This week's assignment was more challenging and difficult but many useful things were learnt along the way. The assignment is about making a mold and casting on it, so it seemed to be a clear workflow to follow.

These are the following materials required for creating moulds for casting:-

STEP- 1 = Prepare a 3D model for the mold using platform and save it as stl file.

STEP- 2 = Export the stl file in  and prepare the toolpath. 

STEP- 3 = Mill it using Modella Wax on SRM 20 Milling machine 

Rough Cut & Finishing Cut

STEP- 4 = Create a Silicon Mold & Cast the final object

3D Design for Mold Using Fusion360

I learnt How to Create a One-Part Mold in Fusion 360 tutorial to help me designing my mold.
It is only four easy steps, but first you need to know the size of the mold cube that will be milled, to know the design boundaries. (Mostly this mold template can be thawed and shaped to the size we want).

• • First, you have to draw the borders of the template (length * width). After that sketch the object you want.

  • Secondly, I “extrude” the objects, and used the “Fillet” feature to twist the heart.

  • Third, extrude the mold frame by its height, to make the mold template. 

  • Fourth, to cavite the objects I design from the template I used the “combine” feature by “cut” operation. I specify the template as the target body and specified the two objects as a tool. 

  • This is the final result ready to mill. 

INTRUDE

EXTRUDE

Steps for Milling the Mold with Roland SRM-20 by using SRP Player

A powerful tool path engine optimizes path quality and tool approach, ensuring quality finishes and faster path calculation times. Roland’s SRP Player software which enhances SRM-20 functionality and streamlines workflow, allowing users to get the most out their state-of-the-art mills. Roland SRP Player supports most popular CAD file formats, including STL, DXF, Rhino, 3D Model and IGES. New and existing monoFab SRM-20 owners can download SRP Player with a few clicks of the mouse through Roland’s included OnSupport software. SRP Player also makes multiple tool path operations and progressive path simulations available to SRM-20 users through a built-in preview feature. Additionally, SRP Player software also incorporates unique editing functions that let users explore new milling capabilities as their skills progress.

I experimented for milling by using “SPR Player” software. I saved models to “.stl” file format for opening them in the SRP Player to make milling routes.

1. Open SRP Player software. 

2. Open the .stl file you exported from Fusion360.

3. Enter the scale at which you would like to mill this geometry. Note: if you would like to mill it exactly as you modeled it, either press 1/1 scale or enter in the dimensions of your geometry manually. If you need to mill all the way to the bounds of the material, you can reduce the amount of scrap material left around your part under Create Toolpaths > Edit > Roughing > Top Surface > Modeling Form

4. Typically this field can be left alone, but if you would like to reorient your material you can do so here. Note: this does not refer to orienting the direction of cutting, but rather the material in the bed.

5. Click ‘Type of Milling’ for next step.

Output of the model after milling

Since, I have designed both Intrude and Extrude, I first tried with the cutting for Extrude of the object in Modella. The outcome of the object after milling is shown below:

The Process for final Molding & Casting

Step 1 : Making the mixture
To form the pouring mixture for the silicone we first mix the silicone and the add hardener about 10ml with syringe and then mix them using a spatula until its gives off some heat.

The volume of the silicone to be used is measured with approximate volume of the total moulds and calculating accordingly.
Step 2 : Pouring the mixtureinto the moulds
Step 3 : Tapping the negative mould and leaving it to set for 24hrs.

Since, the sillicons were expired in the lab, we have bought the SILCOZEST Liquid Silicone Rubber 140.Its a two-part silicone rubber that vulcanizes at room temperature.

Data Sheet::

This is the Food grade Silicone Rubber that can be used for Making the chocolate mould.

Liquid Chocolate datasheet

Specifications:

Color/Appearance: Clear to slightly opaque dark brown liquidAroma/Flavor: Characteristic of cocoa with a pleasant taste and aroma
Specific Gravity: 0.922 – 1.019 at 25C
Brix: 17.679 – 21.421 at 20C
Refractive Index: 1.3600 – 1.3662 at 20C

Ingredients: Water, Ethyl Alcohol, Cocoa

Allergens: None
Kosher: Kosher Parve
GMO Status: GMO Free

Shelf Life: 6 months

Country of Origin: USA

Storage: Store tightly sealed in a cool dry place protected from direct heat and light.

Packaging: Available in 8 oz., 16 oz., 32 oz., and 64 oz., twin neck plastic bottles designed to eliminate additional measuring by providing a
precise pour every time.

Suggested Applications & Usage: Can be used for a variety of applications including bakery, food & beverage, ice cream, etc.: Start evaluation at 0.50% and adjust accordingly

The Process for Casting through Silicon Mould

Preparation of Silicon Rubber liquid for Molding:

After the completion of the milling of the design and for molding I used the Liquid silicone Rubber which is having two parts, namely Part A and Part B based on the User Instruction Mixing ratio of 1:1 as per the required weight. For making the solution with the mixture of 12.5 gm of each solutions in a small plastic bowl and stirred for 10-15 minutes, so that both the both the solutions can mix properly for making the product into a good shape. I placed the bowl in the Mercury Vacuum for around 15-20 minutes so that all the bubbles will be dissolved and to make the solutions ready for molding.

After removing the air bubbles in the mercury vacuum the liquid is poured to the milled work piece and left for 12 hours and the final product is ready.

Final Output.

Casting:

In the earlier phases, I have 3D designed made with a Wax Blocks, Milled the design on the Wax block (Positive Mould) then poured the Silicon to make the Positive Mould and would be Casting using various materials like HydroStone, Epoxy Resin, Paraffin Wax etc. Here I used Epoxy resin which is available in my lab. As I have already dealt with Epoxy Resin in my earlier mold making, I decided to do the Casting with it. I used Epoxy Resin which is of Part-A & Part-B for giving the final shape to the design. Then, I took the Part A & Part B Epoxy Resin with a proportion of 3:1 ratio and poured into a plastic glass.

Next Day, I decided to Cast it with Epoxy Resin. This time I took caution to take more material. The Mixing Proportion for Epoxy Resin is 3:1

Stirring and Bubbles

After We prepared the silicon (Art Epoxy Resin Part-A & B) mix with a ratio of 3:1 (Part A (3) : Part B (1) with adding the red color for a decent look. I mixed the 2-part (Part A & B) (epoxy resin A B resin image) materials with a ratio of 3:1 and mixed properly, if these solutions will not mix the 2 parts, they will not work as expected. After mixing of the silicon mixture, we stirred it properly so that, all the solutions can mixes properly. The problem is, that stirring introduces air-bubbles. This creates challenges, especially if the pot time is in the range of 3 min. Mix, stir, pour & de-gas. Accordingly, we used vacuum chamber for melting of the bubbles generated during stirring of the mixtures.

The Safety Data

The safety data for the molding and casting material is basically the same-

• Wear protective clothing, gloves and glasses, so that the material does not touch your skin.

• Don’t eat or drink it. Don’t eat or drink anything in the working area.

• If swallowed, do not trigger nausea, call a doctor.

• Ventilate. Don’t inhale.

• Don’t do anything stupid with the material.

After that we put the mixture into a plastic glass and put into the We put a small amount of silicon mixture

After that we put the mixture into a plastic glass and put into the oven, so that the bubbles get evaporated.

The solution was kept for curing for 24 hours. And after it, the mold is ready.

I also experimented for making a gift kind of thing with the resin. I Put a small flower with leaves into a plastic cup and pured the remaining resins. Here it looks like this.

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