Plaster Mold and Slip Cast Object

Now that I have the final design for my plate done on Rhino, it's time to export my mold positive as a .STL file. This file will then be imported into Fusion 360 to generate the toolpaths for the milling process on the CNC.

Now that the .STL file is in Fusion 360, the first thing we did was setup file for our purposes. This is done in the Manufacturing window. In this case, it's milling. We also changed the origin in the WCS to coincide with where we want the end mill to start.

 

Next, we input the dimensions of our stock so the CNC knows what we're milling. It's also to make sure our object is within bounds.

Once our setup is finished, we input the specs for the end mill we'll be using and set it as the tool.

Finally, we generated the tool path using everything we've input so far, and then simulated the process. This was important to see if our mold positive would mill properly or if there were any errors.

When my simulation didn't show any glaring errors, I used the post processing file from the class site and exported my file, ready to be milled. My mold positive came out just like how I modeled it, which was exciting to me as this was my first time using the CNC to mill something. 

The rips in my mold actually came from taping it too much onto an acrylic sheet when I was prepping it for the plaster pour. 

Because of how tall and wide my object was, which came from my own confusion on the dimensions of the stock (oops), I ended up using over 5kg of plaster to fully cover my mold positive. But otherwise, I'm very pleased with how the mold negative came out. It does have the marks from the milling process, but I think it gives it an interesting texture.

 

Finally, after two attempts at slipcasting, I got a plate that didn't rip when I pulled it out. It was also an appropriate thickness for a plate. The only caveat is that after we had unmolded it onto a foam sheet, we might have been too hasty flipping it over onto its base because it sagged. 

In hindsight, it would also have been ideal to create a more angled base. I only realized this at the end, after crit, that I ended up with a 90-degree angle from the base and the next layer of the plate. That's definitely something I'll need to be mindful of, for next time.

Otherwise, I think it's a good first attempt at ceramics, and I'm happy with my funky little plate. I'm also really excited with how much more I understand about mold logic and using a CNC now, and look forward to utilizing these processes in future projects.

 

My First GH Definition

 Tinkering with Grasshopper

Grasshopper is such an interesting part of Rhino to me for so many reasons, ranging from the cool things you can do with it down to its UI/UX design, and watching the tutorials made by David Rutten has only reinforced that.

Using the definitions from the tutorials, I experimented with a few shapes to see what they'd loft into and I ended up lofting two octagons, which created a neat shape that reminded me of a gramophone horn. So I ran with it and made a little toy gramophone, modelling it after a picture of one I found on Amazon.

Reference image from Amazon

Mold Positive Design & Prep for CAM

For my final mold positive design, I decided to go with a different object from my initial idea. It occurred to me that my initial idea might be more difficult to de-mold at the slipcasting process, so I went with a plate design instead. 

I did still stick to doing a one-part mold because I think it'll be easier for me to troubleshoot my mold logic since I'm still learning how to do it properly.

 

I reused the polygon I created for the pen holder, but only using it as an accent this time instead of having it as the entire design. I decided to do this to mitigate the amount of complex shapes on my final object, especially during the machining process on the CNC. 

Again, once I was satisfied with how it looked after lofting, I attached it to a base to create the mold positive, 

 

and did a boolean difference with the model of my stock to create the mold negative. This would basically be what the plaster mold would look like after pouring plaster over the CNC milled mold positive.

I'm a little worried about how the curved edges would turn out during the slipcasting, but hopefully it'll turn out. If it doesn't, I probably will need to adjust the angle it sits at so it releases easily. 

 Renders: 

Cast Thinking

To practice mold logic, I decided to make a pen holder cup on Rhino. 

I used the polygon tool to make a 12-sided star and filleted the corners to round them out. 

Then I lofted the curves to create a surface I liked, and attached the object to a square base 2mm thick with boolean union. This finished object is my mold positive. 

To make the negative, I simply had to use the dimensions of the stock we'll be using on the CNC, which is a foam material, and create a model in Rhino. Once that's done, I took that model and used boolean difference while it was over my mold positive. The result is the mold negative.

 I think this object works as a one part mold because it doesn't have any glaring undercuts that could cause problems when slipcasting. It also doesn't have any right angles that could make it hard to de-mold.