Flycutter wears out spindle bearing?

[ksallred]

Hello all,

I am new to CNC machining and was fortunate enough to buy a benchtop Vertical CNC mill to learn with. I will withhold the model for now.

I've had the machine for approximately 2 months and have used it on average 3-4 hours a day, 5 days a week. Suddenly today, I put my 2 inch flycutter on and the machine began to vibrate horribly. I have used this cutter many times with great results. Now today this problem. After speaking with the manufacturers tech support, they tell me that the spindle bearing is probably shot and that this machine was not designed to run an unbalanced tool like a flycutter.

I am somewhat puzzled that Saturday everything worked fine, then today on Monday I have this problem. It is an immediate change in how this tool runs. I removed the flycutter and ran the spindle in air with no tool, the vibration stopped and the spindle ran smooth. I put an end mill in and ran in air, no problems. Put the flycutter on and run the spindle up in air, massive vibrations. I've also pulled on the flycutter while stopped and can't feel any play in the spindle. Turned spindle by hand and feels smooth.

My question is, is this normal after such a short time to wear out the spindle bearing this fast? If it's not the spindle bearing, what could the problem be? What are your experienced opinions about this problem?

Flycutter is NOT homemade, one piece construction, and is made by reputable company. Insert is tight, and even removed with no change.

Flycutter RPM 2000, IPM 4, DOC .005"
Machine MAX RPM 4500, Variable speed spindle, 2HP, R8 Taper

[kd4gij]

What size mill. what size and type flycutter. sounds like you have somthing lose or cracked. Can you post a pic of the flycuter?

[ksallred]

The machine is a Baron XL from CNC Masters. The flycutter was purchased from Mcmaster-Carr and looks brand new still with no visible damge anywhere. I will try to get a picture posted soon.

[ksallred]

Here is my flycutter. No visible damage or cracks.

[underthetire]

A simple answer, yes. Those are terribly unbalanced tools, and at RPM will cause early failure. Even on bridgeports. They have been used for years, simply from lack of a better design, that is up till about 20 years ago. Face mills are now the preferred cutter for surfacing material.

[ksallred]

Ok, so I will cease using the flycutter and go to a face mill.

However, do you think this sudden change in machine behavior is due to a bad spindle bearing? I would suspect that if the bearing was developing wear in the races, that it would be a gradual effect, not instant. I know it is difficult to diagnose an issue without having hands on, but given the details below, what could be the cause of the sudden excessive vibration?

Again, no play back and forth that can be felt in the spindle.

[underthetire]

Could be gibs loose, causing motion in the entire head. Could be a temperature swing, causing parts to not fit the same as the weekend, could be belts/gears. Like you said, cant diagnose to easy without being there.

[H500]

Perhaps you can post a video.

Any possibility that the bearings need lubrication? I find it hard to believe that the small dynamic force produced by the imbalance can ruin the machine so quickly. The bearings are subjected to much higher radial forces during normal use.

[LUCKY13]

I would check the spindle and belt drive very close ( just guessing its a belt drive if its variable).

Loose belts, bearing preload could cause such a thing. IMHO I would not expect a flycutter to be the problem. Yes they are not balanced and the higher the RPM the more this effects things but a many people have run such tooling on hobby size mills without problems.


The sudden change can really be normal when a bearing or other problem starts showing. Like you said it feels fine and without the flycutter it does OK, but sommething is getting on the edge and the flycutter is making it show up.


Its not uncommon to find some bad bearings in the spindle of any of these machines. Being shipped over salty waters and settting in crates sometimes for long periods of time they can draw moisture and then the bearings will not be around long. Or sometimes the preload was not set right, either to tight causing early death, or to loose and gaining clearance after break in. It can be hard to feel sometimes by hand.

Ofcourse I know nothing of these machines, maybe they cant handle such a tool that is unbalanced. One thing is for sure, if its more than just running a tool it cant handle it will get worse and you will start seeing problems without running such a tool ( with normal end mills and such). Problems with surface finish can be a indicator also.


Jess