How much axial force a deep groove ball bearing can take?

[interflexo]

How much axial force a deep groove ball bearing say 6006ZZ (ID=30mm; OD=55mm; Cr=13.2KN; C0=8.3KN) can take at standstill? Everybody says it can take something but... 300N is it safe?

Regards

[NC Cams]

6006 Ball bearings are designed primarily to accept radial loads.

As you apply an axial load, you force the ball up the side of the raceway where the shape is not as conducive to long term survival. In psuedo bearing speak: the raceway is flatter comparatviley speaking as you go farther up the side so it is easier to brinnell (flat spot them) with an axial load.

It is reasonable to apply 1% to 2% of the static loading to a bearing to provide an axial preload. Your 300N is a bit more than that.

The 6006 with that much axial load may or may not live up to any life calculations you're doing because the sides of the raceway groove may NOT be as highly finished (super finished) as you get closer and closer to the top of the groove.

A better question is "Why do you want to put that much axial load into the bearing?"

[interflexo]

Thanks for your answer NC Cams. I didn't explain myself correctly. Those 300N would only appear when the shaft is stopped and on unexpected severe machine malfunction. On normal operation there would be no relevant axial load. I try to design my projects in a way that small accidents don't cripple relevant machine components. How about this scenario?

[NC Cams]

Paragraph 2, in post #2 above pertains no matter how you ask/rephrase the question.

A raceway is actually parabolic in shape. The sides are "flattened" out a bit and they acually get rolled over so there is not a sharp edge where raceway intersects the ring ID. The profile on the sides is not controlled as exactly or as well as the "crotch" where the ball is supposed to ride.

This is why shock applied axial load is something that you simply can't design for nor predict the performance of when it comes to deep groove ball bearings. Empirical wisdom is best served here.

Try it and see is the best I can offer in the way of guidance.

[Geof]

Originally Posted by interflexo ... Those 300N would only appear when the shaft is stopped and on unexpected severe machine malfunction. On normal operation there would be no relevant axial load. I try to design my projects in a way that small accidents don't cripple relevant machine components.....

One approach to take if you are designing the equipment and are possibly incorporating a vulnerable point is to make it easy to replace. Also, and this is sometimes more difficult, design it so a failure here does not have a cascading effect and destroy the whole thing.

You may never get the severe machine malfunction in which case all the time you have spent guarding against it is lost. Sometimes 'playing the odds' is worth it. And keep a spare bearing in stock; I still have a monster bearing used in a large collet chuck sitting on the shelf because the machine it was a back up for never failed.

[NC Cams]

Another albeit more costly option would be to use a 7006A5 or 7006C bearings. The "C" has a 15 deg contact angle whereas the A5 has a 25 deg internal angle.

If, by chance, you're essentially using the 6006 as a ball screw support/thrust bearing, these would fit the package space and provide much more stiffness as well as lower friction under thrust than a 6006. Sadly, the cost will be a bit higher.

If you can find ABEC1's in these sizes, that would be fine enough for a simple infeed device. If you are making a ball screw, these will have higher running accuracies at their more commonly supplied ABEC5 or ABEC7 accuracy levels.

SHould you find a need to preload the device for greater stiffness and/or backlash reduction, the A/C's will provide notideably less resistance even when preloaded QUITE heavily as compared to 6006's.

[interflexo]

Thanks for the input guys. The application is a 600mm diam servo indexing drum for a robot loading device. The drum rotation doesn't cause bearing axial load. The drum shaft (30mm diam) is held by a double bearing T-shape Misumi holder + T-shape single bearing holder. The part snap in/out involves a 50N axial force to overcome a spring loaded ball that fits parts in place. The gripper axial movement that handles the parts on the drum is also servo driven (Bosch Rexroth KF75R linear guide + Siemens 1FK7042 servo). The severe malfunction I was telling you about would be a human error during commissioning where the gripper would press the part against the drum with full servo peak force + inertia. The drum plus full load will weight less than 100kg. As far as radial stress is concerned the system is well over designed. I’ test the 6006 ones for now and I’ll have a couple of spares nearby.