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[Bug] Apparent Bounding Box Calculation Error (Grey Shadow Area w/ Print One at a Time)


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Posted (edited) · [Bug] Apparent Bounding Box Calculation Error (Grey Shadow Area w/ Print One at a Time)

I'll do my best to describe the issue I'm seeing.


I often print multiple parts in a single print.  I want to print one part at a time because they are not tall, and usually take up very little space.  I have printed 9x cap like object before with no issue up to Cura 3.4.  I'm on 3.6.0 now and the size to the bounding box that limits overlap has increased greatly in size.


First to note, I have one extruder disabled to be able to select the Print one at a Time option under special modes.  I have physically confirmed that the default Ultimaker 3 Ext printhead settings are accurate on my printer. On to the show....


So after upgrading to 3.6.0 I don't have the room to put multiple parts on my plate.  The bounding box is way to large, excessively so.  Let's take a 10mm x 10mm x 10mm cube for example.  it has no brim for adhesion, just a cube.  Look at how big the box is!


In the Left-Right "X" direction: 84mm to the left and 101.something to the right.


Looking at the size in the machine settings:

X min Distance from center of nozzle to left of print head

X max Distance from center of nozzle to right of print head.



It looks like the size of the left edge of the bounding box is 2x the Xmin number (83.8mm) and the right edge is Xmin + Xmax (101.8).  Sure enough!  Left and right edges below



Now it's time to go down the rabbit hole...  So I started playing with the printhead settings values to try to determine if I could figure out how the calculation was off.  I couldn't because it's not predictable.  If you have Xmin and Xmax at 10 each, the size of the bounding box is 20mm on each side. 

Xmin=15 and Xmax=10 gives Left: 25, Right 20.

Xmin=5 and Xmax=10 gives Left: 10, Right 15.

Xmin=10 and Xmax=15 gives Left: 20, Right 25.

Xmin=15 and Xmax=25 gives Left: 30, Right 40.

Xmin=25 and Xmax=15 gives Left: 40, Right 30.



It appears to me that the calculation is as such:

if Xmin < Xmax then Left = 2x Xmin, Right = Xmin + Xmax

if Xmin > Xmax then Left = Xmin + Xmax, Right = 2x Xmax

Same behavior for Ymin and Ymax I believe with a quick check (didn't run as many numbers.)


Something is very wrong.  I should be able to put cubes next to each other without having 2x the space needed.

Hopefully this can be fixed soon.


The Y's appear to the flipped.  Using the above, I was able to get the correct spacing:






Edited by Morandir
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    Posted · [Bug] Apparent Bounding Box Calculation Error (Grey Shadow Area w/ Print One at a Time)

    That is strange...

    Do you get the same results when disabling Extruder 2 and enabling 1 ?

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    Posted · [Bug] Apparent Bounding Box Calculation Error (Grey Shadow Area w/ Print One at a Time)

    I did get the same effect for both extruders (individually).  Setting in only per printer, not extruder.  Thus it's probably off a bit depending on where you would print.


    Thanks Tinkergnome!  I spent some time searching for Bounding, Grey area, Limit, and Print One, but they all showed up with posts from 2.3 and 3.1.  Glad to know it's being tracked.

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