Week 13: Molding & Casting

Group Assignment: review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them & compare mold making processes

Individual Assignment:

• design a mold around the process you'll be using
• produce it with a smooth surface finish that does not show the production process toolpath
• use it to cast parts

Design a mold:

First we need to make a design, it should have a flat back, and should not have overhangs in order for the mold to be made. After some thought we decided on a Robot figure based on the following "scary" robot:

And here is our design:

However it was inappropriate because some of the spacing such as between the fingers and between the legs, as well as the neck spacing between the body and head were less than 3 mm, so it cannot be milled properly. Here is our reconfigured (and scarier) version:

Now we had to adjust the size slightly, making the robot shorter, due to size of wax block:

Having completed this, we enter the "manufacture" section of Fusion and create a new setup.

Unfortunately, have no idea about setup the setup, but Ravi showed the tools we have here:

And now working on the setup for milling:

Mainly Ravi helping to set it all up, because he is pro. In the end we divided the milling into 3 parts, each of which has a different tool as they will perform different functions.

The first tool is a 10mm flat drill bit to remove the bulk of material:

The second tool is a 3mm flat to remove material in more detail around the Robot body:

The third tool is a 3mm ball-headed bit to created the rounded edges:

Here is an overall simulation of the 3 stages:

Making the Positive Mold with ProtoTRAK and Ravi:

Here's the glamour shot of Ravi on the machine:

The wax block must be clamped in the vise:

Selection of available tools

Short clip of the milling job in process:

The milling job nearly done:

Finished process:

Making the Negative Mold from Silicone:

We need to calculate the amount of silicone material to produce. For this a clever technique to fill the positive mold with water and subsequently pouring that water into a cup and marking the level. Namita helped. She's very nice.

Now we pour the silicone to that level:

And put the cup on a scale to weight it:

This enables us to add the appropriate amount of the compounding agent. Here we had 116.8 grams of silicone and added 3.2 grams of the agent:

Then mixed it well under the watchful eyes of Mufeed:

Vacuumed out the bubbles / air pockets:

Finally poured the silicone into the positive wax mold

Here's the wax mold filled, and then removed the next morning:

The produced negative mold is not perfect. There are several small areas where the silicone did not sufficiently settle in, particularly in some small areas like the mouth, between the legs, and around the letter 'R'

Casting the figure

At long last, it is time to cast the robot figure. We will mix parts A and B of an epoxy resin.

Again we use a scale to take the appropriate relative proportion. And a little red colour dye.

Finally, we set the coloured resin into the mold and wait...

Next day we wake up early, take the figure out of the mold.. ma sha Allah!: