Printing problems after some time without printing

Hi all,

I haven't use my printer (Prusa i3) for some time. A couple of days ago a friend of mine asked me to print a case for his Raspberry. I checked the nozzle hight, and a couple of things more and I printed the parts. I noticed that the quality was really poor compared with what I used to print.

I wanted to calibrate and do some service to the printer. I calibrated the filament again (E-Steps and extruder multiplier), I adjusted the Z-end stop and leveled the bed so that the nozzle is between 0.05 and 0.10 mm from the headbed. Previously I dried my PLA filament for a couple of days because it was standing on my desk for all this time.

It's taken some time but I got some decent test parts (cube). However when I finally went to print the case again I've noticed some issues.

1- Even though the nozzle is well set in high in the four edges of the bed and also the middle, when I print it seems that the hight of the nozzle is significantly larger when printing. The result is that the first layer is no squezed good enough on the bed. No matter how tight I try to set the Z axis, this allways happens. Further layers semm to be ok and the nozzle is right on the surface of the previous layer.

2- When the part was printing and it began to print non-contiuous sections of one layer, things have gone south. See closeup_1 attached. I don't know if it is a problem of retraction of the filament, but I checked and it's set to only 2 mm. I'm using Slic3r, by the way.

3- I'm guessing that derived from #2, it seems that the flow of filament is not quite right after that. See closeup_2 attached. It seems like it's not constant. I've never seen that before and I don't know how to handle it.

4- Also, if seen from above, you could see quite some filament from one place to another, when the nozzle has to move without printing. from this I would say it need more retraction, but then I guess problems 1 to 3 would increase.

The printer sits on a level table and the headbed is well leveled (with a water spirit). Extruder is a Greg Wades with a fan on the shaft and it's not jamming.

Any help finding some solutions would be much appreciated. I'm so confused I don't know what to do next and I though I could ask first.
Thanks in advance to you all!

having a fan pointed at the nozzle tip to cool the printed part would almost certainly make a substantial difference, although it may not solve your problem entirely. You can make a cone shaped duct out of paper and use any old 40 or 50mm fan. Even better would be a pair of centrifugal fans.

Maybe try slowing the print down to see if you get better results

In addition to kre8, check if the extruder isn't slipping, seems you've got some underextrusion on the top. Do you use auto bed levelling? Increase z offset in 0.1mm increments. It will be closer to the print bed. Make sure you use the correct thickness of paper or gauge to level the bed when doing this manually. 80g printer paper works best, or a metal 0.1 gauge.

Bit concerned about how you level your bed with a spirit level.
Your should not be aligning it to The frame but to the axis's the print head moves in.
There is no way that you will have built the printer to the tolerences neccesary for all of the axis to be perpandicular to each other and aligned to the frame.

You need to put the print head at at least 4 positions on the bed and then adjust the bed till it has the same gap between the nozzle and the print surface.
[reprap.org]

Also bed levelling and the gap between nozzle and print bed must be done when the printer is at full printing heat or the nozxle gap will be different due to the heat expansion of the metals.

Gordon

Hi all,

First of all, thanks for your responses. Sorry I haven't responded yet.

I don't use auto bed leveling. I just use springs on each of the four edges of the headbed. Using a metal gauge, I set it so that the 0.05 mm gauge passes between the gap but the 0.10 mm doesn't. The water spirit is used only to check that the whole setting is level.

What I've been doing yesterday and today is to play with the retraction settings on Slic3r. My original print was with 2 mm of retraction (and 0 mm of Extra length on restart). With 1 mm (and 0 mm) was a little bit better. With 2 mm (and 2 mm) was even better and I've just finished a print with 1 mm (and 1mm) and it looks much better already. Next thing to do is t play with the temperature, I guess.

Thanks a lot!