Help Troubleshooting Print Defects

FIRST POST so please go easy on me.

I'm trying to print a "ball" where the top and bottom have been removed so they are flat. The bottom half of the ball looks horrible but the top half looks awesome. Not only is the bottom half not "curved" appropriately it is also bubbly. It looks like over extrusion and possibly an unlevel bed but after a few trials, it doesn't get any better. It looks like it gets better exactly in the middle where overhang changes direction.

Printer: Qidi Tech
Slicer: Simplify 3D 4.x
Filament: ABS 1.75
Filament Temp: 240c
Bed Temp: 110c
Fan: Off
Supports: No
Print area is enclosed.

Design
Attachment 10957

Print
Attachment 10959

.stl file
Attachment 10958

What do you think is causing the bottom half to look so bad?

Except it is ABS, I don't usually turn the fan on with ABS.

I'm dialing this in. I backed the temp to 220 and was watching the print. After a few layers were down I noticed it doing the same thing. I turned on the fan and dropped the temp down to 215 (why not go extreme!) the ABS layers didn't seem to be having issues sticking together like I thought they would. However, the bubbling and slight deforming were still happening. As the print got about 1/4 of the way up (1/2 way to outer most curve), I could see that every time the printhead moved over the part, the bed was actually being pushed down. There was quite a lot of vibration of the bed moving up and down as the printhead went around the part. I realized the bed was too high and started moving it down until I could see the filament no longer staying connected to the previous layer then I moved it back up just enough to get the layer to lay down correctly. Viola, the outer edge looks great. I tried to grab video of the up/down vibration as the printhead pushed down on the parts but it doesn't look so obvious in the video.

You can see in the picture, the bottom 1/4 looks the same as the bottom 1/2 of the original. Then you can see where I adjusted the build platform and fixed the issue. Then the top half worked like normal. I've been leveling my bed too high all this time!! I've been fighting this issue since almost the beginning (PLA doesn't do it this bad). I'm printing something else right now but when the printer is free, I'm reprinting from the beginning to ensure the problem is gone.

Thanks for all the advice. I love this hobby :-) By the way, does anybody know of an add-on to auto-level the qidi??
Attachment 10962

Yeah, that would work. Was hoping for something a little more automated. Is the bracket available on Thingiverse or another site? I might try this.

Cooling fan is ESSENTIAL - yes even for the horror that is abs :-)
What layer height and speed were you printing at ?

The faster you can set the plastic - particularly when it's building outwards - the better the print will be. Logically - if you could cool the plastic fast enough you could actually print out at a 90 degree angle

Only way to get a clean bottom of a sphere is to have the fan on and use a high resolution, ie: very thin layers.
Running the fan from the second layer will make a significant difference.

Well, I finally got around to printing another one. Temp at 230c, 45mm/s speed, and 0.2mm layer height. I leveled my bed to my new preferred height and it looks nearly identical to the original one with blistering about 1/4 as bad (but only on the bottom half). Next time I print it, I'll turn on the fan and see what happens. Thanks for the tips!