Can not find right settings for a 2D logo.  

RE:

Here are a few pictures.

The first picture is the logo that I want to print with a filament swap. The gray bottom plate should be smooth.

The second picture is what the slicer does under the text, but that is visible. I want a continous motion of the nozzle.

The third picture is when I set the top layers to zero and use 100% infill. The slicer just randomly chooses a line to print. That is even more visible.

In case the pictures don't work, they are also here:

In case the link does not work, try this: https://postimg.cc/gallery/mgRQ7sC

RE: Can not find right settings for a 2D logo.

Assuming the text part isn't sunken into the bottom plate part at all, you just have to turn on Interface Shells so the plate's top layer gets fully printed under the text rather than hollowed out.

RE: Can not find right settings for a 2D logo.

That makes no difference. I have a single extruder and I use manual filament swaps.

Meanwhile I found that when I set the top solid layers to 0 and the bottom solid layers to 1000, then all the bottom layers will be printed from one corner to the other corner in a continuous way. That is a solution for thin plaquettes, but when it is a few millimeters thick, then I would like to use a infill of less than 100%.
To prevent that a ugly bottom layer is printed for the very top layer of the text, I can set the number of bottom layers one less than the total.

RE: Can not find right settings for a 2D logo.

Thank you. Yes, that is my problem. I didn't know that it was not solved.

Workaround #1: Make the logo thin, and use bottom layers for everything with zero top layers and set the infill to 100%. If the total of layers is 20 and the number of bottom layers is set to 19, then the top layer (the very top of the text) is prettier.

Workaround #2: When the logo is thick, use normal settings for infill, but set the top layers to zero. Right-click on the logo, select "Add Modifier", choose "Slab". Set the slab to the upper part of the base plate, change the infill settings for the slab to 100%.

I have meanwhile printed a few thin logos, and they look better than before.

RE:

As Neophyl said, this is a well-known issue, and the rationale is that for most designs, continuing the infill from below will create a more stable connection between the bottom part and the part anchored above it. 

The only "cheat" I have come up with to create a clean top surface is as follows:

• Let's say the object is a base plaque with a logo on top. Use the cut tool to cut the object at the height of the top surface of the base plaque. Make sure you cut to objects, not parts.
• In PrusaSlicer, you cannot lift an object off of the print surface, however, you can lift parts. So add a small helper cube or cone the height of the plaque to the logo object.
• Now reposition the logo to sit correctly on top of the plaque.

When you slice it now, it should finish the top surface of the plaque before starting the logo, and not continue the infill from plaque into logo.

It's a bit convoluted but it works. See attached zip file, with before and after 3mf files. 

RE: Can not find right settings for a 2D logo.

Thank you. That is a lot of work when I want to make a number of different plaquettes.

I make the models in OpenSCAD, so I can prepare them. However, PrusaSlicer does not keep the x and y coordinates of a 3mf file.
It is faster in Cura Slicer. Cura can keep the x,y and z coordinates of a 3mf file. I export two 3mf files in OpenSCAD with each part at the right height and the right position for the build plate. In Cura, I disable the "Automatically drop models to the build plate". Then I import those 3mf files and Cura sees them as separate models, each with its own bottom and top, and they just happen to be on top of each other.