I was recently setting up a new printer in OrcaSlicer and was looking through the default slicer settings for both it and the Bambu printers as reference. Now while only one wall on top layer is enabled by default for the Bambu printers, I was curious as to why only one wall on first layer is disabled by default, as this would imply there was some downside to having it on?
For example, the benefit (similar to one wall on top layer) would be things like more aesthetically pleasing bottom layers due to maximising space given to infill. From what I can tell, this is particularly useful for things like embossed text/holes on the first layer, or multiple colours on the first layer.
Also, it should slightly decrease the print time since infill is printed faster than perimeters, so by reducing the perimeters to 1 and therefore making the infill area larger to replace them, the first layer time should be decreased.
For one wall on top layer, the only downside to enabling it that I’ve seen is that it gets triggered when it shouldn’t (for example on sloping top surfaces) and ends up making the print look a bit worse. However this can be mitigated by using a threshold for the width of the exposed top layer, like OrcaSlicer does.
As a related question, does anyone know if 300% is the best value for one wall threshold?
It’s the default for both the Bambu A1 and some non-Bambu printers in OrcaSlicer, but I’ve seen it be set to different values in other slicers (such as only 100% in SuperSlicer) and I’ve never tested it myself to see what is optimal.
However for one wall on first layer, the potential downside with sloped surfaces is not applicable afaik. The only other downside I can think of is that technically, having only wall does make the print weaker in compression from the sides. But, the fact that it’s only on the top and bottom layers should mean that it barely affects the strength of the part, unless your part is only 2 layers tall, but in that case it would be likely to buckle just from the thinness of the part when in compression from the sides anyway?
So is there actually a reason to have one wall on first layer off, or is the default just wrong in this case?