Week 13

Individual Assignment

This weeek we need to Design and build a mould and also to cast on it. It is a process of manufacturing by shaping liquid or pliable raw material using a rigid frame called a mould or matrix. This itself may have been made using a pattern or model of the final object.

Casting is a manufacturing process in which a liquid material is usually poured into a mould, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mould to complete the process. Casting materials are usually metals or various cold setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods

3D Mould Designing

For this week, I'm going to cast a phone holder. So I designed the shape of the holder first.


Then I made a block of size same as that of the wax brick I'm going to use as the mould(127x77x52mm). And then I created a recess of size 77x77x32mm in the block and I placed the holder inside.

Mould Making

I'm using the shopbot for milling the mould. So first I have to set the tool details and make the tool paths using Fusion 360.
Go to the Manufacturing Section in Fusion 360


Go to Setup and click on New Setup.


A Setup window will appear on the screen. Now I need to set the origin for the design so that the tool path will start from that origin point.
Set the Orientation as "Select Z axis/plane & X axis"


Set the Z axis


Set the X axis


Set the Stock Box Point


After setting the origin, the tool parameters should be fed to the software. I'm using 2 types of tools for milling the mould. The flat end mill is used for rough cut and the ball end mill is used for finishing cut.


To feed the tool parameters into the software, Go to Tool Library in Fusion 360 and click on New Tool.


In the New Tool window under the Milling Tools select Flat End Mill.


In the Cutter section, I filled up all the required parameters by measuring the tool using a vernier calliper.


In the Cutting Data section, I filled up all the cutting parameters as follows, And then click on Accept.


Now the Flat End Mill parameters are fed to the software.
To set the Ball End Mill parameters into the software repeat the same steps as follows.






Now both the tool parameters are fed to the software. Now I need to set the tool operations and tool paths. The first operation should be Rough Cutting and it is done using Flat End Mill.
In the 3D section I selected Pocket Clearing.

And then I selected Flat End Mill tool for this operation and then set all the parameters as follows.












Click OK and the Pocket Clearing operation is ready.

The Rough Cutting operation is done to remove a large quantity of material, this operation does not make the surface of the model smooth and finished.
So to obtain a finished surface Finishing operation is done using Ball End Mill
I selected Morphed Spiral operation using the Ball End Mill for making the horizontal surface smooth and finished. Follow the steps below.














At last I used the Contour operation using the Ball End Mill to conduct a final operation to make all the surface even and smooth. Follow the steps below.














Then I counducted the Operation Simulation offered by Fusion 360, and check if all the operations are done properly.


Then I exported the G-Codes of the operation using Flat End Mill by right clicking on the Pocket Clearing operation and clicked on Post Process.


I selected the machine to be used as ShopBot and clicked Post


Next the Morphed Spiral and Contour operation are done using the same Ball End Mill, So to obtain a combine G-Codes I selected both the operation and right clicked and selected Post Process


I selected the machine to be used as ShopBot and clicked Post


Download Design Files

I then fixed the Wax Brick on the ShopBot table using strong double sided tape.


Set the tool to the same origin.

Silicone Moulding

For silicone moulding I'm using Smooth-On OOMOO 25 silicone rubber composite. It consist of 2 parts (Part A and Part B).


Both these Parts must be mixed in a specific quantity of 1A:1B by volume or 100A:130B by weight and cures at 73 degree F or 23 degree C in 75 min.
I used the weight method to create the mixture
100g Part A = 130g Part B
ie. 1g Part A = 1.3g Part B
so, 83g Part A = 109g Part B


Then I transfered both the Parts into a container and mixed thoroughly.


After obtaining a uniform mixture I poured the mixture into the mould and filled it upto the brim. Luckily the quantity of mixture I took was correct and there was no wastage.
Then I kept the mixture for curing for 75min at room temperature.


After 75min the mixture hardened and I took the silicone mould out.

Casting

For casting I'm using Smooth-On SMOOTH CAST 305 Bright White Liquid Plastic. It consist of 2 Parts (Part A and Part B).


Both these Parts must be mixed in a specific quantity of 1A:1B by volume or 100A:90B by weight and cures at 73 degree F or 23 degree C in 30 min.
I used the weight method to create the mixture
100g Part A = 90g Part B
ie. 1g Part A = 0.9g Part B
so, 35g Part A = 31.5g Part B


Then I mixed the mixture thoroughly and poured it into the silicone mould. But this time the mixture became excess and I had to waste the excess. So it is ideal to take 20g of part A and 18g of part B.


I placed a 6mm acrylic sheet with a 7mm riser hole on top of the silicone mould.


After 30min the Liquid plastic mixture cured


Then I removed the cured plastic out of the silicone mould


The Phone Holder is ready to hold the Phone.



Resin Casting
For Resin casting I used Easy Cast Epoxy Resin-33. There are 2 parts for the compounds, Part A is epoxy and Part B is hardner. Both these parts should be mixed in the ratio 100:50 by weight. I also used red pigment to give colour to cast part.


After mixing the mixture thoroughly and pored it into the mould.


After letting it cure for 24hrs, I took the cast from the mould.


Metal Casting
For metal casting I used Bismuth. It is a brittle metal with a silvery white color and has one of the lowest values of thermal conductivity among metals. It is relatively nontoxic and has a low melting point just above 271 °C


Then I heated and molten the metal using Hot Pot.


Poured the melted metal into the silicone mould.


keep the molten metal for curing


When the metal solidified, I took it out of the mould. The surface of the casted metal was not finished, It can be because of the water content in the silicone.