Today i have made a great improvement to the k8200, and it is a very simple one.
After i had printed the z-ax motorholder improvement and placed this holder, there was also a great improvement, but stil i had some woble.
Also i have a flexible motormount, but stil some z-ax woble.
Todat i have removed the top holder for the z-ax, the one with the bearing. The ax moves now completly free.
And now i have great results in the printed objects.
I can see the layers, but don’t see any wobble anymore.
Hope that others have the same results when they remove the bearing holder.
[quote=“dutchronnie”]Today i have made a great improvement to the k8200, and it is a very simple one.
After i had printed the z-ax motorholder improvement and placed this holder, there was also a great improvement, but stil i had some woble.
Also i have a flexible motormount, but stil some z-ax woble.
Todat i have removed the top holder for the z-ax, the one with the bearing. The ax moves now completly free.
And now i have great results in the printed objects.
I can see the layers, but don’t see any wobble anymore.
Hope that others have the same results when they remove the bearing holder.[/quote]
How about trying that one? : thingiverse.com/thing:648925
With a little modification it sould work for the M8 rod too …
cheers,
Christian
Yes, almost the same i see.
But the motor is now hanging on top.
I don’t see the advantage of mounting the motor on top.
Maybe there is?
It would reduce the effect of the Z rod “whirling” around while moving up and down cause it hangs down.
That way it doesn’t swing sideways that easy if turned, as if it was sticking out to the top.
cheers,
Christian
EDIT: sorry dutchronnie, just read your post again and realised you still have the motor at the bottom.
So it’s the same effect but done differently. If you have two shafts that are not alligned and connected in some way, they must both flex to some extent.
In our case, one maintains the allignment of the print head (we don’t want that to flex in the X or Y axis) and the other controls the vertical height of the print head (so long as it doesn’t flex in the Z axis it can be made from string as far as we are concerned).
Anyway unless the Z axis drive rod is a streight as the support rods there is a problem. To reduce this we make the Z axis drive rod as floppy as possable in the X and Z axis to reduce the effect it has on the support rods (or replace it). Ways to reduce this include reducing the number of places the rod is fixed or increasing the distance from the fixings (what you have done). With a limited short burst travel that the Z axis this is not a problem. Not recomended for X or Y axis.
Hi dutchronnie, I’ve done the same thing - not as advanced as yours though. I just reused the standard items.
From my tests it’s important to not have the nut under the bearing as the gains are reduced. If you want to keep the lower nut, then don’t tighten it fully. As the threaded rod is a ‘sloppy’ fit in the bearing the chances of tightening it exactly in the center is very slim and that just makes things worse again.
At the end of the day the bearing is only there to take the weight, if your concerned about backlash put another nut under the bearing with a spring above it. You’ll note that I still have the solid coupling (still testing to find out where my upgrade money will be best spent).
Anyway here is a single walled cylinder printed with the above mod.
Interestingly there is a poor section near the top. I used a raspberry pi, running octopi to control the printer. As the print took about 45 mins and I had finished the work I was doing, I used octoprint to to log into the raspberry pi and view one of the timelapse videos I had made earlier. I remember thinking to my self as I started to download the video the printer started to ‘dither’ (the sound it makes when doing a a very thin perimeter infill) as opposed to the nice smooth sound of a circular perimeter. I suspect that each time the print ‘paused’ due to delay in getting it’s next command the nozzle ozzed a little to create this effect. I’ll have to check this but it looks like it’s not a good idea to download videos from the pi whilst it’s printing.
I assume that we have only moved the problem to the other end of the Z axis and that the closer you get to the motor with a rod that isn’t straight the greater the problem becomes. This will do for the moment and when I start printing 200mm tall objects I’ll address the issue.
; generated by Slic3r 1.0.0RC3
; layer_height = 0.2
; perimeters = 2
; top_solid_layers = 0
; bottom_solid_layers = 3
; fill_density = 0
; perimeter_speed = 30
; infill_speed = 50
; travel_speed = 200
; nozzle_diameter = 0.5
; filament_diameter = 2.90
; extrusion_multiplier = 1.00
; perimeters extrusion width = 0.42mm
; infill extrusion width = 0.42mm
; solid infill extrusion width = 0.28mm
; top infill extrusion width = 0.28mm
; first layer extrusion width = 0.33mm
So now all vertical forces are directly exerted to the coupling and motor?
That’s where the upper bearing is for I think, to take the axial forces.
The motor should only drive the spindle, via the (flexible) coupling.
I doubt if this is very good for the motor lifetime…
[quote=“hbzandbergen”]So now all vertical forces are directly exerted to the coupling and motor?
That’s where the upper bearing is for I think, to take the axial forces.
The motor should only drive the spindle, via the (flexible) coupling.
I doubt if this is very good for the motor lifetime…[/quote]
That’s one reason why i made mine to hang down against the (bearing supported and loosely countered) flex coupler.
The motor takes no axial load.
cheers,
Christian
Hi all.
One of the first things i “upgraded” on my K8200 was the Z Axis.
Will say, i replaced the solid coupler with a flex one.
The result was absolutely bad.
Therefore i changed back to the solid coupler.
What i did then…i checked the original 8mm “leadscrew” and i removed all wobbeling from this srew.
To do so, roll it over a realy flat surface, in my case the diningtable, and slightly bend this screw until it is realy straight. (May best doing this during your wife is on a shoppingtour…)
Second i did was liftening the upper bearing so that it only guides the screw in a sideward direction.
Remember…there is absolutely no backlash in the motor since it contains 2 realy strong ballbearings. So, no need for the upper bearing to remove any backlash.
After this procedure, i am realy happy with the original Z axis.
Regards, Paul