Cura slices parts I deliberately float above the build plate like they are ON the build-plate...

[D-3PO 1]

Hi,

 

I have recently started to use a work flow of designing 3D objects that are prepared in such a way as to create multicolour prints using a single nozzle printer. The slicing technique to generate such objects requires that some parts be sliced in mid-air above the build plate and not in contact with it. I am having two difficulties:

 

1. Despite my NOT having 'Automatically Drop models to the build plate' tuned on, Cura slices all parts that are visually floating above the build plate as though they are sat flush with it anyway!!! I don't know why I can turn the setting 'Automatically Drop models to the build plate' on and off or what use it is other than being visually pleasing, if all parts are sliced as though they are sat on the build plate regardless of this setting...

 

2. Parts which are positioned, floating more than a certain height above the build plate will not slice AT ALL!!!!!!!!!!!!

 

I don't know whether with is a bug or whether these two annoying features have been deliberately invoked by the programmers in order to protect novice 3D print enthusiasts from doing silly things... but the point is, sometimes there is method to people's apparent madness and I ABSOLUTELY NEED to be able to slice things at any point in mid-air and have the height of the first layer be the height of the object above the build plate and NOT the height of the first layer.

 

Is there a setting I am missing? Is this a known bug? Is it deliberate? Is there a way around it? Does anyone know?

 

Any help would be greatly appreciated. Thanks. 🙂

Edited April 14, 2021 by D-3PO
I wrote the name of the setting wrong

[gr5 2,265]

Wow!!  You are correct.  That does seem like a bug.  Here are 2 work arounds:

 

1) You can add two lines of gcode to tell the printer to print the part higher.

G1 Z10   <-- NOZZLE 10MM ABOVE GLASS
G92 Z0

 

Look for the Z commands and if your bottom layer is 0.3 then look for the "Z 0.3" in your gcode.  Just before that put the above two lines and it will move the nozzle to 10mm above the glass and then tell Marlin that *this* is now z=0 and will do what you want.  Change the "10" to the hight you want to raise the part.

 

2) In cad, you can add a cuboid say 3mm by 3mm on the base and 0.5mm tall (at least as thick as the "initial layer height".  then move you "actual" model up higher than this cuboid by the height you want to raise your model.

 

 

3) Maybe report this bug in github - you need to create a free github account if you don't already:

https://github.com/Ultimaker/Cura/issues

 

[D-3PO 1]

Thankyou so much. 🙂 This has really helped me. Your first solution is the right one for me. I don't know why I didn't think of it myself as I am always doing this with gcode for my CNC machine. I guess it didn't occur to me to do this as it's not usually something we do with 3D printers ie. re-zero one axis after a print has commenced but it's a great and simple solution until the bug is fixed. I have reported it through the link you sent me. 🙂

[nallath 1,124]

There is also a remove empty layer setting in cura.

[D-3PO 1]

Oh ok... maybe it's not a bug then. Where is this? Do I have this turned on?

[gr5 2,265]

@nallath Sounds familiar but I can't find that feature.  I searched for "empty" "remove" "layer" and a few other terms and can't find it in Cura 4.8.

[nallath 1,124]

It becomes visible if you have support enabled.

[D-3PO 1]

Ok. I have unticked that box. Initially, doing so appeared to work. However, now Cura just slices as though the object is on the bed again. So, this IS a bug after all.

[nallath 1,124]

Do you have good reproduction steps? I've tried it a few times and it worked when I tried it.

[D-3PO 1]

It's got worse too. It seems very random. If I untick the remove empty first layers box it sometimes works, sometimes slices as though on the build plate and sometimes puts the model at a RANDOM height that it wasn't at. I can explain how I did it easily enough but don't really want to go posting my models on here as I am selling some of them. Just try slicing a simple cube model at several random heights above the build place, maybe 5 or 10 times and check each time that the fist layer of that model is at the exact height you placed it at. I bet it works sometimes and not others. If it works for you, I guess it could be something else in the profile I'm using. Is there a way I can save and send you my profile?

Edited April 20, 2021 by D-3PO

[gr5 2,265]

Don't send the profile - save your project: do "file" "save project as..." and post that file.  It will contain your model, your printer/machine settings, your profile and overrides.  Basically everything we need to duplicate the problem.