Layers not connecting to the wall

Snapmaker 2.0
1

I switched brands of filament and started to have nightmares printing. I also changed my model around the same time so I have been chasing issues ever since. Gotten most ironed out at this point but my layers are not connecting to my walls. It is always the same spots. I am starting to wonder if it may be a bug in cura/luban.

Temp 205/60 to 205/50 after first layer with 1.4 walls.

What I know it is not.

Unlevel bed - printing on glass
Under extrusion - have calibrated with this filament
Layer adhesion - it is always happening in the same place on glass and the print plate.

Known issues

Lots of play in the print head - I am getting 1 to 1.5 degrees of wobble in the print head when going left to right. Have opened a support ticket. Still waiting for first contact.

Thing I have thought-

Partially clogged nozzle? Have been printing on the same head for 6-7 months
The head wobble
Bug in cura.

Hey guys I need help I have tried everything I can think of at this point.

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2

in addition to the great things others will post, could you do this test after bed levelling head is not consistent height when jogged - YouTube and see if you have same issue (you may need to do it at each calibration point) - the point of the test is to see if the z-offset at each measured point feels the same on the card or not. (i have open support case on this, want to see if others have the same issue).

3

It kinda looks like itā€™s under extruding, but only in certain locations. It is consistent about where itā€™s under extruding, or does it vary layer to layer?

If itā€™s the same places every layer, it could be a filament feed issue. Like the filament is binding up on something and not able to feed at the proper rater. If itā€™s random every layer / attempt, it could be a filament quality issue. If the filamentā€™s diameter varies, it can cause problems.

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4

You are right. I ended up doing the rail righting process last night and moves the filament inside the enclosure.

I am 99% sure that the tension from a tightly wound filament out side the enclosure was causing all of my issues. This frustrates me as that was my guess nearly 2 weeks ago but was told that couldnā€™t be the problem on the Facebook group.

Snapmaker really needs to consider redesigning the filament feeding process for the enclosure. It is bad when cheap filament performs better because it is wound less tightly.

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Thanks for the encouragement to go back to my first guess at the problem.

5

yes the facebook group has a tendency to dismiss issues, blame users and the snapmaker machine is handed down from on high as a perfectly constructed thing made by angels.

Can you tell i have PTSD from them :slight_smile: glad you got issue identified, now wondering if any of my issues have been caused by the same thing.

Would a bowden tube (is that what those silcone tubes are called?) help reduce friction?

6

Hereā€™s my solution:

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7

You can try this and remove all the friction.

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8

thanks, do you have a guide you are using inside the enclosure that you prefer too? (i currently use the one that looks like a huge slot)

PTFE ordered on its way :slight_smile:

9

I like this one, with a vinyl sticker wrapped on the bottom lip to reduce friction further

I will say I broke one of them so print it with a higher infill density.

10

thanks, yes thatā€™s the one i am using, good tip on the vinyl sticker, thanks

11

I am not using one right now as it was for testing. If I have to print tall and wide items at some point I will redesign and put one in but where it stands now and the height of my models it is not needed.

12

Thatā€™s what people call them, but their usage is just plain wrong. A proper Bowden cable is used to transmit force, and the tube is what the cable rides in (and constrains the force the cable exerts). The usage that most people have seen is brake cables on bicycles. Bowden cable - Wikipedia

A more proper name for these tubes is a ā€œfeed tubeā€. The most common analogy is wire-feed welders (either with flux or with shielding gas), where the material to be added to the joint is pushed through a feed tube as part of an integrated whip that also transmits electrical power and (often) shielding gas.

A filament moving in free air experience almost no friction; a filament moving through a feed tube does have friction. So it doesnā€™t remove friction, but adds it.

What it does do is to reduce variation in the force required to pull filament off a spool. For example, filament grinding is what happens when the force required to overcome, say, a tangled spool is greater than what the feed roller in the FDM head can manage. Using a feed tube creates a predictable feed path so that bad accidents in filament geometry donā€™t cause problems.

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13

All of that plus additionally the enclosureā€™s sharp plastic edges create a lot of drag as the filament enters taking a 90 degree turn. The tube at the entrance greatly reduces that friction

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