Can anyone tell what these lines are in print?

defaveri

I am having a hard time getting more faithful results with my A5. I installed TL smoothers on the X and Y axes and I don't know if it's related to these lines. I also put a stabilizer for the Z axis spindle that moved unsteadily. I verified that the X-axis belt is tensioned correctly. Look the image. PLA white, 195° nozzle, 0,15 line height and 20 mm/s.



Thanks if anyone can help with this issue.

Stephen Todd

Never had it myself, but I'd say that is z banding - and probably a direct result of tethering the top of the z rod - top of rod is supposed to wobble if rod is bent, rather than the middle of the rod, that will then make the x-axis move in relation to the wobble

defaveri

@Stephen Todd You're right and probably the cause. I will remove this item and test. Soon return with the result. Thanks!

Samuel Pinches

Could also be misaligned z-motor-couplers. If they are installed wonky, or stretched, it can also cause the z rod to wobble like @Stephen Todd was saying. Good luck.

defaveri

Hi @Stephen Todd and @Samuel Pinches ! I removed the TL smoothers and also the part that locks the anti-wooble Z axis spindle. I disassembled the side where the axis appeared to be more out of center, but none of that worked. So I decided to do some tests and I noticed that every 4 mm the line happens. This means a complete rotation of the Z axis. However, I cannot understand how it occurs.

I think it was a bad deal to acquire this model = (

Stephen Todd

A few ideas in this article:

http://www.mackenziewall.com/2015/10/12/z-banding-troubleshooting/

Samuel Pinches

When you rotate the Z axis, what is the part that is wobbling? There must be something mechanical is wrong, almost always either a bent z lead screw, or a damaged/misaligned motor coupler.

Laser8302

So after reading that article, I can tell you that the full step distance on our threaded rods is 0.02mm, so multiples of that should be your target layer height. So 0.1 or 0.2, and others like my favorite for detail and speed, 0.14mm layer height.

Laser8302

Since I am having a very similar problem with my printer, I did a very intensive investigation on my X gantry. I made sure it is level by measuring from the top of the gantry to the top of my print head. Then I just did a G1 Z250 then G28 to move the gantry up and down.

What I found was that my solid motor couplers were causing the linear rods to bow in and out as the gantry was moving! More so on the left where the x motor is than the right.

So I put back in my flexible coupler and I can say the bowing is down by 90% or so. The right side is still on the solid coupler, I might change it back.

In your case, you might look into swapping out you couplers.

Also, try doing a PID autotune for both your bed and hotend. Temperature fluctuations in your bed especially will cause it to physically move up and down during your print. You may have to modify your firmware to add PID control to the heat bed.

defaveri

@Stephen Todd @Samuel Pinches @Laser8302
First I thank you for the information and help. Well, I have to say that I did a lot of work here to try to solve the problem and I still haven't found it. See the image below:



These are 20mm cubes with a single shell without bottom layer for test. Even with the lines, I can't feel the bumps when I run my finger across the surface. It's very subtle.

A pattern of lines is occurring every 4 mm. So I verified that it is exactly one complete revolution of the Z axis. I dismantled the entire mechanical system of all the axes. I noticed that on the Z axis the smooth bars and the threaded spindle are in perfect condition, without any warping.
I cleaned the entire system carefully by removing any older lubricants, dust particles or anything else that could influence the problem. I used the Da Hai Zhu video on YouTube as a reference
In addition I cleaned the entire hotend, checked the extruder gear and there is nothing wrong, but the lines insist on appearing.
Could it be that there was a problem with any of the engines? Regarding the PID, I honestly don't know exactly how to do this verification, because I'm not sure what it is. Is there a tutorial here? Is there any reset I can do to test? Or, could it be something in the Cura slicer?

I sincerely thank you for your help and keep trying to solve this problem.

