The bigger the better

[James Rogers]

Do you remember the Rancor monster model I 3D printed around a year ago? It's an 8 inch tall model of the Rancor from Return of the Jedi.

Well, I got bored around a month ago and so decided the best thing to do was to print the model again, but this time, I'm printing it as a 3 foot tall model! I had to break the model down into around 40 pieces then come up with a way to pin them together for accurate reassembly. Here are a few pictures of my progress. I've got 18 pieces printed so far.

After I finish printing all the pieces, which should take another month, I'll glue and pin the pieces together, then fix the seams and get it ready for painting. This thing is going to be huge! I don't have any room for it in my house, so I'll probably sell it on Ebay. More pictures coming!

 

[James Rogers]

So, how do you break down a model for 3d printing?

The first thing you have to do is decide on the scale. I decided to make the model 3 feet tall, a little less than a meter. Setting the scale is important so you can figure out how big each peace can be. You see, a 3D printer has a set area it can print in- a set volume. My printer can print 220mm x 220mm x 250mm. Anything bigger than that will be beyond its range.

Here is a picture of the model with the first piece removed from the model.

What I did was make a cube that had the same dimensions at the volume I would be able to print, 220x220x250. I then positioned the cube over a section of the model, in this case, the top right quarter of the Rancor's face. You have to make your choice of area for each separate piece strategically. After positioning the cube into the model, I told the program to subtract the area of the model that was inside the cube from the rest of the model. I'm leaving out a few steps, but, essentially, that's the process. You keep moving the cube around the model until the entire thing has be broken down into pieces.

Here is a colored parts map that shows all the pieces I made.

There are also steps you must do to make the model hollow, but with a thickness. 3D models have no thickness. Unless you define the inside area of a piece, it will have no thickness and will not be printable. I had to make a core model that I would subtract from the inside of each piece, thus giving me a model piece with both an outside and an inside.

Here is an Xray picture that shows the core model inside the Rancor model.

Here are a few pictures that will give you a better idea of the role the core plays.

Here is a shot of all the pieces in an exploded view. You can see there are a lot of them and they all have a thickness.

Each piece is brought into a 3D printing slicer program where it is set up for printing. In the next picture you can see one of the pieces set up. You can see the gray supports that will hold the piece as it prints. Since the picture is showing a cross section of the part, you can also see that the inside of the piece has a support grid (in orange). The grid is a continuous support that is printed inside the piece to provide structural support. You can also see in the picture that I built holes into the mating surfaces of the model. They are cylindrical spaces that will have alignment pins pressed into them. Each neighboring part of the model has identical pin holes, so that when I pin them together, the pieces will line up perfectly.

So, now I have to finish printing all the pieces then move on to assembly. with a model this large, I'm sure there will be some challenges.

More updates coming...