Force top surfaces to be fully covered

[orestis]

I have a model that is basically a “base plate”, with some raised letters on top.

You can see a simplified version here Onshape

When slicing, it seems like the slicer “anticipates” that there’s going to be extrusions over the base plate’s top surface, and leaves a hole in there:

However, that results in the top surface layer pattern to be filled unevenly, travelling back and forth to fill gaps left behind. Also, the walls for the lettering are printed just on the edge of the solid infill layer, which makes them not so stable.

What I want to do is to force the top surface of the base plate to be filled entirely, e.g. with a monotonic line, with a smooth finish (perhaps even apply ironing to that), before proceeding with the next layer above.

For example (simulated screenshot where I just removed the top extrusion):

I have tried exporting the model as a single unit or in parts, but it doesn’t seem to make any difference. When I split into objects, predictably, I can’t move the extrusion on top of the base plate.

NB: this model is very simple for the sake of discussion, but imagine there would be lettering where the disk is, with much more smaller details.

When googling for this, I came across this Ultimaker Cura Forum Post that has this proposed fix:

I separated the letters from the top layer (in the model) by .02mm enough so that the slicer doesn’t create a hole at their base. That way the top surface prints as one uninterrupted flat area, then adds the letters on top starting on the next layer.

And also:

there is a Cura setting that can close holes called “Top Skin Expand Distance” (not a setting I could find until I was told about it) for which if you increase the value, it eats away the walls around holes until they are completely closed.

Is this something that can be done today in Bambu Studio, or should I try the trick where the two parts are separated in the model? I have searched also in Orca Slicer and Prusa Slicer but I couldn’t find any setting that does what I want…

[Olias]

First, thanks for posting such clear screengrabs with articulated descriptions. Hopefully this response will do your efforts justice and I hope I didn’t misinterpret what you stated and if so, please help me clarify.

To restate how I understand your post and feel free to correct me.

1. You have a model with a base plate and raised letters on top.
2. In slicing, the slicer anticipates extrusions over the base plate and leaves a hole.
3. This results in uneven top surface filling, with the slicer going back and forth to cover gaps.
4. The walls for the lettering are only printed on the edge of the solid infill layer, making them unstable.
5. Goal: force the top surface of the base plate to fill entirely (e.g., monotonic line) for a smooth finish before adding the next layer.
6. Found a potential fix on the Ultimaker Cura Forum:
   • Separate letters from the top layer by 0.02mm to prevent holes.
   • Use the Cura setting “Top Skin Expand Distance” to close holes by expanding the top layer.
7. Question: Can I do this in Bambu Studio, or should I separate the parts in the model? Also searched Orca Slicer and Prusa Slicer but found no relevant setting.

The answer to question in line 7 is; Yes, this can be accomplished in a number of ways. I can think of 4 or 5 immediately but I’ll list the first three that come to mind.

1. Create a Boolean merge and then use a modifier.(messy)
2. Use the logo as a modifier by duplicating it and adding it back into the assembly. Probably the best solution if you only want to impact the characters and if let’s say your model is one contiguous shape–Your OnShape example was two shape–This is tricky however and requires the most steps.
3. Keeping the imported model as separate objects then modifying only the logo. Your current model exported from OnShape already does this.(easiest)

I’ll focus on the easiest(Example #3) using your model from OnShape. Simply import your model and in the objects menu, select the logo and change the wall loops to a higher amount. This will trick the slicer into creating a solid

[orestis]

Thanks for taking the time to reply! Using multiple walls is definitely an improvement, at least the solid infill will be fully covered.

However, it still doesn’t address the top surface having a hole:

I tried “print infill first” which seems a bit better perhaps, as the walls will be printed last, but it still takes into account the extrusion and does this weird dance:

[Olias]

@orestis

However, it still doesn’t address the top surface having a hole:

I don’t think I’m following that. If you’re speaking to the fact that there is a gap between the top surface and the logo. That can be remedied in two ways. The first is to increase the number of top layers in the model. Or second, you can increase the bottom layers in the logo and sink the logo one or two layers inside the assembly. Both methods force the slicer to strengthen the material under the logo.

Last but not least, you can use suggestion #2, which is to use the logo as a modifier but increase it’s height. If my description isn’t clear, let me know and I will post a quick tutorial on how that can work.

