Z wobble because of bad Auto-leveling?

[Dragon2781 0]

Hi,

I started 3D printing with a Wanhao D6.

I was very frustrated because I was not able to get the first layer to stick due to my missing experiences in manual leveling the bed.

When I ordered the UM3 one week later I was soooo happy to get a auto-leveling function!

 

I first leveld the bed manually and activated the 'auto leveling' with the 'before every print' setting.

As excited as I was, I watched the leveling process.... but I noticed that the nozzle pressed down on the front of the bed and bended it slightly.

Well the first layer sticked very good but there was a continuous crackle sound while printing.

When I layed my finger gently on the Z thread-rod I was able to feel a tiny jump every time with the crackle sound.

So I think the sound was the Z axis adjusting the bed automatically while printing.

 

Well the object had bad Z wobble so I tried to deactivate the auto leveling.

Sadly there is no direct option for that!

 

I learned that there is a difference between the frequent measuring process and the auto leveling while printing.

The UM3 saves the alignment of the bed after he measured it. Even when you deactivate the measureing process you still get the auto leveling while printing.

I first had to deactivate the measuring process and then make a manual leveling to overwrite the saved alignment and to deactivate the auto leveling while printing.

 

Have I overlooked something?

 

Since I deactivated it, I have no Z wobble anymore.... but I'm very disappointed and upset to have spend money on a cool function and not be able to use it.

Every time I see a review video on youtube mentioning the 'COOL' auto leveling function I get goose bumps!

 

 

What are your experiences? Did I something wrong? Is there something wrong with my hardware?

[SandervG 1,521]

3 hours ago, Dragon2781 said:

but I noticed that the nozzle pressed down on the front of the bed and bended it slightly.

That is how it measures any offset in your bed leveling. 

 

3 hours ago, Dragon2781 said:

So I think the sound was the Z axis adjusting the bed automatically while printing.

That is correct. It does this during the first 10 layers of a print. 

 

Do you have a photo of what you considered to be Z wobble?

 

You can define in what frequency you what active leveling to happen, which can also be never. I.e., turned off. 

But not during a print. You have to decide if you want to change your active leveling frequency before your print starts. 

 

Can you elaborate what you mean that you have to make a manual leveling to overwrite the saved alignment. What do you mean by overwrite it?

 

 

[Dragon2781 0]

Hi,

 

 

18 minutes ago, SandervG said:

Do you have a photo of what you considered to be Z wobble?

Sadly I have no picture. I fear to activate the auto leveling again. My bed is leveled perfect now and you should not change a running system....
Well I want to open a new topic to fine tune my settings. Therefore I will set everything to default and start from scratch. I will activate the auto leveling again and make pictures of course.

 

If everyone here is using the auto leveling and nobody has a problem then something is wrong on my side...

 

Quote

You can define in what frequency you what active leveling to happen, which can also be never. I.e., turned off. 

But not during a print. You have to decide if you want to change your active leveling frequency before your print starts. 

 

Can you elaborate what you mean that you have to make a manual leveling to overwrite the saved alignment. What do you mean by overwrite it?

 

 

My theory is the Auto Leveling consists of two functions.

1st the automatic Measuring. You can activate this in the menu and you can set the frequency (before every print).

2nd the active Leveling. You can not activate/deactivate this. Once the automatic Measuring detects a slight dealignement of the bed the active Leveling will correct the bed hight while printing so the printed object is always aligned to the bed.

 

When you activate the automatic Measuring the position/alignement of the bed gets saved and the active Leveling will always adjust the bed hight while printing.

Even when you deactivate the automatic Measuring before the print, the active Leveling is still active because it thinks that the bed is oblique.

You first have to do a manual Measuring (Leveling) to overwrite the saved position of the bed. Now it thinks that you aligned the bed correct and deactivates the active Leveling while printing.

 

... that's my theory.

Edited February 16, 2018 by Dragon2781

[kmanstudios 1,120]

I am not sure what you mean by 'Z-Wobble'. I  have my active leveling set to always. I still have to go in every once in a while and do a manual leveling because the buildplate platen can go a bit out of whack due to several factors:

1. Mechanical drift--this will happen to any system over time. It is just forces like gravity and movement acting on it. Active leveling will help compensate for that as it happens....at least until it gets too far out of whack. This you can tell by how much you hear the first ten layers 'clicking' while printing. The less the better, of course.
2. Sometimes if I have a part that curls and the nozzles whack into it, you can see it get banged a bit up and down. This will affect it over time
3. Sometimes I have lifted the plate out to remove the print and it can yank the platen around if not slid out properly.....usually happens in middle of night when print finishes and I am a bit bleary eyed.
4. Since I use several glass plates, some may not be the exact same thickness and that can cause an issue over time as it over corrects a bit in some cases.
5. I take out a buildplate with the print and replace with cleaned buildplate. Wipe with alcohol and use a slurry of recycled PVA. To get the print to cut loose I put it in water when it cools a bit (no need to shock the glass) and when the layer of PVA is dissolved, the print cuts loose. Some prints can just cut loose on their own as they cool if they are high temp materials.

But I do not have any issues of prints showing slants or skewing due to this process. That is the closest I can figure for what you call 'Z-Wobble'.

