Excessive stringing

[Hansen]

Guys... I need your help...

I've had my RMv2 for 5-6 weeks now, and I have spend the last three weeks trying to get rid of stringing with PLA. This is the best my printer can produce:

I feel like I've tried everything:

* Tried every temperature ranging from 160 to 210 degrees.
* Tried four different kinds of PLA
* Tried every extrusion multiplier from 1.1 down to 0.50.
* Tried Z-lift from 0.2 to 6 mm
* Tried with and without Wipe
* Retraction speeds from 25 to 100 mm/s
* Retraction lengths from 2 to 10 mm
* Slow and fast print speeds
* Small and large layer heights
* Tried Slic3r, KISSlicer and CURA
* Cleaned the extruder
* Lubricated the Bowden and nozzle with Canola Oil (yes, Canola Oil... https://groups.google.com/forum/m/#!top ... 5-false%5D" onclick="window.open(this.href);return false;)
* Polished the outside of the nozzle (thinking that the PLA might stick to the outside of the nozzle)
* Machined my own nozzles with different orifice diameters and lengths
* Machined a new PTFE liner

NOTHING helps

To start somewhere I have a few questions, which you are probably able to answer:

1. I took the hot end apart (again) to check the PTFE liner. Does this liner seem wrong to you?

2. When I assembled the hot end, I noticed that the nozzle is not completely perpendicular to the heated bed. I took the hot end apart again, and it seemed that the threaded part of the PEEK is a bit "crocked". Does this PEEK look wrong to you? Will issues with a molten PEEK result in stringing?

3. I have found that I have to print at about 175 degrees (the first picture was printed at that temperature). Isn't that kind of low?

4. I also see a lot of oozing. Is this related to stringing in any way?

5. By accident I found that if I turn the layer fan completely off, I get no stringing (??). Of cause that is not feasible, because the object will look awful. Any thought on that? What is actually the effect of too much cooling?


Please, answer any question you can - I really need all the help I can get

[McSlappy]

Hi!

These are the settings I use to reduce stringing. These are by no means perfect but you should get better results.

1. Find the lowest temp you can print reliably. I routinely print at 180, and it may be just that your thermistor reads low, so if you can print at 175, then go for it! Test the temp by extruding 50mm at a temp, then lowering/extruding until it starts stalling the extruder. Up that temp by 10º and you should be good.
2. Extrusion multiplier should be set to the 'correct' amount that will produce a solid top layer without excess. This is a whole art unto itself, but once this is set for your material, don't change it.
3. Retraction speed doesn't seem to affect it too much. 25mm/s should be fine.
4. Z-lift height isn't that critical. have some, but just pick an amount and leave it. I use 1.5mm for all filament.
5. Retract amount matters. I tend to use 5mm for the stock hot-end
6. Wipe matters a lot. I use 5mm, but don't be afraid to go higher. (Kissslicer lets you set wipe length)
7. Don't use Slic3r, it's the king of ooze.
8. Canola oil shouldn't matter with this hot-end, it handles PLA very well.
9. The PFTE liner doesn't look too bad. A little tapered but that shouldn't matter.
10. The peek part looks a bit mangled, probably from disassembly. Not terrible though, I don't think that should matter.
11. Create inner walls first. Use this if the dimensions of the print aren't critical. Really cuts down stringing.
12. Not sure how much print speed affects ooze.
13. Not sure why you'd get less strings with layer fan off. That doesn't seem to make sense :/

Anyway I hope these help, you should be able to print with far less stringing than what you're getting there, so don't give up!

[McSlappy]

Well I thought I'd put my money where my mouth was, so here's a test print I just did using the PLA settings I generally use.

- 175º hot-end temp. 60º bed temp.
- 5mm retract, 5mm prime, 5mm wipe
- 15mm/s retract speed
- 1.5mm z lift
- 100% layer fan speed
- 2 wall loops
- 0.5mm extrusion width
- 0.2mm layer thickness
- loops go from inside to perimeter
- outer loops 23mm/s, solid 48mm/s, infill 35mm/s (these are just the last settings I used, you could up this, it's rather slow)
- wipe and destring (kisslicer)

Here's the result: (ignore the wobbly walls, I'm adjusting the loose cheapskate as I type this)

http://imgur.com/a/olYAO" onclick="window.open(this.href);return false;

Some minor stringing, I bet increasing wipe length would remove this altogether.

[Hansen]

Hi McSlappy. Thanks for your reply!

