I made the huge mistake of showing it to my son who promptly wanted such a prop too!
We agreed on starting with the helmet, and if things turn out well move to the other parts, this is a work in progress but I wanted to share our path for others.
We bought the files from the do3d.com sale. The whole mk85 printer friendly files cost 99$. Sure I might have gotten them cheaper or helmet only but we wanted the mk85.
First things into consideration were how to scale the helmet to make it fit my son. For that we use https://www.thearmoredgarage.com/ which was a huge timesaver since we had no misprints due to wrong size.
Another problem was the orientation of the pieces. We had to consider structural strength, vs. speed, vs. support needed, but things turned out nice. The backside of the helmet needed quite some sanding, the other parts were nearly perfect.
We printed on a Prusa i3 Mk3s.
On Prusas own PLA.
Infill was 5% 0.2 layer hight and sliced with PrusaSlicer 2.2.
I printed the backside of the helmet and then he whole jaw area. Usually I glue sliced parts together, but I was never happy with the results.
I learned about a fantstic new technique using a cheap soldering iron.
I just lightly pressed a few Xs in the seams and then smoothened out the ridges. Those parts stick together like it came out of the printer in one piece!
First coat of primer
Above you can see little round nobs where the faceplate alligns with the jaw. I was trying to figure out how to hold the faceplate in place, and we settled with neodyme magnet which I glued to a piece of an old credit card and inside the faceplate!
This was a cheap but very pleasing fix!
In a few hours I'll post the final colours!
Hope you had fun reading through that and if you have any questions just ask.
(sorry for any spelling mistakes, englisch is not my native language)