Destring settings

[pjr]

Hi Guys

Need some advice here about the destring settings.

This is using an Afinibot - a Chinese version of i3 with what appears to be a Mk8 extruder.

When using Cura, I could stop stringing almost completely by setting retract to 6mm and 45mm/s. However I think read somewhere that setting retract distance too high could cause some issues, so within KS I have tried a variety of distances up to 6mm, with speeds set to 15 (prime) and 45 (suck). But I still have major stringing.

I have reduced the extruder temp to 195, which is about the lowest I can get to and maintain a good print. I also have Z lift set to 0.3mm.

I really would appreciate your advice here.

Many thanks in advance.

Peter

[pjr]

Guys

An example of the strings. PLA @ 195, with 6mm suck/prime, suck @ 45, prime @ 15.

Or is this normal?

Thanks

Peter

[plexus]

Try it without Z lift. one way to manage stringing is so move the print head as fast as possible especially after a retract. the Z lift is going to spend time in one spot moving up and then down giving time for filament to ooze out. so i'd turn off Z lift and try it. no need to print a whole print but just enough to see if its the culprit. if not (if you still get stringing), quit the print and try something else. no need to waste filament. let us know if that helps.

[pjr]

Hi Plexus

Many thanks for your input.

I have now tried a variety of settings, with the best result being a 10mm retraction at 50mm/sec with no z lift, at 175 degrees, with reduced speed to compensate for the lower temp.

Unfortunately, although better, it is still really bad. And this was with Cura and a small test print - printing directly via serial interface.

I hadn't tried Cura recently and assumed that the prints would be OK. Slapped wrist for me then!

OK, so I have to look at what's changed. Well, the nozzle has changed and also the barrel, The original nozzle blocked on an overnight print last weekend and I had a couple of spares arrive Monday. I damaged the PTFE tubing in the barrel when I was removing the blockage and replaced that at the same time as the nozzle.

The barrel is pretty much the same as the original, so I don't think that's the cause, but the nozzles are quite a bit smaller than the original (6mm a/f vs 8mm a/f). They are also not marked with the size (although I ordered 0,4mm).

I have noticed that filament does rather stream out of the nozzles at the end of a print and then continues to fall out while cooling down.

I wonder if there is a problem with the nozzles, or could they be oversized?

Hopefully, some more nozzles will be arriving early next week.

Thanks again for your help.

Peter

[pjr]

Solved

OK, I eventually found that it was not the software, nor the changed barrel/nozzle combination.

I suspected temperature issues, so using a probe I have for checking R/C Nitro engine temps, I checked out the hot end and was getting readings of 235 degrees in places, when the extrusion was set to 190.

So today, I took the hot end apart. I found that the PTFE sheaths on the thermistor wires were about 2mm short, which allowed them to touch and also to short to the heater block.

A small piece of kapton tape between and around the end of the wires and the strings have disappeared. Yay!

Thanks again for your input on this.

Peter