I tested the model I posted and the overhang of the top 5mm or so might be too much to print. You can test by in studio cutting the model maybe 10mm from the top, discarding the bottom, set zero bottom layers, and add some brim.
If it fails you could fix it by cutting the top few mm off the model and stretch back to size in z axis only.
I had a sneaky suspicion⌠which is why I went easy on you. But hey, at least you created something from scratch which is a hell of a lot more than what many in these 3D forums and Reddit can say. 
Itâs only unprintable until your designer decides to tweak it. 
Look, youâve had your printer about a week and youâve already lapped most folks whoâve had theirs a lot longer. What Iâd recommend is to create a model that has less of a slope but still has the aesthetics. Thereâs a sense of pride that one can only know when one creates something and you know you did it. What I might suggest is consider using going into CAD and designing less dramatic slope and printing that.
Hereâs the concept I am referring to.
Take your original globe.
And using a spline, change the opening slope to be more of an upside down vase. Youâll have to experiment with which slope will work best for your filament combo.
There is another technique you can use that requires a whole lot more trial and error but could give you that last mile of precision youâre looking for. Although we rarely address the issue of speed in favor of layer lines and infill patterns which are far easier to manipulate, speed can be tweaked if one has the patience. To be candid⌠I do not have that kind of patience so I rarely use it. However, it is worth noting.
Hereâs a great video that popped up three months ago. The YouTuber really goes through a number of little-used slicer features, one of them being the speed menu.
What is vase mode, and what does it do?
So actually it was around 18 hours to print. It just finished.
I am not at home, so I cant remove the support, but so far it seems to look way better. No visible issues at the sides, top looks great.
Actually I had it placed with small hole to the top (= upside down), as this is actually the visible part when its hanging from the ceiling.
This gave it a more stable base to stand on as well.
Gonna check the overall result when I am back home. Could be that there is still some issues around the big hole once I remove the support, however since this is a) the top of the lamp b) will be covered with a lid once its installed in the lamp, it should not be an issue
Ok so this is the second attempt, with support as recommended, and variable layer height.
2 Issues:
I cannot seem to remove the support, it sits there really tight. I tried to remove the outer support with a knife, and as you can see, I already damaged the part with this. How do I get the support off of it? 
Theres still a vertical line which looks ulgy. I think this is the point where the extruder is going around in circles, and then returns. So this is the start/end point of the circle. For a single layer circle, this might barely be noticeable, however it seems that for all layers, the circle start/endpoint is at the same position, resulting in a vertical line. For some reason, at the widest layer, the line also gets bigger. This looks a bit weird.
Ok, maybe even 3) issue: At the top it seemed to have printed a couple of layers thicker, which results in a visible roughness. I guess this was because of the variable layer height. Maybe I should revert this setting?
So maybe I should have printed the support in PLA, but the support interface in PETG. I heard that PETG does not stick to PLA, and thus the whole support comes of easily without damaging the part. I didnât have PETG, but Iâm gonna order a new spool of PLA as well as PETG.
@Olias I donât want to change the shape of the lamp if possible, I try to resemble the original as closely as possible.
So if it was doable, I would prefer to keep the model shape.
This is the âplay with the Z heightâ mentioned earlier in the thread, they mean experiment with Z height for support interface when supports and interface are like material (the whole print one filament). Generally you add Z distance to the support interface to facilitate removal but at the expense of the support doing its job (supporting the print). For dissimilar support interface you would close up the Z distance.
The vertical line is the seam, marks the start of each new layer. You might try playing with âscarf seamâ in the settings (a pretty new method for seam hiding).
Yeah the VLH might be causing some striping on the model, but I donât think thatâs what explains that ring on the top side.
I just finished a project similar to this using supports. I wish I had taken photos. However, Iâll discuss the technique that often works and show an example.
This is one of those examples where you may want to use tree supports. You will be challenged with the bottom though and the workaround there is to elevate the model using a faux assembly. If need be I can explain that but this post is already too long for the TL;DR crowd. 
