Stringy prints on new eMaker Huxley

Here are some prints from my newly commissioned eMaker Huxley #310. The kit was purchased back in Oct. 2011 by a friend who was too busy to put it together (it was just sitting in his garage, unassembled, collecting dust). He mailed it to me and I was able to assemble it without much issue, and print some halfway-decent parts out.

I've seen a lot of other badly-printed out parts at our makerspace and around the internet. The parts below, I think look pretty good for the most part (and they measure up to be reasonably accurate and square).

The only thing I'm concerned with is the extreme amount of little stringy "hairs" that happen after a retract. I've played with the nozzle temperature, external fan, retract distance and speed, etc. and I can't really get it go away.

The turquoise filament is "JustPLA" brand 1.75mm PLA, purchased from Amazon.com (I'm in the U.S., and haven't put an order into Faberdashery who I hear makes really great filament). The folks at my local makerspace seem to think that it's just bad filament, but I get the same issue with the Faberdashery Arctic White PLA as well.


















Here's a picture of what I pulled out of my nozzle during its first cleaning:



And here's a picture of it with the Faberdashery Arctic White PLA.



I'm currently running the nozzle temp at around 160, as any higher, and it turns into a melty mess. Not really sure how accurate the thermistor is. I'm imagining the tip is getting a bit hotter than 160.

The bed temp is set to 65 and I've had zero problems with parts coming loose mid-print. They stick incredibly well, and it's often difficult to remove the parts without lifting the machine.

Oh, and I'm using Slic3r with a modified eMaker preset. Currently 2.5mm retract length, 1.5mm lift Z, I've calibrated the E-steps per mm and have measured my filament, and pretty much everything else is per the eMaker preset.

Any ideas?

Thanks,

Neil

Reduce your extruder flow rate, you are over extruding a bit. top surfaces should be smoother and not bulge up like in your prints.

If you are using a Wades type geared extruder, generally you should be around 1mm of retraction. Lower your Z lift to double your layer height. With 2.5mm of retraction the hot-end sets in one spot on the print much longer than it does for 1mm retraction, this will cause little blobs on the exterior of the print.

I think your stringing is coming from a combination of your extruder flow rate, retraction distance, and Z lift.

Less retraction and less Z lift will decrease your overall print times as well.

Edited 1 time(s). Last edit at 12/31/2013 06:13PM by Dirty Steve.

Quote
Dirty Steve
Reduce your extruder flow rate, you are over extruding a bit. top surfaces should be smoother and not bulge up like in your prints.

If you are using a Wades type geared extruder, generally you should be around 1mm of retraction. Lower your Z lift to double your layer height. With 2.5mm of retraction the hot-end sets in one spot on the print much longer than it does for 1mm retraction, this will cause little blobs on the exterior of the print.

I think your stringing is coming from a combination of your extruder flow rate, retraction distance, and Z lift.

Thank you! Makes sense, I'm going to give it a try and report back.

Have your retraction and Z-lift speeds as fast as your machine can run.

So after looking at it for a bit, I see two ways that I could go about lowering my extruder flow rate, assuming that slic3r sets the extruder feed rate based off of a combination of the X/Y feedrate, filament size, nozzle diameter, and is limited by the max feedrates of the X/Y steppers, and the extruder stepper.

#1: Lower XY feedrate (Print Settings -> Speed -> Speed for print moves) in Slic3r (I see no way to lower the extrusion rate in my version of slic3r, so lowering XY feedrate would be an easy way of doing the same thing, more or less)
#2: Lower "max_feedrate[3]" in configuration.h, in the Sanginololu Sprinter firmware. The only negative point here is that it would limit the retraction speed, which needs to be set to as fast as possible. My version of Sprinter doesn't allow different max feedrates for retract -vs- extrude, although it would probably be trivial to implement it.

I tried the #1 option first.

Here were my slic3r settings before changing them:




I changed the speed settings to 25, 20, 20, 30, 30, 20, 30, 30, 20 respectively.
Retraction length changed to 1mm.
Lift Z to 1mm.

Still stringing like crazy. Maybe a little worse.


I'm going to try a branch of slic3r from eMaker that may resolve some of the problems I've been seeing. I was running bleeding-edge version 1.00RC1 before, direct from slic3r.org.

wrong settings to mess with for extrusion.

Filament settings>filament>extrusion multiplier

Think of 1 as 100%. Try a .95 and a .90 then dial in tighter to fine tune.

When you are getting there, you will be able to see a difference between .92 and .93 as an example

Extrusion rate is completely seperate and not influenced by 'printer speeds'.

However a faster X/Y speed will often require a little higher extrusion rate.

Edited 1 time(s). Last edit at 12/31/2013 08:17PM by Dirty Steve.

Ah. Well that makes a lot of sense in retrospect. I guess I thought the extrusion multiplier was for something else like a modifier of the filament diameter.

I'm mid-print and it looks the best it's ever looked. I feel like a bit of an idiot for missing that.

Thanks for all your help.

No problem, easy to answer