Molding & Casting
This week's assignment is to design a 3D model, then we have to machine it and cast from it.
I decided to make a single part mold because this is the first experience for me than later i will try for two part mold.
I will be creating a mold for "AKGEC FABLab" using OnShape.
Work Flow
1. Prepare a 3D model for the mold using platfrom which supports boolean operations and save it as stl file.
2. Export the stl file in ASPIRE and prepare the toolpath.
3. Mill it using Modella out of hard wood.
Rough Cut
Finishing Cut
4. Create a Silicon mold
Cast from the mould using Epoxy
3D model using OnShape
As discussed already i will be making AKGEC FABLab logo
First setp is to make a cuboid on which molud is to be made
Cut a section of this cubiod so that materail can be poured into it
In this design i will be requiring a thin layer below the letters , so extrude a part from the cubiod
Sketch the AKGEC on the previous section surface and extrude it.
Similar to the above step repeat it for FABLab
Then to make the logo first i downloaded the logo of FABLAB and then vectorised it using Inkscape. Now save this file as dxf and load it in OnShape. Now make a extrude from this
Final Design
Tool Path
Rough Cut
Finish Cut
After Rough Cut
After Finishing
Since we are having 0.8mm mill bit in our lab and the dimension of the mould are defined as a result the finished product was not upto the mark. So i decided to make another mold that can be finished easily using 0.8mm mill bit
The other mold which i decided to make is shown below. I had used Onshape to make this one part mold
Finished part
Again i have used ASPIRE to make toolpath for rough cut and finished cut. The finsihed mold is shown below
Casting Silicone
We have MURTISIL 1010 silicone rubber RTV. It has two parts PART A and PART B which are to be mixed and poured within an interval known as pot-time before it starts setting and is not workable anymore.
Since Part A and Part B is to be mixed in ratio 25A:B, below you can find the snapshots of the measurement taken.
Next Step is to mix the the part A and part B. They are mixed in the ratio A:B::20:1.
After mixing i began to pour it into the mold.I tried to follow the advice to allow only a hin stream of resin to flow so that the bubbles pop on the way down but it was harder in practice. To achieve the thin stream i had to pour it from great height, and due to momentum the liquid acted like non newtonian liquid and started pilling as solid and these could create more bubble. Also while being too careful of the way i pur and trying to do everything perfect I ran out of time and the silicone began to set quickly and had become far less viscous by the time I was finished with one cavity. I had to now hurry up and manage with this material and You'll see it didnt turn out that good in second cavity. It took 2hrs for silicone to settle.
Cast removal After 2 hours when the silicone set to a rubber. The silicone could be easily separated from the hard wood. I was a little concerned about the narrow edges. But overall it was an excelent cast.
Casting
I used epoxy as casting material. This also has two parts Part A and Part B. They are mixed in the ratio A:B::2:1.
It took one day for epoxy to settle and hero shot is given below.
