Aperture

Background

This model fulfils a dual purpose. Firstly, it allows me to scratch and itch that I've had for a while - to build a servo operated aperture or iris. Secondly, it may or may not be a part of something I'm planning for my workshop, but we can neither confirm nor deny that!

The bottom line is that its a really cool 5 blade aperture that can be opened and closed using a simple micro servo. I have build this specifically for the TowerPro SG-90, but it should work with most similar servos.

I've included my original FreeCAD file here to make it easier to customize. The hole through the aperture is 50mm.

Building

Printing

• 1x base.stl - The main chassis for the device. Print with support for nut holes.
• 1x ring.stl - Driven by the drive gear and opens and closes the blades. No supports
• 1x drive.stl - Attached to the servo and drives the ring gear. No supports
• 1x top.stl - Holds everything together so that it doesn't come apart while being operated. No supports when printed upside down.
• 1x plate.stl - For mounting the servo to the base. No supports
• 5x blade.stl - Open and closed by the ring gear. No supports when printed upside down.

I printed mine with luminous white PLA just for fun, but any high quality PLA would be fine. 

Additional Items

• 7x M2 bolts
• 7x M2 nuts
• 7x M2 washers
• 5x M4 washers to be used as spacers. About 4 - 4.5mm inner diameter
• 1x SG-90 Microservo
• (optional) Servo tester for convenience or other circuitry for controlling the servo.

Assembly

Once all items are printed and assembled, we can begin assembly. 

1. Place the base on a flat surface and put one M4 washer over each of the 5 shafts that protrude from it. These washers can be fairly loose as their main function is to act as a spacer so that the ring gear doesn't touch the base directly.
2. Place the ring onto the base so that each of the shafts in the base go through one of the long slots in the ring.
3. Add each blade so that a shaft from the base goes through the hole in the blade and the pip on the ring meshes with the slot in the blade. When looking at the assembly from the top, the slot should be to the right of the hole.
4. Once all five blades are in place, place the top over them. Each shaft from the base should lock into a recess in the top.
5. Insert a M2 nut into each recess in the bottom of the base
6. Place a M2 bolt with a washer into each of the shafts and screw into the corresponding nut from #5. Screws can be tightened as the shafts act as a spacer so that the blades should not get locked up.
7. Place the mounting plate in position under the base and pass a M2 screw through from the top of the base.
8. Place the servo in position on the place and fasten with a M2 nut and washer.
9. Finally attach the drive to the servo so that it meshes with the ring gear. There is a recess in the gear to accommodate the screw to fasten it. Care should be taken to ensure that when the blade adjacent to the servo swings open, that it doesn't get hung up on either the drive gear or its screw.

Now you're all set to play. Enjoy! I used an Arduino because the servo tester doesn't allow for the full range of movement and so the aperture didn't open far enough. With the Arduino it opens fully. Micro servos can be connected directly to an Arduino.