First few layers help (PLA) - Ender 3

I'm printing calibration cubes on my Ender 3 and I'm getting some pretty good results overall with the "Normal" Cura settings and a .4 nozzle. However, my first couple of layers are rubbish.

The cube on the left is my first test on Normal settings with 200C nozzle and 60C bed (PLA 1.75). .15 layer height, .2 initial layer height, .4 width. Infill 10%, Grid. Print speed 60, infill 100, initial layer speed 30.

Cube on the right has a lower bed temperature at 30C and lower printing speeds. Print speed 40, Infill 40, initial layer speed 20.

The print quality for the cube on the right is overall a bit poorer with more visible layers on the outer walls, and also the corners are less sharp. But more importantly, the lower bed temperature and the slower speed did nothing for the first few layers.

I have also included a photo of a cube that I stopped after the first couple of layers. As you can see it is not looking good at all. There are deep grooves for every pass of the nozzle. The grooves can be heard when the nozzle passes over the same area in the other direction as it scrapes the layer underneath.

Any ideas on how to fix this?

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you probably want to increase your z gap.
Ie: make the offset distance between the nozzle and the print bed a little larger.

I usually increase by 0.1mm untill you get a balance between a clean first layer and it not sticking to the bed.

If you calibrate with fairly thin paper this is a common problem.

Quote:

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Originally Posted by curious aardvark

you probably want to increase your z gap.
Ie: make the offset distance between the nozzle and the print bed a little larger.

I usually increase by 0.1mm untill you get a balance between a clean first layer and it not sticking to the bed.

If you calibrate with fairly thin paper this is a common problem.

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I did manage to try exactly that earlier this morning and it did give me a much better result. But it also resulted in one corner either not sticking or warping. The cube eventually also came loose. So one problem solved and two new ones have presented themselves.

Question about the z gap. Do you calibrate with both turning the knobs And digitally through the interface?

yes :-)

The initial calibration with the knobs is to try and get the bed as level as possible. It's the single most important aspect to getting good prints.

The z gap from the slicer, is to adjust how much downward 'smoosh' you give the filament. THis varies depending on how 'sticky' your actual print surface is.

Try adjusting in 0.05 mm steps.
And also recalibrate the bed.

I find that replacing the normal bed levelling nuts with locking nuts, helps. That way, once it's physically level - it should stay level. Vibration will cause normal nuts to move over time.

Quote:

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Originally Posted by curious aardvark

yes :-)

The initial calibration with the knobs is to try and get the bed as level as possible. It's the single most important aspect to getting good prints.

The z gap from the slicer, is to adjust how much downward 'smoosh' you give the filament. THis varies depending on how 'sticky' your actual print surface is.

Try adjusting in 0.05 mm steps.
And also recalibrate the bed.

I find that replacing the normal bed levelling nuts with locking nuts, helps. That way, once it's physically level - it should stay level. Vibration will cause normal nuts to move over time.

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Thanks again. I found that I had to download a plugin for Cura in order to change the Z offset. Did a quick and dirty yesterday and it seems to have worked. Much easier that way. Will do a proper bed leveling in the coming days and also get some locking nuts to hold it tight.

Next on my list is to get rid of the initial layer "blob". The nozzle leaves a small blob of filament when it puts down it's first layer. And it subsequently hits that blob when it comes around to the same spot. You have any handy tips for that?

most slicers (cura really isn't much good) will offer either a purge strip, or an outline round the print that gets rid of the blob and helps prime the nozzle.

I use a 2 line outline on the delta and purge strips on the others. I'll often use an outline as well - just to really make sure.

Outline and brim settings are often the same.
so you make a 2 line brim that is 2-3 mm offest from the print. A 0mm offset should make a brim.