Molding and Casting – Stage I

Stage 1 of the Molding and Casting prototypes were sacrificial molds used with Alja-safe. Look at our page for Stage 2 to look at our Molding and Casting prototypes made with permanent molds with Smooth Cast 305 (liquid plastic).

1st Molding and Casting Prototype

Our first molding and casting prototype aligns with our third CAD prototype. We used the squeezing component of our third CAD to mold and cast three pieces: OOMOO (the dark purple) and Smooth Sil 940 (the light pink). The overall goal was to improve on our molding and casting process from the initial assignment and compare the two materials to see which one works better for our application. During the casting process, we used eye drop bottles themselves to create the cavity where the eye drop bottles go in the device. We struggled with orienting the device and the bottles straight, as they kept floating up during the molding and casting process. Overall, we found that the silicone was harder to squeeze than we expected, and wanted to try and make the thickness of the walls smaller. We also decided to think of a way to focus more pressure towards the middle of the bottle to make it easier to squeeze.

We also realized that when comparing the OOMOO and Smooth Sil-940 to each other, OOMOO was much easier to squeeze than Smooth Sil-940 was. This also made sense according to the two materials’ respective shore hardness values, with OOMOO having a lower shore hardness of 30A as opposed to the higher value of 40A corresponding to Smooth Sil-940. Hence, we decided that our subsequent molding would be completed using OOMOO instead of Smooth Sil-940 as our material of choice.

2nd Molding and Casting Prototype

For the second prototype, we wanted to improve our shortcomings from the first prototype. We tried making the device more cylindrical to thin out the walls of the device and make the silicone easier to squeeze. Unfortunately, we made a mistake in the CAD and elongated the bottom of the device larger than necessary, so we will shorten that in our next prototype. We also decided to add 4 hard points to the middle of the device to focus pressure on the eye drop bottle. To do this, we used CAD and 3D printed a design of a cylinder with 4 divots. This cylinder would be placed in the mold with the casting material, and create these bumps or hard points as seen in the 2nd image. With this prototype, we also struggled as we started to run out of OOMOO, so the top of the device is a little thinner than expected. As mentioned, the device also needs to be shortened.

3rd Molding and Casting Prototype

In order to improve upon our device, we needed to find a better way to focus the pressure from the hands on the middle of the device. We came up with two different inserts, which are different parts that would be added during the casting process to create the cavity where the eyedrop bottle sits in the device, The 1st insert option is the cylinder with the hard points as mentioned above. We wanted to make these hard points larger compared to the first cylinder

The 2nd insert option is an angled insert. We thought that this 2nd option would also be a good idea because the middle part of the cavity would angle in and apply more pressure to the desired middle portions of the eyedrop bottle.

The mold for the squeezing component also changed, which is seen as the black piece on the rightmost side of the image. This piece is similar to the yellow component, but is much shorter to get rid of unnecessary silicone at the bottom. It also has a flat bottom instead of coming to a point, as we wanted to see if we could easily make it rest on the table.

As mentioned above, we had 2 options for the inserts we had created to focus the pressure applied to the bottle. The 1st option is the cylinder with pressure points, the 2nd option is an angled mold insert. The concept behind the two inserts is described in the documentation above, but below you can find pictures showing how the inserts appear physically.