Stringing with PLA
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@toddm said in Stringing with PLA:
What would you change first?
Both at 195C on the extruder,I always run at 210'C for PLA and get excellent results!
To me it looks like the stringing is as the plastic is not molten enough, so stretching rather than separating as a liquid. -
@toddm 20mm/s max extruder speed you've specified is probably the cause of your problem: it's too slow for retraction. I run 40mm/s, 4-6mm retract on my bowden with PLA anywhere from 195 to 230 deg. I have yet to find PLA that's reliably happy under 190 myself.
Try at least E2400 in M203, with slicer settings to match. FWIW: My experience has been that the retract speed is just as important as distance, if not more so.
Let us know how you get on!
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Thanks for all of the tips! I have Changed to 1/16 micro stepping, adjusted the max extruder speed to allow 45mm/s as called for in Cura (good catch Lo-Fi) and started running at 210C.
The calibration cube looks better in some respects especially the sidewalls. There is not nearly as much over extrusion and the layers look flat. The infill has gaps and does not appear to be extruding properly and the top 2 layers are way too light. You can also see the ripples in the outer wall from where the nozzle is getting bumped out of its path by dollops left from the ends of the infill lines. I'll include the G code that I used since I didn't save the slicer settings. The black mark is where I turned on Pressure advance at 0.5.
SRMAXV32_xyzCalibration_cube 210C.gcode
Next up is the stringing tests. The one on the left is pressure advance off and the one on the right is pressure advance at 0.5.
Current Config.G:; Configuration file for Duet 3 Mini 5+ (firmware version 3.3) ; executed by the firmware on start-up ; ; generated by RepRapFirmware Configuration Tool v3.3.10 on Mon Mar 21 2022 07:51:19 GMT-0500 (Central Daylight Time) ; General preferences G90 ; send absolute coordinates... M83 ; ...but relative extruder moves M550 P"My Printer" ; set printer name M665 R142.875 L288.08 B133.35 H335 ; Set delta radius, diagonal rod length, printable radius and homed height M666 X0 Y0 Z0 ; put your endstop adjustments here, or let auto calibration find them ; Network M552 S1 ; enable network M586 P0 S1 ; enable HTTP M586 P1 S0 ; disable FTP M586 P2 S0 ; disable Telnet ; Drives M569 P0.0 S0 ; physical drive 0.0 goes forwards M569 P0.1 S1 ; physical drive 0.1 goes forwards M569 P0.2 S0 ; physical drive 0.2 goes forwards M569 P0.3 S0 ; physical drive 0.3 goes forwards M584 X0.0 Y0.1 Z0.2 E0.3 ; set drive mapping M350 X16 Y16 Z16 E16 I1 ; configure microstepping without interpolation M92 X80.00 Y80.00 Z80.00 E94.4 ; set steps per mm M566 X1200.00 Y1200.00 Z1200.00 E2700.00 ; set maximum instantaneous speed changes (mm/min) M203 X18000.00 Y18000.00 Z18000.00 E2700.00 ; set maximum speeds (mm/min) M201 X1000.00 Y1000.00 Z1000.00 E1000.00 ; set accelerations (mm/s^2) M906 X1200 Y1200 Z1200 E1900 I30 ; set motor currents (mA) and motor idle factor in per cent M84 S30 ; Set idle timeout ; Axis Limits M208 Z0 S1 ; set minimum Z ; Endstops M574 X2 S1 P"io0.in" ; configure switch-type (e.g. microswitch) endstop for high end on X via pin io0.in M574 Y2 S1 P"io1.in" ; configure switch-type (e.g. microswitch) endstop for high end on Y via pin io1.in M574 Z2 S1 P"io2.in" ; configure switch-type (e.g. microswitch) endstop for high end on Z via pin io2.in ; Z-Probe M558 P8 R0.4 C"io3.in+io3.out" H5 F1200 T6000 B1 ; set Z probe type to effector and the dive height + speeds, B1 turns off the bed heater during probing to stop the noise. ;M558 H30 ;*** Remove this line after delta calibration has been done and new delta parameters have been saved G31 P100 X0 Y0 Z -0.3 ; set Z probe trigger value, offset and trigger height M557 R85 S20 ; define mesh grid ; Heaters M308 S0 P"temp1" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin temp1 M950 H0 C"out0" T0 ; create bed heater output on out0 and map it to sensor 0 M307 H0 B1 S1.00 F100 ; enable bang-bang mode for the bed