1. Find the lowest temp you can print reliably. I routinely print at 180, and it may be just that your thermistor reads low, so if you can print at 175, then go for it! Test the temp by extruding 50mm at a temp, then lowering/extruding until it starts stalling the extruder. Up that temp by 10º and you should be good.
2. Extrusion multiplier should be set to the 'correct' amount that will produce a solid top layer without excess. This is a whole art unto itself, but once this is set for your material, don't change it.
3. Retraction speed doesn't seem to affect it too much. 25mm/s should be fine.
4. Z-lift height isn't that critical. have some, but just pick an amount and leave it. I use 1.5mm for all filament.
5. Retract amount matters. I tend to use 5mm for the stock hot-end
6. Wipe matters a lot. I use 5mm, but don't be afraid to go higher. (Kissslicer lets you set wipe length)
7. Don't use Slic3r, it's the king of ooze.
11. Create inner walls first. Use this if the dimensions of the print aren't critical. Really cuts down stringing.

I'm at work right now, but I'll "reset" everything I have done in the past three weeks and start over with your values. Initially, when I got the printer assembled I printed the two fan shrouds with ABS, which went fine. Then I borrowed some green PLA from a friend, and I can't remember seeing any stringing at that time. It actually produced some very nice prints. During that time I also tried a few meters of Taulmann Bridge (which requires about 235 degrees) and T-Glase, but once I got my own PLA, I am quite sure that the stringing started. My point is that I think "something" has happened to "something", and that "something" could be related to the slanted hot end.

BTW: The temperature mentioned is not what I see on the display. The temperature reading is about 7 degrees lower than the actual hot end temperature (inside the barrel), so I typically have ~168 degrees on the display.

8. Canola oil shouldn't matter with this hot-end, it handles PLA very well.

Well, I wouldn't think so either. People mostly use it to get rid of clogging, but desperation sometimes calls for desperate methods

10. The peek part looks a bit mangled, probably from disassembly. Not terrible though, I don't think that should matter.

As mentioned I did try the Taulmann Bridge at some point, but I am quite sure that my hot end has never been above 240 degrees, which shouldn't be too high for the PEEK. I am wondering, though, if the slight tilt of the nozzle could produce these strings, as the side of the nozzle closest to the heated bed might drag hot plastic around.

That brings me to another question: I have been looking at upgrading to the E3D v6 hot end. Do you think that it would solve most of the stringing problems, or is it likely that the root cause is hidden in the extruder or the bowden tube somehow?

Anyway I hope these help, you should be able to print with far less stringing than what you're getting there, so don't give up!

Thanks for the cheer-up

- Hansen

[teoman]

Summing up your post:
It was perfect, then I got my own PLA.


Maybe the PLA you got is contaminated.

[Hansen]

Maybe the PLA you got is contaminated.

Yes, I only have three spools of PLA from the same supplier, so I thought about that too. However, I got a few meters of PLA from a different supplier, and it does the exact same thing...

[McSlappy]

Yeah it could be the PLA. You might also try drying it out (put it somewhere warm like in a box on an oil heater for a few days) and then try again. I know that my translucent purple PLA doesn't print as nicely as my other PLA too, not sure what happens with the translucent, but solid colours might be better.

This same test cube done on my e3d v5 has absolutely zero strings at all and I use less retract and wipe. The downside to my v5 is that it had trouble printing PLA and so I have to use Canola oil (LOL) to have it print PLA. The v6 doesn't have the same issues I understand. If you're thinking of a hot-end that's a damn decent one to get.... Though GenericDefault's new head is my next one... I'll have an e3d v5 on one machine and Generic's on the other. Then the Prometheus will arrive and maybe my v4 will get replaced by that!

Yeah ooze goes away almost completely with a fancy hot-end.

[Hansen]

I began the procedure for determining the correct temperature, and I seemed like I could actually decrease the temperature by another 5 degrees, so... I end up with 170 degrees (163 on my display).

I went ahead with determining the best extrusion multiplier, so I drew a 10x10x3 mm solid box and printed it at various extrusion multipliers down to 50% (with KISSlicer and the settings that McSlappy suggested). I started to notice something "funny": The (clearly under-extruded) lines on the top surface were not equally spaced. So I rotated the box 45 degrees and printed it again, and now the lines were equally spaced. My printer seems to have a geometric problem, which I have to solve before I can determine the correct extrusion multiplier.

So... I printed three boxes each rotated so that I had the top layer lines perpendicular to each tower, and this is the result:

My guess is that my Z tower has some kind of problem, and I will take a deeper look into it. Do you agree with me on this?

Sadly I still saw a lot of stringing between the solid layers, but that will come in second...

