Solved Prints started failing

Yeah I can send some pictures, I'm not going to get home until real late tonight but I'll take some and post them before morning. I've seen pictures of the smooth rods connecting with the top cover through a groove thing, but mine doesn't touch the top.

This is the first time I've heard that the bearing mod is bad, I've found a bunch of forums where that completely fixed the z artifacts. Is there a better way to get rid of the z ribbing?

 

I tried it for a while and due to the nature of coase threads the nut naturally wobbles. This pushes on the smooth rod and if it's fixed in place it causes the carriage to shift back and forth. I experimented with it for a while and it was just a tremendous waste of time.

 

well... is there a sure way to fix z artifacts?

 

Try adjusting your helical couplers or contact robo3d for help.

 

Have you read Ziggy's guide for fixing z ribbing?
http://forums.robo3dprinter.com/index.php?threads/Z-Axis-Artifacts---Known-Issues-and-Fixes.2576/

 

I have, that's where I got my info about the alternate layer heights for the 5/16th rods. There was also a few people who completely reduced their z artifacts with reseating the couplers and adding a ball bearing. But if that's a bad idea then I'm not sure where to go with it.

 

bearing ball meaning this: http://image.made-in-china.com/2f0j00sMLavVjtElqF/AISI420-Stainless-Steel-Ball-0-5mm-25-4mm.jpg

Not a ball bearing like a skate bearing.

Whoever decided to name those the same things should be kicked in the keister

 

Hahaha agreed, so taking a 3mm steal ball and placing it on the stepper motor IS a step in the right direction? sorry for the confusion

 

Yes correct, We'll call it a BB because that's kinda where the name originated (Not really but yeah).

The BB goes inside the helical coupler on top of the stepper driver shaft. There's a groove cut into the center of the shaft for it to align in. Then you put the threaded rod back in so it rests on the BB. I think Ziggy has a drawing of it.


The issue I was describing before was capturing the threaded rod with a ball bearing. This can lead to torque stall, or ribbing along the X. Almost all printers I've come across have the Z lead screws floating.

 

Gotcha, I think I've seen some models where the z stabalizer also grabs the threaded rod but has a bearing there for smooth spinning. I thought it was overkill. So right now I'm searching for a local shop to buy a small handful of BB's instead of bulk online. then I'll reassemble the motor/clamp/rod assembly as per Ziggy's document.

Oh, and I forgot that I have enough time to drop by home after work, so I'll probably snap a few photos of my printer for you in about an hour and a half.

Thanks for all the help, I'd probably be ripping my hair out if not your you guys

 

Here are the pictures of my printer, the smooth 8mm rods are about 1cm or so away from the top of the case.

I stopped by a bike shop for the bearings, and ace hardware to get the other random stuff to do the z rod fix. so that should happen sometime in the next few days

 

If it has a bottom cover it's most certainly M8 rods. That lid is confusing though.

 

Well, I'm pretty sure I have the 5/16th rods. When disassembling to do the Z ball coupler mod I noticed a few things. First of all my threaded rod was covered tape to make it fit into the coupler. And secondly the stepper motor shaft did not have the hole in it for the bearing. According to Ziggy's pdf notes on the 5 fixes to z ribbing, having tape on the threaded rods is a sign of 5/16th rods.

So, I have the bottom cover but I also have 5/16th rods and the older style top cover. did they throw a bottom cover on an older one and ship it to me? and do you think it's possible that my z rod stepper motors are the wrong ones?

 

Tape isn't indicative of anything. Got a caliper? Measure the thread pitch.

 

Yeah I measured it with some calipers haha should of done that from the beginning. I do have 5/16th rods.

This weekend I spent a ton of time working on the printer, I printed out custom couplers with a spot for the bearing mod and set to fit the 5/16th rods instead of 8m. This didn't make the prints any worse, but it didn't fix the ribbing issue either.
I then put the stock couplers back on and had the motor shaft just slightly lower than the opening of the 8m side so the bearing had a place to sit centered. This helped the ribbing slightly but not by much.

I'm running the firmware update that prevents power from kicking on and off for the z steppers, found in Ziggy's guide.

at this point I'm spending more time working on the printer trying to get it to work well, than I am actually printing stuff. It's extremely frustrating that this ribbing isn't going away.

 

Worse than the ribbing, it's been randomly printing a 20mm calibration cube too tall or too short by 2mm+ I have a pile of about 10 cubes from various fix tests

 

Try scheduling a 1 on 1 for the ribbing. They might be able to get it sorted out.

 

it's about all I can do at this point. Thanks again for all the help, you've been awesome

 

Hi All,

If you are getting bad prints and inconsistent walls on your prints the first thing you should check is that the threaded rods are not loose in the couplers.
With Z Wobble/Ribbing and have found that the issue is primarily from the rod not sitting directly in the center of the coupler. If the coupler is over tightened it will cause the rod to sit off center. This is corrected by adding some padding like the teflon around the threaded rod to keep it from over tightening to grab the rod.

 

Here's what I don't get: how can Z wobble and ribbing possibly be caused by the same thing? It seems unlikely, if not impossible, that wobble (movement side-to-side in the x-axis or y-axis directions) would be caused by the same things that would cause banding/ribbing (ie. scaling larger/smaller layers in the x or y dimensions, or both)

From what I understand, the "Z wobble" has actually nothing to do with movement along the Z-axis, but is actually related to movement side-to-side (x/y), which makes sense.

On the other hand, it sounds like "Z ribbing" is caused by problems with movement up and down the rods along the Z-axis, which also makes sense -- if the layers are not being applied at identical distances, they could end up being different thicknesses (for example, the nozzle could be scraping along a previous layer, applying more and sort of "flattening" it out a little wider) Now, in theory, going to metric should have fixed some of this (I have not measured my threads but presumed them to be the newer M8 version); the only other thing I have heard about is slippage along a nut at certain intervals (this, too, would make sense if it is bumping up or down slightly), or threaded rods that are not completely flat/level on the bottom, which could also make sense depending on how they are seated -- do these rods lie flush with something (which would bump/push them slightly if a slanted bottom rotates)?

I haven't dissected mine because, well, I really don't want to (unless I was certain I could get the Z-ribbing eliminated by doing so)