DFM Project 2: Popsicle Molds
This project was the second major project in my design for manufacturing class. The focus for this project was to develop skills in CAD surface modeling and two new manufacturing processes: casting and vacumme forming. I did this project with a team member and we decided the way we wanted to practise these skills was by making custom popsicle molds of highly organic shapes. At first my project partner and I were planning on each making vacume formed and cast parts but due to material and time constraints we ended up splitting the two manufacturing processies. I worked on the vacume formed parts of a foot and a fish.
Above on the left, concept sketches for the top and front view of my foot shaped popsicle negative. On the Right concept sketches for the top and front view of my fish shaped popsicle negative. Both Designs feature postive draft angles and no overhangs and the vacume form mold would have to be rigid. Below is a concept sketch for a silicon popsivle mold. The pliability of the silicon mold allowed for much more complex shapes as well as smaller draft angles and slight overhangs.
The biggest challenge with this project was working with SOLIDWORKS surfaces. I've had a goal for a while of becoming more proficent with SOLIDWORKS surfaces but continued to face challenges in this project that ultimetly limtied the final design of the popsicle molds. I learned through this process that the techniques I was using to model my negatives did not mesh well with the parametric style of modeling solidworks uses. I tried to skeletonize my designs which lead to solidworks creating some very odd surfaces to satfiy the skeltons I was creating.
An example of some of the strange geometries that I created while trying to model my vacumme forming negatives.
To solve this probelm I ended up simplifying my mold negatives. While this was a bit disaponting it ended up in design that was much easier to manufacture and much more usable as a popsicle mold. The final desings feature a minimum of a 5 degreee draft angle and are flatter than the orginal concept sketches. Once I had finilazed CAD for the popsicle mold negatives they were printed out on our Stratasys printers and then used as negatives in a vacume former. The positve popsicle molds were made of food safe HDPE and were easy to manufacture both taking the shape of the negatives and then seperating from the negatives easily.
An isometric and front view of my final cad for my vacuum form negatives.
The other two major problems I ran into were not sucking the plastic down well enough in between the toes of the foot mold, and the printer running into an error mid print on the negatives. To make it so that the plastic was better sucked into the space between the toes I simply needed to add more holes for the vacuum to flow through. This update was easy to make and didn’t affect the manufacturing process outside of adding the extra holes. The printer failing mid print was a bit more challenging but was fixed by restarting the print on the failed layer line and gluing the two pieces together.
Left: the final mold negative with the two different prints glued together. Right: the mold positive being released from the negative.
Popsicles being removed from the mold.
Ultimatly the molds came out quite well. The popsicles made in them were removed eaily and mantianed the desiered shape. While the issues I ran into with surfaces limited the complexity of the designs, for this project it actully helped the final deliverable. My struggles with surfacing in this project led me to rework my process for DFM project three where I had much greater sucsess.