[Dragon2781 0]

Thank you @kmanstudios for your response.

I will activate it again and make some tests and pictures over the weekend.

[kmanstudios 1,120]

Here is the thing to keep an eye out for is the worm gear they use to drive the z depth. If it is loose in any way or the unit driving it is off, it will affect things.

 

Keep in mind that this is a sophisticated machine that can get damaged in shipment. Anything goofy can go wrong between assembly and arrival to your domicile. It can go through many hands and it can be subjected to really, really crazy type delivery people. Throwing, dropping, all sorts of bad actors along the way doing a lot of stupid things.

 

If your system persists to give you issues, you need to speak to your reseller and maybe get a replacement. @korneel has a bunch of them. I have two. We seem to have fairly bulletproof systems that have just worked. The law of large numbers speak to the ability of the printers to be worth the price. And, you are correct, you should expect something from a printer this expensive.

 

But one machine, or even a few, is not the whole line. Especially when you see reviewers who get early prototypes and there are other biases at work. For instance Joel Telling gave a glowing review of the Raise N2+. But since then, I have heard about many not so happy customers and all of them have pretty much the same complaints. Whereas with the UM3(X) it seems to be a different issue and not that much.

 

To me that says occasional fault and not system issues. But it must suck something fierce to be the unlucky soul that gets something like this that does not work correctly and that must lead to a lot of frustrations.

[Dragon2781 0]

21 minutes ago, kmanstudios said:

But one machine, or even a few, is not the whole line. 

Absolutely right

That's why I'm here and ask for experiences and help to get rid of the issues.

Quote

But it must suck something fierce to be the unlucky soul that gets something like this that does not work correctly and that must lead to a lot of frustrations.

I'm not yet frustrated, just disappointed. I still believe that I can get help to fix that issues.

If all the help still leads to no good results -> THEN I'll be frustrated

Edited February 16, 2018 by Dragon2781

[kmanstudios 1,120]

Make sure you do not pass the time of being able to return the machine. And, yep, this is a good community to get help from.

[gr5 2,173]

I've never used auto leveling for a few reasons but the way auto leveling works is there is a sensor in the bottom of the print head that detects the distance (capacitance) (very inaccurately which is fine) to the metal below.  it can detect tiny changes in distance/capacitance.  When the nozzle hits the glass and it keeps moving it realizes that the capacitance hasn't changed it knows that it already hit the bed.  It's probably very fast so in milliseconds it can go back up a bit and recheck - not sure - I've never tried it.

 

The point it it's supposed to push into the glass and then push a little farther.  This is a feature not a bug.  It's also I think why the rear center screw is looser than the other 2.  The other two rely on "z wobble" so are okay with the stronger springs.

[Brulti 177]

I'm like @kmanstudios: i have autoleveling set to always, and I redo it from time to time, especially when I change the plate because they can vary in thickness, and they also vary in bend, unfortunately.

 

You can deactivate the autoleveling completely, so the printer will just print and not do the 'push the printhead against the glass' thing at the start.

 

But, usually,once you've done your manual leveling at the start then let the printer do the autoleveling, you should be set.

[Dragon2781 0]

27 minutes ago, Brulti said:

You can deactivate the autoleveling completely, so the printer will just print and not do the 'push the printhead against the glass' thing at the start.

Hi,

like I said I have other experiences. Yes, you can deactivate the automatic measuring at the start of the print but the active leveling while printing is still active untill you do a manual leveling.

[Brulti 177]

Ok, I'll have to test that when the printer isn't busy, since I keep automatic leveling always on.

[3dcase 37]

Hi dragon,

 

1,5 year ago I bought the first UM3 for the school I work.

As an old fashioned wooden UM1 user I was very frustrated with the auto levelling also. 

A total disaster...... took me 3 days off sweating before I could show the first decent print...

Almost returned it  to swap it for 3 UM1s.

But after using the old-fashioned Eyeballing method of levelling for a few days.

I saw White plastic shavings? in the printer. 

The cover off the stepper motor right in the back was hitting the Z platform.

Autoleveling did not like to pull down the platform. 

After fixing - no problems until now. The best printer I ever bought (from someone else's money )  

Good enough to my me a private one...

 

Another thing/problem/bug/whatever to keep in mind and check.

Are the springs of your bed still tensioned??

There is some miscommunication in the firmware when manual levelling.

The steps in the manual levelling settings are easy the follow, and work fine.

But after 5 or 6 times you have start by manually all by yourself!!!

Lower the bed a few mm extra before You use the wizard in the firmware.....

 

Skip the rest if you like, perhaps I should post it in another thread or mail.

 

Regards kees

 

If you follow the manual levelling procedure from the menu.

The only thing you end up doing with the springs is loosening them.

Give it a try yourself, but as I recall it....

Step 1 .

use the knob/wheel to get 1 mm clearance in the back......

then right front  left front.

Step 2.

use the card and the screw.... blah blah rightfront leftfront.

 

Problem.

You have lowered the tension in the springs by .6mm? 

the difference between 1mm and the thickness off the card.

 

Anyhow after a while you run out off springtension and that results in a mess...