Hi All,
I would appreciate some help.
I have installed the 0.4 obxidian HF nozzle on one of my X1Cs, it works in that it is producing clean benchys.
I have installed the profile from the bambu website but when I select it slice times are no different from a standard nozzle. I can see the Max volumetric speed has increased to 29 and that the speeds have been adjusted (see screenshot) so why do the slice times not show it as being quicker on 17 hour print?
The slicer’s core algorithm for estimating time is notoriously inaccurate. There have been countless posts about this, and after chasing the root cause for a while, I’ve simply given up hope.
Part of the confusion is that print calculations don’t always follow the same sequence as the actual print, and even when they do, they’re not precise. A simple example is wall line width: you’d expect increasing line width (thicker walls) to speed up prints because fewer passes are required. Yet that’s not what happens.
Here’s an example:
Supposedly, this change increased internal solid fill time from 2m44s to 3m6s. The math doesn’t add up.
This is just one example. There are countless others, but ultimately, fixing this hasn’t been a priority for the developers.
In addition to @Olias explanation on the slicer print time estimates, there are further factors preventing an exploitation of shorter print times. They do depend on the model and individual key settings though.
If, for example, the model contains many overhanging regions with “slow down for overhangs” enabled, this will overrule other settings.
Similarly, printing at low layer heights can prevent the printer from actually reaching max flow.
Another item to consider is the minimum layer time. If the print is slowed in a given region to allow more cooling time, the high flow will not play to its strengths.
And of course, line widths make a bit of a difference.
& 
And yet another restraining factor: high speed needs long straight lines to reach the target speed. Very small models or models with jagged walls are constantly accelerating and decelerating and the printer never reaches the set speed.
The choice of infill also has a big impact for the same reason. E.g. I really like gyroid, but it doesn’t allow for high speed no matter how big the model is. crosshatch is much better due to the long straight lines in most layers.
