Assignment
This week assignment is to design a 3D mold, machine it, and cast parts from it following these steps:
> Design a 3d model
> Mill the part out of a wax block to create the mold
> Create a reverse plastic mold from the wax block
> Fill the reverse mold with a casting material(In my case lead),
to form the final part.
Since we could mold and cast anysthing we wnanted, I decided to
make a Batman Boomerang 'cause i find it so cooool!!!
Design a 3d model
I used solid works to built the 3d model for the positive mold.The Design dimensions had to be precise and the size of the wax block also needs to be taken into account while creating the 3D design.
Design File-Download
Milling the Mold
Inorder to create the first mold by milling, make sure that the wax block is properly glued to the base of the milling machine by a double sided tape.
The Milling process consist of 2 steps:
1-milling the rough surface using a 1/8" fine end milling bit.
2-milling the fine surface using a 1/8" ball end milling bit.
Since i used a large block of wax, i cut out the section of the block that was unused and mold was ready.
Making the reserve mold
I used mold max 60,a silicone rubber compund,
to create the reverse mold.The mold max 60 consist of 2 compunds,
part A and part B.Both needs to be mixed in a certain ratio.
First i needed the exact volume part A required to make the mold.
So for that, I filled the first mold with water and the emptied
it into a transparent plastic cup and then marked the water level.
Then I emptied the cup and filled it with part A compund upto the
marked level.Then measure its weight excluding the weight of the
glass.This weight is important factor for adding the second compund.
The ratio between part A and part B compuond is 1:100. So take care while adding the part B compund. Only a 100th of part A should be added.
Now the mixture of both part A and part B needs to be stirred thoroughly.
Next step is to pour the mixture into the wax mold.There will certainly be trapped air bubbles in the mixture. To get rid of the
bubbles,i repeatedly tapped the wax mold containing the mixture against the table surface.This allowed the trapped air bubbles to escape.
molding from nizam on Vimeo.
Now i have to wait till the mold sets.
It took around 24hrs for the mold to solidify.Here's a pic-
Casting
First i tried csting with white liquid plastic,
the smooth-cast 305.Like the mold, it also contained two parts A&B
which needed to be mixed in equal proportions.
Any color of our choice can be added to the mixture. Once both parts are mixed, stir thorouhly and pour into the mold before 7 minutes.
It took about 20mins for the mixture to solidify.Once it did, i seperated it from the mold and presto....
Next i tried lead for casting.I set the furnace at 300°C for melting the lead.
The melting process took just 2 minutes.I poured the melted lead into the mold using tonks and gloves.
Make sure that to use gloves if you dont want to burn your hands. The lead solidified in just about 5 mins. After cooling, I seperated it from the mold and smoothened the edges a bit using
a drummel.
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