20° Watering Can
02/2018 - 04/2018
Create a functional watering device with a minimum capacity of 1/2 gallon.
The 20° Watering Can gives you precise control over the pouring of water. The parallel relationship between the spout and handle provides intuitive handling, the long and narrow spout allows water to be poured slowly and steadily, and a shallow angle of 20° in the handle makes it easy to carry. The 20° Watering Can is made by slush casting urethane resin in a silicone mold.
This is my second project for the IPD527 Industrial Design class at the University of Pennsylvania.
Sketches & CAD
The fundamental idea behind my design is the parallel relationship between the handle and the spout. After experimenting with different angles for the handle, I decided on 20° due to its gentleness and ease of carrying. I created a CAD model of the watering can in Fusion 360. Then, instead of resorting to 3D printing, I decided to make a silicone mold for my watering can and use slush casting to produce the final physical model.
CNC Cutting the Foam Master
I imported the model into Rhino, and designed the master to be cut out on a CNC router in high density polyurethane foam. The master would later be used to create a brush-on silicone mold, so I added a fence surrounding the design to limit the flow of the silicone. I also added registration keys in the model so that the two halves of the silicone mold would self-align.
After the CNC cutting is completed, I noticed a few defects on the master, which I fixed using some wood filler. I then carefully sanded out all the scallops left by the 1/4" ball end mill, and sealed the entire top surface using Smooth-on SuperSeal.
Mold Making & Slush cASTING
I used Smooth-On Rebound 25 for the brush-on silicone mold, and Smooth-On Plasti‑Paste II for the mother mold. One important thing when making the brush-on silicone mold is to make each layer a different color from the previous one. This helps ensure uniform thickness throughout the entire mold and prevent weak (thin) spots.
After the silicone mold has cured and before making the mother mold, I laser cut a 1/4" MDF sheet and placed it flat on the foam master right outside the fence for the silicone mold. This MDF piece would later become part of the mother mold, and would allow the two halves of the mother mold to be easily bolted together.
For slush casting, I used Smooth-On Smooth-Cast 65D. In my first attempt, I made the mistake of not calculating how much material I need beforehand, and ended up with a watering can that weighed over 1 kilogram and was almost completely filled up. For the second attempt, I calculated how much material I need based on the volume information in Fusion 360, and achieved much better result.