Whats with the "ribbing" on my prints

Before you start installing "wobble arresters", you should first inspect your z smooth rod bearings carefully. If there's too much play between the bearings and the rods, then you're likely to have the problems show in this thread. In my Mendel, I adjusted the tension bolts so that I can see all the bearings move when the z axis moves and I can't turn the bearings with my fingers when the carriage is stationary. A lot of people produce excellent prints without additional hardware on the z-axis of the Sell's Mendel.

nophead Wrote:
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> Do the layers bulge all the way round are are they
> simply displaced laterally? The former implies a Z
> / flow rate problem, whereas the latter is an X /Y
> problem.
>
> One thing to check is that the hot end is solidly
> attached. If it can wobble very slightly where it
> is joined to the extruder it can give a big offset
> at the nozzle.

As far as I can see without better eyes or magnification it appears to bulge all the way around.
I've tightened down the hot end mount and the extruder idler, next I think I will recalibrate my steps/mm.

Entropy Wrote:
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> I have been noticing this "ribbing" on my prints
> lately. I have recently switched to the newest
> versions of prontoface and slic3r. Not sure if
> that has something to do with it. Other than that
> I haven't changed much, and this just can into
> existence in the past week or so.
>
> Slic3r or SF(depending on the part) --> Marlin -->
> RAMPS 1.4 --> JHEAD. ABS
>

Do you happen to be using the Lift Z feature in slic3r?

Dale Dunn Wrote:
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........
> Since installing the isolators, I haven't printed
> any parts that don't have sections so thin they
> end up being filled 100% despite Fill being set to
> 35%. I was thinking that perhaps the bulges are a
> symptom of a slight overfill condition resulting
> in a periodic overflow. I need to try a part now
> that has room inside for properly sparse fill to
> see if that looks any metter.
>
> There are no guarantees that what I'm seeing and
> what Entropy is seeing are two instances of the
> same problem. I just don't think it's clearly a Z
> wobble problem. I'll try to remember to report
> back here what I find.

I just remembered. I printed a Yoda with the same SFACT settings and there is no sign of this bulging I saw on the walled part. So, I think for me at least it is a subtle flow problem. I'd fix it, but I just ran myself out of that material. Perhaps I'll get the flow under better control for this next kg of ABS.

tsb4k Wrote:
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> nophead Wrote:
> --------------------------------------------------
> -----
> > Do the layers bulge all the way round are are
> they
> > simply displaced laterally? The former implies a
> Z
> > / flow rate problem, whereas the latter is an X
> /Y
> > problem.
> >
> > One thing to check is that the hot end is
> solidly
> > attached. If it can wobble very slightly where
> it
> > is joined to the extruder it can give a big
> offset
> > at the nozzle.
>
> As far as I can see without better eyes or
> magnification it appears to bulge all the way
> around.
> I've tightened down the hot end mount and the
> extruder idler, next I think I will recalibrate my
> steps/mm.

I took a closer look at some of my recent prints, and I'm not sure what is going on.
In some cases it appears that a layer or two after a bulge, there will be a perimeter that appears not to be pressed down enough (hairline gap between layers). If I were skipping steps on Z I don't think this would happen (wouldn't "catch up" and cause a layer to be too high).

Just to throw this out there, I can't really see any way that the "wobble arrestors" could perform as promised.

The stiction of plastic on plastic when the weight of the x axis and motor is resting on it must be higher that whatever wobble force is created. That means that the wobble is then transmitted. Just like without the wobble arrestors. If you put some sort of bearing / sliding interface in there then I could see it working better.

Isn't the best answer to all of this to use thinner threaded rod and thicker z shafting?

Hey Entropy, have you solved this problem?

I'm having the same problem with my prusa V2...my problem

tinyenormous Wrote:
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> Just to throw this out there, I can't really see
> any way that the "wobble arrestors" could perform
> as promised.
>
> The stiction of plastic on plastic when the weight
> of the x axis and motor is resting on it must be
> higher that whatever wobble force is created. That
> means that the wobble is then transmitted. Just
> like without the wobble arrestors. If you put some
> sort of bearing / sliding interface in there then
> I could see it working better.
>
> Isn't the best answer to all of this to use
> thinner threaded rod and thicker z shafting?

You overestimate the friction between plastic pieces. For ABS anyway. The isolators I designed can be seen moving independently of the X axis assembly.

You are correct about rod sizing being the better solution, though.