Best,

Leo

Stephen Todd

The original firmware has some wrong settings - the community firmware fixed some errors by correcting the values in the firmware

Those cubes look better than the white model which had equal light and dark spacing

If you've gone back to the original stepper motor drivers, have you actually set the voltages of each one to the ideal voltage - info is somewhere in facebook group - maybe in the wiki as well

I've never had z banding, and never set PID which is temperature calibration - makes it more accurate - but that is not your issue - I'm thinking extrusion rate may be relevant - was way off in original firmware

Stephen Todd

As you have almost fixed the banding, I'm thinking that the z stepper motor is not getting sufficient voltage - maybe not enough torque for every complete turn of the lead screw - or some resistance every complete turn - possible mechanical machining error on the lead screw/screws

Never had to fix this issue, so guessing now

Stephen Todd

I would try a different slicer, just to eliminate it - but I'm suspecting incorrect stepper motor driver voltages

Stephen Todd

You will notice that the z motor needs a higher reference voltage than any of the other motors

https://jgaurorawiki.com/a5/stepper-drivers

Samuel Pinches

I still really think you guys are not chasing the most common cause - the consistent periodic nature points most strongly towards a mechanical nature. If you disassemble the Z axis and take the lead screws out, you can roll them on a table and see if they are bent. If bent, they must be replaced. If not bent, then it is likely the motor couplers. Can you please take out both z-axis motor couplers and upload a photo here?

defaveri

Hi @Stephen Todd  and @Samuel Pinches.  Thanks again for the replies!
Well, I agree with Samuel that the problem is still related to the mechanics of the Z axis. See, this problem happened after the installation of these "stabilizers" that I printed. I believe that by holding the tip of the threaded spindle, it forced something that was deformed. https://www.thingiverse.com/thing:3380716
As I had problems with some lines that insisted on appearing, I believed it was a problem because of the Z axis wobble. But I was certainly mistaken and ended up causing a bigger problem.

Here are the images of the couplers as you requested



I didn't notice any visual problems, but it is something very subtle that is causing the defect. The line appears every 4 mm exactly, which is equivalent to a complete turn of the Z axis. Taking advantage, both the screws and the flat bar are perfect, without any bent problem. I put them on a glass table and checked carefully that they are perfect. Now there are the couplers, motors or some problem that I didn't notice. This is driving me crazy!

Thanks a lot!

defaveri

Hey, thinking about the couplers, I had the idea of ​​starting the engine only with the coupler to check for any deformity in the centering of the part. Despite being flexible, one of them is completely off center and causing a very sudden movement, while the other is practically perfect. Even though it's flexible, this decentralization of the bore probably causes serious problems, since the axis system is sensitive to this movement.

Samuel Pinches

Yes, that coupler is damaged. I would recommend replacing it. Sometimes they can be installed slightly tilted, but I think that one is stretched. See how you go.

Stephen Todd

Have you put the other "perfect" coupler on that motor and see how it turns - maybe the motor shaft is bent

defaveri

Hi @Stephen Todd I checked the shaft of the motors and they are aligned. The problem is even with the couplers. I already ordered 2 new ones and I must receive them within 2 days to install and test. Soon return with the result.

Thanks a lot!

defaveri

@Samuel Pinches @Stephen Todd @Laser8302Thank you for all the help you have offered me. Finally I was able to solve the problem of the lines and it really was the coupler of one of the engines as I mentioned above. Although I did not buy the original piece due to time constraints (it would take time to arrive in my country) I placed a similar piece with identical measurements.
Right now I'm printing some test models and I just noticed a loss of print quality, but I will make finer adjustments in the next few days to try to improve. The main problem with the lines that was extremely bad no longer occurs.

Thanks again for the help you gave me!

Best,

Leonardo from Brazil

mannymiller

defaveri 

Thanks for this post - i was suffering the same problem. i had already converted to an e3d v6 hotend so came to the conclusion is was heat related so had been playing around with thermistors etc trying to improve the print. You could feel the uneven walls too, but it was only visible in the white. in the black the print seemed ok, Anyways came across this post and checked my couplers, and mine were alot worse than yours. i had lots of spare new ones laying around so spent a few hours working through them trying to fine a a good set.. to be honest i think that is very rare to find. my only issue now is i got rid of the patterns, but now have very slight uneven walls.. so something else to look in to.