bearings selection help

[cnc123]

Hello
I recently had a custom spindle fabricated and am unhappy
with the selection of bearings selected for the spindle. This spindle will be used for the machining of wood and metal on a 3 axis cnc machine. The spindle speed will be from 100 to 8000 rpms. I`ve conducted tests at 1000 rpms for a period of 45 minutes and the spindle and bearings are getting very hot. It seems very unlikely that 8000 will be possible with the existing bearing. I am looking to upgrade the spindle bearings to a better class of bearing.
One company recommended a 6209 T P/5 13,200 RPM and NILOS RINGS.
The quote was too high at 243.00 per bearing set. I believe I`m looking for a lower priced product for this application. The bearing must be shielded as this is a dusty work environment. I`d appreciate your recommendations.
Here`s a link to a pic of the spindle

http://www.woodsolutions.com/shoptour.htm

Here are the specs on the current bearings
Manufacturer: EBC China
Part Number: 6209Z
ID.................: 1.772
OD................: 3.347
Height............: .746

 

[Philrock]

It may not be the fault of the bearing. It's not unusual for high speed spindle bearings to require forced cooling.

 

[laundry]

HI
THE BEARING YOU HAVE IS A 6209 THE MANUFACTURER RPM WITHGREASE IS 7500 AND WITHE IOL IS 9000 THAT IS SKF.
RHP, IS 8400 GREASED AND 11400 OILFED THESE BEARINGS ARE DEEPGROOVE BALL BEARINGS. THE ABOVE BEARING DOES NOT SEEM
TO BE THE RIGHT ONE,AS I WOULD HAVE FITTED A PRESISION
BEARING. ALSO DOES YOUR SPINDLE HAVE A BEARIND AT EACH END
IF SO YOU MAY HAVE AN ALIGNMENT PROBLEM
REGARDS LAUNDRY

 

[Tmoose]

how hot is hot ?
Was it designed and built by the same house ? They >probably< owe you an explanation.

Temps over >140F at 1000 rpm may be as simple as too much grease, but may well be some sesign/mechanical issues too. Do you have some drawings to show the construction?
Alignment, preload, grease and quantity used, and having to withstand the belt load with such close coupled construction all are speed reducing factors.

If you want to go fast you need spindle bearings with their attendant manufacturing tolerances. Heck, the fancy grease alone is going to cost nearly $100.

That belt drive is going to hurt your ears and the surface finish.

 

[icrman]

Seems like a good price to me.
With some of the highspeed ceramic bearings the price is much higher than that. Also all high speed machine tools and even the not so high speed ones use spindle chillers, to keep the temps down and hold the tolerances.