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ponut64

Feature Request for Cua: Disable Walls for First Layer Only

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Hi,

With PETG in particular, if I have any first layer with meticulous detail (on my Wanhao i3 V2), what will often happen is during printing the walls, the plastic will stick to the nozzle on a travel move and remove all or some of the previous printed wall from the build-plate. It will also stick to the nozzle and gum up and future walls, so if this happens once, it generally ruins the entire print.

However, if I pay attention and it doesn't happen too badly (with PLA mostly), I can clip off the nerds of curled up filament and try and "baby" the print through until its done with the walls and it starts moving to the infill. What sometimes happens is there ends up being no walls left on the first layer (because I removed them all) and the first layer fill starts. This prints wonderfully, and the print continues just fine.

So for PETG, in order to achieve this level of first-layer detail, I NEED to disable the walls. The only way I can do that in Cura right now is set the wall width to 0. This disables the walls for the ENTIRE print, so in order to properly fill out the model, I have to move to a very high fill ratio (95+ or more). This is far from ideal.

So I have a simple feature request: The option to disable walls for first-layer only. This setting will also remove the bottom layer fill offset so it will expand to fill the area that would normally be occupied by walls.

Thank you for reading. This feature would be so helpful for me.

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Hi, that's an interesting idea and it may well be worth investigating.

Here's my experience.... I am printing PETG and have found that first layer adhesion is helped hugely by raising the nozzle 0.1 or even 0.2 mm above the normal first layer height. PETG doesn't seem to like being squished onto the build plate. I don't mean use a thicker layer but keep the layer thickness the same and raise the nozzle. Some printers provide you with a way to raise/lower the nozzle manually (aka baby-stepping). I can do that but have recently created a mod for Cura that let's you raise/lower the nozzle from a setting in Cura so you don't have to remember to fiddle with the printer controls. For me, that makes a big difference in the quality of the first layer when using PETG.

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.... I am printing PETG and have found that first layer adhesion is helped hugely by raising the nozzle 0.1 or even 0.2 mm above the normal first layer height. PETG doesn't seem to like being squished onto the build plate.

I have found the same thing. On my Robox printer I have the ability to go in and raise the Z-offset , .05mm seems to work well on that printer. However, with the Ultimaker 3 Extended, I have not found a way to adjust this setting in Cura. You say you have recently made a mod to cura to accommodate this, would you be willing to share this mod?

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You say you have recently made a mod to cura to accommodate this, would you be willing to share this mod?

Of course, it's already in the PR queue waiting for the Cura devs to consider it. Another PR that is pending is the ability to specify the height at which part cooling fans turn on. At the moment, they always start on layer 1 but I have found, again with PETG, that I get much less shrinkage at the bottom corners if I delay turning the fan on until, say, 5mm (or whatever).

With luck, these PRs (or variants) will find their way into 2.8.

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Hi, that's an interesting idea and it may well be worth investigating.

Here's my experience.... I am printing PETG and have found that first layer adhesion is helped hugely by raising the nozzle 0.1 or even 0.2 mm above the normal first layer height. PETG doesn't seem to like being squished onto the build plate. I don't mean use a thicker layer but keep the layer thickness the same and raise the nozzle. Some printers provide you with a way to raise/lower the nozzle manually (aka baby-stepping). I can do that but have recently created a mod for Cura that let's you raise/lower the nozzle from a setting in Cura so you don't have to remember to fiddle with the printer controls. For me, that makes a big difference in the quality of the first layer when using PETG.

I did try that! It helped *a bit* but not enough, and not in the right way.

What ends up happening in that case is the walls still don't adhere completely, and the fill ends up curling up on itself so the nozzle knocks into it anyway.

But thanks for the hints about the fan. I always tried to turn the fan on earlier with PETG, so the plastic would curl up less. Maybe I just take that bad philosophy from PLA...

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My trick for printing with PETG is to print the first layer at the top-end of the temperature range listed for the filament. In my case, its 240c.

This makes it flow like hot honey so its doesn't get pulled around on travel moves. It also sticks better to the build plate (PrintBite, in my case).

After the first layer, I reduce the Nozzle Temp to my normal setting for PETG (220c)

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Unfortunately my printer can't go any higher. I'm printing at 245 C and any higher and the machine will go into DEF mode (temp safety) after a bit.

And that, as you might imagine, is a bit of a problem when I am using a stainless steel nozzle and the filament manufacturer suggests 250 C. But if the prints finish, they come out fine.

I managed to finish the print using a raft. I'd like to have not had to use a raft, but ah! One can dream...

Edited by Guest

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I noticed this morning that there is also an option in CURA to "Print walls after infill". Wouldn't this help solve your problem as well?

Robert

The "Infill before Walls" setting does not apply to top and bottom layers, as that's not technically infill, that's the "skin" of the model or otherwise technically an entire layer of walls. That setting applies only to layers in which there is infill affected by the infill settings parameters (like infill percent, pattern, and so on).

All of that to say, turning that setting on or off does not make the first layer fill the layer before it prints the walls. Even if it did that, I am certain the walls would still screw up.

I have also tried printing very slowly. I mean, down to 15mm/s. That didn't help either. I appreciate everyone's suggestions, though I am in a unique situation where I feel as if I have tried almost everything I can, and it probably won't be a complete solution to disable walls for the first layer. But it would help me.

Even after all these tweaks, I still think I would be better off replacing my control board and/or the wiring to fix the massive temperature fluctuations my machine gets. That way I could print at a higher temperature.

Putting gluestick on the tape would probably also help.

But further still, changing the printing pattern would help, too.

Edited by Guest

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