Super stringy prints on newly assembled Rostock MAX

[jasonwebb]

I just assembled my Rostock MAX v2 a couple weekends ago and have been able to get pretty rock-solid performance out of it in most respects. However, all of my prints are terribly stringy and I can't seem to figure out whats causing it.

At first I was using the MatterControl settings recommended by the official User Manual (6.8mm retraction @ 110 mm/s), but have tried tweaking these values quite a bit with no changes in my results.

So far I've tried 2,3, 4, 6.8, 10 and 12 retraction distances at 20mm/s, 50mm/s, 110mm/s and 150mm/s retraction speeds, but no difference in my results.

I'm printing with ThriftyMake White PLA at 190C nozzle, 70C bed.

I'm also using an E3D v6 hotend, if that makes any difference.

Some photos of the attempts: http://imgur.com/a/ozS6s

I'm completely new to Bowden extruders and retraction cabliration - anybody have some suggestions for where to start?

[Windshadow]

How did your printer do with the supplied SeeMeCNC hot end with ABS?

as a side note the E3Dv6 is at its best with high temp filaments and is know to be a little bit finicky with PLA esp with retractions...

I am still using the stock hot end and it works very well with PLA and ABS, but is stressed to reach temperatures needed by things like Nylon with out melting its PEEK section, so I have a E3Dv6 to build when I get to using nylon. but I expect to keep using the stock hot end for PLA. I have made my effector assembly as a quick change with plugs for all the wiring and I that way I can select the right hot end for the filament it likes the best

[Eaglezsoar]

Have you tried lowering your temperature at 5 degree increments? Your on the right track with the different retraction settings and it is sometimes difficult to hit the correct temperature and retraction.
I am of the opinion that it can be virtually impossible to completely eliminate stringing with some filaments but you should be able to find a sweet spot where stringing is minimal.
Best of luck in finding these sweet spots.

[Polygonhell]

Eliminating strings in PLA can be something of an art form and it depends a lot on the PLA is question. On some filament it's close to impossible to eliminate entirely.
PLA doesn't behave like ABS when it melts, the hotter it gets the more liquid it gets, and the more strings it produces, ABS on the other hand is pretty much either melted or not.

IME to minimize strings in PLA, you want to be printing at as low a temperature as you can reliably extrude it, with as much cooling as you can get on it.

If your patient enough you can run test prints to tune retraction, I use 4 cylinders arranged in a square, you want to tune retraction to the point where it doesn't improve, you want it as short as possible and as slow as possible. On the stock hotend that's still going to be 5-8 mm, and you likely won't eliminate strings entirely with retraction alone.
You can try a small Z-Hop/Lift before a move, this can help, if you have enough cooling it can snap the filament, it can also make things worse.
KissSlicers wipe is extremely useful, not all slicers have an equivalent.

[jasonwebb]

I have not used (or even assembled) the stock hot end, actually. I got my kit through MatterHackers and thought that the E3D V6 was a pretty obvious upgrade. Given all the soldering and wire work that has to be done, I would really hate to have to swap out hot ends (ever, lol).

In addition to the strings, I'm also seeing lots of large, diagonal globs forming when the print head moves away from parts. Is that due to the same issue?

What is an appropriate value for a "small" Z-lift? Seems like it could help (especially since I have 3 layer fans running), but have no idea what a good value is.

I did realize last night that I was misreading a lot of guides I had come across. When they refer to "speed" I assumed they meant retraction speed. But it looks like that really refers to "travel" speed during non-print moves. In MatterControl that was set to 300mm/s by default! I lowered it down to 20mm/s and got this result: http://imgur.com/9dRu9Yr Still not good though.

Will try bringing down the hot end temperature to see if that helps.

[Polygonhell]

For an E3DV6 you want the retraction under 2mm at around 30mm/s, anything bigger and you will very likely jam when printing PLA, it's a very different design to the stock hotend and requires very different settings.

[jasonwebb]

I've been printing with between 2mm and 8mm distances and between 30mm/s and 150mm/s over the past couple days and haven't experienced any jams with PLA yet. Weird.

I have also lowered my hot end temperature to 185C and 180C, but it's hard to see if there is any difference yet.

Here is a simpler print that I just printed a minute ago using 2mm retraction distance, 30mm/s retraction speed, 180C hot end temperature and 150mm/s travel for non-print moves: http://imgur.com/3Iu3veU

Any thoughts about which of these to change for the next tests? My pile of failed experiments is growing pretty large, and I don't know that I'm making a lot of headway figuring out which variables to focus on.

I don't remember having these issues with ABS, but I only printed a couple of items with it. But I thought that PLA was the "easier" filament to work with? Maybe I should just stick to ABS o.0

[Polygonhell]

ABS has it's issues, but stringing isn't one of them.
ABS warps and splits, PLA gets stringy and tends to jam because it has a thixotropic state that ABS doesn't. You can however print it without a heated bed and it warps less than pretty much any other plastic.
What's "easier" depends on what your trying to do.
There is significant variation in plastics from different manufacturers, and even within the colors from a single manufacturer. With bad manufacturers it varies roll to roll or even inside a single roll.
Try a couple of mm z lift, drop the temperature further if you can get away with it.

[Ail]

This is the guide I used for dialing it in, it really helped to see the difference when changing settings.

https://www.matterhackers.com/articles/ ... -to-oozing

That said your last picture doesn't look too bad. Aside from that link you could also try heating to 160 and manually extruding, if it works try printing at that temp, if not bump up 5and try until it comes out nice. I usually bump up 5 from there just as a buffer. Color can make a difference too, transparent pla seems to string more for me than the darker colors I have.

[Eaglezsoar]

This is the guide I used for dialing it in, it really helped to see the difference when changing settings.

https://www.matterhackers.com/articles/ ... -to-oozing

That said your last picture doesn't look too bad. Aside from that link you could also try heating to 160 and manually extruding, if it works try printing at that temp, if not bump up 5and try until it comes out nice. I usually bump up 5 from there just as a buffer. Color can make a difference too, transparent pla seems to string more for me than the darker colors I have.

Thanks for the link to the Matterhackers article, it is good reading!

[jasonwebb]

Just for a bit of closure on this topic, I had much better success by playing with the temperature settings. I had no idea that PLA temperatures could vary so much between colors and manufacturers! One filament I have prints best at 173C, while another seems to like ~205C. May actually experiment with using ABS more often, since my early test prints with it went without a hitch.

Better results: http://imgur.com/a/emWIv

p.s. is there a way to attach images to posts on this forum? I'm able to upload my photos as attachments in the editor, but when I hit submit they don't show up. Maybe that is on purpose, I don't know.

[Xenocrates]

p.s. is there a way to attach images to posts on this forum? I'm able to upload my photos as attachments in the editor, but when I hit submit they don't show up. Maybe that is on purpose, I don't know.

Next to the attachment line, it will have a button labelled place inline. That's how you add attached photos to a post. Otherwise you can just embed them in the text with a link like so, with the spaces removed:
[ img]http://i.imgur.com/Wg7FPJP.jpg[/img ]

[img]http://i.imgur.com/Wg7FPJP.jpg[/img]