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Coasting being applied randomly, cura 4.90


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Posted · Coasting being applied randomly, cura 4.90

I have found the experimental coasting setting in Cura Version 4.9 very useful. However whilst trying to print a piece recently that starts as several small prints and then merges into a larger print I've found the behaviour of the coasting rather odd.

Coasting has become very important to me since starting to use PETG as the pressure in the bowden tube means it keeps extruding for a good while after a print line finishes.

It works really well on continuous outer surfaces but for more intricate designs it doesnt behave as expected.

I would have expected coasting to be applied prior to every move, or prior to retract, however this doesn't seem to be the case.

When a small value of coasting is applied, it appears to insert additional travel moves as you'd expect, though even here the bottom two blocks do not appear to coast.

Small coast value:

462035709_smallcoasting.thumb.jpg.9d0379d1b05100c8a272ccac64700607.jpg

 

when coasting is exaggerated the problem becomes even more apparent.

Here, you can see the full 15mm of coasting applied to the top block and the other blocks have varying levels of coasting applied.

This means some blocks will under extrude, some will be okish and some will blob.

Large coast value:

1398467609_largecoasting.thumb.jpg.fb18155f10c0a1c5271a608592fad9fc.jpg

 

For reference, this has no coasting applied:

1521413192_NoCoasting.thumb.jpg.174fa710118c475981105255d1f4ad6d.jpg

 

Is this something that could be addressed in a future update so that coasting is applied consistently every time a line is laid?

Large Coasting.gif

No Coasting.gif

Small Coasting.gif

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    Posted · Coasting being applied randomly, cura 4.90

    This is strange.  What happens if you set "minimum volume before coasting" to zero?  Does it do it correctly then?  I'm wondering if that's related to this bug (at least it looks like a bug).

     

     

    Also this might not be relevant but maybe it is.  It looks like you have around 1.2 or 1.5mm line width.  Do you have a 1.5mm nozzle?  What are your values for:

    outer wall line width

    inner wall line width

    top/bottom line width

    wall thickness

     

    I'm wondering if your inner and outer wall are different thicknesses and that somehow messes up coasting.  They appear the same.

     

    Is it doing this inconsistent coasting on every layer or just the bottom layer?

     

    I'm also wondering if it's keeping track of the volume printed before it does the coast and if you don't hit the minimum then maybe it does a partial coast?  Or maybe the volume since the last retract?  Or volume since last coast (and ignoring retractions)?  I can't think of a scenario that explains your pictures.

     

    By the way when adding pictures to a post, drag them all in and then find the spot where you want to insert the picture, place the cursor there and then go down with the mouse and hit the PLUS sign at the bottom of your post where the appropriate picture is.  That way you won't get 2 of each picture.

     

    It would be good if you could post your project file so people can duplicate this.  It will include your model so hopefully that's okay.  In cura do "file" "save project..." and post that file here.

     

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