Why are there seams?

Bambu Lab Software
1

So I was quite active when 3d printers fist appeared. Build my own printer with custom milled hotend and self designed parts and all that. So have a beast of a printer, but it also needed lot of maintenance and twiddling when I want to print with it. So over the time I sort of lost interest in 3d printing cause of how much work it was to set up prints.
Then after several years now I recently decided to look into the 3d printing world again and got a Bambu printer which I love a lot. Just choosing what to print and send it without first fiddling with the printer for half an hour is a blessind.

But I was quite surprised that I get pretty obvious seams every time.
Because that is something that was solved several years ago to a point where none of the parts I have here that I printed some years ago have no visible seams at all.
We first used gcode scripting to insert modifications but I remember some slicers having added that too.
So I wonder what happened?
Has this knowledge been lost?
Or can’t modern printers not use those methods any more cause of the speed?

The method usually was printing inner wall first and on switching to outer wall the print direction was reversed so basically if inner wall was clockwise you print outer counter clockwise. Then on the end of the outer wall there was a calculation based on pressure and filament flow to determine how much material is still coming out of the nozzle when you stop extruder motor without doing a retract. Stopping the extruding on correct distance to the end so rest of material coming out of the nozzle fills the rest of the wall. Then have the nozzle coast about a mm over the start of the outer wall to iron the start and end together. This made seams so minimal that you couldn’t see it with the naked eye on most materials.
There was another variant where going from inner to outer wall was not a 90° jump but done at a 30° angle and calculations were done on the change between the walls so that material overlapping the lines at the end is minimal. Still needs the coast at the end of the outer wall to push the angled line together.

So I would understand that a full U turn could cause some issues with high speed prints cause of inertia of print head mass. But reducing speed would solve that or use the angled change of walls.

2

This sounds like the “experimental” scarf joint seams. I love this feature and it mostly hides the seams.

3

Question is why is it an experimental feature now when a few years ago it was kind of default? Lost knowledge? Or some patenting stuff behind the scene so it had to be taken out of slicers?

4

Not sure, but I always use it. I like it way better than the default seams.

5

Scarf seam is a very recent development and has nothing to do with what the OP describes.

BambuStudio / Orca Slicer also provide all the features like coasting etc. I haven’t played with coasting myself. But in my opinion, the problem is that you have to fine tune a lot of settings to match each other and also for each filament. So if e.g. somebody changes the speed, you also have to retune coasting or you risk gaps instead of a smooth seam. I think it is a very susceptible feature that is disabled in most slicers by default.
So I think, BambuLabs decided not to use it in their default profiles to avoid all the trouble that might come with it.

But I guess you are free to do the tuning as you did before.