BTW: I have attached the three GCode files (with 50% flow to exaggerate the lines), if anybody else wants to do this test

- Hansen

Extrusion multiplier calibration 50% X tower perpendicular direction.gcode

(39.45 KiB) Downloaded 264 times

Extrusion multiplier calibration 50% Y tower perpendicular direction.gcode

(39.45 KiB) Downloaded 250 times

Extrusion multiplier calibration 50% Z tower perpendicular direction.gcode

(37.71 KiB) Downloaded 292 times

[Hansen]

I've had a few hours to troubleshoot and adjust the temperature and the extrusion multiplier, and I think it now produces the nicest top surfaces I have seen.

But... I still have stringing (even at 170 degrees and 95% extrusion multiplier). I can't go any lower in temperature, and I have stringing even at 50% extrusion. I have absolutely no idea what to do now

It seems to me that the PLA sticks to the nozzle somehow. I doesn't help to polish the nozzle or wipe it with PTFE oil. Could it be a small burr or other defect in the orifice itself?

[teoman]

Anyone know where to find retract and wipe on mattercontrol?

[Captain Starfish]

Retraction is in Slice Settings/Printer/Extruder 1
Wipe shield is in Slice Settings/Print/Output Options

[teoman]

Thanks,
I dont know how i missed that.
Looking at it again, they seem to have magically appeared. Not sure if they really did pop up or this late night/little hours hobby is making your mind go all wobbly.

[teejaydub]

I have very little to add, except that I'm in the same boat - stringing wherever stringing could occur, and I've tried tweaking every setting in the slicers.

Another factor I've been wondering about is humidity in the ambient air - I started really noticing the stringing when the weather got hot and humid. But so far I've tried to control that a little with an air conditioner, and a 12% change in relative humidity hasn't made any difference.

Or, I wonder if the nozzle or something else in the hot end has gotten damaged, mainly because filament comes out in a curl, and often curls up and sticks to the side of the nozzle.

[Tinyhead]

If it makes any difference, I've noticed that with my printing that the filament quality makes a huge difference. Most jobs turn out great, but the ones that I've use my 'cheap' filaments on always have problems. Slight layer separation, poor surfaces, stringing, etc. I have my 'nice' filaments that turn my prints into art.... and my so-so filament prints that look like they were made by my butt.

[teejaydub]

I have no doubt that different filament brands (and lots, and spools) vary in quality in various ways. And I agree, some spools just seem like bad news - though I still generally assume that I have some settings wrong.

But, I also see that I sometimes get a great print from a spool, then later on some bad prints, and then maybe some great prints again, all from the same spool. And I once did a medium-sized print that was totally unusable due to stringing, then tried it again the very next day with the exact same settings (this was an older printer), and it came out perfectly! Those two days were humid and dry, respectively, so that's what started me getting suspicious about the weather.

I would love to see a community-curated wiki of decision trees for troubleshooting things like this.

[teoman]

If it makes any difference, I've noticed that with my printing that the filament quality makes a huge difference. Most jobs turn out great, but the ones that I've use my 'cheap' filaments on always have problems. Slight layer separation, poor surfaces, stringing, etc. I have my 'nice' filaments that turn my prints into art.... and my so-so filament prints that look like they were made by my butt.

I suppose your butt is kind of an extruder

[Tinyhead]

If it makes any difference, I've noticed that with my printing that the filament quality makes a huge difference. Most jobs turn out great, but the ones that I've use my 'cheap' filaments on always have problems. Slight layer separation, poor surfaces, stringing, etc. I have my 'nice' filaments that turn my prints into art.... and my so-so filament prints that look like they were made by my butt.

I suppose your butt is kind of an extruder

Haha! Good call.

[Hansen]

I have very little to add, except that I'm in the same boat - stringing wherever stringing could occur, and I've tried tweaking every setting in the slicers.

Another factor I've been wondering about is humidity in the ambient air - I started really noticing the stringing when the weather got hot and humid. But so far I've tried to control that a little with an air conditioner, and a 12% change in relative humidity hasn't made any difference.

Or, I wonder if the nozzle or something else in the hot end has gotten damaged, mainly because filament comes out in a curl, and often curls up and sticks to the side of the nozzle.

It sounds like you're seeing the same thing as I originally did, and if it can help you in any way I can tell you that I found the root cause of MY problem. I "accidentally" discovered that the set screw for the pulley on the Z tower motor had come loose. This meant a tremendous amount of slop in certain movement, again leading to the nozzle digging into the hot glob of plastic just printed when starting a travel. When I fixed that 90% of the stringing disappeared! This explains why NONE of the remedies like lowering the temperature or tweaking any other settings (like retraction) did absolutely nothing to the stringing.

