Just use Fusion 360. 
But yeah that is a nice design!
Thanks for your responses!
I need to clear up family time to learn onshape or fusion 360. I have no idea how to design stuff.
I might use the Frankenstein Duct by KevinAkaSam.
The 4010 fan will be replaced by a Sunon 4010 fan that has PWM so I can stop the heater in case of fan failure using a macro.
I think it took me around 100 hours to complete the design, but that was with some moderate prior Fusion experience. The most difficult part is to clearly define your design requirements, followed by getting the reference geometry and measurements. The decide where to place all the components in space and finally identify how to keep it all together so that it is sufficiently strong and stiff and that it can actually be assembled together… If you can devote the time it requires it can be a lot of fun and is quite educational - and that’s speaking with almost 30 years of work experience as an engineer.
IMHO every single 3D printer must have fault detection on the key operating parameters such as temperatures (naturally), heat break fan failures, etc.