed the internal plastic gears that I could.
I am making Limit and Home mounting brackets, When I cut aluminum, the spindle gets HOT. So hot that it is hard to touch. Is this a result of adding a belt drive or do I have some other issue going on?

[mactec54]

Hi,

I am almost done with CNC-ing a Grizzly G8689 Mini Mill. I have X, Y and Z Steppers running, I added a belt drive and replaced the bearings on top and bottom of the spindle. I removed the internal plastic gears that I could.
I am making Limit and Home mounting brackets, When I cut aluminum, the spindle gets HOT. So hot that it is hard to touch. Is this a result of adding a belt drive or do I have some other issue going on?

Sounds like to much preload on the bearings, being to hot will damage the bearings

[CEStanley]

Thanks Mactec54,

I looked up Bearing preload and it does seem like that is the reason for the heat.

[109jb]

Did you perform a break-in of the new bearings?

[Pariel]

Get yourself a handheld, IR temperature probe and measure the actual temperature. You will want to verify the bearing temperatures directly if possible. If not, you can probably assume that there's a minimum of 10°F difference increase from the outside of the spindle to the bearing seats. It may be much higher than that.

Are you still running tapered roller bearings? Or have you installed angular contact bearings?

Have you increased the RPM you're running at?

How did you set the preload when you reassembled the spindle?

The question about spindle break-in is a good one as well.

[CEStanley]

Hi Mactec54, 109jb and Pariel,

I fixed my problem with the bearings. I purchased a spindle and bearings from LMS and those were not good parts for my Grizzly Mill. I ordered and installed bearings and spindle from Grizzly and things are running smooth. When I turn the Spindle Speed up to 4100, the bearings get a little warm but not HOT. If I get a chance, I'll install roller bearings but I'm afraid they will have run-out.

[albator131]

I got the same problem, my spindle becoming very hot in a few minutes and without any load.
I found that the number of pole was set to 4 in my VDF while there is only 2 poles for this spindle.
I should have notice that when the motor speed indicated by the controller was 2 times lower than reality...