skirts and overhangs

[maker2]

I won't presume this is a bug but I reckon it's suboptimal!

As per attached image part has an overhang.

The skirt ignores the overhang, passing underneath it.

There's support underneath the overhang and so the support passes over the skirt.

I didn't pay attention to this detail but now, well into the print, the support has started to detach because it's first layer didn't go down well on account of the skirt.

(As an aside, wouldn't it make sense for support material to obey 1st layer underspeed settings? Support needs help to stick too!)

[zemlin]

This hasn't cause me any trouble, except on one part where the overhang was very shallow and the brim layers bonded to the supported area - a little extra cleanup required.

I thought support did obey the first layer underspeed setting.

[dkightley]

I thought support did obey the first layer underspeed setting.

You're correct to say it does. Just checked a model with overhang, and with the first layer set at 10%, the first layer of the support shows at approx. the same speed as the skirt & perimeter.

In fact if you look closely at the above preview.......the first layer of the support is showing as printing slow.

[maker2]

True, it does do "underspeed" relative to its normal setting.

In fact, I'd argue there is a case for looking at this in a different way.

When we make special settings for the 1st layer, is it not because of the mechanical difficulties of that layer to stick well?

If we have a thick layer height we might want to reduce it...

If we have a thin layer height we might want to increase it (to prevent bald patches)....

If we are printing fast we will want to slow it down...

(If we have fast XY moves we'd like to slow those down too!!)

Now, when we slow our printing down it's not in a way that is "relative to any of the other speeds it might have been printing at otherise - ie according to feature type". Rather we want to choose a speed that we think will help the plastic stick best.

So I'd argue that it would be appropriate to

a) set a 1st layer speed as an absolute (eg 12mm/s) to be applied to all types of feature (perimeter, infill, support...)

b) set XY 1st layer speed as an absolute too (and keep it low to avoid "ripping up" bits of plastic);

c) set 1st layer height as an absolute - eg 0.15mm - a number based on the characteristics of our bed, its flatness, surface and the plastic in question that we'll want to apply regardless of what layer height setting we choose for all the other layers. (A further advantage of that is that if we then change the layer height for the rest of the print we don't have to remember to go back and tweak 1st layer settings.)

Just a thought!