[orestis]

I have tried adding a 0.2mm negative part (it’s in the OnShape model)

I get a warning that there seem to be floating regions but at least the top layer is continuous. It seems like the logo on top has a bottom layer that is an overhang wall plus bridge:

I will try a test print to see what that looks like.

[Olias]

I think I know what may be happening. Can you post an image of the entire sliced screen, to include the “objects” tab and the error message:

Or better yet, just upload the 3MF file so I can directly examine how the model was loaded and sliced.

[orestis]

Oh, the warning is just about the floating regions.

Here’s the project with the negative part that takes a layer off between the logo and the base plate:

logo slicing test.3mf (33.6 KB)

[Olias]

I think I see know what is going on. Here’s some examples of what I mean by changing the wall thickness and the affect it will have on the underlying structure. Let me know if this is what you reproduce.

At 4 walls for the logo. Note the holes appear at layer 19

At 5 walls thickness. Note the holes are diminished but still there.

And finally at 6 walls, the shape underneath is solid.

Off course you’ll have to increase the number of walls depending on the size of the logo.

Here is a better illustration side by side where three copies were made with differing parameters.
logo slicing test.3mf (47.4 KB)

[orestis]

Thank you very much for taking the time to go into this. It has me helped me understand a few of the issues at hand.

However, my desire is to get a solid red surface (top layer) before the logo walls are printed. This will lead the nozzle to do a single monotonic line pass across the area without any movement, leading to a very smooth and consistent top surface.

I will try doing a few basic shapes with extra walls as that does help with combining the solid layer together with the new shape on top.

[Olias]

Do you by chance have a photo of the lack of smooth surface that you are finding undesirable? I think I understand what you mean but I don’t understand how that can influence the appearance of the top layer? Why is it so important for the top layer to be unbroken if it is being covered by the logo?

[orestis]

You can see the linked post in the Ultimaker forums for examples (I’m having similar issues but I don’t have good photographs).

Additionally, having the logo walls already on the top layer, means the nozzle will cross them from time to time as the top surface is printed. Either that, or the nozzle will travel over the top layer to actually print the walls.

I think this might be a bit of silly exercise, since I have found a way (just slice away a layer and Bambu Studio will compensate by adding bridges and overhangs)

[Lenyo]

I think the very fist picture in the thread evidences the issue you are talking about.

We can see the start of the O with a light blue layers as a base (bridge) we can see the thin walls of the O barely filled with infill, so there will be another bridge on top that has to resolve in ‘top shell layers’.

This could all result in some ugliness of the top surface of the O. What to do about it? Not sure of the best way to handle it but you could just put a modifier around the O and a few layers down into the top surface in question and bump the infill way up for that area. There is probably a better solution but I think you get the idea.

[Olias]

Here’s one approach that worked.
logo slicing test 3.3mf (350.9 KB)

This was using the new Bambu PETG-HF. Also, ironing was applied to only the base, not the lettering. See attached 3MF for details. It is set for a P1 so you will have to change it to your printer.

[rclaus]

It’s hard to get a solution without a layer gap.
The only one I found is this:

• import STL/OBJ with separate text/base objects
• go to object mode, split to parts
• duplicate the objects (using copy/paste so the position doesn’t change)
• from the 1st copy: delete the text part
• from the 2nd copy: scale down the base part in X and Y direction only, move it to the side, change it to negative part (can’t delete it unfortunately or it won’t slice/text will drop to floor)

• slice with supports off

[geppetto]

I have a need for a solution with no layer gap. I tried following your directions, but once I change the base part of the 2nd copy to a negative part, it drops the text to the floor. My current solution is to just print the super-small/resized base part moved way off to the side which continues to force the text part to the top.

Do you have any suggestions about what I might be missing?

[Brodyttu]

So this is a little late, but I was trying to do the same thing, and it was difficult to find. This was one of the first answers in google so hopefully this will help someone who comes across this in the future. In order to do this you need to enable “develope mode” by hitting ctrl+p to load up preferences and tick the box. Then go to strength settings. and click the box for “interface shells” here’s the forum link I found the solution to Stacking prints, setting solid layer between color changes now just set the number of bottom layer infill, in the objects process, for the upper part to set how many filled layers are on the base/lower part.