3D printing lets you create many personalized and detailed objects. In this case I modeled a little pumpkin shell containing a cylindrical silhouette to project Jack faces on the pumpkin surface. Printing the shell with a material which lets light pass through, the shape would be seen from the outside, as in 3D renders. Moving the cylinder with a servo or a little stepper motor (usually servos only turn 270°) driven by Arduino or another microcontroller, you should be able to automate the shape changing.
Unfortunately I've not yet tested this project, and some details are still to be personalized, as servo support and led hole, these depend on the type of devices you want to use.
This 3D object has a diameter of about 10 cm, which is enough to keep a little servo inside, among with batteries and a microcontroller. The little dimensions will let you print it without paying too much, but if you want make it bigger you can certainly enlarge all the model.
I will show you fast steps to create this in 3D Studio Max.
Step 1: The Working Principles
The model is composed by four pieces: the base of the pumpkin, the cover, the moving cylinder with figures, and a shield to direct light through a figure at a time.
There is not much to say about working principle... as you already understood the light of a led is directed on a portion of the cylinder where some shaped holes let it continue against the pumpkin surface. Since the pumpkin material lets light pass through (pay attention to choose the right material in printing process), the figures will be projected on the outside surface of the gadget.
If you don't want to use a motor or a servo to rotate the cylinder you can add a pole in center of the pumpkin base, so it will keep the cylinder lifted, you can always rotate it by hand... The shield has to be glued in place after setting up LED and battery. As Halloween present I give you the 3DSMax file if you want to modify and print it ;-)
Step 2: The Sphere
To create the basic pumpkin body there are many ways. I decided to modify a sphere extruding and beveling all the 12 slices, then I smoothed the result.
Step 3: Push It
Then I modified the vertices to give the pumpkin a better flattened shape. you can also move some vertices to remove the perfectly symmetric geometry.
Step 4: Split
I also split the shell in tho parts, to let you inserting the cylinder, the shield and the electric devices. After splitting apply the shell modifier, so to give a thickness of about 1 mm at the base and also the cover of the pumpkin. As segments value choose 2, so you'll be able to create the dovetail.
Step 5: The Dovetail
To make a better junction between base and cover extrude on them half of the border inner surface, so the two extrusions will make a dovetail.
Step 6: The Stalk
Time to model the stalk. To do that create a star and make it follow an arc with the loft modifier, then enlarge the base and add some noise.
Step 7: The Cylinder
Now let's make the inner cylinder. Crete a pipe, convert it into a poly, then enlarge its inner vertices so it look more like the pumpkin shell.
Step 8: The Shield
The shield has to be very close to the cylinder, since its purpose is to block light to going in other pumpkin areas. So copy some faces from the inner surface of the cylinder, and create a shield, not too big so it lets some space for the servo.
Step 9: Light Stopper
Close the back of the shield. You can drill the holes for the led in a second time. Check it is at the right distance from the cylinder.
Step 10: Cylinder Braces
Since the inner bottom surface of the pumpkin is occupied by shield, servo, probably also batteries and controller (you have to enlarge a bit the model to make space for them too), the cylinder has to be hanged up. Let's make some braces to connect it on the servo gear.
Drill the holes for your gear after printing the object.
Step 11: The Figures
Now it comes the funny step. We need to draw the shapes to cut the cylinder. I traced the lines and the extruded them into a solid. With the boolean tool substract that solid from the cylinder.
Step 12: Almost Done
Rotate the cylinder 90° and draw the next three shapes. When you'll have perforated the cylinder with all four figures, you'll obtain a funny 3D object as shown.
Step 13: Get Scared!
Good! You have now all the components to make your Jack O' Lantern!
Here you can see the next three Jack's "faces" and a short video of the working gadget... and also a little lengthen pumpkin which seems a pear.
I hope you like this unusual a a bit technological pumpkin design :-)Here it is the video happy halloween from my Vimeo gallery :-)
Step 14: UPDATE
So to easy build it I enhanced the design and enlarged the pumpkin so it contains now Arduino and a normal servo. Probably there is room for a battery too, but you can add a plug and power it with an external psu.
The pumpkin has now 20 cm diameter and 18 cm height, so it's pretty big to print. I modeled a support for Arduino and a standard servo motor, and also there are now some joints to lock the shield and the support on the bottom of the pumpkin, which has been flattened and thickened so to add stability. The stalk could now be printed as a different piece and then connected to the cover through some teeth.
Time to make it reality! Come on guys!