Feature Request for Cua: Disable Walls for First Layer Only

[ponut64 0]

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.

[burtoogle 510]

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.

[Traveler218 1]

.... 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?

[burtoogle 510]

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.

[ponut64 0]

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...

[DaHai8 74]

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)

[ponut64 0]

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 August 12, 2017 by Guest

[burtoogle 510]

Have you tried printing the first layer really slowly? I ask because I have just had a problem with PLA walls not sticking to a particular build plate surface and solved the problem completely by reducing the first layer speed to 20 mm/s. Maybe that would work for PETG?

[Traveler218 1]

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

[ponut64 0]

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 August 14, 2017 by Guest

[CumpyRules 0]

Hi @all,

So this is my first post, and first I will say a "Hello" to all. ... And Yes, I've seen that the thread is 2 Years old 😉

 

My question is, whether this feature was already implemented ? I have the problem, that I want to print an I/O cover frame. For this I placed the frontside of the frame to the bed on a glass panel to get a very smooth surface. But in the cover are a lots of holes for the connectors and the printer head have to move to a lot points to start the walls and also for the infill the head must start, stop and move to new start points for printing. Now I had the idea, that I add a completly closed layer with 0.2mm thickness to the model, which I will cut off after printing. I mean, the first layer is a closed surface without holes (This I have add to my model) and after the first layer, it will start with the walls of the lot of holes. The problem is, that when I start the print, the areas in the first layer, where later the walls will be, will printed now first with a closed surface, the moving of the head is in this case the same. If I could disable the walls for the first layer, I would get a evenly distributed matrial output from the print, because it must not move between al lot of new points for extrusion. Especially for covers it would be perfect to get an evenly surface. 

 

Greetz CR

[printnewb 2]

My I second this feature request?

 

For me it is exactly the same as the OP but also with PLA. Starting without walls on the first layer would be the solution

[GregValiant 1,141]

Just so I understand...

You want a single layer raft 0.2mm thick that will actually be part of the print, and the holes will be cleared out later as a post-process cleanup?

Have you tried using a Support Blocker configured as a Cutting Mesh?

 

Bring in a blocker.  Make the X and Y dimensions larger than your model.  Make the Z "Initial Layer Height" thick and set the blocker so your model rests on it.  Here the blocker is shown as a rectangular gray shadow a bit larger than the model.

In the Per Model settings set the blocker to "Modify Settings for Overlaps" and as a cutting mesh.

Use the "Select Settings" button and from the Mesh Fixes select "Remove all holes".  Check the box.  It will be the only setting.

This is the first layer with no holes.

 

This is a higher layer.  You can see that the 3 holes don't go through because of the blocker.  (The middle diameter has a split and so it doesn't qualify as a "hole".)

 

 

 

Edited March 1 by GregValiant

[printnewb 2]

Perhaps I misunderstood the OP. Please see my screenshot

 

 

in my scenario those holes on the build plate, which are walls, almost always fail. They come out curled up and are getting stuck on my BL touch. In my scenario the outer walls are not a problem though.

 

If we could just start with the bottom skin only on the first layer I thing the walls on the second layer will stick much better.

 

The alternative is to baby sit my print and remove all the failed circles (walls) during the first layer.

[printnewb 2]

correction, they are a combo of inner wall and a shell

[GregValiant 1,141]

That's actually a "build plate adhesion" problem.  When I have models like that I use hairspray as an adhesion promoter.  A glue stick would work as well.

An oddity here is that I actually wrote a post-processor to re-order gcode and print the first layer walls first (it was for a multiple model problem someone had) which is the exact opposite of what you want to do.  It required slicing 3 times, each with slightly different settings, and then melding the 3 files together into a single file that would be printed.

If you slice the file in "relative extrusion" mode you may be able to copy and paste the "Skin" section to place it between the Skirt and the Inner Wall section.  You might need to hand code some travel moves but its tedious rather than difficult.  It isn't something you'd want to do all the time, but for a single gcode file production part it would work.

[printnewb 2]

I'll admit it is working around the issues my sub par quality printer brings.

 

Thanks for the suggestion, I'll take a look at it and if I get stuck then I do not mind baby sitting 😉 it's not too long of a wait before I can leave the print.

[Dustin 84]

Yea I will agree with GregValiant.
This is a build plate adhesion issue.

Actually looking at the pathing generated for solid infill lines and the fact that some features require the shell to be first laid down to anchor to.. trying to resolve this issue with no shells would actually just result in more issues than you already have.

Would recommend focusing on the hardware issue and addressing that.

It could also be you are just trying to print the first layer too fast.. reduce the speed 30-50%