First layers going funny

Question

I've just bought my first 3D printer (Malyan M200 V2). For the most part, it's been really good and I've had no issues, apart from when printing the first few layers the printer doesn't seem to extrude enough material and doesn't form the correct shape. Whether it's a circle, rectangle, or anything else. So for example I've printed the below part.

The raft prints perfectly:

Then when it starts the first few layers of the actual print it extrudes a bit of material which then hangs from the nozzle and is dragged about the surface of the raft before stopping as more material is extruded. So when the print finishes the first layer looks messy like the one below:

But everything after the first few layers is perfect for example the top of the same print:

I've tried adjusting the temperature of the nozzle and the print bed neither has made a difference. The bed is level I've double-checked that. Trying to find the issue online keeps bringing me back to temperature or bed levelling.

I'm using this PrimaValue PLA Filament

The leaflet in the box recommends printing at 210 °C, I've tried 210, 215, and 220 °C.

The print bed I've been keeping at 60 °C which seems to have been working but I've tried printing down to 45 °C on the print bed and the same issue occurs. I'm not sure what an ideal temperature is for PLA, I've seen some posts saying that a heated bed isn't needed for PLA and others saying that it should be heated to between 50-70 °C (my printer only heats up to 60 °C).

I've looked at some of the settings in Cura and there are various settings for things like initial speed and first/last layer speed which sound like they might help but I don't know anything about them. I have tried slowing down the print but again I just watched it happen more slowly, albeit that did help some as that's when I've realised it doesn't appear to be pushing out enough material on the first few layers. Any help or suggestions would be greatly appreciated.

Answer 1

PLA doesn't need a raft.

Try printing without a raft. If you print with a raft because of adhesion problems, solve those first. A raft is only needed for filaments that shrink a lot and/or are printing at very high temperatures.

If you want a raft, check the distance between raft and print object and know that a raft never gives a smooth bottom. This is because in order to prevent fusion of the print object to the raft a distance between the raft and the print object is accounted for. A property that controls the distance between the raft and the print object is called Raft Air Gap in Ultimaker Cura. Default for my setup this is 0.3 mm which I find rather large.

For example (not raft, but support with a solid top layer, which is quite similar to a raft), I have used support structures with a roof to support large flat overhanging areas that where printed at 0.2 mm distance, this gave relatively good surface quality and barely no fusion to the print.

Answer 2

It seems to me that the problem is over extrusion. Those temperatures might be a little high for this PLA. In my settings I usually put it on 200 or 205 °C (when printing faster). But the real problem might be a wrong extrusion multiplier for the first layers or a mixed with temperature, low speed, or no retraction.

My advice:

1. Try a little bit lower temperature
2. Try reducing the first layers extrusion multiplier
3. Try increasing the retraction a little bit

For the problem of not extruding plastic at the beginning, you should print a purge line (as Ender 3 does) or print a skirt (instead of a raft, that you might not need). This problem is very normal and is easily fixed.

The bed temperature is correct for PLA (60 °C). Maybe, only maybe, your nozzle is a little bit high. It should squash the plastic on over extrusion, which I think is not happening in your setup. My advice for this is to use a paper sheet and fold it once.

Answer 3

In Cura, you can indeed set the height of the first layer separate from the subsequent layers. So if the first layer is printing nicely, that's a good sign. That's usually the place prints fail. There are a few settings, but here are a few things to just double check:

• Is your nozzle set to the right size
• Is your raft layer height and regular layer height wildly different? Try setting them to the same, or if same, try making them different. There may be a 'raft top thickness' that's wrong for the nozzle size, (try 0.2 for a 0.4 mm nozzle)
• Layer height of your regular layers should be no greater than 80% of the nozzle width
• Print cooling (on), but initial fan speed (0)
• Supports: try printing with, or without. Look at Enable Support Interface (or disable it)
• Try just disabling your raft and see if it gets past the danger point. that will indicate if there's something misaligned with your Z.
• Check your axis rollers too! from this question, First 3 mm prints poorly, then fine after that

Answer 4

Hi Thanks for all the suggestions. I've been experimenting with various prints using some of the different settings and it appears that I needed to increase the initial layer height. Now the first layers are printing as they should.