Print the template for the drill spacing. wow this really speeds things along!
The template marks off 32 mm on the ends and 45 mm between the spools

!Print one rack as downloaded and print one that is Mirror or flipped on the Z axis.!

My pvc pipes were 740 mm long.
Be sure to cut the pipes exactly the same length. You may need help putting it together. I personally had the wife hold it together while I drilled a small pilot hole from the back and inserted a short wood style screw for attached the pipes to the rack.

I printed the rods with the slots pointing in the air with no supports. This is why I had the fillet. I printed 40 at a time and they came out wonderful. A slow drilling into the pipes yields a tighter hole and a snugger fit. When your arm is hurting from the 224th hole stay slow! The drill I used was a 7.84 mm or 5/16" Inch. I drilled small pilot holes first, this is why I drilled 224 holes... Ouch!

My rack is 285 mm x 205 mm I included the source files so you could chop the rack down to a smaller print bed.
My rack holds 16 x 7 = 112 spools.

Questions/Comments.. message me.

My printer is modded to print 372 x 214x 200 mm
If you have a Robo 3D you can do it too! Just replace the belt, Rods and print 2 of these
https://www.thingiverse.com/thing:2216671