2-4rd Layer Underextrusion

[deepshots 2]

Pretty much since I have had my UM2 I've suffered from slight under-extrusion in the layers just after the bottom layer. This is usually worst in the 3rd layer when the fans fully kick in.

I print PLA with 0.1mm layer with slightly slower speeds. 210C for nozzle and 60C for bed. Otherwise standard settings.

My parts are usually mechanical with tight restrictions on the outer diameter so I don't level the bed super close to avoid the first layer gain/squeeze. I still get nice solid and flat first layer though.

I have 0.6mm bottom/top and 0.3mm initial layer so my printer does 4 layers before starting infill. The layers 2-3 are usually the worst... the fill ends up being bit like webbing and you can see that the two ply walls are not perfect either. By the 4th and 5th layer everything is proper solid already. Looking at the final piece from side you can see this also as a little indent before the things clear up. Generally I'm happy with the overall results.

I would not be too fuzzed but the first couple layers are actually the most crucial for my designs as that's where my gear teething are supposed to mesh. I've read the Visual Ultimaker Troubleshooting Guide by 3DVerkstan

Any ideas how could I further improve my second and third layers?

Regards

 

[IRobertI 435]

Perhaps you could try kicking the fans on more gradually if that's possible for your design. That way the head will have more time to compensate for the extra air flow. Since you say it coincides with the fans going up to full speed I'm guessing that the PID loop doesn't quite have time to react to keep the temperature stable.

You could also try printing a little bit hotter so that there's a larger temperature margin for the plastic to stay hot enough.

 

[gr5 1,120]

I suspect it is nozzle temp is too cold for the underextruded layers. Leave the printer in the TUNE menu while printing and monitor the temp closely when going over the problem layers. Consider increasing the nozzle temp a bit if thats the problem. There maybe some temperature isulation factor between the temp sensor or the heater and the block causing the PID controller to oscillate for the bottom/problem area.

Consider printing at anywhere up to 240C (240C is a safe temp for PLA but don't go any higher). The warmer you go the easier the plastic flows (less viscous).

 

[deepshots 2]

Instead of doing the fan control from the printer's own menu can I gradually bring in the fans via the expert menu? I've seen the fan settings there but It wasn't clear if I could increase like +10% each layer or so until 100%