So, I designed and printed this part (actually two mating parts), and got a rather elegant pattern of stringing where the print head jumped across from one stiffening flange to the one on the opposite side if the diameter. (The strings and blobs are hanging in space on the centre-line of the split cylinder, not attached to the cylindrical face.)

I'm happy with the print quality overall, and it was very easy to clean the strings away, but I was just interested in the way the strings got progressively longer on each layer, leaving a small blob a bit further out on each layer, and then starting again from the face of the print a bit further up.

Has anyone seen this before? Does it indicate an opportunity for "tuning" to improve print quality further? Or should I just accept it as an interesting artistic artefact?

(Prusa Mendel with Ramps v1.4, printing in PLA on a heated bed.)

Edited 1 time(s). Last edit at 10/06/2015 01:24AM by julianh72.

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What are the print settings? Speed, retraction, temp, etc..
PLA usually is easy to print string-free.
-Olaf

Never seen anything like that before, though if I was to hazard a guess, you had very fine stringing occurring and were possibly running a little hot for the material. After subsequent passes, the heat coming off of the hotend was enough to re-melt the fine stringing, causing it to build up and blob onto other nearby strings.

Just a guess. Shot in the dark.

... I had similar stringing with white glass filled 'smart ABS' without active retract ... reduced it greatly with retract, but then changed for easier to handle material

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Viktor
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I usually print at very high temperatures (ESUN PLA does not stick well otherwise) and slowly (my printer has a weak structure), and that pattern is definitely very, very common in my prints. I enjoy observing it while it grows. It is easy to remove anyway. I saw it occasionally online on pictures of other printers.

Reducing temperature, increasing speed of non-printing moves and increasing retraction may help to reduce it.

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Cristian
Reducing temperature, increasing speed of non-printing moves and increasing retraction may help to reduce it.

+1 for this recommendation. I don't have much stringing, even with nylon, flex or PLA it prints pretty cleanly. Bowden setups are more prone to stringing since the retraction distance needs to be larger. It's important that the retraction speed is high enough, around 65 or higher is recommended. This prevents leaky nozzles from leaking filament. The quicker the retraction is done the better. If you've got problems getting the speed up, try reducing the acceleration. It sounds counter intuitive but inertial mass prevents high accelerations. Even so 1500mm/s² is plenty. Usually this is set 3000mm/s² or sometimes even higher.

Thanks for all the feedback. I've been pretty happy with my recent prints, and haven't had many issues with stringing etc - but for some reason, this particular print was getting some stringing, but it was very easy to clean off.

I've made a few hardware and firmware improvements recently, which has improved the quality and reliability a lot (new all-metal hot-end, bearings on all axes, etc), and it looks like a few more firmware setting tweaks could improve things even further.

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