Cyclical Under extrusion???  

Re: Cyclical Under extrusion???

I'd take a close look at the extruder gears. This looks like it could be happening roughly once every turn of the extruder stepper, which makes me suspicious that there's something causing it to lose it's grip at the same point every rotation.

For example, there could be a piece of debris on the Bondtech that pushes the two gears slightly apart when the debris comes between the gears.

Re: Cyclical Under extrusion???

Thanks for the feedback, I have done cleaning and first layer is good. But when it moves towards the next layer it reappears.

The speed of the next layer is significantly faster, however, it seems to be the same issue.

The pulsation could have been contributed to by the gears, however I am wondering if it is also due to speed of the flow?? Sorry, I'm guessing so not sure.

Regards,
Andrew

Re: Cyclical Under extrusion???

Thanks for the feedback, I have done cleaning and first layer is good. But when it moves towards the next layer it reappears.

The speed of the next layer is significantly faster, however, it seems to be the same issue.

The pulsation could have been contributed to by the gears, however I am wondering if it is also due to speed of the flow?? Sorry, I'm guessing so not sure.

Regards,
Andrew

someone else had a VERY similar issue. I have NO idea how this can happen... you seem receptive to DIY fix it... so help us help you. 😉

I have an idea, that didn't get answered the last time I saw this happen...

Look into your feed assembly. (maybe with a camera would be easier?) and turn the extruder. (no need for filament) EDIT: E-AXIS under the move axis menu... your not gonna turn it by hand. 😉

Does the bondtech gear on the RIGHT side of the assembly, the one mounted to the stepper motor, have a "wobble" to it?

The only thing that makes sense is a "shaft" is bent. there's two shafts. the idler shaft, and the motor shaft. If the idler shaft was bent, I would not think it would cause this issue, however if the motor shaft is bent... it makes perfect sense.

The concept of a cyclic issue like that is nearly impossible.

E.g. if the coast gear, was crooked, it would either always be loose and slip... Or be or Still work Fine.
Exact same story with the motor shaft. Even if it's assembled wrong,and crooked, it will be all or nothing.

The ONLY thing that could cause it, that I can envision, is a bent motor shaft.

Re: Cyclical Under extrusion???

I have checked the shaft, and it "looks" ok. Just wondering could it be a bad batch of filament??? Something consistently incorrect in the filament by a length?

I noticed that there was some discussion around the PID sensor and that temperature could be an issue playing with prints. Again, just throwing things out there...

Re: Cyclical Under extrusion???

I have checked the shaft, and it "looks" ok. Just wondering could it be a bad batch of filament??? Something consistently incorrect in the filament by a length?

I noticed that there was some discussion around the PID sensor and that temperature could be an issue playing with prints. Again, just throwing things out there...

I have some 1.70mm... uhhh.... .... "you are an idiot and using that WILL CLOG YOUR NOZZLE"-ment... and uhhh.... let's just say the bondtech gears have NO issues feeing that consistently.

If you run your fingers along your filament and don't feel a "ripple" effect, it's not your filament doing that. Makes no sense.

it COULD be cold-extrusion... in fact that's almost EXACTLY what it looks like.

Easy solution to test that.

Crank your layers up to 225c. (yes it's hot, yes, it would be ugly, and string to the ends of the earth...) But if it's extruding smooth, we found the issue. If it prints the same even at those temps, there's no way it's thermal.

Watching Octoprint... My hot end, bounces around a whopping ±1c... You may watch the temp on your printer, and see if it's bouncing around a whole lot. If it is, you need to recalibrate your... stuff... which I have *NO* idea how to do... So I'm not the person to ask for that. lol

Re: Cyclical Under extrusion???

Firstly, thanks for your help. I can see what you are talking about regarding "cold extrusion". This is where experience counts...

