Thank you for your kind reply.
Actually, the guy is an official service man in my country.
I asked him to print this because the printer has very serious extrusion problem.
Firstly, I thought it is because of the nozzle clog. So I learned Atomic method and solved the problem. But the problem continued.
As the number of the layers increases, the more clogging happened. When the service guy printed, he tried 20mm cubic which means very small ones. That was Okay.
But the same problem happened again.
So I watched carefully, then i found the extruder grinds the filament and the filament became thicker and went into the tube. that part caused the same clogging problem. It is mainly because of the retraction.
So I sent the machine to the official service guy, then he tried and answered me that. He must have tried to change the settings such as speed, retraction; He must be better than me at the setting part.
He said "it is originaly, naturally impossible to print and cannot be fixed..... from this printer. And it is because of the 2.85mm filament."
However, my DIY printer a lot cheaper than the Ultimaker 2 go, can print the eiffel tower.
He asked me to ask the main company...
I really doubt the same way as you "korneel" said.
The problem is must be caused from the setting(especially the retraction part) or the extruder itself.
I believe changing the extruder into new one will or would solve the problem.