KL-300 spindle bearing heat

[skrubol]

I just installed my replacement KL-300 spindle after the front bearings on the original burned out.
To try and make sure I do everything I can to not have a repeat, I'm trying to break in the bearings (can't really hurt.) I've been increasing the speed in 10% increments (6000 RPM at a time,) with at least 10 minutes per step at the lower speeds (up to 24k I think,) and 20 minutes on 30 and 36k.
Thing is, at 36k, the front of the spindle is getting quite a bit hotter than the rest of the spindle. My VFD is also reading around 50 watts with absolutely no load on the spindle.
Is this normal?

[skrubol]

Beefed up my cooling circuit a bit and continued breaking the spindle in last night. At 54,000, with the water being luke warm, the front of the spindle was again very hot, and the VFD read 60-80w. I briefely ran it up to 60k, and the VFD read 110w. Over a third of the rated power of the spindle just going into the bearings. I'll probably stick to 48k and under on this thing, as it really doesn't seem to be able to handle its rated speed.

[D3Spindles]

Originally Posted by skrubol I just installed my replacement KL-300 spindle after the front bearings on the original burned out. To try and make sure I do everything I can to not have a repeat, I'm trying to break in the bearings (can't really hurt.) I've been increasing the speed in 10% increments (6000 RPM at a time,) with at least 10 minutes per step at the lower speeds (up to 24k I think,) and 20 minutes on 30 and 36k. Thing is, at 36k, the front of the spindle is getting quite a bit hotter than the rest of the spindle. My VFD is also reading around 50 watts with absolutely no load on the spindle. Is this normal?

When performing a break-in-procedure on a spindle... it is very common to have it run hot. If after the break-in and the spindle still runs hot, I would either run at lower speeds or check the bearing preload.

[cristobalmunoz]

I would like to upgrade my PCB drilling machine by using KL-300 Spindle to take advantage of its high speed (60.000rpm), but I am concerned that those RPM are "maximum NO load speed" instead of working speed. I would like to hear about other experiences with KL-300.
I think heat is not that good, neither for drilling, nor for bearings.

Cristobal

[skrubol]

Well my experience with two of the units is that 60krpm is the max intermittent speed. I've run mine at 48k for several hours without any apparent ill effect, but I wouldn't recommend running past 50 for any amount of time.

Note that I don't know what the actual speed the spindle was running at. Induction motors have torque slip, which means they run at lower RPM's than set by their frequency, the more torque, the lower the RPM. Given how much heat the bearings were putting off at 60k set (1000 Hz,) I'd guess the thing was actually closer to 50k. When I set it to 48k (800 Hz,) probably in the low 40's.
Given Automation Tech's lack of response on this, I'd keep away from these. Go with a Dremel or something cheap. (Or go with a 'real' high-speed spindle at $1000+. Might be able to find a deal on a Westwind on Ebay.)