HUT - FAB Academy Course Projects

Molding and Casting - Assignment Week 12

Assignment tasks for Week 12:

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

extra credit: try other molding and casting processes

Individual assignment

design a mold around the stock and tooling that you'll be using,

mill it (rough cut + three-axis finish cut),and use it to cast parts

extra credit: use more then two mold parts

Contents

Review the safety data sheets
Compare test casts
Try other molding and casting processes
Design a mold
Milling the mold (rough cut + three-axis finish cut)

Review the safety data sheets

For the group assignment I have used the following materials:

Smooth-Cast™ Mold Max™ 25 Silicone
Smooth-Cast™ 300 Hard Plastic
Release® 200
Black Clay

Mold Max™ 25 Silicones are tin-cured silicone rubber compounds that have exceptional working properties and library life. Mold Max™ Silicones feature Smooth-On’s exclusive “Libra™” catalyst for long library life. Mold Max™ silicones can be pigmented with Silc Pig™ silicone colorants. The mix ratio is 100A :5B. Pot life for the Mold Max™ 25 is 60 minutes and cures overnight at room temperature.

To download the data and safety sheet for Mold Max™ 25 please follow the link:
https://www.smooth-on.com/tb/files/Mold_Max_Series_TB.pdf

The Smooth-Cast™ 300 Series of liquid plastics are ultra-low viscosity casting resins that yield castings that are bright white and virtually bubble free. I used Smooth-Cast™ 300 hard palstic to casta gem stone.

To download the data and safety sheet for Smooth Cast 305 please follow the link:
https://www.smooth-on.com/tb/files/Smooth-Cast_300q,_300,_305___310.pdf

Ease Release® 200 is an Mold Release Agent that came with the the other Smooth-Cast products. I did not have to use it because the wax molds I made do not attach easily to silicone. The same goes for the hard plastic and silicone, it easily came off.

To download the data and safety sheet for Smooth Cast 305 please follow the link:
https://www.smooth-on.com/msds/files/ER200.pdf

Fig.4 - Emergency eyewash and body wash station in the lab

My fellow students casting materials, safety sheets and test casts can be found on their project documentation sites:
Dorian Somers' documentation
Lisa Schillin's documentation

Compare test casts

Fig.6 - Bees Wax sprue to be added to gem stone

Fig.7 - Bees Wax sprue added on to gem stone

Fig.8 - Mold Max 25 silicone used for the creation of a mold

Fig.9 - A silicone mold has been created with the gem stone and beews wax sprue inside. The mold has been cut to size with a scalpel.

Fig.10 - With a scalpel a zigzag cut has been created to release the gemstone and bees wax sprue

Fig.11 - The zigzag cut helps to close the cut and avoid liquid plastic to leach out of the mold.

Plastic test cast — Fig.12 - Hard plastic test cast.

sislicone mold cut open with white hard palstic cast visible — Fig.13 - Silicone mold cut open with white hard palstic cast visible

I had some silcone mix left over that I poured into a rubber glove to see how quick it would harden. The next day it was still soft because the room temperature was below 6 degrees Celsius(Australian winter. I took the glove plus filling to my office that was 23 degrees Celsius and within 24 hours the silicone was hardened. This was a good lesson for the donut cast.

Try other molding and casting processes

The maker space and workshop space is next to the ceremic studio where we have a large range of ceramic molds that students can use to cast clay modells. I tried out a few molds together to come up with a complex vase as illustrated in the photos below.

Fig.18 - Several molds stacked together.

Fig.19 - Finished vase object made from black clay

Design a mold

The task was to design a mold around the stock, in this case Ferris Wax and tooling that I did use to cnc route the mold for a donaut shape out of the wax. The Process

A simple donut shape was created in Fusion 360, this was my first experience with making a mold using a CNC-router and I wanted to keep it as simple as possible.

A donut shape created in Fusion 360 — Fig.20 - A simple donut shape created in Fusion 360

Next step was modelling the bottom part of the mold including an air vent for air release while the liquid silicone is poured in, and a sprue, which is a funnel shaped opening in the mold where the liquid silicone is poured into the mold.

For further explanations and mold and casting related terms please follow the link to Aero Marine Products.

Fig.21 - A simple donut shape created in Fusion 360

Fig.22 - The negative shape of half of the donut

Fig.24 - Almost finished bottom part of the donut mold,registration marks missing.

The registration points are missing,the bottom part will have two positive sticking out registration marks. The to create the positive and negative registration marks I coppied the bottom mold and made it the top mold, creted two spheres and booleaned them. The end result is two molds bottom and top that fit perfectly together. The registration marks assure that they won't move and hold together.

he bottom mold copied and moved on top, blus two sheres added to make the registration marks. — Fig.25 - The bottom mold copied and moved on top, blus two spheres added to make the registration marks.

Fig.26 - The finished models of the bottom and top mold to cast the donut

Now that the models are completed I can start with the process of computer-aided manufacturing (CAM). During this process Fusion 360 allows me to set the material to be milled, tools to be used and simulate the milling process before creating the code that goes to the CNC router. Here at the makerspace at Southern Cross University we are using a Roland MDX-40, that means that I have to create NC Gerber code. NC code is the main output from FeatureCAM that is used to drive automated machine tools.

Fig.27 - Setting up the machining or milling process in Fusion 360

Fig.28 - A new set-up has been created for the part to be machined

Fig.29 - The simulation of the tool in progress

Fig.30 - The tool has been chosen and the tooling path set.

Fig.31 - The simulation for the bottom part in progress

Fig.32 - The simulation has been completed for the bottom part of the mold

Fig.33 - Three sets of NC code have been created: 1. Routing the registration marks, 2. rough cut of the donut shape, 3. fine cut 3-axis.

Summary
The modelling of the molds was simple. Setting up CAM was more challenging. My tutor explained it all but I needed to do a CAM tutorial by Lars Christensen on Youtube.

Fig.35 - How to learn Fusion 360 CAM Tutorial - Basic - Chapter 2

The biggest challenge was to select the correct tools, tools settings for the job and the material used to mill ot the molds. The notes I took during our tutorial was very helpful in determining the settings and routing tools.

Milling the mold (rough cut + three-axis finish cut)

What first looked like a walk in the park project tuned out to be the hardest task so far. The Roland MDX-40 had problems with routing through the hard Ferris wax. It needs a more powerful router. Whenever it became to hard for the router it los it's focus and direction and I had to either use a different thicker tool or restart the routing process overe and over again.
It took me a whole week to finish routing the molds and they had some imperfections that I had to patch up with bees wax before pouring the silicone in it.
Lot's of lessons learned.

Fig.36 - I used double sided sticky tape to hold down the block of wax

Fig.38 - The two tools selected in Fusion 360 for routing, first tool on the left for clean-up three axis cut.

Fig.39 - Router has started the cut outside of the wax block area due to wrong coordinates for G56 point

Fig.40 - Broken tool due to wrong off set coordination

The force of the router is too strong and therefore the double sided sticky tape couldn't hold down the block of wax. I deceided to use timber screws to hold the block of wax down. It worked for a while but tension was too strong at one corner and the wax split off the block.