Cant get rid off of this ribbing...

Hi all. I have this prusa i3. It is calibated, really well calibrated. The only issue I have had is this (now I know what it is) z ribbing.
For a long time I suposed it was a problem related to filament quality, extrusion problems, layer shifting, and other theories. In the atached picture, it really looks worse of what it is. This "banding" is really small, you can see it more when white plastic is used. If I print in other colors, it is there but because of a visual effect of color/shadows, you barely notice it is there, but it is.
Recently, there was a post here and I participaed after seeing the pictures, they were showing the same problem than me. Theories were: extrusion inconsistency, layer shifting, as always. Nobody thought about z ribbing. A couple of days ago dont know why but I measured teh separation between bands... they were exactly teh threaded rod pitch. The banding is not consistence. There are areas with more bnding, less, etc but always the separation between bands is = to the threaded rod pitch or a multiple of it.
So finally I think I know wich my problem is. I never suspected of this because my printer from the very beginning has installed this:
[www.thingiverse.com]
and this

[www.thingiverse.com]

Both of them were suposed to avoid the Z ribbing problem. The conectors are great, the threaded rods are center, as much as they posibly can. and the Z isolators are doing their work because if I remove them, the banding gets a lot worst.
yes, I have this z ribbing problem, really small to be fare but it is there and I think it is the only thing between me and a really perfect print, can someone help me with this?





thanks in advance

Print surface quality problems are often associated with unwanted movement of the extruder nozzle relative to the print bed. Such movement can come from the printer's frame flexing, guide rails flexing, play in bearings, etc. Threaded rods are literally always bent- the process of making them causes them to bend. Using printed parts of limited accuracy and rigidity to compensate for poor design/part selection (bent threaded rods, flexible end supported guide rails, flexible frame) can only go so far in fixing the problems. If you want to get close to perfection, you have to correct the problems, not apply band-aids. You need a solid frame, guide rails that don't flex, quality bearings, and lead screws instead of threaded rods.

It sounds like you've done all the calibration and applied all the usual band-aids. You may have reached the limits of your printer's performance without making major changes.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

What material is your frame made out of? Wood? Cheap Plastic? Try mounting your components on a P3Steel frame. Checkout "P3Steel" in the Wiki. P3Steel frames cost about $120 US and can be bought either on eBay or from the manufacturers listed in the wiki.

Are you trying to use some type of z-axis constraint? Don't!!!!! They only make matters worse.

Using Z-axis isolators like the one you show may help if they and your X-axis ends are perfectly smooth where they meet. Even then they still can not overcome a weak frame.

You may want to use stepper motor isolators ( [www.ebay.com] ), but this is like putting a band aid on a shotgun wound if your frame is weak.

The frame on my first printer was made of wood and contorted all over the place. I had bad z-wobble which caused me months of frustration until I switched to a steel frame.

My frame is made of steel

Grab your extruder like Trump would grab a pussy and try to wiggle it. See it moving? Find the parts that are allowing it to move and replace them with parts that don't allow that motion. Quality linear guides (not counterfeit Hi-Win parts that are all over the Chinese deal sites) solve both flexy rail and sloppy bearing problems in one go. Hi-Win parts are supposed to be good, but you never know if you're going to get actual Hi-Win stuff of counterfeits when you order. I buy used Japanese made guides (THK, NSK, etc.) via ebay for about the same price as new Hi-Win stuff sells and have had great results. I design and build printers myself, so I don't limit my parts choices by designing the machine and then shopping for the parts to fit my design. I get the parts, then design the machine around them. That way I can take advantage of whatever good deal I can get on linear guides. Ebay shows thousands of listings for linear guides, and the vast majority are much too expensive, but buried among those overpriced listings are some great deals. You just have to dig and be patient. Even small linear guides are spec'd for forces that are orders of magnitude greater than anything a 3D printer will throw at them, so size isn't really important as long as the rails are long enough. You can cut rails to needed length using a cut off wheel on a chop saw or a grinder.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

If you have a steel frame, make sure all screws are tight.

If you have weak materials making up your X-axis you can try using all steel parts for your X-axis as seen below:

[www.ebay.com]

The carriage in this setup is a little heavy, a may not be optimal for your use.

I use this item on my Prusa I3s:

[www.ebay.com]

I had to widen the hole around where the threaded rod goes and use an isolator to get this to work with a P3Steel frame. May be more work than you want to do.

Replacing printed plastic parts with metal is always a good idea.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
Grab your extruder like Trump would grab a pussy and try to wiggle it. See it moving? *snip*.

If someone doesn't find that disturbingly funny then they are a different level of sanity to most.

This can also sometimes be caused by the heated bed flexing when power is applied. Try turning the power off on your heated bed and use blue tape, see if the banding is still happening.

It doesn't look regular enough to me, to be Z wobble.

Once you're eliminated heatbed warp, I'd go through the other suggestions and ensure that everything is locked down solidly, including checking your motor grub screws.

Check the hotend when it is hot. Mine was snug when cold, but loose when hot.

Quote
GRAYWOLF

Quote
the_digital_dentist
Grab your extruder like Trump would grab a pussy and try to wiggle it. See it moving? *snip*.

If someone doesn't find that disturbingly funny then they are a different level of sanity to most.

I thought veering into Trump territory was frowned upon

We cant assume all readers on this site are men. For me the"humor ' in the Drumph comment was the mental image of a clueless know it all grabbing a hot extruder aggressively and getting his tiny hands burned.

OT
..and it started oozing immediately