Solved Potemkin - print: great front, messed up back...

[Upperbottom]

I need some help to start debugging my printer with some VFA:s

After one year it was time to upgrade my printer, the quality was bad, terrible VFA mostly wood-grain and I couldn't fix it.
After the teardown a part of the problem was obvious: I had too much gear-mesh in the past in the CW2 and ground down my main-gear, so even adjusting that would not help since the. gear was ground down on one side.

To prevent future cable-beaks and get a cleaner build I went Canbus and a new CW2 with helical gear.
After basic tests and doing some dial-ins (e-steps, first layer, pressure-advance, extrusion multiplier and input shaper) I printed a "mihaid-wedge" to see if i still had VFA.
Good news: no more woodgrain!
Bad news: the VFA in the X-axis front facing wall is gone, in the y-axis I got a diagnoal wavy pattern towards the back of the print which leads to artefacts in the back-facing wall of the wedge
(se image below the front is facing towards the lightsource) .


The error is even visible when printing a cylinder in vase-mode (print parameters in the end)
Front: Nice

Back: not so much


What I think are possible causes:
1. Gantry racked
2. Belts uneven
3. Insufficient cooling
4. bad/insufficiently lubed linear rails

Parameters:
Orca Slicer
PLA
.4 nozzle
210 degrees print temp
60 degrees bed temp
print speed: outer wall 120mm/s*, 3000mm/s2 accel
open printer

*due to layer time limits the wedge first printed at about 7 mm/s but i manually upped the speed 600% so about 56mm/s, the cylinder printed at roughly 108mm/s after reducing the layer time from 8 to 1 second

 

[NoGuru]

That wood grain looks like extruder. It could be some of the things you listed but I am leaning towards extruder.

 

[Upperbottom]

Maybe.. but why only in the y-direction/back...
If it were extruder it should be visible all around, especially on the wedge.

 

[NoGuru]

Maybe.. but why only in the y-direction/back...
If it were extruder it should be visible all around, especially on the wedge.

Good point.
When the motors are not energized, does the toolhead move freely? Like no binding at all?
Maybe an idler is too tight?

 

[Upperbottom]

Yup!.. have to test that, I'll basically redo everything from gantry racking, belt tension and all the rest... Unfortunately I'm off to vacation (wait! that's NOT unfortunate so it'll be a couple of weeks before I'm able to work on the machine...

 

[NoGuru]

Yup!.. have to test that, I'll basically redo everything from gantry racking, belt tension and all the rest... Unfortunately I'm off to vacation (wait! that's NOT unfortunate so it'll be a couple of weeks before I'm able to work on the machine...

lol, enjoy your vacation and we can pickup when you return.

 

[Badnoob]

make sure you are at 100% part cooling fan. if you slow down, does the problem go away?

 

[Upperbottom]

Sorry.. I forgot about this thread....
I de-racked and had indeed some tension in my system.. but that was not the problem:

I solved it by simply tensioning the grip on the gear tensioner, and also screwing in the "Anti-Squish-Thingmajig"... yea..

the filament was loosy-goosy so everytime the y-axis moved forward it was enough extra friction to affect the feed rate.. while mowing back the friction released and the feed-rate was fine...

After adjusting it's fine.. I still have some minor artefact, but that is probably due to belt tension and lubrication (rather lack thereof) of the linear rails.