I've been working on making a Sentry Lv1 from Team Fortress Two for the last little while, after I decided that the Portal turret can in no way support a paintball gun. The sentry will have at least 3 different modes of tracking: Manual, Disparity Mapping(distance mapping), and Color Tracking.

I will be showing step by step how I fabricated the sentry using my Ultimaker 2 3D printer and the Autodesk Inventor(student) software.
However, I will not include any of the programming files or 3d model files since I plan to sell it as soon as I am happy with the final result.

The steps include:
-Modeling and Printing

-Assembly and Painting

-Mechanical and Electrical Parts

Step 1: Modeling in Inventor

I used Autodesk Inventor to model my Turret. However, you have to keep in mind that the whole build will not fit onto a 3D printer, so it will need to be split up into pieces, and screw holes to assemble them together will need to be added. I used 0.3175cm holes for my screw holes and #6 machine screws to go with it. You will also need to think about how it will print out on your printer, try giving each piece a large flat surface to print on and as little overhangs as possible so the final piece will look top notch.

I chose to print at 0.1mm layer height since 0.025mm would take literally forever. At 0.1mm, each piece takes at least 24hrs to print out, so you might want to choose 0.2mm instead.

Important note: 0.15mm for a tight fit on your parts and 0.3 or 0.4mm for a loose fit.

Step 2: Assembly and Painting

Now that everything is printed out, go ahead and assemble it together and spray on a few coats of Rustoleum Primer. After the primer has dried, use a large flat brush to paint on whatever color you wish. If there are multiple colors involved and you do not have a duel head printer, use Frog Tape for a nice, crisp color transition.

After it has been painted and primed, use Krylon Crystal Clear Acrylic Coating to seal in the acrylic paint to give it a high gloss finish, and to keep the paint from pealing off.

Update 12-5-14:
-I found it useful to sand the model down with wet sandpaper where the two or more parts meet after you tightly screw them together. It makes the transition hardly noticeable.

-it can be useful to use some sort of epoxy or wood fill if there are any gaps between pieces. Sand it down with wet sand paper after it dries.

-I removed all of the paint and plan to buy an airbrushing kit next time I attempt to paint the model. We will see how well that goes.

Update 12-10-14:

-before airbrushing, rub in wood fill across the print and sand it down with fine grit sand paper. it should feel almost as smooth as injection molded plastic. Repeat as many times as needed. Then start airbrushing on your primer & paint

Step 3: Mechanical and Electrical Parts

I used Stepper motors and a Raspberry Pi to control my turret. You might want to use a switch so the pi knows where the Home setting is(forward facing) when it turns off and on, so it always starts where you want it to.

The gun and hopper itself is fit into the chamber basically side to side instead of a hopper being on top of the gun. An electrohopper feeds balls into a tube, and those balls travel into the ball feed of the gun. That is the theory at least. I'll update this when I find out how well it works in practice

That's about it. it's not too complicated. Just make or find some good tracking software and you got yourself a turret. Best of luck to anyone who wishes to make one, or message me if you wish to buy one from me after it is completed.