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[Cura 2.4] "Initial Layer Speed" independent of "Wall Speed" ?

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- Cura 2.4, Ultimaker 2+ (with firmware Dec8 2016 13:57), UltiGCode flavour

I have issues with adheasion to the buildplate (ABS/PLA from RS components), especially if the first layer consists out of many walls:

IMG_20170319_131858.thumb.jpg.bc0ddf6bdbea6a10b6e047821efc6c39.jpg

The walls are printed independantly and, if not sticky or if some oozing added material to them on top, they may get moved by the printer nozzle while travelling. To prevent this, I already set the "Initial Layer Height" the same as the general layer height and ask the printer do avoid printed areas.

I found some speed which makes adheasion good enough and thus adjusted the "Initial Layer Speed". However, it seems that it doesn't influence the "Wall Speed" of the initial layer at all (the most crucial bit in my scenario). Thus, I had to set the overall "Wall Speed" for the whole print very low to meet the requirements for the initial walls/circles, which obviously extents the printer time drastically.

Is this the intended behaviour, or is this a bug? Thinking about a solution, I may not change the initial layer speed at all. Instead I rather change the overall speed in the printer settings when printing the first layer? I personally don't like this too much since it occupies me a lot for the first moment (Seeing a print happening is still too fascinating :D )

IMG_20170319_131858.thumb.jpg.bc0ddf6bdbea6a10b6e047821efc6c39.jpg

Edited by Guest

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Hmn, well yes it does! I have never seen different speeds on the intial layer. I.E. if print speed is 50mm/s amd initial layer is set to 20mm/s, everything on the intial layer gets printed at 20mm/s. I will cc @nallath in here as I have no idea why you are seeing this.

Yes you have a tricky print there. I would suggest

1st layer print speed no faster then 15mm/s

Reduce the nozzle to bed depth (yes I know you have probably done auto levelling) to make sure that 1st layer is really being squashed down - you can always back it out if you go to far

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Initial layer height is actually to improve adhesion (as you slightly over extrude, making it stick better). Glass plates are not that flat. I seem to recall that they are +-0.1 mm, which is why we use 0.3 for the first layer.

As for what the engine does with those settings; I don't have a good view on that.

I've had decent results with increasing brim or using raft. Another thing I tend to do is to use concentric fill for bottom layer.

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Initial layer height is actually to improve adhesion (as you slightly over extrude, making it stick better). Glass plates are not that flat. I seem to recall that they are +-0.1 mm, which is why we use 0.3 for the first layer.

As for what the engine does with those settings; I don't have a good view on that.

I've had decent results with increasing brim or using raft. Another thing I tend to do is to use concentric fill for bottom layer.

 

Can you set concentric fill for bottom layer only?

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