Hi,
during my usual calibration routine i printed a califlower from vector3d and found that my printer prints very skewed. Usually i would add a skew correction to the printer.cfg, but as this is not intended (as the files are protected). What is the official way to deal with it?
I already performed the suggested way for belt tensioning as uneven tension could be a possible cause.
After material shrinking compensation:
See Advanced Mode in the printer menu.
Also strange. I got zero degrees on my first crack at the Califlower while trying out ASA.
Hi @Wombley
I don’t want to activate this option because it could result in warranty limitations according to the dialog. It’s an out-of-the-box problem, so I expect an out-of-the-box solution.
It seems you know about inaccuracies and the possible causes of wrong scew correction settings.
In this case I would simply use the advanced mode because the machine will not break because of this correction.
Anyway, you could open a ticket and get sure it’s ok.
https://snapmaker.formcrafts.com/support-ticket
@Simon_Zhi, maybe a future wiki topic?
OK, I’ll keep an eye on it—I’ll check on Monday.
Is there any information available on what the belt tension should be and how it can be checked? I don’t mean how it is adjusted, but how you can check whether it is actually correct.The wiki only mentioning it should be checked monthly but not how. (https://wiki.snapmaker.com/en/snapmaker_u1/troubleshooting/adjust_xy_timing_belt)
Great suggestion—I’ve already passed it on to the WIKI tech team. They’ll work on making the page description more detailed.
I’ve double-checked with the tech team: belt adjustment boils down to these steps:
Use a 2.0 hex key to loosen the two screws shown in the picture.（Do not unscrew the screws completely）
Grab the print head and move it to all four corners of the space (see GIF below).
Re-tighten the two screws.
Run the vibration compensation calibration once more.
This Guide only shows how belt tension should be adjusted. But still the question is how to check if the belt tension is applied correctly. e.g. by moving the printhead to a certain position and strum the belts and compare a frequence in Hz like Prusa did it. For example i performed the belt tension as shown but my gantry is still skewed. If i move it towards the front only one side is touching, on the other side there is still a small gap. i assume that the belt tension is not correct mybe the automatic tension is not working correctly but as i don’t have any values to compare to this is just a guess.
If you want to test it yourself, you need tool：
1.Belt Tension Gauge（As shown in the image below）
2.A reference fixed position
——————————————————————————————
Here is a more detailed process from production for testing whether the belt tension is reasonable：
Loosen screws No. 1 and 2, and the torsion spring at the green-marked position will tension the timing belt in the direction of the blue arrow.
Test the timing belt frequency. Move the X-axis to the middle of the Y-axis and park the toolchange to the side.
Aim the instrument at the belt position indicated by the green arrow (middle of the X-axis).
As shown in the image, aim the testing device at the front of the belt, gently pluck the belt with your hand, and wait for the device to read the parameter.
The test results of both the upper and lower belts must fall within the production-line frequency range: 90–100 Hz.
If you’ve confirmed it’s not a belt issue, the tool-head coordinates may be inaccurate; try adjusting them by referring to this WIKI article.
U1 How to adjust the pick & park coordinates | Snapmaker Wiki
Thank you very much @Simon_Zhi , these instructions are very helpful.
I measured the frequency and got 90Hz (upper belt) and 82Hz (lower belt).
Love this guide! Thank you! Now I’m going to test my belts.
Where did you get the Belt Tension Gauge? It’s not something many users will have , can’t be cheap.
Yea they go for around $250.00 US on Amazon… Hard pass on that.
A simpler check of if it was successful is to look at the resonance scan graph after you’ve done the standard auto tension and measured the resonance again.
Note: this isn’t conclusive, of course. Other things can generate bad mechanical vibrations. But if the scan is clean like these, I think the problem is not belt tension or any of that.
On the fluidd page, you can scroll down to the Jobs folder, navigate to shaper_calibrate folder, then click on the most recent images of the graphs. I’d expect to see a single narrow peak for both.
Good:
When the tension is bad, you may start to see broader, multiple, or lower frequency peaks:
This is an actual example from my U1 during beta testing, before they started recommending auto-tensioning as part of the unboxing after shipment. Again, bad results may indicate problems other than belt tension. But a clean resonance at least suggests it’s not bad.
My skew is a lot more, basically the most I have seen on any of my printers. Has anyone else sich high slew values?
Has the OP issue been resolved?
I had many conversations with support for many other reasons to get the machine going and one was that I had to adjust all toolheads numbers manually because the XY system is not perpendicular to the toolheads mounts and the housing. Just made this test because Its my routine for new filaments and got those results.
Thats much worse than my skew value. The worst i got was -0.22°.
I fixed it by applying skew correction to the printer.cfg. I got it down do a perfekt score of -0.02°
Have you checked and measured your belt tension?
Is your gantry alligned on both sides if you move it all the way to the front and the Toolhead to the left or right? Or is there a gap on one side?
due to other issues i did the auto tensioning cycle approximately 30 times. the graph also looks fine. for the measurement i would need special tools if i understand the thread correctly. I really would like to fix the mechanical issue somehow before fixing it via config. But somehow i cant get support to give me guideance on the mechanical part.
Yeah. I actually got zero degrees first try while testing shrinkage compensation for ASA. 
Should be adjustable in the config though.