heater and set PWM limit M140 H0 ; map heated bed to heater 0 M143 H0 S120 ; set temperature limit for heater 0 to 120C M308 S1 P"temp0" Y"thermistor" T100000 B4138 ; configure sensor 1 as thermistor on pin temp0 M950 H1 C"out1" T1 ; create nozzle heater output on out1 and map it to sensor 1 M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit M143 H1 S280 ; set temperature limit for heater 1 to 280C ; Fans M950 F0 C"out3" Q500 ; create fan 0 on pin out3 and set its frequency LAYER M106 P0 S1 H-1 B0.5 ; set fan 0 value. Thermostatic control is turned off M950 F1 C"out4" Q500 ; create fan 1 on pin out4 and set its frequency HOT END M106 P1 S1 H1 T40 B0.5 ; set fan 1 value. Thermostatic control is turned off ; Tools M563 P0 D0 H1 F0 ; define tool 0 G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C ; Custom settings are not defined ; Miscellaneous M501 ; load saved parameters from non-volatile memory -
I then calibrated the extruder using the method Paedrux linked to above. I printed the object recommended with the recommended settings and had some weird results:
The brim was over extruding (?) and smearing on one corner and along one side, but the area where it was the thinnest due to my build plate not being flat (?) did not smear. Its definitely the thicker parts of the brim that had issues. On the walls there are adhesion issues/under extrusion that tended to get better as it printed. By the time it got to the seam it looked pretty good on the inner wall. The outer wall has the same look to it but it would start out looking good and get worse as it made its way closer to the seam. Both inner and outer walls were printing CCW except the first or second layer. I tried to get some light behind the print so you could see the patterns of gaps.
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@toddm I’ve only seen such a weird print "quality" on my printer in two cases: once with some screws coming loose - clearly mechanical problems with two axes playing havoc … and once with a filament which drove me nuts: over- and under-extrusion, blurbs, stringing, clogged nozzle … short: a hell in 3D.
I suggest you to check the mechanics of your printer carefully - forget any tuning and tweaking as long as the basics do not work properly. Every printer should be able to deposit some filament in a somehow regular fashion - slow, surely not perfect, but - more or less - reliable.
Without PA and all the other bells and whistles RRF (or the slicer) has to offer, any printer must be able to lay down evenly formed extrusions in an ordered way, at least at low speeds (20-40 mm/s max).
If that doesn’t work, try another filament. Sorry that I can’t be more specific, but your pictures tell me at least two stories: mechanical issues and erratical extrusion - the third story could be about speed …
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Can you post a video of that print in action?
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@infiniteloop I tend to agree with you. I was watching it put down a first layer and the extrusion is inconsistent, some of it is obviously squeezing out past the nozzle making a wider track and bunching up and some of it is just barely stringing and not even bonding to the bed. I was trying to figure out if it was related to speed or just the extruder. This printer is not very rigid in my opinion, but slow speeds like you mentioned should be ok I would think? I tightened all the bolts holding the uprights to the base and the top a few weeks ago. The rounded off square print above was printed at 30mm/s at the fastest. The outer layer was only 15mm/s ( I missed that in the slicer settings, intending it to all be 30mm/s). I have also thought about moving the extruder from the top of the machine to about halfway down so I can use a shorter bowden tube. Its about 700mm right now. The frustrating thing is that this printer worked a few months ago before all of the upgrades (aside from stringing), but the stock PEEK heatsink in the hot end melted and destroyed the hot end. That was why I decided to upgrade everything. That might have been a mistake!
