In my K8400 the Z-axis screw resonates while going up/down at high speed. The free end of the screw vibrates like a tuning fork - clearly visible by eye.
The noise stops if I touch the free end while it turns with a finger (mechanically damping it, of course).
It is not a lubrication issue, and the axis moves freely (checked unlocking the motor joint).
In my opinion the free end of the screw should be held steady by a vibration dampener support. No problems while printing, but such a vibration will quickly deteriorate the plastic female screw.
[quote=“Wrong Way”]I have been going through the manual.
Is the coupler properly mounted?[/quote]
I think so. It is a simpla part, and moving at low speed all works. Unplugging the motor the movement is smooth, no problems with the bearings.
I had some experience with steppers driving long screws. It is a bad thing, the stepper has a wide vibration frequency spectrum, and always tries to put everything in resonance. So, a free end for a long rod is a bad idea. But that should happen to other K8400, not only mine
You could try to swap the Z stepper with one of the other steppers.
Could be an issue with the stepper itself.
If so, by swapping you should see an improvement to the vibration.
The Z stepper might work fine on the x or y axis.
[quote=“Deskstar”]You could try to swap the Z stepper with one of the other steppers.
Could be an issue with the stepper itself.
If so, by swapping you should see an improvement to the vibration.
The Z stepper might work fine on the x or y axis.[/quote]
Of course I may try, but the stepper works well if I touch the screw and the torque is excellent. Knowing how a step motor works and is made, I strongly doubt that it may be defective.
I wait for an advise from Velleman.
I already lubricated it with some lithium grease. I will try adding some, but it seems to me free and smooth. Haven’t you seen similar vibrations in other printers?
I currently mounted my K8204 leadscrew upgrade kit on my K8200 and had similar problems, but not “that bad” as you found.
Now i’m printing the last part for an updated mounting which will hang the axis down from the top instead
of “stacking it” on top.
I think your leadscrew begins shaking because the resonance makes it’s centre of gravity to fall outside the
Spindle so it tilts (falls) sideways and then bumps back while it turns along.
[quote=“Wrong Way”]You could try turning the lead screw upside down to see if that helps.
It may not work but is something to try that is fairly quick and easy.[/quote]
That’s a good idea. I’m busy now, but I will try that.
I can confirm a very strong vibration, too.
The cause may be a rod that is not very straight like mine. I’ll try to replace it with a quality A-grade rod next week and will tell you my experiences with it.
The vibration stops nearly immediatedly if I just hold the tip of the z-rod with my finger in place while it keeps on turning.
So it would be a good idea to build some plastic part to be mounted at top just to hold the rod in place.
If there would be a bearing to hold the rod in place then I’m very sure that this problem would be eleminated…
I did some more tests. Lubricating the screw helps a little, I used lithium grease after checking the compatibility with Iglidur plastic (it has no problems with lubricants in general). Reversing the screw does not change much. The play between the screw and the Iglidur part is wide, one of the two is not a precision part, it seems.
This is, however, not the major issue; only annoying. Belt pulleys and belt positioning in general are the weak points, IMHO.
@Spin: How is your Z Coupler mounted?
The manual http://manuals.velleman.eu/article/19-mounting-the-z-stage-18.html states: “[color=#0000FF]Make sure the rod is inserted fully[/color]”, but this seem wrong to me in this case the rod is fully inserted trough the flexible part of the coupler ant thus it is losing its function. I have inserted my axle ends just til the flexible part (easy to see using a flashlight).
On my printer the axle is somewhat off centre at the top, about 1mm you can clearly see it wobbling when homing the Z-axis, but there is no resonance.
