The hot weather of summer is squarely upon us. With increasing temperatures comes the desire to enjoy a tasty treat – ice cream! Now most people would go about their business of rapidly consuming ice cream and cooling down during the dog days of summer. Most people. Every now and again the desire to understand the how’s and why’s of a design will (barely) outweigh the desire consume a double-scoop of icy cold deliciousness! Such was the case during one of my last visits to Cincinnati and 3DVision Technologies headquarters.
After purchasing a double dip and heading on my merry way, the shiny, pink spoon caught my eye between bites. I noticed a very slight amount of sink, an injection molding defect, along the top face of the spoon. Sink in plastic parts is something that I’m sure a good plastic part designer would have gone to great lengths to avoid. I continued inspecting the spoon between bites and noticed the large rib on the underside of the spoon causing the sink. Obviously, that rib must be there for a reason! Thus, a series of blog projects was born, though they would have to wait until I finished my current bowl and gathered a few more spoons with the help of a few co-workers!
The first order of business is to re-create the spoon design in SOLIDWORKS. This required a scan of the spoon and my trusty digital calipers. The scanned image is inserted into a new sketch to be used as a Sketch Picture in SOLIDWORKS. Upon insertion, I did need to re-size the image such that the reference would be the correct size to begin the Surface Modeling tasks. Also, I chose to use Surface Modeling techniques for the re-design as this allows greater flexibility than the mostly prismatic modeling features of normal boss-extrude type features. Basically, without Surface Modeling, there is no spoon!
The initial surfacing tasks include creating the top surface of the handle as well as the bowl end of the spoon. These were built using a few different sketches to capture the profile of the body from the top view (scanned image) and side view (measured with calipers). There are two things I did in the initial steps for building the spoon that are not readily apparent. The first is that I over-built the top surface of the spoon so I can trim it back to size later. The second is that I created two sacrificial surfaces for the side rim and bottom midline of the body to help with creating a smooth bowl.
These two main portions of the spoon need to be trimmed back to allow for modeling in the transition from the handle to the bowl. This is one of the tricky parts of the design. The transition has to go from a concave handle to a convex bowl and still maintain a nice, smooth finish just like I see on the real spoon in my hand. Between bites of the next bowl of ice cream, of course! To accomplish this portion of the design I used a Filled Surface rather than a loft or sweep. This provides more control for how the transition joins the existing surfaces. Turning on the option to show a mesh preview with zebra stripes is a great way to visualize how the surface will flow from one end to the other.
Once the main surfaces are built, I use the Thicken command to migrate the spoon from several surfaces to have volume. The next steps were to cut the shape of the spoon’s profile from the oversized body, add the rib feature on the underside of the handle, and add a few fillets and rounds to soften the sharp edges.
There are a few more steps needed to wrap up creating the spoon, such as add a split line at the end of the handle and add configurations for versions with and without the underside rib. The split line is for an upcoming SOLIDWORKS Plastics blog, with the bullseye where I need to specify the gate location.
The configurations of the spoon are for comparing the spoon’s performance structurally with SOLIDWORKS Simulation as well as the injection mold capability of the design, for other upcoming blog posts. Finally, I plan on creating a 3D Printed part of my spoon to compare it to one of the spoons I have collected. You didn’t think I visited the ice cream shop once and called it a day, did you? Special thanks to Teresa, Cody, Eli, and Pam for sending me their spoon pictures and supporting this blog! Now go make your products better with SOLIDWORKS and SOLIDWORKS Simulation!
Check out part 2 of this blog post where I discuss the plastic injection molding analysis of the spoon.