Stringing problem printing filament roll-off parts SOLVED

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Stringing problem printing filament roll-off parts SOLVED

Post by Mike »

I have tried and failed around 15 times now to print the filament roll-off parts that I downloaded from the accessoires folder, and I think I really need some help please.

I have a DIY Felix 3.0 Dual extruder with LCD and print with blue PLA bought with the printer from Felix. I download the gcode file for the Single extruder 3.0 printer, since I have not managed to align the two hot-ends and thus only want to print with the lower one. Then I print the downloaded file from SD-card. (First question, is the gcode for the single extruder printer good for use with the dual extruder printer if I only heat and use one extruder?)

It usually looks fine for the first 5-10 millimeters or so, but then stringning over the holes becomes more and more problematic and I stop the print when I realize that the quality is not usable.

I heat the bed to 58C and have no problems with bed adhesion. I always home all manually and have less than a paper width distance between nozzle and bed. Bed is leveled, and the nozzle-print distance is fairly constant throughout the print. I do all interaction from the LCD. No computer attached to USB. 20C room temperature, no draft. The 40x10 test print prints just fine with high precision, although the walls are not entirely water proof, with some needle size holes.

I have tried;

1. All hot-end temperatures from 195C - 235C in 5C increments. Higher seems somewhat better, since the edges of the part looks better and the part becomes stronger, but the print still gets messed up after a while. Temp i constant throughout the print according to LCD.

2. Increasing the flow from 100% up to 120%. Perhaps somewhat better with higher flow, but still no solution.

3. Tensioning the extruder arm back and forth. I have checked that the wheel grinds tiny teeth marks in the filament, and I can't stop the filament feed with my fingers. Should be OK then, right?

4. Manual extrusion, and a fine nice string of filament comes out, curling up after a while on higher temps.

5. Different fan speeds from 25% to 100%

6. Different print speeds from 50% to 100%. No significant diff, although somewhat better on lower speed.

What I noticed and that might be related, is that the Z Home is unreliable. I usually need to click Home Z (or Home All) 3-6 times before it is actually home. It often stops before real home. Could this cause the above problem?

Í would be really thankful for tips and advice on how to deal with this. What more can I try? Many thanks!

I solved this by connecting all optosensor Vcc cables (red) to 5V standby (purple) through one 180 Ohm resistor per sensor (so to limit the current to 20mA per LED thus avoiding blowing the LEDs). It turned out the optosensors triggered sporadically during printing and hence sporadically prevented Z-axis upward movement, which eventually built up enough overgap between surface and hotend so to cause stringing. I suppose that also X-axis and Y-axis movements sometimes stopped short from the target, contributing to the problems building up. After this bypass operation, my Felix 3.0 with electronics board version 2.1 and Vishay TCST2103 optosensors, works perfectly! I am really impressed by the results..
Last edited by Mike on Sat Jun 14, 2014 9:35 pm, edited 1 time in total.

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