Vol13: Molding & Casting

In my Witchy Era


This week we learned about Designing for Mold-making, molding and casting processes and maybe side-hustle in suncatcher-making.

Requirements

    Group Assignment
  1. Review the safety data sheets for each of your molding and casting materials
  2. Make and compare test casts with each of them.
  3. Compare printing vs milling molds.

Individual Assignment
  1. Design a mold around the process you’ll be using, produce it with a smooth surface finish that does not show the production process, and use it to cast parts.

Softwares 💻

  1. Fusion 360
  2. MeshCAM
  3. openBuilds Control

Group Assignment

In this week we're making silicon molds and casting polyester. We covered three topics: Safety, Milling vs Printing processes, materiel test.

Safety

The most important practicies are: wearing gloves, sitting in an good air-ventilated area. reading materials' data sheet if available. We had at the lab polyester so when I researched I found this data sheet for polyester and resin.

Milling vs 3D printing

This is not my first time making molds, I tried making a mold of the bust of bastet. An Egyption god with the head of a cat. But I didn't use the process of milling but 3D printing.

safety

But milling was new to me. In the printing process you only need the object itself and then you create the negative silicon mold using clay. you can find a very easy way by following this guide by Prusa

In milling, you start by making the positive mold first then pour the silicon to make the negative mold.

Material tests

Then we went and tested different mold materials & cast materials. We tested different silicon to hardener ratio. My ratio was 30 grams of silicon with 1 grams of hardner which made the silicon not fluid enough and It was a pain to stir.

Amr & Doaa tried different ratios and we came to the conclusion that for each 100 g of silicon we use 1g of hardener. Also we casted some candle and here are the final results.

safety

Mold Design

In Maker Faire Cairo, beside working at Fab Lab Egypt's booth I attended a suncatcher-making workshop that used recycled materials. I enjoyed so much. My idea is to design a crystal shape then cast transparent polyester.


Design Process

  1. I started by creating a sketch of the crystal that'll then be revolved.

    Sketch

    Revolve

  2. I split the body and placed them on the same level.

    3. Splitting

  3. I created an offset plane tangent to the top curve of the crystal, Then created a sketch, projected the crystals and designed the keys with 5 mm diameter & vents.

    4. keep in mind two things. The 1st thing is I'll be using a 3mm bit so the space between the keys & walls should be bigger by 3mm by at least 0.2mm. The 2nd thing: the vent shouldn't be vertical

  4. Then Finally I extruded and combined the two pieces with the mold.

Milling

We used chemical wood since it's a very soft materiel easy to make molds from.

We used a different CAM tool called "MeshCAM". It's unfortunatlely paid software but it offers a free trial so I signed up for it and started playing. I followed the tutorials and Thanks to Amr we tried a feedrate of

Parameters

First we had to define some parameters like the tools. We're gonna use two endmills one straight for roughing and the ballnose for finishing.

  1. We add it from the "Job Setup" menu, These are the parameters for the flat endmill and added the same for ballnose.

We import the STL from "file" menu, then from the "toolpaths" menu we choose our operations.

Roughing + Drills

These the parameters I used for roughing in my case I wanted the roughing to be parallel which appear cleaner after fabrication.


My drills didn't appear in the roughing operation so Amr suggested to make drills and they were detected automatically as shown here.Then I exported the toolpath from "Save Current Setup "


Finishing

I chose paraleel finishing operation and added these parameters.


Fabrication

I went to our China router and operated it as shown in previous weeks using OpenBuilds Control.

After Roughing
After Finishing

Molding

Molding

I used this silicon which we used in our group assignment I used this spray as a release agent.

Materials used

Here're ratios I used.

Then I poured the silicon and waited for 24 hours.At first there were a lot of bubbles so I shaked the mold a bit.

Mold without bubbles

Casting

I went home 4AM in the morning and I returned and waited until 2PM and I pulled the silicon. The first half was good but when I went to the seconcd half with the pulging pins I noticed that maybe I released it a bit early.

The not-so-good-mold

I poured this half again and waited properly. Then Voila!

Time for casting the polyester! I wrapped the mold with tape then put to wood

I used the cutter to post process the mold like cutting the edges.

I poured polyseter using the ratios mentioned in Doaa's documentation. I tried to break the vent around the hole but it's so hard to break, I'll try using wet sanding techniques.

Multiple Hero Shoots!



Files

  • Design Files