Can anyone recommend a good temperature test? I’m being plagued by stringing on my multi-material Prusa at 20 degrees below recommend temperature with an extra 1.5 mm of retraction. Retraction might be a tad too high, on some prints I’m starting to see a small gap. Maker Geeks PLA.
Edit: filament may have absorbed some moisture, it’s been out a couple months but I wouldn’t think it would affect print temperature or stringing this significantly
@Adam_Steinmark Here are some steps I follow:
Raise the nozzle about 35mm off the bed and heat it to the mid temp range of the filament you are using. Extrude a steady state strand (load filament for me) and watch the behavior. If it curls up under the nozzle and never drops down then it is too cold. If it produces a clean vertical strand and coils it like a rope and when you stop the extrusion it leaves a vertical strand touching the nozzle tip then it is just right (at least within +/- 5C for future tuning). If the vertical strand sags and tips over leaving a spider web it is too hot. Leave part cooling off for this test. That is the basic start.
On the retraction I set a basic distance and a speed. For me it is 25mm per second and 2.5mm. If I get stringing running a test piece I will first drop the temp by 5C since that is generally within the test range of good extrusion. Then I increase the speed of the retraction but no more than 35mm/sec. Then I will increase the distance but no more than 4mm.
Another setting that can help is the travel speed. Set it fairly high. I generally use 60 - 80mm/sec.
Your numbers will likely differ but that is the sequence of adjustments that I make. I offer mine as a relative gauge of adjustment.
Turn on Combing All in the slicer (Cura) don’t know what it might be called in other slicers. Runs the head around holes and spaces to limit the need for retraction. Doesn’t directly solve the stringing problem but it does result in better prints.
Most of the time I get really good results. Every once in awhile I will run into a filament that I just can’t get to stop stringing completely.
If there is moisture in the filament that can aggravate stringing as the steam expands and pushes out blobs. In some filaments it does not seem to be significant and in others it can be quite bad. This is relating to PLA. For me the degree is relative as I live in a high mountain desert with low humidity.
@Jeff_Parish Ah I forgot about the curling test that’ll give me someplace to start.
I had plans to re tune retraction after fine tuning temperature. Prusa default profile is 4 mm but I was having stringing with anything below 5 mm.
Travel speed is 120 mm/s by default. Combing in Simplify3D and Slic3r is called "“Avoid crossing outline for travel movements” or “Avoid crossing perimeters” . But for multicolor prints this is mostly useless because it has to travel back and forth to wipe tower.
I may just try drying the spool before testing if I keep having issues.
If a print has too many retracts the filament will cool off and become unstable temperature, mush inside the printing head because of unevenheating. Solid objects are fine to print because of even filament flow, but objects with too many retracts and the properties of the filament can cause this problem. Not all objects are suitable for all filaments.
@Nathan_Walkner Yeah I’m starting to suspect the thermistor is off. Do you have any recommendations besides an expensive FLIR camera?
@Jeff_Parish I’m getting a vertical strand anywhere from 180 C to 250 C. I didn’t even bother testing it outside that range, it literally behaves no differently except for different levels of ooze after extrusion. It seems to be fine at 210, not much ooze and still easy to extrude. Drying has helped but not enough. I’m doing some more tests now.
@Nathan_Walkner where do you put it though? It’s too large to go in the nozzle. And FLIR works pretty good, are you thinking of the cheapo laser thermometers?
@Adam_Steinmark That is pretty much the entire melt range of the most common printing materials combined. Strange that you see no difference. There should be some point where it is too cold to extrude well. It might start to build up chip on your hobbed gear. What size nozzle are you using? What are the extruded diameters at the several different temperatures across the range?
I’d go with as cool a temperature as you can where it is still easy to extrude without chipping. Maybe 210 is that number?