I have some older PETG and various other spools of PLA. The white PLA I'm using was fresh out of the bag a few weeks ago after I gave up on the older spool I was using. The new spool made no difference.
Last night I read that a partially clogged nozzle could possibly cause this. I have noticed that if I just extrude plastic at the max rate, about 6.5mm/s that it almost always curls back to the tip of the nozzle and it will also get really thick after a few seconds especially after the end of the plastic makes contact with the bed. I am running it really hard at that point, the extruder will start skipping at 6.7mm/s. While taking the nozzle out I broke the ground wire to the hot end fan. Now I need to find a way to release the broken pin so I can crimp on another one. Once the wire broke, I shut it off and walked away.
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@toddm said in Stringing with PLA:
Once the wire broke, I shut it off and walked away.
Sorry for the lack of luck with your printer - more than enough reasons to walk away. I had a similar run when I started to print with a fresh roll of PETG - never had problems with PETG so far, but with that material, everything went wrong. I ended up with wild theories, replaced many parts of my print head (and some other mechanics as well), tried zillions of adjustments in RRF - to no avail. With some PETG from another manufacturer, the problems finally vanished over night.
PLA is more forgiving, but more hygroscopic as well. Old PLA can often be revived by drying it at around 50 °C in an oven for 4-6 hours. But if the manufacturer can’t hold the diameter within very narrow limits, you have no chance to get a proper extrusion. Happened to me.
The good thing about those struggles is that we learn a lot about our printers - one thing, for example, is to print slowly in order to achieve good quality for cheap. 20 vs. 40 mm/s can make a huge difference with fine details. Of course, a long bowden (mine has 700 mm, too) promotes stringing, but in your case, that is a secondary problem.
First, bring up your hotend again. Then, use some other filament. This is especially true if you encountered a partially clogged nozzle: you’re right with your suspicion, that can cause all kinds of trouble - but it should not happen at all, as long as the chemistry of the filament works. If not, some ingredients burn to debris which accumulates on the walls of the heat break and the nozzle itself.
One final thought: In most cases, even the most complex intricacies have a simple reason - which you will know when you find it
. Wish you luck on that way. 
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@toddm, I have found out that the point where the extruder skips is not the limit. Even before that, you run into irregularities with flow. Having said that, if 6.7 mm/sec gives you extruder skipping, I would think 5 mm/sec should be safe.
I would also check the entire filament path - how easy is it for the extruder to pull filament off the spool? A long Bowden tube can introduce a lot of friction and how easy does the spool unroll? Have you checked tension on your feed rollers? You could have insufficient pinch pressure on the feed rollers introducing variable flow.
30 mm/sec should be achievable by a printer built with chop sticks
You could try a 'cold pull' on the nozzle. I would be tempted to remove the nozzle and see if filament easy easily pushed through the print head - there should be no obstruction with the nozzle removed. You could try a new nozzle or, if you have a brass nozzle and a plumbers torch handy, burning out the nozzle always clears things up for me.
Anther, less likely reason for inconsistency - Is your slicer set to the right filament diameter (I overlooked that once)?
Looking at your pictures, it seems that filament is laid down properly in one direction but the layers get really bad in another direction - that would seem to indicate mechanical slop in one direction but not the other. I think I would tend to ignore mechanical issues with head positioning at this point and try to concentrate on one issue at the time which would be filament flow. There are a lot of possible problem areas in a 3D printer and unless you tackle them one by one it can get very overwhelming and basically impossible to work out what is going on.
Good luck .... don't tear out too many hairs during trouble shooting .... -
@infiniteloop Thanks for all of your suggestions and encouragement! I fixed the wiring and loaded up my spool of PETG, made the slicer print everything at 30mm/s and got this:
This looks much better to me. One side had a small section where the layers didn't bond very well, but overall it makes me happy! I didn't even calibrate the extruder! It needs some tuning still but at least its consistent! I need to find some better PLA. I'll probably throw what I have in the vacuum oven for a bit, but I think its probably a lost cause.
