Poor prints; stringy, won't stick

I’m having problems with getting good prints. I’ve made some good prints:

but generally the PLA doesn’t stick, it collects on the nozzle and then the nozzle pushes the mess around, resulting in something like this:

and this:

That’s supposed to be a square and is obviously leaning on the extruder (I canceled this when it was clearly not going to work out).

The bed is slightly higher in the center than the corners–but not much, with just enough space to pass a sheet of paper between the bed & nozzle. I’m using these settings:

Extruder temp: 190 C
Printbed: 50 C
Speed: 100
Extract: 5
Retract: 5
Autofan: off (this is PLA but cooling seems to make things worse)

This is all new for me so all help is welcome.


Are you sure your extruder is at 0.5 mm from the heated bed? Stringing is usually caused by printing from too high. The PLA needs to be slightly smeared agains the heated bed while printing, giving a line and not a string.

Use sanding paper on the heated bed and then degrease with isopropyl alcohol. There is no need for tape.

I put the extruder head at 0.25 mm from the heatbed (better a bit more than less but 0.5 mm seems too much to me).

If you’re using tape don’t overlap the strips as it increased the thickness at one particular spot and the extruder will scrap the plastic.

I’ll try sanding a little, but is the problem that the PLA is stringy or that it’s not sticking? If it would stick then I don’t think there would be a problem.

You can try this
Heat the bed to 55-60c
Find the highest place on the bed
Use 1 sheet of printer paper folded in half.
Home the Zaxis on top of the paper
Adjust the Z end stop until the paper drags a little
Turn off the motors in the software
Now move the bed around by hand with the paper under the nozzle making sure it just drags a little
Level the bed while you are doing this
Check one more time without the paper but watch it carefully so it does dig into the bed
Do not put tape on the bed
Then try to print some

Do this at your own risk