Slicing in Cura add "empty" layers at the end

[FrozenLaser 0]

I'm slicing several components using the "print One at a time" option, but when looking at the preview I will often get empty layers at the end of the print. Additionally, there are often layers that start at a corner of the print bed and try to connect to an object that could exist or might not have been printed yet. I am printing with a Sovol SV07. I have used the Cura Mesh tools to examine the parts I'm printing and they all come back fine. Often this behavior is linked to a single object on the build plate, but it's not always the same object. Has anyone else encountered this issue? Please see below for images in Cura 5.8 for Linux.

knobs.3mf

[GregValiant 1,342]

Is that printer definition from Sovol Cura?  If it is then it does not use the "Sovol Base" definition but draws directly from the fdmprinter definition.  That means you are getting the default "Machine Head with Fans" which is a very small 20 x 20, and the default "Gantry Height" which is a very tall "99,999,999,999mm".  Looking at a picture of the printer the gantry height appears to be around 25mm.

You need to be very careful in regards to model placement on the Cura build surface when printing tall objects with short ones in "one at a time" mode.

Another problem is a bug in Cura that does not move the print head to "Transit Height" after the last model.  If the last model is short, it is possible that the print head will move to park itself at the indicated location and travel there by crashing through a print that was taller.  Make sure that a tall model prints last and you should be fine.

 

The Cura print preview can have display errors for a couple of reasons.  Spiralize is one reason, viewing a gcode file that was created with "Arc Welder" active is another reason, and "one at a time" mode is a third reason.

If you save the gcode file and then open the gcode file in Cura you will get a much better preview BUT it will preview as an "All at once" file.  There is no way around that as every model starts on LAYER:0 and the Cura Gcode reader puts all the LAYER:0's together for the preview.  Other than that aberration, it is a better preview and the gcode will print in "once at a time" mode even though the gcode preview does not reflect that.

 

Think of the Cura preview of a slice as the "theoretical toolpath" and the preview of the actual gcode file as the "real toolpath".

 

[FrozenLaser 0]

I used the Sovol Printer profile as a start, but then measured the print head and gantry height and changed them to more accurately represent the printer. I didn't know about re-openeing the gcode as a better preview, that seems to be a much better representation of what the printer will do.  I was mostly concerned that the printer would fault out because of the issues displayed in Cura. But it looks like the gcode files are all OK.

The plate displayed above was an example that showed the issues I was seeing. I made the mistake once of not checking the print order, not I do it every , making sure to print front to back on the plate and shortest to tallest.

Thanks again.

[GregValiant 1,342]

I mentioned that "last travel" bug and I have a fix for it.

In this example, the last model is 12.4mm tall.  The model in the left rear corner has already been printed and is 20mm tall.  The Creality Ending Gcode has a "Present Print" move that sends the print head to X=0 Y=MaxY.

You can see that the travel to the left rear corner goes right through the tall model.

 

I dabble in post processors and I've put together a collection of "not-often-needed-but-handy-when-you-do" scripts that I call "Little Utilities".  Under "Show bug fixes" is "One-at-a-Time Add Final Z move".

With that script active you get this instead:

The nozzle moves up to a safe height (the "MaxZ" of the print) and no more crash.

 

Another script for "One-at-a-Time" prints is "Renumber Layers".  That goes through the gcode and renumbers all the layers to "All-at-Once" mode.  And that gives you an exact gcode preview in Cura.  It does not change how it prints, just how it previews.  There is an interesting side-effect.

You could "Renumber Layers" and then run Pause at Height and then with a second instance of Little Utilities running you could revert to "One at a Time" numbering.  That gives you different options for Pause at Height.

 

At any rate, here it is.  It will go into your Configuration Folder and the "scripts" sub-folder.  It will be available with the other post processors under "Extensions" in Cura.

As always, let me know if there are issues.

LittleUtilities_v15.zip