When using standard supports, I always set the the support/object distance from the default of 0.35 to 1.35. What that does is two things. It increase the gap next to the model and allows for easier tool support removal. The second is that it allows for the insertion of a tool more easily to separate the support material. This is in the advanced section and one must have advanced enabled in the slicer.
The second thing I do is to increase to increase the size of the base pattern. This creates less contact points with the model underneath the supports and makes it much easier to pull supports. This doesnât come without a cost. That cost is the underside will look horrible and in your case because itâs supposed to be a light shade, may introduce artifacts that change the light in unacceptable ways. Or it could do the opposite and create a pattern affect that may be desirable. Thatâs a matter of prosomal preference and aesthetics.
If you do these two things, donât be surprised if the supports stick to the plate when you pull the model off.
Also, try using tree supports.
Thatâs a fairly easy one to remedy for this type of model. What you want to do is to change the seams settings to random. The seams will still be there but they will be scattered. I only use this in round models. Youâre essentially camouflaging the seams, not removing them. It will leave a stipple affect but for this type of model, it works well. I just used this for another project. Note the use of tree supports here too.
But you will appreciate the dull blade the first time this knife slips. I kid you not, I keep a box on my work station just for the inevitable.Very informative briefing⌠a bit short but informative nevertheless⌠especially the dull knife and the band aid parts (not that ⌠comprehensive -read âlongâ - as my usual legal briefs or memorandas, but youâre definitely on the right path to catch up).
I skipped Cub Scouts and went straight to Boy Scouts. We were taught that a sharp knife is a safe knife. It will cut with minimal pressure and is easily controlled. A dull knife requires more force to cut and that extra force makes precise control difficult. Thatâs why a dull knife slips in the first place, while still being sharp enough to do major damage to skin.
The sharp knife will dig into the material and cut, and if you still manage to make it slip, the pressure you were applying was small enough that it is easy to regain control.
If, because of carelessness or lack of planning, you do manage to cut yourself, the wound from a sharp knife will heal much quicker than the wound from a dull knife. The edges of the laceration are severed cleanly, not torn, and there is no bruising in the area. Thatâs why surgeons use sharp scalpels instead of used lawn mower blades.
I clean up supports with utility knives and hobby (Exacto) knives, and sometimes very sharp wood chisels on flat areas. Picks and needle nose pliers are also helpful.
That is absolutely true and you clearly earned your whittlinâ chip.
However, what I was referring to was that when prying away supports, you really want something as dull as a butter knife because you specifically do not want to cut, which is why I gave that example. Even a screwdriver can cutâjust ask my half-empty box of bandages.
Would it be better to set the print speed to a slower speed?
Thanks for the explanation! Iâll try this next.
How should I set the 3 fans? I have the front door open (not fully, as I suspect that the vibrations during print could make the printer sway more when the door is fully opened). The top cannot be opened since the AMS is standing on it.
Just use PVA for ur supports. When ur prints is done put it in some water and the supports will wash away. Its good for PLA and PETG
why not design 2 halves, then glue it.
I would try printing in vase mode, however while all3pd states that vase mode can not print overhangs, on the very top they show a sphere which is pretty much what I want to print, and state âVase mode is great for printing lamp shadesâ. Thats a bit confusing to say the least?!
Meanwhile I printed again with support settings as advised by @Olias as well as random seam settings. Good thing was: I was able to pull of the support easily, and the seam was no longer visible. The bad thing was that I forgot to set variable layer height & smoothing, and probably as a result, the overall surface looked rather bad.
Iâm about to print again using all the correct settings from the first 2 attempts, and see how it goes.
Should I try vase mode after all? I mean support must be disabled, and I donât think this can turn into anything good without supports, or can it?!
I couldnât hurt to try, if it doesnât workâŚgo back to what you were trying before.
For a stronger Vase Mode, use these settings.
You can trick the slicer into producing a vase-mode print. Hereâs how:
First, itâs important to understand what vase mode is. Essentially, it takes the STL model and prints a continuous ribbon of single-layer filament without stopping until it reaches the top. To see this in action, try the following:
Youâll get a slice that looks like this (shown in the image below). It will obviously fail when it reaches the top, but it looks cool and doesnât take long to printâso why not? 
