Offset problem at first print with N2+

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jonatan.jacobsson
Posts: 5
Joined: Wed Apr 04, 2018 5:13 am

Offset problem at first print with N2+

Postby jonatan.jacobsson » Wed Apr 04, 2018 5:24 am

Hi!

We bought a Raise3D N2+ at work. It arrived yesterday and after the calibrationcube of 2x2x1cm got printed perfectly, i decided to give the printer a real challenge to test its features.

So i printed the eiffeltower featured on thingiverse: https://www.thingiverse.com/thing:912478
Sliced it with template called "High Quality - N2 Plus - PLA"
PLA 205 degrees (Raise3D Premium White Filament, that comes with the printer)
Bed 60 degrees

Some hours later into the print something went wrong, se attached image.

At first i thought that the X-belt tension was set to low, but i flicked it and it didnt seem that loose.
What do you guys think it could it be?
Skipped steps on the motor?
Aprox. 1cm offset in the X-axis.

Again, this is the first print, so im not that dissapointed :)
Attachments
IMG_1016.JPG

jonatan.jacobsson
Posts: 5
Joined: Wed Apr 04, 2018 5:13 am

Re: Offset problem at first print with N2+

Postby jonatan.jacobsson » Wed Apr 04, 2018 10:47 am

I just read the FAQ. It seems like a misalignment of the gantry is a possible problem.
Is there any guide to realign the gantry avaliable on the forums?

Jetguy
Posts: 2697
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: Offset problem at first print with N2+

Postby Jetguy » Wed Apr 04, 2018 1:15 pm

Exact same STL, just scaled bigger, same basic failure, same basic solution viewtopic.php?f=8&t=7093#p28312

Or a more direct link to the suggestions for overhangs
viewtopic.php?f=8&t=7176#p28307

jonatan.jacobsson
Posts: 5
Joined: Wed Apr 04, 2018 5:13 am

Re: Offset problem at first print with N2+

Postby jonatan.jacobsson » Thu Apr 05, 2018 7:05 am

Thanks for the tip!
Ill try removing the right nozzle next time. Thanks!

Jetguy
Posts: 2697
Joined: Tue Mar 22, 2016 1:40 am
Location: In a van, down by the river

Re: Offset problem at first print with N2+

Postby Jetguy » Thu Apr 05, 2018 8:45 am

jonatan.jacobsson wrote:I just read the FAQ. It seems like a misalignment of the gantry is a possible problem.
Is there any guide to realign the gantry avaliable on the forums?


No, actually, I would not say this was the problem. Here's the logic and stuff you flat out need to know operating 99.9995 of all consumer 3D printers.
#1 They use stepper motors without feedback of position for cost and complexity reasons. If you have position feedback- that is called servo because you have a control loop where you have data feeding back into control. It's a personal gripe of mine when a total noob calls a stepper motor a servo and lets me know up front they haven't done even basic homework (I'm not in any way saying this about you, just making a general statement). A stepper motor is a simple 2 phase motor with no electronics or brushes. They are made in such a way that they are very good to go to exact positions or steps of a rotation VS a motor made to just continuously rotate- hence the name stepper. The key here is "the massive assumption" that since there is no feedback (we call this open loop control system), the stepper driver just keeps stepping the coils to rotate the magnetic field alignment and that the rotor and thus shaft follow that alignment. This all goes to plan as long as the load is less than the torque and speed capabilities of the motor. However, if load (friction or dynamic) exceeds the motors torque, a step is skipped and now every position after that is shifted. The way I like to describe it is a giant game of Simon says. The 3D printer controller is reading the print gcode file line by line and sending step and direction commands to the stepper drivers. This is again, like Simon saying move 10 steps back, then 6 steps front, then 20 steps back, then 30 steps right, then 40 steps left and so forth. If you make a mistake on any one move, all moves after that are shifted.
#2 So if you have bad layer warping from a failed overhang, and you have the second nozzle and it catches, that is the dynamic part of load or a nozzle strike. It's also possible to attempt to move too fast and that can cause a skip, but is rarer.

So, just looking at your print and why I can say with confidence in troubleshooting why gantry alignment is NOT the likely answer.
If you had multiple skipped steps at different layer heights and this happened over and over and over no matter what model you printed- that points to excessive and binding friction in a misaligned gantry.
If you only have one or 2 skips, and they correspond to a certain layer type or position on a model like an overhang or bridging section- then nozzle strike is far more likely the answer.

zemlin
Posts: 354
Joined: Sat Oct 21, 2017 2:02 pm

Re: Offset problem at first print with N2+

Postby zemlin » Thu Apr 05, 2018 4:31 pm

I also think some support is in order for the lower arches.
I looked around at some of the other examples of this part being printed and didn't see anyone running support, but almost all of them have significant droopage at the top of the arches.

jonatan.jacobsson
Posts: 5
Joined: Wed Apr 04, 2018 5:13 am

Re: Offset problem at first print with N2+

Postby jonatan.jacobsson » Fri Apr 06, 2018 5:19 am

@Jetguy, surely the overhang caused this. The reason why i concluded that it could be a missalignment and later realigned the gantry, was because i couldnt manually move the extruder close to X=0 - but at X=~300 the extruder moved freely. But again, the overhang looks to be the cause of this :)

@zemlin, yeah, some additional support would probably fix the issue quite easily.

Thanks for the help!

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robpauza
Posts: 59
Joined: Wed Apr 20, 2016 11:50 pm

Re: Offset problem at first print with N2+

Postby robpauza » Sat Apr 07, 2018 1:42 pm

Hi Jonatan. I think Jetguy is agreeing with you that it was in fact a glob of filament that caused either the primary or second extruder to catch and skip about a centimeter on the X and/or Y stepper motor(s). Since the motors have no positioning feedback, it continued printing thinking everything was fine. I'm actually pretty impressed that it continued printing as well as it did after getting offtrack.

Anyway, I agree with him. The best solution I've found is to slow down your print speed and move that second nozzle up out of the way to minimize it hitting something.


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