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Cura Improvement Suggestion - Overhang Speed Option to Apply to Layer/Layer Range


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Posted (edited) · Cura Improvement Suggestion - Overhang Speed Option to Apply to Layer/Layer Range

Hello everyone, i read about my issue on a previous post but OP had considered his issue resolved with the addition of the experimental overhang wall speed setting. I am here to sort of revive the issue again as I believe the current implementation of the setting is lacking. 


I am starting to find that the Overhang Speed option does not work well when dealing with actual overhang curling at corners no matter how low I go with the setting. My leading hypothesis on why this happens is that my overhanging corners don't have the sufficient length such as to produce enough additional layer cooling time, while slowing down my print speed too much at the overhang instead has the alternative effect of adding too much heat and causing excessive sagging or sticking to the nozzle. Because of this, I am forced to slow down my entire print instead of just those overhang layers or tediously find the overhangs using the Overhang Speed setting using Preview view and manually reducing speeds for those layers using ChangeatZ.


In light of this, I think it would be an improvement to the current software if overhanging wall speed could be set to affect the entire layer or a range of layers for which the overhang of a certain angle was detected. Likewise, if it is found that overhang curling is more directly related to layer cooling time, then perhaps a setting for minimum layer time could be implemented instead of a speed percentage.


My other opinion of as to why curling happens on overhanging corners is that residual tension from the PLA pulls up overhangs on corners as these have no layers underneath them to grip on to. This residual tension is worsened as print speed is turned up, extrusion becomes less accurate, and the PLA being printed out becomes more stretched out onto the last layer. I have not yet tested this as I do not really know how to, but if this is the case, another better implementation of the overhanging wall speed setting would be to have a setting for an additional length for which to apply the overhanging wall speed too. For example, instead of just having 50% print speed for the overhang, the speed reduction would extend for 1 mm before the start of the overhang and 1 mm after the end.


TLDR: Overhang Wall Speed can be improved by adding additional options to apply the speed reduction to the entire layer/range of layers, or possibly also for a certain distance before and after the overhang. These suggestions are in contrast to the current iteration of the setting where the reduction is applied only directly to the overhang area.



Edited by juspch
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