Stringing 

Finally! I have got the first good print on my Anycubic i3 Mega printer. But, it was real, real pain to get there. See my first print and the current one. This is a cover for the encoder display which is going to be a present for my dad's birthday. Firstly, on the bottom side, i.e. the side where the print starts, there is visible stringing. Secondly, there are gaps between each pass. It looks awfully. 

<Picture here>

During printing I heard some noise from the inside of machine. I was suspisious it is the PSU since I recently replaced the fan and never printed after it again. Still, the PSU was not noisy at the beginning of printing as the power transistors are cold, so I didn't concentrate my self on this issue at first. What truly bothered me were the gaps between each printing pass. I started to think that the infill motor has no power since I also replaced the drivers and I thought the driver perhaps does not have enough power to push enough filament through the nozzle. I also noticed that there is no re-track before the rapids. In Cura, I checked the options for retrack and Z-hup, but as I said the re-track was not occuring during printing. So I thought it hast to do something with the motor. OK, I opened the printer and set the voltage to 1.2 volt, thinking this is surely sufficient. Assembled printer together and start to print..... and …. no difference. Damn.

Ok, then is the driver not working properly - I still didn't see any real retrack. Or perhaps the motor is not working? I checked the motor windings, they were OK. Then I opened the printer again and replaced the driver with the one, which was originally installed. It did not help again. Oh boy!

The PSU started to make a noise again. This was now the third issue. I looked from the back I notice that the fan is really not turning. I opened the printer for the third time, replaced the motor driver again with the better TC2208 and also opened the PSU. After some time I concluded that the circuit managing the fan is not working and therefore I decided to connect the fan to permanent 12V. During the work I somehow messed up the fan and it stopped to work. I'm ordering a new one, but for now I'm using an spare fan 8x8 mm which I found in my garage. It is terribly loud but at least PSU does not suffer. I put all together and started to think why I have the stringing there.

OK, at first I want to see how the print looks with the old Owls model delivered with the printer. I found out that the owls are not anymore on the SD card and I had to delete them. Good there is the freeware Recuva with which I was able to recover the G-code file. I started to print the owls and noticed that the retrack works! OK, it must be something with the Cura settings. I recalled that my friend told me he had a terrible results with the Cura 4.0 (I have Cura 4.2.1) and for this reason hes switched back to Cura 3.6. I decided to the same. I also made a couple of changes in the settings to match the Owl example (although I'm using smaller speeds). The print was now much better, but the stringing was still there. The gaps almost disappeared. But here I don't think it was Cura's settings problem, the reason was probably the distance of the nozzle from the bed - it was to large I guess. OK, the gap issue is solved. What the hell is with the stringing. The motor does not retrackes before rapids as it was clearly visible with the Owls. 

I started to compare the g-Code generated by Cura and I noticed that many rapids are broken into 3 lines. And now the bells started to ring. If the rapid is only described by one line and distance is larger than 1.5 mm, than there is a command for retract. But, if the rapid is coded on 3 lines and the first G0 command rapids by less than 1.5 mm than there is no retract no matter what value is given in the next G0 rapid.  Here is an example from my code:

G1 X44.473 Y99.638 E51.5538
M204 S3000
M205 X10 Y10
G1 F2400 E45.5538 ; here retract since in the next G0 is the travel distance larger than 1.5 mm!
;MESH:cover.STL
G0 F3600 X47.354 Y103.835
G0 X47.354 Y105.354
G0 X47.965 Y106.294
M204 S1800
M205 X8 Y8
;TYPE:WALL-INNER
G1 F2400 E51.5538

But here the retract command G1 Fxxxx Exxxxx is missing:

G1 X47.965 Y106.294 E51.59687
M204 S3000
M205 X10 Y10
G0 F3600 X47.867 Y108
G0 X47.996 Y108.729
G0 X54.376 Y120.628
M204 S1800
M205 X8 Y8
G1 F1200 X54.35 Y120.941 E51.61149

After few minutes I noticed that there is an option for Combined Distance Retract. This is set by default to zero, which means that this function is not turned on. I changed it to 2.5 mm and generated the g-Code. Opps. Nothing happened again. What? It can't be right. OK I clicked on z-Hup enable, generated the code once again and Hurrai! Retract is there!

G1 X44.473 Y99.638 E51.5538
M204 S3000
M205 X10 Y10
G1 F2400 E45.5538
;MESH:cover.STL
G0 F3600 X47.354 Y103.835
G0 X47.354 Y105.354
G0 X47.965 Y106.294
M204 S1800
M205 X8 Y8
;TYPE:WALL-INNER
G1 F2400 E51.5538
G1 F1200 X47.9 Y106.387 E51.55909

If I disabled the z-Hup again the retracked ….. showed or not ???? check << It seems that Cura 3.6 does not update the 

Look the final print! Awesome.

So what is the current setting ? This one and I don't think I will it change again:


I should also



thought that the infill motor does not have the power to feed