Hello,
I’d like to try making a FX prosthetic out of curiosity.
I’d like to design the part by sculpting it in Blender, and then one way or another make a mold out of it so I can cast it using a soft material.
I only know basic stuff about all this, and for now I was considering making the design in Blender and then remaking the sculpture in clay in order to make the mold. I’m unsure about the use of 3D printing to make the mold if the object is too big, though I’ve decided this project could use a little bit of budget so I guess it will depend on other factors as well.
I’d also like the object to be hollow and I have no idea how to do it with a cast
Does anyone have tips or resources to share with me about it? 
The process you are describing would work like this…
Create your part in Blender, after the sculpting is done save it to an STL file.
Import that STL to a 3d printer slicer… ( it will really depend on the size of the object as to whether it will need to be broken down into smaller sections and joined after printing)
Print it…there are now 3d resin printers that print in 8k resolution for less than 400$ and the quality rivals commercial printer sites. EXAMPLE HERE
Now Make a hollow wall silicone mold…
you can cast it in either Foam Latex or Silicon for a SOFT prosthetic…
Something like Dragon Skin 2-part Silicon…
Thank you so much for the informations and links! I think I understand how it works for solid objects, but do you happen to know how the process would work for hollow objects (like gloves or masks)? I am not sure of what to search to get informations on that kind of stuff
As for 3D printing the model, isn’t there also a way to order it? How much details can I get with a cheaper model than 8K? Would it be a good idea to print a version that doesn’t have many details, and then add the details with clay for example in order to create the mold?
The molding process would be the same, you need to separate the mold into two ( or More ) parts especially if there are undercuts…
Then there is a process called Slush Casting…watch this…
Sure, having it printed would be cheaper than buying your own printer…and since it is to be just used for a mold then you could get away with a 4k print without starting to get your typical 3d print ridges…a 4 k print is very smooth just not as smooth as 8k…
Adding Green clay or Beeswax to smooth and add details is a very good idea, the more work you put into the part, the better the mold…
You have to remember that the molding process is not very forgiving and will pick up any and all blemishes, so the smoother it is the better…
Thank you so much! I have one last question, how could you use a human part as a base so it fits perfectly, would you use photogrammetry to base your 3D model around?
Either that or you could just take a plaster cast of the part, even the face…a hand is easy if you cast half and let the mold set, then cast to the other half…once set you could make a positive cast and have a base to work off of…
For something like the face, I used Dental Alginate to make the mold ( an older product used in the dental process of making a life cast of teeth to make dentures or the like…
after making the mold I usually went back and covered the Alginate with a layer of Plaster Bandages for a mold form to hold it in its original shape, as Alginate is very soft and flexible without it ( like a cast of a face ), you don’t want it being flexed out of shape when you fill it with plaster for example…