[Solved] I need your help identiying the issues  

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Nexusmarit
(@nexusmarit)
New Member

Hi everyone!

This week I've got my Prusa MK3s kit as a birthday present.
Yesterday night I finished the assembly (btw, i had a blast!) and today I'm running my first test prints using the files on the SD card.

I have never been involved on the 3d printing community before, so I have no idea how to "name" the issues I'm having, so I'd be grateful if you point me in the right direction so I can do my research on how to solve them.

So, here's what happened:

https://imgur.com/KI2cZ8r

These are the first 3 Prusa badges that I printed. The first one is the one on the top.
As you can see, 2nd and 3rd are both sorter in width. On top of that, there were errors on the A and the U. 
Between these prints, I didn't change any settings other than the first layer z leveling.

https://imgur.com/RZGMrwd

As you can see, on the first print, the first layer didn't seem right, that's why I configured Z again, and in that regard, I think the new setting works best.

Fearless as I am I gave it a try to the tree frog, and here is the result:
https://imgur.com/PmZLSL3
https://imgur.com/0zMWZMH
Front right leg is a mess, but the same layers on the front left leg are perfect. ¿¿??

I seem to have a few x axis shifting on the first layers -that's the name the prusa team gave it on the first prints troubleshoot page- but then is fixed. 

Also, the picture is not very clear, but the back left leg is quite messy while the back right leg is ok-ish.

In case it helps, I have printed a couple other models, and there are always messy parts on the left side of the model, no idea why.

 

Can you please help me identify these issues ?

Thanks in advanced!

 

 

Posted : 31/10/2020 4:46 pm
Dave
(@dave-7)
New Member

It looks like you are having semi-random mechanical slippage on x or y drivetrain.   You said this was a fresh build from kit,  have you gone over all the screws to check tightness?  I'd start at the two set screws that hold the pulley cogs to the stepper motors.   They may not be holding under speed.

Assembling the X-axis motor pulley (part 1)

Posted : 31/10/2020 5:45 pm
--
 -2
(@-2)
Illustrious Member

The images show two likely issues:

Common problem for skips are:

Bearings held too tight. If the skip is X (right left) then loosen the screws near the bearings on the back of the extruder. If the skip is Y (front back) then check the U-bolts: they should be snug, not tight.

Lack of grease of the bearings (they really need to be packed with grease before installation). Place a few drops of oil on the rod and move the extruder back and forth a few time to work the oil past the grease seals and into the bearings. Do this for X and Y.

Common problem for large skip minor layer shifting:

Loose drive gears: if they are installed without following the FLAT-FIRST rule, they aren't really tight and will come loose. To install the gears, start with both set screws loose so the gear can spin freely. Then align and tighten the  set screw on to the flat of the shaft. Then, and only then, tighten the jam set screw.  You're done. To remove, loosen the jam set screw first, then the set screw on the flat.

Belts are loose: belts need to be tensioned to about 6 lbf - the LCD menu for belt tension is, well, a joke. Those numbers are fairly useless.  Great for showing a sticky bearings and axis friction, but not good for belt tension. Easiest way to gauge tension is to

1) Move the extruder far left, bed far back
2) Apply 200 grams force on the center of the lower belt of the pair
3) Adjust tension so the X belt deflects about 6 mm, the Y belt about 5 mm (about a quarter inch for both).

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 31/10/2020 8:12 pm
Dave liked
Nexusmarit
(@nexusmarit)
New Member

Thanks for your directions, I'll check the motors , the bearings, and the belts.  

Additional information, yesterday when I first run the xyz calibration I got a perpendicular result (yay), however today I tried to recalibrate and it failed. 

🙁

The only thing I have done is the first few prints but until now I haven't touch the hardware so I'm quite puzzled as why today it fails when yesterday the result was great.

 

Posted : 31/10/2020 10:15 pm
Nexusmarit
(@nexusmarit)
New Member

@naz615 @tim-m30

Thank you both for you help.  Following your advice I was ablet o locate the issue. One of the screws on the X-axis pulley was loose and causing moset of the issues.

The XYZ calibration issue was most likely due to zip tides bumping into the power source case. Tightening and reposition the locks solved the problem

I'm pretty happy with the results:

Tree frog comparison:
Side: https://imgur.com/EJITZtl
Front: https://imgur.com/MPq5QUC

 

 

Posted : 01/11/2020 3:52 pm
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