Layer adhesion issue

[helpmeplz 0]

Slicer: Cura 5.1.0

There's a long delay between layers when printing large parts, especially when ironing.
This causes poor adhesion of some features.
Is there a setting to slow down print speed of these islands? Or some other solution. Without using a cutting mesh.

[Slashee_the_Cow 410]

Ironing is a very slow process by design, so there's not much you can do about the delay there (you could speed up the ironing, but it would defeat the purpose . To slow down those islands you could use a post-processing script to lower the speed once it's finished the main body. The ChangeAtZ script which comes with Cura can do that.

(BTW: it probably won't make a difference to this problem, but it's generally best to run the latest versions of stuff - Cura 5.1.0 is over two years old by now and 5.8 is the latest)

[helpmeplz 0]

14 hours ago, Slashee_the_Cow said:

Ironing is a very slow process by design, so there's not much you can do about the delay there (you could speed up the ironing, but it would defeat the purpose . To slow down those islands you could use a post-processing script to lower the speed once it's finished the main body. The ChangeAtZ script which comes with Cura can do that.

(BTW: it probably won't make a difference to this problem, but it's generally best to run the latest versions of stuff - Cura 5.1.0 is over two years old by now and 5.8 is the latest)

ChangeAtZ script looks okay for some scenarios, but counterintuitive for parts like this.
The ideal solution is a setting that decreases speed relative to previous layer area / island area

[gr5 2,224]

When you say "without using a cutting mesh", do you mean a "mesh modifier"?  As that's what I recommend.  A mesh modifier and you can have it change the print speed for any region.  If you've never used them, there's some great youtube tutorials.

 

You don't have to design your own mesh in cad, instead in cura, just select "support blocker" in PREPARE mode, click on your model, then you can move that around, change it's height/width/depth, duplicate it (if you need more than one), and switch it to be a "mesh modifier".

[GregValiant 1,342]

"The ideal solution is a setting that decreases speed relative to previous layer area / island area" 

 

Yes, but that would require a ton of work for a niche problem.  Better to do as gr5 suggests and use a mesh modifier.

The blocks do have a downside when used this way.  A cutting mesh will create a seam if it intersects a wall.

 

The island on the right will be fine as the changes happen at a layer change only.  The island on the left will have this seam where the mesh modifier has "cut" the wall of the model.

 

Since your model has islands then all the changes will happen at a layer and you won't get the extra seam.

[helpmeplz 0]

Thanks for the insights, and yes I meant mesh modifier. 
Although again, not practical with complex parts and printing a large number of variants

[Slashee_the_Cow 410]

8 hours ago, helpmeplz said:

The ideal solution is a setting that decreases speed relative to previous layer area / island area

As @GregValiant said, that would be a ton of work. I'm just wondering if you could use the time the previous layer took (easily accessible to a post-processor) as a "close enough" value of it.

 

What material are you using by the way?

The only time I've ever had a problem with something like this was printing ABS, and that's because it can barely adhere to itself in the best of circumstances, and it'll warp if you so much as look at it the wrong way 🤨 - not that you should be close enough to look most of the time because the fumes are poisonous.

If you're using PLA it definitely shouldn't matter. PLA doesn't even need a heated bed and the layer below should provide more than enough surface area for adherence. I've done art prints which have had large areas printed slowly then ironed and I can still print stuff that goes further up (even islands) fine.

PETG loves sticking to itself even when you don't want it to - which is whenever you'd like to retract it. I've actually gone back to stuff I printed a few hours before but left on the bed because I wasn't there when it finished or I couldn't be bothered dealing with it at the time, thought "I'm not happy with the surface quality on top" and printed a couple of extra layers straight on top (don't try that one at home unless you know how to properly mess with gcode).

TPU has much the same properties in this regard as PETG except double or triple as much, with the bonus that it will adhere to other kinds of filament as well as itself.

[gr5 2,224]

On 8/23/2024 at 4:38 PM, helpmeplz said:

not practical with complex parts and printing a large number of variants

 

I'd have to know more but if you want, the mesh modifiers can come from your cad software.  if that helps.  That way they can be precisely located.  You can load in the mesh modifier STL files just like you load your main model.  There is an easy way to get Cura to honor the relative positions of the 2 STL files.  The second STL file (the mesh modifier) can have one or many separate solids in a single STL file.

[gr5 2,224]

You could also create a post processor in Cura.  They are pretty easy to create.  I created some without even knowing Python (although I am a programmer so that helps a lot).

 

I'd start with the "tweak at Z" post processor (I forget the exact name - it might be tweak at layer?).  Look at the code and you just want to make a few changes.  The speed is in the "F" part of the gcodes.  So anytime you see "F" on the layer that you care about - change the F value to the speed you want.

 

The whole post processer will be maybe 20 lines of code.  maybe only 10.

[Slashee_the_Cow 410]

5 hours ago, gr5 said:

I'd start with the "tweak at Z" post processor (I forget the exact name - it might be tweak at layer?).  Look at the code and you just want to make a few changes.  The speed is in the "F" part of the gcodes.  So anytime you see "F" on the layer that you care about - change the F value to the speed you want.

You mean "ChangeAtZ"? That's about the worst built in script to try and use as a base. It's incredibly slow, seems to have been written in the Python 2 days and only received the minimum of updates to make it valid Python 3, and despite being more comments than code its logic is inscrutable and impossible to follow, implements its own helper functions for things built into Python, fails to use generics resulting in a massive amount of code duplication... I think I've made my point.

 

Eh, nut to this. I'll make my point again. Here's the size of all of the included scripts:

You're aiming to create one of the ones which is 2-3 KB. Not the biggest one. Also I'm going to poke @GregValiant here and say that AddCoolingProfile is a lot bigger than it needs to be if it were written more efficiently, which would help make my point because the bigger the delta between the sizes of ChangeAtZ and the next biggest script is the point.

[gr5 2,224]

insertAtLayerChange.py sounds good then.  Short, simple, and some of the code will be the same.