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@toddm that does indeed look a lot better. I wonder why there appears to be diagonal lines on the verticals.
There also seems like a bit of under extrusion between the brim and the model in your first picture.
Looks like there needs to be some pressure advance tuning to improve the vertical seam.
The bottom line though is that you have something that you can work with! Good show! -
@toddm Great! As @Jens55 said, now you have something to work with. Some lack of layer bondage (plus a certain brittleness) is a known problem with PETG - well, with some of those filaments. It’s all about the chemistry: colours, add-ons, … I’ve finally found a filament with good layer adhesion, mechanical stiffness and elasticity - a perfect match with the characteristics of my printer. With PLA, that’s less difficult, good idea to try some other brands.
The diagonal pattern @Jens55 already mentioned is an indicator for some mechanical problem, but I can’t help you with that: you have a fancy Delta, my poor old bed-slinger is quite different … Maybe you should follow @Phaedrux’s advice and post a video of your printer in action? I suggest you start a new thread on this.
Finally, thank you for the imagery: made my day to see such a progress!
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@jens55 I think that separated when I pulled it off of the bed. I wasn't very gentle because I wanted to see how the layers stuck together. I definitely have some issues with the flatness of the glass bed which isn't helping that either.
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@infiniteloop This color and reflectivity made it hard to take pictures. In person in looks smoother than the pictures would indicate. It definitely does have some angled lines and texturing. Per @Phaedrux's advice I did take a video of it. I think I will start a new thread as you suggest since this isn't really about stringing or PLA anymore.
I'm also seriously thinking about cutting out a metal frame on my boss's laser to help with the rigidity. This printer was given to me and I think the age and the tab and slot melamine frame is close to its expiration.
Thanks to everyone who posted! I read them all even if I didn't reply directly.
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@toddm lol ... tab and melamine frame .... I had no idea how close I was when I said that even a printer made with chop sticks should be able to do 30 mm/sec.
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@infiniteloop said in Stringing with PLA:
Some lack of layer bondage (plus a certain brittleness) is a known problem with PETG - well, with some of those filaments.
I have never seen a PETG filament that had layer bondage and brittleness. Those are PLA issues and not PETG issues. PETG has stringing issues instead. I suppose it is possible to get that with PETG as well if you have setup issues or bad filament but I would not call it a 'known problem'.
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@jens55 said in Stringing with PLA:
… but I would not call it a 'known problem'
What term do you suggest: 'unknown Problems'? Why then is the web full of pages dealing with the problems I named?
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@infiniteloop, while I can't say that I have heard or read about great inter layer adhesion in 53.75 cases and 5.037 times about adhesion failure, my overall 'feeling' and 'understanding' is that PETG has much better inter layer adhesion than PLA. Also, PLA has, IMHO, a much higher incidence of brittleness.
In addition to what I have read about others having experienced, both of these characteristics are well supported by my own experience.
Feel free to disagree with me. Both views are anecdotal to a large degree as I am not aware of definitive studies on these subjects (although there might well be).
Late edit: Maybe you and I are just reading different web pages ? -
I did a bit of searching and found this article interesting:
https://www.3dprintbeast.com/what-causes-poor-petg-layer-adhesion/
It lists a number of causes for inter layer adhesion issues... and yes, you can screw up anything if you do not set up your printer correctly for the material you are printing with.
A quote from the article:
Poor PETG layer adhesion is perhaps the best example of such an issue, with many enthusiasts switching to PETG filament to benefit from its naturally strong layer adhesion capabilities but being greeted with the complete opposite.
The key being the 'natural strong layer adhesion' and experiencing failures due to poor printing practices. -
@jens55 I read more than I write, so I learned a lot about PETG problems - and how to solve them. In short: had I used the word ‘properties’ instead of ‘problems’, you were right. Stringing is such an unwanted property of PETG which is hard to avoid, except of by design of your parts. Maybe we can agree on this. In addition, we should agree not to capture someone else’s thread.
