What does Layer Print Time mean?
I'm trying to learn more about part cooling. Would anyone be able to explain to me what exactly is meant by the Layer Print Time and how it is defined/measured? It sounds like it's the total times it takes to print one layer of your model, but that doesn't make sense given this is different in every object. Appreciate your time and help learning!
Below is an excerpt from the Prusa Knowledge Base article I'm referencing to.
Cooling thresholds
Enable fan if layer print time is below
If the layer print time is estimated below this number of seconds, the print fan will be enabled and its speed will calculated by interpolating between the Min and Max speed.
Slow down if layer print time is below
If the layer print time is estimated below this number of seconds, print moves speed will be slowed down to extend the duration to this value. The slowing is done by scaling the print speeds, so some moves will still be faster than others.
Min print speed
The minimum speed that PrusaSlicer will scale the speeds down to. Printing at extremely low speeds for extended periods of time could lead to problems such as heat creep.
Keep in mind that by raising this value too high, you may partially invalidate the minimum layer time set by Slow down if layer print time is below. Because even when printing at this minimum speed, the layer time might be shorter than the set value.
RE: What does Layer Print Time mean?
That's exactly what it means. Seems clear enough to me.
Large models that take lots of time to print a single layer in theory need less cooling as the layer will naturally cool down to a suitable temperature before the next layer is deposited on top of it. So you have a setting that says only cool if the total layer time is below, which is the "Enable fan if layer print time is below" setting.
Its why you will see a lot of filament profiles with Min and Max both set at the same values and with the Keep Fan Always ON tickbox enabled.
The slow down if layer time is below is the problematic one in practice. For very small items (think something like a 3mm diameter column as an example) the default settings will have it slowing right down. In practice this leads to too much heat being pumped in and you get a very poor result.
With even relatively decent cooling from a modern printer you can drastically reduce that value. On my filament profiles I generally have that set to 1-3 seconds as I don't want it slowing down and keeping the hot nozzle there longer.
Of course go too thin and theres not a lot you can do about it anyway. In those cases the common technique is to print 2 instances spaced apart so that it can cool while its printing the layer on the second object.
RE: What does Layer Print Time mean?
Thank you, that helped! Appreciate your time responding to me 🙂
RE: What does Layer Print Time mean?
In those cases the common technique is to print 2 instances spaced apart so that it can cool while its printing the layer on the second object.
That's my preferred method if I have small details with short layer times. Saves me fiddling with profiles.
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