Vertical Axis Chatter

[rocko]

I have been getting chatter on the plunge of the Z-axis for a while now. I finally measured the slop and it is 0.007". When I reduce the weight on the z-axis by lifting the router support while it is plunging, then the chatter goes away.

I think this is causing the z-axis to miss steps, so now it has become an issue. Has anyone had this occur and how did you fix it?

Thanks!
Rocko

[cabnet636]

got any loose bolts, vibration, have you lubricated it lately? maybe a spot of 3n1 oil

jim

[rocko]

No, the mfr recommended lube is graphite, but that doesn't affect the slop. I need to eliminate that. Anyone else have any feedback?
Thanks!
Rocko

[nwrepair1]

If this is a Larken, it may have a leadscrew and not a ball screw with ballnut. Remember that a new rolled ballscrew has .004 slope in it no mater what the factory states. If you have a leadscrew, the nut has composite nylon or delrin threaded block instead of ball bearing nut. Maybe even a metal threaded bushing. If that is the problem, call Larken and get a new nut. Also check the linkage between the motor and the lead screw. All Larken and Camtec routers suffer from out of round pins and links after hard or long use. They do the job for a starter price but the are not built like tanks. Three D work is really hard on these machines if you are doing that kind of work.

[rocko]

NWrepair1, this is certainly a ballscrew, and the thing is made with 1/2" aluminum all around, so I can't really see how you say it isn't built to take a heavy load. What do you consider more robust?

The slop is all in the ballscrew. If there were a weakness to the Larken design, it would be in the lack of dust protection on the ballscrew housing and shaft. I haven't seen any such systems up close, but imagine that a really good system keeps the dust and dirt from getting into the bearing surfaces.

So now I am still facing slop, but again, only in the Z-axis.

Regards,

Rocko

[Larken]

The Z axis nut is not an anti-backlash. We machine it from delrin. The x and Y are anti-backlash Kerk nuts.

Generally if the cutter is sharp, the Z backlash is not a problem since gravity keeps it tight.
Have you checked the Z axis linear bearings for tightness ?

Larry K

[rocko]

Can you advise on how to do that check?
Thanks!
Rocko

[Larken]

When I reduce the weight on the z-axis by lifting the router support while it is plunging, then the chatter goes away.

Are you drilling a hard material ? Is your cutter designed to plunge ?

Check the bearings for play, grab the router and wiggle it to see if there is looseness.