Home made spindle lubrication

[RainbowsParticipant @rainbows]

So after that thread a while ago about aliexpress spindles it seemed they wouldn't work and that I could probably do better myself for the same money.

Here is my initial sketch model of the spindle. The hiccup of today is trying to keep the spindle lubricated, seems much simpler for horizontal spindles than vertical ones. Spinning in the region of 10,000 RPM I need to have oil lubrication of some sort.

My current plan is to have the oil injected through a port at the top above the 16009 bearings and have it rain through the bearing and down to the EX35 bearings then collect at the bottom in the "drain" flange. Not shown would be a sideways pipe to suck the oil back to a tank.

Would this lay out work adequately?

Somewhere on the SKF website that I have now lost I worked out I needed about 1 liter per minute or a bit below that. Aside from knowing if the general premise looks ok I also can't find a pump for that flow. Peristaltic pumps are undersized and the rest are over sized and I dont know how well they would work under capacity. The other worry is how well £20 chinese pump will last. Last issue is that this is all flying about on a fixed gantry mill so either has to be small enough to mount on the head or powerful enough to give lubrication from a way aways (which also adds some piping issues).

If no one knows a good pump could they refer me to a book or guide to designing them? Internally debating making a piston pump for high pressure oil jet lubrication.

[RainbowsParticipant @rainbows]

[David George 1Participant @davidgeorge1]

Have you thought of using an air oil mist lubrication as I have seen this on many CNC mills that I have had to repair. The positive air pressure also keeps out any contamination although you need to run a compressor and a oil level air pressure system needs failsafe monitoring.

David

[Neil WyattModerator @neilwyatt]

> Somewhere on the SKF website that I have now lost I worked out I needed about 1 liter per minute or a bit below that.

That seems an awful lot of oil…

An SKF pdf says:

Guidelines for the quantity of oil to be
supplied to each bearing for very high speed
operation can be obtained from
Q = 1,3 dm
where
Q = oil flow rate [mm3/h]
dm = bearing mean diameter
= 0,5 (d + D) [mm]

Doesn't that mean you only need to supply about 60ccs an hour?

10,000 rpm doesn't really seem beyond the limits of grease lubrication anyway?

[RainbowsParticipant @rainbows]

On the 16009 bearing with a Ref speed of 20,000RPM and limiting speed of 12,000RPM. After getting in a muddle of the Reference being higher than the Limiting I now have the second epiphany that while grease would reduce the reference speed it would still be above the limiting speed. Before I was reducing the limiting speed to accommodate grease.

Well damn made myself look a bit silly now. Would go for 25,000 RPM as the EX 45 with oil can take but can't find any backup bearing to match the speed.

[HOWARDTParticipant @howardt]

I would have a word with one of the lubrication equipment suppliers to see if cost becomes the decider. A couple of things with the design though. To help retain lube in the upper bearing, put a disc close to the bearing on the shaft and with od to outside of bearing diameter. Also reduce the spindle bearing spacer od to reduce inertia and put a filler piece into the bore to reduce the open volume.

[Author]

Posts