Overheated our spindle motor on a Mori Seiki last week and now I'm paranoid

We were running a tough 17-4 stainless job and pushed the feed rate too hard without coolant through the spindle. The thermal alarm kicked in after 45 minutes and we had to let it cool for two hours. Has anyone else dealt with heat damage on older machines and is there a way to check if the bearings are still good?

2 comments

2 Comments

west.alice1mo ago

Ran a tough 17-4 job without coolant through the spindle? That's absolutely wild, you're lucky the thermal alarm even caught it before you cooked the whole assembly. I've seen shops try that and end up with bearings that sounded like a blender full of gravel. For checking if they're still good, you gotta run a simple heat test at idle and listen for any grinding or uneven noise. Also, if you have a vibration analyzer, check for any spike in high frequency readings that usually means the preload is gone. Honestly, I'd be paranoid too after that, those Mori bearings aren't cheap to replace.

taylor9291mo ago

Yeah I worked at a place a few years back where some guy ran a 15-5 job dry for like 20 minutes before anyone noticed. By the time the alarm went off the spindle was hot enough to fry an egg on it. We did the idle test and listened for grinding, but the real kicker was when we pulled the encoder cover and the grease had basically turned into black syrup. Ended up having to pull the whole cartridge assembly and send it out for a rebuild. Those Mori spindles are tough but they have their limits for sure.