dipper

thingiverse

The first 3D shape shows a cross section of a dipper that uses air pressure to hold water. Holding the knob on top between your index and middle finger, submerse the container in water. Then plug the hole in the knob with your thumb and lift the dipper out of the water. Water will stay in the container until you remove your thumb. The project is to explain the physics involved and make a design based on them to demonstrate how they work. How I Designed This This was designed in FreeCAD using only basic primitives. Project: Dipper Objectives: This is an introduction to CAD learning boolean operations on primitives to make more complex shapes. Also to learn basic physics of atmosphere, gas and pressure. Audiences: This project could be a part of teaching the physics of atmosphere, gas and pressure. Preparation: A basic understanding of primitives, position, and boolean operations. Also a basic understanding of the physics of pressure. It is a simple design that should be easy to make in any design program of the instructors choice. Steps: First design the outer shape as a solid, combining cones and cylinders. Then make a similar, smaller core inside the outer shape. I have copied the core outside the solid shape as an illustration in one of the pictures. Then subtract the core from the solid shape, leaving about 2mm walls. Finally use the "Fillet" tool to make the edges nice and round. Remember to use the "Fillet" tool on the core also, or the walls may be cut to thin. Use the "cross section" tool to check the walls before printing. Also make sure you don't have to much overhang or you will have to use supports. 45 degrees should be safe. Results: Innovative designs based on the physical principles should of course be rewarded. I would say the important design consideration are overhang to avoid support structures, at least internally, matching the core to the surface so the walls have consistent thickness, and ergonomics. Also a better understanding of the physics of pressure.