For our final assignment, we were tasked with creating a two part mold through the use of various molding substances and the CNC machine. The object had to have some sort of curvature and be more complex than just a sphere. After browsing Thingyverse and GrabCAD for some ideas, we ultimately decided on creating a bowling pin.

The first thing we did was download the bowling pin file and import it into Fusion 360. This software is useful for developing tool paths for cutting complex objects and is better than Easel for this, however we found the software was not user friendly, and quickly went to the internet for some tutorials. After struggling for two hours on splitting our bowling pin in half, we learned that Fusion 360 simply will not perform these operations on mesh objects, and so we had to scour the internet for a bowling pin that was a full 3D object. Once we found this, operations went much smoother and we were able to split the bowling pin down the middle and delete the other half. The half pin was then placed below the z-axis and parallel to the xy plane. The g-code was then developed using settings provided by Peter and Professor Wettergreen (thanks!). The only requirement for our settings was that the narrow neck of the pin would have to be reasonably large and not too narrow.

Importing the g-code to Flash Cut was not a problem, but a few lines of code had to be deleted because they were incompatable and would cause the code not to run. We did not notice any problems that this caused. The drill bit also had to be changed out for one with a ball tip in order to cut the curves properly.

This attempt came out well, and we determined that we needed to edit our g-code to make the area around the positive part flat in order to allow for a mold to be poured in properly and take away the positive to create a negative.

We did try to use the band saw to remove the extra material rather than using the mill, but it was far too imprecise.

After waiting in the queue for the CNC machine, we finally were able to cut two copies of the altered file, which came out well.

The pin was reasonably smooth, and enough area had been flattened out in order to create a space to pour into. All that was required was a little touch up with sandpaper and a knife.

We then created a box around our wax mold with Styrofoam, and poured Oomoo into it to create the negative.  We also used a mold release spray to ensure it was removed from the wax properly. This turned out well, and we used a knife to cut away the extra parts.

Liquid plastic 325 and 300q were then used to make the final bowling pin, and we combined the two halves by pouring one half, letting it dry, then pouring the other and placing the solid one on top. We created two liquid plastic 325 pins colored red and black, while the 300q was left white.

This caused them to fuse. Some sandpaper and knife work was necessary at the end to ensure the pins were able to stand, and the bottom of the mold is probably the least successful part of the process, as it is more rounded at the end then it should be. Overall though we are happy with how the molds turned out, especially with the small amount of time we had.

Thanks for reading,

Ray and Tim