If you peel back the layers, youâll notice that vase mode simply creates a single wall of filament. This is why itâs ideal for printing items like lampshades or quick decorative vases.
Now I havenât used vase mode since v1.8 of Bambu Slicer so it may have changed but if it still works the way it did six months ago, if you try to print a complex object(Non-symmetrical) it should create a faulty geometry. Hereâs an example.
The full model
Notice the ghosted areas that the slicer simply wonât render. This will create a spaghetti mess. 
If you go into the slicer and change these settings, it will create a similar function as vase mode albeit not as a single ribbon of filament. This will mean that while you wonât get the advantage of the speed of vase mode, you will get near the âthinnessâ of vase mode.
Here is the 200mm sphere example from before. Turn off Infill and make wall loops 1. Note that your model will need supports so this isnât a free trade-off, youâll have to compensate, possibly by painting in manual interior supports.
Then if you want to really be daring, change the wall thickness. This will get tricky and be prepared for some trial and error until you find the right combo for your filament. You may have to go into cooling settings and increase fan speeds. This may make the model more solid at the expense of being more brittle. Again, nothing is free, itâs a ânegotiationâ between, you, the slicer, the filament and the laws of physics. 
If you look closely or zoom in on the image, you can see that the outer wall is two layers but it is much thinner than the standard width.
While this last trick is only âpretendingâ to act like vase mode, it is very temperamental.
And then it just gave me this:
No idea which settings I messed up, maybe some of my short vase mode attempt carried over (in vase mode it also stopped after 10mins and the chamber being full with spaghetti).
My second attempt printed really well, except for the horizontal glitches. No idea why I got this now. It was supposed to be default settings + tree support + 1.35mm distance + adaptive layer height + random seam, nothing more 
Is there an option to revert all settings back to default?
[edit] ah I also changed the threshold angle for support, in order to have a bit less support at the base. Maybe this was the reason.
Okay so I am still struggling with this. I updated the git repo with my latest changes to both the model (made it a tad wider) as well as the project settings:
What I end up with my current attempts is this:
I aborted the print half-way because of the weird structure which had been printed on the last layers. For some reason, at some point it starts to print in really bad quality, and I donât know why. On the lower layers, it made perfect circles, while towards the middle it seems like it was no longer doing circles but some kind of zig-zag instead.
Also, there are those little crumbs scattered over surface, and I have no clue why I am getting this now.
I really donât know where this is coming from, especially because on my second attempt (Please help me print this part :) - #25 by user_4055716108) it really came out with a smooth surface mostly, apart from the seam-position which drew a vertical line.
I think it might have to do with adaptive layer height; in attempt 2 it was not set I think (donât 100% remember).
Please ignore the rough surface on the top of picture 1, this is where I removed the support, and I just gotta sand this a bit to smooth it out after removing the support.
Iâd do one of the following two things:
Idea #1:
Cut it in half. Put the two hemispheres face-down in the slicer, use supports on the inside where they will never be seen.
Glue the two halves together after printing with super glue (cyanoacrylate glue).
You may have to fiddle with elephant foot compensation to get a perfectly smooth join of the two halves.
If illuminated from the inside, you will likely still see the cut.
Idea #2:
Design supports in your CAD software. Iâd try a set of ribs that go around the bottom, creating a kind of âradially ribbed bowlâ for the sphere to sit in.
Make the ribs ~1mm wide. Space them radially around the bottom. You could space them maybe 1/3" apart once the sphereâs slope gets to about 50 degrees - that way, down on the very bottom they will come together at a point, and provide more support on the more extreme angles.
Make the âribbed bowlâ so that it is ~.15 mm from the outside of the bowl, and follows itâs curve precisely until it ends around 50 degrees from horizontal.
Make one tiny connector in the bottom middle (1mm cylinder), that links the sphere and the ribbed support bowl - this will make it easier to deal with as a single part in the slicer.
