Stringing reduction tips?  

Re: Stringing reduction tips?

I think you next move is to try PLA from a different vendor. I have had good results with Hatchbox black PLA.

Re: Stringing reduction tips?

Thanks. Yeah, I was also wondering if different vendors would be more or less stringy. I have the Prusa PLA that came with the printer, so I can try that today. I was thinking of ordering some Hatchbox soon too.

Re: Stringing reduction tips?

if you use simply3d you could check out matteo's settings or at least adapt them to a slic3r profile.

❗ he made a pretty good job to optimize settings for small prints and high details.

➡
furthermore: is your front fan running at full speed ? maybe reducing it to 35%, with the option to blip the fan to full power when comming from idle, would help.
another option that might help is to use a vertical lift (z-hop) of about 0.6 - 1.0 mm when retracting.

and of course: checking out another pla manufacturer would be a good idea... but don't go for the cheapest stuff, economically priced will do :D.

Re: Stringing reduction tips?

Thanks. I tried reducing the fan speed to 50% with no noticeable improvement. I'll try decreasing it further. I also tried reducing the flow to 95% but the spires on my test piece didn't even print, so that's not going to work either. I'll try increasing the z-lift and see what that does.

I did switch filaments too and that worked. Here's how things look with just the standard pre-sets using Prusa PLA.

Just the smallest bit of stringing at the very tip of the spires. I get that different vendors' plastics will perform differently, but I wonder if all plastics can be dialed in or if some are just a lost cause.

Re: Stringing reduction tips?

Follow-up from yesterday: I tried increasing z-lift to 1mm. No improvement there. I'm thinking there's no way to improve things with this ProtoParadigm PLA.

Re: Stringing reduction tips?

Lowering the nozzle temp 5-15 degrees may help with that stringy PLA.

Edit, never mind, I just saw that you'd already tried that

Re: Stringing reduction tips?

Then in the second piece (middle) I adjusted retraction length to 2.0 mm. For the right piece I changed retraction length to 2.5 mm.

Be careful with retraction length, I clogged my cold end by trying 1.8mm. After my mistake, reading around I found out that you should never go above 1.5mm. Personally I wouldn't take the risk and stay at the default 0.8 as it's much easier to clean up the strings than it is to fix the extruder. 🙂

Re: Stringing reduction tips?

... reading around I found out that you should never go above 1.5mm...
that's curious. i went up to 5mm with that cheap nylon filament (that i couldn't tame anyway until now)... and got no clogging problems with the nozzle and/or the heatbreak.

i guess the amount of allowed retraction length might highly depend on the construction of the extruder, especially the cooling of the hotend and the ptfe-tubing.

Re: Stringing reduction tips?

See the bottom of http://wiki.e3d-online.com/wiki/E3D-v6_Assembly

"Excessively long retractions will cause issues by dragging soft filament into cold areas. E3D-v6 hotends need less retraction than most hotends. For direct extrusion systems you should use anywhere from 0.5mm-1.0mm, for bowden systems you might want to go up to 2mm. Retraction beyond 2mm is likely to cause issues."

I don't remember where I found the 1.5mm number, but I only went from the 0.8 default to 1.8. I guess this may also depend on the material (I was using the Prusa PLA that came with the printer.)

Re: Stringing reduction tips?

With the direct drive system, you should not exceed 1.5mm retraction.

With a Bowden system (multi-material) I have had retraction up to 7mm without clogging, using the same hot end.

However there is a big difference between the two and an easy fix for the direct drive system which will allow greater retractions.

The PTFE tube has a square-cut end on the DD system. The top of the heat break is chamfered, which leaves a very small gap between PTFE and heat break where filament can solidify and clog.

On the MM upgrade, the PTFE is also chamfered so that no gap exists. This can be achieved with a pencil sharpener - the PTFE angle will be greater than that of the heat break, but that's not an issue.

When inserting the chamfered end of the PTFE tube, unscrew the heat break half a turn, insert and lock the PTFE, then tighten the heat break. Should end the jams with higher retraction.

When working with higher retraction values, you may also find that increasing the maximum extruder speed can help. This was limited (in earlier firmwares - I haven't looked at the latest offerings) to 25mm/s.

In my start GCode I have the following:

M203 E80 Z25 ; Set MAX speeds.

I tend to use retraction suck of up to 80mm/s and prime around 40. The Z speed increase (from 12.5 - older firmware - to 25) reduces the time it takes when using Z-Lift, which can also induce stringing.

You can also try removing wipes and increasing the move speeds and MAX acceleration which also helps with stringing.

Generally, the quicker you can get from the end of one line to the start of the next, the less the stringing

Peter

Re: Stringing reduction tips?

❗ great explanation ❗
for the hotend of my MK2 the time for a regular inspection is near (maybe this weekend).
i'll take this in account and have a look at the tip of the ptfe tube... and maybe have to dig out the old pencil sharpener

Re: Stringing reduction tips?

Jeff

Please remember that you will have to start with a slightly longer tube. I usually cut the top end once installed. And ber very careful with the sharpener; it is very easy to go too far.

Also it seems that many PTFE tubes as supplies are not quite as square as they need to be. That is one reason why some users with larger retraction get the clogging and others don't.

Peter