Ok, so I have done a couple of things, and I know this is not good problem solving process, however, completed the following:

1. Dropped the PINDI probe a little lower and confirmed that it is lower as the test print has reduced the number for squish what I think is good print.
2. Recalibrated the printer again with this change.
2. I upped the print temp to 220 and this definitely helped. Smooth print.
3. Upped to 225 for a short period and could not see any significant change in the benefit over 220.

Even 220 may be a little high: Just.... it is sitting at 215 for the base print then 210 for the next level.

So I will continue to test this out and see if this is indeed the issue. But so far it looks like it is.

Regards,
Andrew.

Re: Cyclical Under extrusion???

Firstly, thanks for your help. I can see what you are talking about regarding "cold extrusion". This is where experience counts...

Ok, so I have done a couple of things, and I know this is not good problem solving process, however, completed the following:

1. Dropped the PINDI probe a little lower and confirmed that it is lower as the test print has reduced the number for squish what I think is good print.
2. Recalibrated the printer again with this change.
2. I upped the print temp to 220 and this definitely helped. Smooth print.
3. Upped to 225 for a short period and could not see any significant change in the benefit over 220.

Even 220 may be a little high: Just.... it is sitting at 215 for the base print then 210 for the next level.

So I will continue to test this out and see if this is indeed the issue. But so far it looks like it is.

Regards,
Andrew.

I'm not sure how to do it, so I don't wanna steer you in the wrong way, but I'm thinking you need to do a "PID Tune". My printer just worked out of the box regarding this, but this may be your solution.

Re: Cyclical Under extrusion???

Yep, I hear you. I am tending to agree with you.

At present running 215 on bed and 220 on rest.

Working fine, but this PID tune I think has something to do with it.

Now to start getting experience. 🙂

Thanks for the help. Now the Easter Break is not just frustration hahahahaha..

Regards,
Andrew

Re: Cyclical Under extrusion???

Well Issue is back and is worse when on fast speed printing...

I have not changed anything.

All that has been done is that I have turned it off and later in the day turned it back on, pre-heated the bed for 10 minutes and noticed the following:

1. Small prints OK, if not good.
2. When completing 1st layer, all looks good.
3. When doing the 2nd and subsequent layers, periodic problem in layer occurs.

NOTE: Occured on different prints using latest Slic3r to generate GCode.

Hypothesis testing:
1. "Cold extrusion" is the problem: tested by increasing the temperature up to 225. No change. Increased flow rate to 120, no change. In fact may have got worse. Set back to 210. No change.
2. Gears are not cleaned: Cleaned Gears, no change.
3. Head is dropping height: Put fingers onto Z-Axis screws, noticed changing Z positions.

I'm at a standstill.

I am thinking that I will need to reset from the start yet again to see if this helps, however, I am starting to believe this is a basic issue.

I am a noob so really needing help with this. 🙁

Re: Cyclical Under extrusion???

Well the printer seems to have problems pushing enough filament fast enough. The first layer is probably working better, because it's printing slower and the extruder doesn't have to do so much work. It explains also, why increasing the flowrate makes things worse.
Does the extruder motor click when underextruding? If he does he doesn't have enough force to drive the filament at the speeds requested.

My first guess would be, that you are printing too cold but you say you allready checked that. Your nozzle may also be clogged and you would need to clean it like that.

Re: Cyclical Under extrusion???

Ok, so basically, I'm an idiot and there is nothing wrong with the printer..... or at least not as yet. So basically my apologies for wasting peoples time. Thanks for the help.

So the issue: I did not include the nuts in the Idler Assembly...... What a d%7kh&8d!!!

Basically what was happening is that at slow speeds the Idler Plug provided enough tension to hold the Idler door in and enough pressure on the filament to ensure correct printing, however, when speed was increased the filament must have been "slipping".... Ahh!!!

What has occured in the meantime is that I have added some lithium grease to the idler bondtec Pulleys and bearings...
Learned more about the possible issues associated with "cold extrusion".... will know it next time...
Learned a bit more regarding flow rates etc.... some interesting experimentation...

Again, apologies for the wasting of peoples time. I will do better next time. 🙂