You can quite easily check this by telling the printer to "Go home" (which leaves the motors holding the cheapskates), and then try to move the cheapskates up and down by hand. If you can move one of them (with reasonable force applied of cause), you could have a loose pulley in that particular tower.

I got to the conclusion that ANY kind of slop could result in stringing, so it might be worth to check the belts and arms too. I, for example, suspect that one of the arms on my printer is too loose, because I seems to be able to move the effector slightly without moving the cheapskates (??).

I hope some of this can help you!

[teejaydub]

Great idea, thanks - I wouldn't have thought of that being relevant to stringing. It's good to know you got to the bottom of your issue!

I will look into the pulley set screws (will have to do some reading, as I don't know where those are). I can't move the cheapskates by hand when the motors are engaged, though. I did just tighten up my X and Y cheapskates a bit, but it doesn't seem to have reduced the stringing.

I think my favorite theory now is that I scratched the nozzle while cleaning it, so I may have to explore replacing it.

[Hansen]

I finally found the culprit causing the last bit of stringing that I've been struggling with: Z-lift, Z-hop or whatever it is called. I disabled the Z-lift (lifting the head when retracting), and ALL strings disappeared. For some reason I thought that Z-lift was invented to decrease stringing (because the strings would break), and to avoid having the nozzle bump into corners curling upwards. The latter is true, but Z-lift turns out to be causing the stringing - at least with my printer and my filaments.

My theory is that the hot plastic just printed "sticks" to the plastic inside the nozzle orifice, which is pulled out of the nozzle, when the nozzle is lifted. The plastic sticks to the outside of the nozzle, and this becomes strings, when the nozzle is moved somewhere else.

Now, I am able to print every kind of PLA I throw at it using the same settings without having ANY string. My settings are:

Hot end temperature: 195 C
Retraction length: 5.4 mm
Retraction speed: 100 mm/s
Z-lift: 0.1 mm (That is very close to the maximum value I can use without having strings)

I hope that can help you

[lightninjay]

Now, I am able to print every kind of PLA I throw at it using the same settings without having ANY string. My settings are:

Hot end temperature: 95 C
Retraction length: 5.4 mm
Retraction speed: 100 mm/s
Z-lift: 0.1 mm (That is very close to the maximum value I can use without having strings)

I hope that can help you

Am I reading that properly? You print your PLA at ninety-five degrees celsius?

[Hansen]

I am sure that printing at 95 degrees will produce no strings at all, but that was a typo. It should have been 195, and I just edited my post to say that instead.

[teejaydub]

Thanks for posting your settings! They didn't fix it for me, but it was a good thing to try.

It seems like there are a lot of distinct things that can cause stringing. The world needs a good automated 3D printing troubleshooter!

[Tinyhead]

I'll have to try those settings. I think a lot of it depends on the filament and brand too. Some PLA is super oozy and you can pull 10ft of 'hair' out of the hot end trying to break the stupid string and others will let go right away. That's a pretty quick retract feed.

A while ago, I had found the opposite with the Z-Lift. I used to have mine at the default setting but then changed it to 5mm on someone's suggestion and I've had much better results since. There are so many factors to play with on these machines. No two are the same.

[drunkenmugsy]

I know this is an old post but I am going to add my two cents anyway.

Set your non print move speed higher. I have set mine to 250mm/s with 4mm retraction for some black MakerShed ABS I got. Of course this is not the only setting you need to adjust. You still need to calibrate your temp, heated bed temp, extrude, cooling etc etc to working settings along with speed for the material you are using. But I have found speed to be the best way to get rid of strings.

Why? Well with bowden you are going to not get as much effect with retraction. The melted material in the hotend is not going to retract at all regardless of what type hot end/extruder you have. Best you can do is relieve a little of the pressure pushing it. 3-5mm retraction is plenty. The trick I have found is less time between non printing moves means less ooze. Its that simple. Dont give the hotend time to ooze. Move that shit quick! I went from stringy cubes to perfect in 3 test prints the first time I tried this.

Try this - Make 4 x 10-15mm cubes space them out 10-15mm, 20-30mm and 40-60mm so you get something like this

Code: Select all

 []  []    []        []

Then raise your non print move speed until it stops. You can also raise your retraction in .5mm increments starting at 2mm. Print with sane print speeds. Start at 40mm/s print moves. When you can do that reliably then go faster. As always you may have to adjust this again for each type/brand/color of filament. Your Hatchbox ABS Blue might like 250mm/s non print while MakerShed ABS Black may only need 190mm/s. Dont go crazy with the non print speed or you will just shake everything apart eventually. That said a delta can handle pretty high speed moves in general.