PLA - how to get rid of "strings"  

Re: PLA - how to get rid of "strings"

I tried the oven method and I'm quite not sure I will do it again.

The glass transition of PLA is quite low (around 60 °C) and it's very easy to make the filament getting deformed. Domectic oven are not very easy to be set precisly at low temperature. So this need additional monitoring for temperature to stay at ~50°C.

In addition, The smell was very persistent and took several days to fade away :/

Re: PLA - how to get rid of "strings"

Shree

If I recall correctly, you are in India? A very nice place which is quite often warm and dry?

When you mentioned that the filament had been opened for a year, I didn't bother taking it further because of your climate 😀

Peter

Re: PLA - how to get rid of "strings"

Christophe: Thanks for your input. I will have to think twice about drying now -- the smell part makes me think twice about requesting help from friends.

Peter: I am in Bangalore. We get rain here all year round. Right now, we have a lot of rain due to the monsoon here 🙂 Humidity is 65-75% I think.

Re: PLA - how to get rid of "strings"

Shree

If you have one of those machines for drying fruit, that should do the job.

Apologies for getting your location wrong.. 😉

Peter

Re: PLA - how to get rid of "strings"

Fruit drying machine is an interesting idea, Peter. Unfortunately, I don't have that either.

I verified the brand of the filament - it is eSun. Will see what method can work for drying the filament.

Re: PLA - how to get rid of "strings"

Hi Shree

Something like that should be a better solution:

http://www.instructables.com/id/DIY-3D-Printing-Filament-Dryer/?amp_page=true

Re: PLA - how to get rid of "strings"

That looks like a very good suggestion, Christophe! The space requirements for this seem quite less as well. Thanks for sharing that.

I read a few reviews of the filament I was using in this thread (eSun "wood"). Folks have prominently mentioned that this is very stringy. That surely matches my observations too. I am taking a break right now. Will be back in a few days and try some of the suggestions.

Re: PLA - how to get rid of "strings"

Shree

You had previously said that it was wood colour and not particles. Yes, wood filament can be very stringy; I use a nail brush to clean up the prints after printing with wood...

Peter

Re: PLA - how to get rid of "strings"

I ended up printing this as a two piece model. A "base block" with the text cut into it, card & pen holders. Text was printed separate (flat on the print bed).

This gave me the worst of both worlds. I had to cut the fiber both on the base block & the text. I had to use a dremel to clear some of the mess. The text was pushed into the base block. Ended up with a reasonable result, but not something that I very pleased with.

My wife seems to be reasonably satisfied with the result. The piece is intended to be kept on the table & looks OK from a distance. So, I may not print this again.

If I had just printed one block with everything in it, I would have had a much easier task cutting the fibers.

I also spent some time thinking of drying this filament. Does not seem worth the trouble to me. I think I will just keep aside this roll & use it on models that are suited for it.

Thanks to everyone who gave suggestions on this thread!

Re: PLA - how to get rid of "strings"

I'm not sure if anyone mentioned it, but I've found the best way to reduce stringing is to reduce the extrusion rate while raising the travel (non-printing) speed. That way the filament doesn't have much momentum and pressure before travel movements. There are two primary ways to reduce the extrusion rate: lower the print speed and print shorter layers.

Also, fast retraction usually helps. I used to reliably retract 3mm at 80mm/s on the Original Prusa i3, but my new MK2 has messed up prints badly with those settings. I think it's trying to pull the filament from the spool too quickly. I'm limiting retraction to 0.8mm at 40mm/s until I figure out what changed.

Z-hopping usually hurts because it increases the travel time. I wish I could tell my slicer to only Z-hop to the extent that it has no effect on travel time.

Unfortunately, high travel speeds also increase the risk that a stepper will miss a step, so I rarely set the travel speed higher than 120 mm/s.

Final thought: watch for ooze when you load the filament. Sometimes filaments ooze forever, while some filaments, at the right temperature, never ooze until the extruder pushes them. Filaments that don't ooze produce much cleaner results.

Re: PLA - how to get rid of "strings"

I used to reliably retract 3mm at 80mm/s on the Original Prusa i3

Oh no, you didn't....

Maximum feedrate for the extruder is set to 25mm/sec within firmware. That is unless you modify the firmware to your own specs.

There is also an issue with the V6 which some people have encountered with retracting more than 1 mm and ending up with a blocked extruder. The defaults now provided by PR set retraction at 0.8 mm.

Your points regarding non-printing speeds and Z-Lift has been made previously, but it is good to have you reinforce those setting; there are occasions where Z-Lift is essential and it is certainly quicker with the Mk2 than the Mk1.

Travel speeds are reliant on the acceleration settings; as long as acceleration is in order, movements in excess of 150mm/s work without issue (in high power mode).

Peter

Re: PLA - how to get rid of "strings"

All I know is my printer seemed to retract much faster when I told it to retract at high speed. Subjectively, the extruder turned rather quickly during retraction. Maybe there was a firmware bug that kept it from enforcing the limit. More likely, there's a wetware bug in my head that made me think it was faster. I'll never know because that MK 1 is now an MK 2. 😀

Even with all the weird settings I've tried, my Prusa extruder has never jammed, even after going through around 6 kg filament in PLA, ABS, PETG, and TPU (flex). It has slipped a bit, but rarely. Yay Prusa!

That's a completely different story from my first home built 3D printer made in 2010, which hardly did anything but jam. 😆

Thanks for the reminder about high power mode, I should try that next time I want to make something big and I'm having trouble with strings.

Re: PLA - how to get rid of "strings"

Shane

What appears to be happening with higher retraction settings with the V6 is that melted.soft filament is drawn back to the point where the PTFE tube meets the heat break. If there is a small gap at that point, the material can harden in the gap and jam.

This has happened to me once with the Mk2, but I rebuilt the extruder and it has never happened again. I also use the V6 on the Mk1 and it has never happened with that. The problem appears to be caused by an imprecise hot end build.

Peter

P.S. Before I responded earlier, I did check the 2.2.3 firmware to confirm the extruder max speed was the same in that.