What caused this 'shifting' when printing?

[Tim]

Testy, perhaps, but also with the useful tip that tightening the set screw may not solve the problem if the loose set screw has ground into the shaft behind it, in which case you will likely have to file the shaft down flat before the set screw will hold it properly.

[ednisley]

Hooray. A patronizing reply. So helpful.

Forgive me; six hours of driving around a day trip to The Relatives does that.

Next time, I'll sleep on it for a few days...

[metrons]

So I tried a new print over the weekend after tightening the X motor screw.

Something interesting happened. It printed with the exact same shifting on the latest print...so I took a look at some of my other prints that I've done and I noticed it does the shifting in the exact same area as well? So I don't think it's those little screws on the X & Y motors I have no clue what could be causing the shifting in the same spot for all of these prints?

[metrons]

i'm about to put on the loctite for the pulley screws and i thought i'd see what you guys think about the tension of the rubber bands on the motors? i'm applying my finger to the bands with basically no pressure and they move that much.






i'm not sure if thats normal, loose, needs to be firmer? hoping to get more amazing advice from the community. so tired of the shifting printing...

[jimc]

the belts are a tough thing to explain how tight they should be. if you pluck one with your finger like a guitar string there should be a slight twang......if that helps. they should not be floppy nor should they be extremely tight. too tight can cause missed steps from the excess force required for the motor to move. on the x axis, too tight a belt can also cause the top the the printer and rail to deflect causing the hotend to get closer or farther away from the bed in the center of its travel. another thing to mention is that if the steps are happening in the exact same place on the model each time you print it then thats a good sign that its a fault in the model or gcode. do this happen at the same z height on other models?

[metrons]

I printed something a month ago and saw it had the same skip heights compared to the one I printed last night. It's really odd and frustrating.

Have an idea for that g code error you speak of? Some s3d calibration?

Cheers

[jimc]

No, it would be an error or problem with the model itself causing a slicer to produce bad gcode. If it does it with a different stl file of a different model and its at the same height then i doubt it would be a problem unless you have something strange going on where your using multiple processes and those are the process change layers.

[Tim]

If you're using Simplify3D, then any error that is caused by the slicer would show up in the toolpath. While I've seen their slicer do some very weird/bad things, I've never seen the toolpath view show anything other than the exact path the extruder will take. So if the shift doesn't show up in the toolpath, then it's mechanical.

Also I'd like to point out that I had a shift caused by a cracked motor mount that was very confusing for a while because it, too, produced a shift in exactly the same place on a print several times in a row. It's because the extruder wasn't so loose that it was shifting around all the time; it took a bit of pressure against the side of the nozzle to knock it slightly askew. That pressure came from an overhang on the print, where the plastic over the overhang area would tend to curl up. There was one point in the print where the movement of the extruder would bring it up broadside against the edge of the curled up plastic, and that's where it would get knocked out of alignment, at the exact same point, time after time. I'm not saying that that's your problem, but just to let you know that there are times when a problem looks exactly like one thing but is actually something entirely different.

[metrons]

I've screwed in the pulley screw with loctite. Can someone tell me if my extruder looks normal?

https://www.dropbox.com/s/58f1zo2dx87ym ... 7.mp4?dl=0

I'm slightly trying to rotate it and move back and forth. It moves very easily. I'm not sure if this is normal or not? My printer has always done this.

I looked at the extruder mount and tried to find a way to secure the extruder. I could tell find anything that it's supposed to tighten to. This is why I'm assuming this is normal. No idea.

Can someone enlighten me again please. Looking to get all the bugs worked out before I print again.

Cheers

[jimc]

It is supposed to rotate fairly easily but shouldnt wiggle back and forth quite that easily or atleast how easy it looks in the pic. I dont think this is your layer shifting though. Layer shifting is and abrubt change which stays in place. The wiggling would just cause irregular perimeters or print artifacts where layers wouldnt quite line up. Basically print quality would not be real clean. You should put a filament drive first on your list though of things to print to remove that slop.