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italianmaxx

little thing to try to minimize Z axis wobble

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hi Umakers,

after several days fighting with Z axis wobble i put down this one:

http://www.thingiverse.com/thing:182295

it's a little piece to help Z axis top end to keep its place, and togheter with the brass z nut movement COULD help to reduce vertical wobble in printed objects.

It seems to work. does'n eliminate it but seems to reduce it.

Remove vertical wobbles in printed objects seems related to several different things:

z axis problems

bed problems

under/over extrusion problem

slicer poblems (netfabb seems to produce the best slice in terms of vertical wobbles against Cura. need to try kisslicer too)

hope could help someone...

 

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You also should try a flex shaft coupler like these ones for the direct-drive upgrade. For instance this one: http://openbuildspartstore.com/5mm-8mm-flexible-coupling/ (I don't know anything about this shop).

 

The biggest advantage over the standard UM one is the clamping system. This will help you to improve your print quality for just a few €/$.

 

Besides this I really like the surface quality which KISSlicer produces.

 

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You mean you put in the flex coupler and the leadscrew stops wobbling?

I have the problem that, when I print really high prints (which I don't to because of the problem), the slider block actually collides with the leadscrew because the screw leans forward that much. I noticed that while assembling the UM, when I moved the Z-stage by hand...

 

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You mean you put in the flex coupler and the leadscrew stops wobbling?

I have the problem that, when I print really high prints (which I don't to because of the problem), the slider block actually collides with the leadscrew because the screw leans forward that much. I noticed that while assembling the UM, when I moved the Z-stage by hand...

 

The flex coupling certainly doesn't stop the z axis from moving in x-direction for different z. But it reduces the tension which is induced by this x/y-movement onto the bearings, the whole z stage and the z rails. The results should be less wobbling in your print.

The collision issue is caused by the positioning of the brass nut. I have the same issue but it just works. Therefore I think it's not a construction fault but something that requires some mechanical tuning...

 

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I haven' yet tried to enhance my z-accuracy so forgive me if i bring up a topic that was already there but could a ballscrew be of any use? As far as I know they are really expensive (around 80€ for a 8mm one in our size) but much more accurate than leadscrews (and they have 30% less friction, but i don't think that this is of any use in the slow-moving z-stage).

 

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I don't see how this would improve things. One thing that might improve the overall stability/accuracy, is adding rods with linear bearings in the front of the machine. This would increase the rigidity of the Z-stage.

I think the reason why this is not implemented in the UM1 by default is that it is simply not necessary (the UM1 already prints pretty well in standard configuration). But it might improve things a little. Also, it might help with particularly heavy build plates like basalt or massive aluminum heatbeds.

 

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In the Reprap community many have changed from M8 to M5 on the z-axis. The M5 is not rigid enough to "over rule" the smoothrods. They also use flexible z-couplngs and add flex in the Z-axis motor mount....

On the BFB Touch they use arms to hold the moving z-platform, but the arms from the lead screws are not constrained in x-y on the platform to avoid z-wobble.

Johan

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