- Review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them
- Design a 3D mold around the stock and tooling that you'll be using, machine it, and use it to cast parts
You can view the group assignemnt here: Group assignment Opendot
The object I chose for molding and casting is a coffee cup. I've designed this cup in Rhinoceros 3D, and again in this software I modeled the mold.
The master of this object will be devided into three parts. Two for the body of the cup and one for the top. I paied several attention to avoid the undercuts parts. I decided to cast the cup in upside down position. So the hole for the casting of material and the channels for the escape of air are on the bottom of the cup. Then I exported the three parts in three different .stp files.
For the CAM part of the project, I chose Fusion 360. Fusion has a very powerful CAM engine, with lots of modes and settings. I imported each .stl file in a different fusion document.
To have a good quality of milling, i chose to use three different kind of tools. First tool was a flat tool, with 6mm diameter and 4 flutes. This is perfect for a quickly roughing of the object, and also for machine all flat areas. The second tool was again a flat tool but with 3 mm of diameter and two flutes, for machine the smaller flat details. The thirs tool was a 3mm spherical tool, perfect for rounded shapes. I needed to design these tools into "Tool" menu of Fusion360 CAM.
The path strategies of your milling process depend by geometry you have to work. For my project I use following operations:
I made the same with the other parts.
Now I could export the .nc paths files, one for each tool change. On the Roland MDX-40, I can start with the milling of the molds. I milled on Polyurethan foam block.
For the second path, I needed change the tool. To have a good zero setting of Z axis, i chose to level in the same way as in Electronic Production Week. So I applied a piece of alluminium tape on the sacrifical plane, and whit a led and a battery I found the exact zero level as for the previus tool. I made at the same for all other tool change.
Then I continued on the other parts.
On one part, there is an hole. It was an error in Z leveling, but with a piece of adhesive tape I delete the problem, because the region was not crucial for the molding.
For the casting of master I chose the following silicon rubber with its cathalyzer.
To mix the cathalyzer with the silicon rubber I needed a stick. From a waste piece of 5 mm plexiglass i cut these sticks by laser. I mixed 5% of cathalyzer with 95% of silicon rubber, then i casted in the molds.
After 4 hours the master were ready.
Finally I could assembly the masters and made the cast of the cup. I chose for casting of the cup a material very close to ceramic as consistency and as density: ceramic gypsum powder with just a little it of water.
After 1 hour the cast was ready. Opening the mold was so exciting.
With a knife i cut away the excess of gypsum on the bottom of the cup, then with sand paper I've delete all the little imperfections and smooth the surface. The result was awesome.
You can download CUP 3d files here: